VOLATILES ON SOLAR SYSTEM OBJECTS: CARBON DIOXIDE ON IAPETUS AND AQUEOUS ALTERATION IN CM CHONDRITES more

VOLATILES ON SOLAR SYSTEM OBJECTS: CARBON DIOXIDE ON IAPETUS AND AQUEOUS ALTERATION IN CM CHONDRITES by Eric Edward Palmer ____________________________ A Dissertation Submitted to the Faculty of the DEPARTMENT OF PLANETARY SCIENCES In Partial Fulfillment of the Requirements For the Degree of DOCTOR OF PHILOSOPHY In the Graduate College THE UNIVERSITY OF ARIZONA 2009 2 THE UNIVERSITY OF ARIZONA GRADUATE COLLEGE As members of the Dissertation Committee, we certify that we have read the dissertation prepared by Eric Edward Palmer entitled Volatiles on Solar System Objects: Carbon Dioxide on Iapetus and Aqueous Alteration in CM Chondrites and recommend that it be accepted as fulfilling the dissertation requirement for the Degree of Doctor of Philosophy. ______________________________________________ Date: 15 October 2009 Robert H. Brown ______________________________________________ Date: 15 October 2009 Dante Lauretta ______________________________________________ Date: 15 October 2009 Roger Yelle ______________________________________________ Date: 15 October 2009 Jonathan I. Lunine ______________________________________________ Date: 15 October 2009 William Boynton Final approval and acceptance of this dissertation is contingent upon the candidate’s submission of the final copies of the dissertation to the Graduate College. I hereby certify that I have read this dissertation prepared under my direction and recommend that it be accepted as fulfilling the dissertation requirement. ______________________________________________ Date: 15 October 2009 Dissertation Director: Robert H. Brown 3 STATEMENT BY AUTHOR This dissertation has been submitted in partial fulfillment of requirements for an advanced degree at the University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library. Brief quotations from this dissertation are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his or her judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author. SIGNED: Eric Edward Palmer 4 ACKNOWLEDGEMENTS The quest for getting my Ph.D. has been a long one that started shortly after I completed flight training in the United States Air Force. I began the task of getting some necessary background courses in physics, chemistry and geology such that I could apply to the University of Arizona's Planetary Science Program. Dr. Terry Spell, and Dr. Ron Metcalf at the University of Nevada, Las Vegas provided me a great background and insight into geological processes and its application to how the world works. I always had an eye as to how it would apply to planetary science, and they were very accommodating dealing with my questions and my Air Force driven sporadic schedule. Dr. Charles Wood, who was the department head at the University of North Dakota, also had a strong influence during my quest into planetary sciences. He sent me to my first Lunar and Planetary Science Conference and greatly supported me in my quest to get my Ph.D. To my committee, I’d like to thank them for their support and dedication in developing my professional career. Their tough questions and subsequent discussions proved to be insightful and greatly helped me understand the complex set of relationships that I was investigating. I would like to also thank Dr. H. Jay Melosh and Dr. John S. Lewis, though could not be at my defense, spent many hours helping me and advising me through my journey. I give my heart felt thanks to Jason Barnes, Nicole Baugh, Brian Jackson, Diana Smith, Jason Soderblom, Kat Volk, and John Weirich. Long hours they have spent on insightful discussions that helped me to clarify my research, its analysis and its presentation. Knowledge, understanding and wisdom are goals we all share and I hope they achieve them. To all the grads, I thank them all for their support, interest and general discussions that enriched my time at LPL. I would also like to thank Pam Street, Glinda Davidson, Virginia Pasek, Maria Schuchardt, Brett Lawrie, Bill Verts, Dyer Lytle, John Pursch, Chris Schaller, and Joe Plassman for their help in the non-academic portions of getting my Ph.D. To thank my parents, Carl Palmer and Wanda Palmer, I'd like to thank for raising me a nurturing environment and a desire to learn. Finally, I would like to thank my wife, Cristina, and my kids, Jenna, Thomas and Anna who have traveled with me through this quest. Many times they had to give up what they wanted to do because my schedule required it of them. Their patience, humor and support have been essential. 5 DEDICATION To humanity The goal of discovery is one of the most driving forces of man. May we never lose the desire to look over the next ridge, to turn over another rock, to ask the hard questions, and to be amazed at how things were made. 6 TABLE OF CONTENTS LIST OF FIGURES.........................................................................................................8 LIST OF TABLES ........................................................................................................10 ABSTRACT..................................................................................................................11 CHAPTER 1 INTRODUCTION ...................................................................................13 CHAPTER 2 STABILITY OF CARBON DIOXIDE.....................................................16 2.1 Introduction.........................................................................................................16 2.2 Model..................................................................................................................17 2.2.1 Thermal Model ............................................................................................18 2.2.1.1 Insolation..............................................................................................18 2.2.1.2 Black Body Radiation ...........................................................................22 2.2.1.3 Latent Heat Transfer .............................................................................22 2.2.1.4 Thermal Diffusion.................................................................................25 2.2.2 CO2 Transport..............................................................................................29 2.3 Results ................................................................................................................33 2.3.1 Ablation Rate...............................................................................................33 2.3.2 Polar Caps....................................................................................................35 2.3.3 CO2 Escape Rates ........................................................................................41 2.3.4 CO2 Resupply ..............................................................................................45 2.4 Discussion...........................................................................................................47 2.5 Conclusion ..........................................................................................................50 CHAPTER 3 A POSSIBLE TRACE CO2 POLAR CAP................................................52 3.1 Abstract...............................................................................................................52 3.2 Introduction.........................................................................................................52 3.3 Model..................................................................................................................53 3.4 Results ................................................................................................................54 3.5 Predictions of a Polar Cap ...................................................................................58 3.6 Conclusion ..........................................................................................................66 CHAPTER 4 PRODUCTION OF CARBON DIOXIDE ON IAPETUS ........................67 4.1 Abstract...............................................................................................................67 4.2 Introduction.........................................................................................................68 4.3 Method................................................................................................................70 4.4 Results ................................................................................................................78 4.5 Discussion...........................................................................................................85 4.5.1 Applicability to Iapetus ................................................................................85 4.5.2 Production of CO2 on Iapetus.......................................................................88 4.5.3 Quantity of CO2 on Iapetus ..........................................................................92 4.5.3.1 Dark Material (Leading Side)................................................................93 4.5.3.2 Bright Regions (Trailing Side and Poles) ..............................................95 7 TABLE OF CONTENTS - Continued 4.5.3.3 Transition Between Bright and Dark Regions........................................97 4.5.4 UV Photolysis as the Source of CO2 ............................................................99 4.5.4.1 Complexed CO2........................................................................................99 4.5.4.2 Photodissociation ....................................................................................102 4.5.4.3 Radiolytic Production..............................................................................104 4.6 Conclusion ........................................................................................................105 CHAPTER 5 AQUEOUS ALTERATION OF KAMACITE IN CM CHONDRITES 107 5.1 Abstract.............................................................................................................107 5.2 Introduction.......................................................................................................108 5.2.1 Traditional Alteration Sequence .................................................................109 5.2.2 Location of Alteration................................................................................111 5.3 Analytical Procedure .........................................................................................113 5.4 Results ..............................................................................................................116 5.4.1 Samples .....................................................................................................117 5.4.2 Kamacite....................................................................................................127 5.4.3 Tochilinite..................................................................................................130 5.4.4 P-rich Sulfide and Accessory Phases in Tochilinite ....................................140 5.4.5 Tochilinite/cronstedtite intergrowth (TCI)..................................................150 5.4.6 Cronstedtite................................................................................................153 5.4.7 Iron Oxides ................................................................................................155 5.4.8 Troilite.......................................................................................................157 5.5 Discussion.........................................................................................................159 5.5.1 Proposed Alteration Sequence....................................................................159 5.5.1.1 Alteration Products of Water with S....................................................160 5.5.1.2 Alteration Products of Water with Si...................................................170 5.5.1.3 Alteration Products of Water with Limited Reactive Components .......171 5.5.2 Indicators for Post-Accretion Parent-Body Alteration.................................175 5.5.2.1 Tochilinite growth into matrix.............................................................175 5.5.2.2 Regional alteration..............................................................................176 5.5.3 Indicators for Pre-Accretion Parent-Body Alteration ..................................183 5.5.4 Model for alteration ...................................................................................189 5.6 Conclusion ........................................................................................................191 CHAPTER 6 CONCLUSION......................................................................................193 APPENDIX A FULL LISTING OF EMPA DATA .....................................................195 APPENDIX B SUMMARY OF ALTERATION .........................................................221 REFERENCES............................................................................................................224 8 LIST OF FIGURES Figure 2.1: Bond Albedo Map of Iapetus ......................................................................20 Figure 2.2: Effective Inclination ...................................................................................23 Figure 2.3: Energy Balance and Temperature ...............................................................24 Figure 2.4: Buffering Effect of CO2 on Temperature ....................................................26 Figure 2.5: Distance of CO2 for a Single Time Step ......................................................32 Figure 2.6: Ablation Rate..............................................................................................34 Figure 2.7: Long Term Ablation Rates..........................................................................36 Figure 2.8: Thickness Evolution of a Seasonal Polar Cap..............................................37 Figure 2.9: Long Term Loss Rate of CO2 from Iapetus' Surface....................................43 Figure 2.10: Net CO2 Loss Rate....................................................................................46 Figure 3.1: Iapetus' Temperature Map............................................................................55 Figure 3.2: Flux of CO2 ................................................................................................61 Figure 3.3: Thickness of Removed CO2 ........................................................................62 Figure 3.4: Polar Cap....................................................................................................65 Figure 4.1: Thick Film Cryogenic Sample Chamber .....................................................71 Figure 4.2: Sample Images ...........................................................................................74 Figure 4.3: Deuterium Bulb UV Flux............................................................................76 Figure 4.4: CO and CO2 Production, Warm ..................................................................80 Figure 4.5: CO and CO2 Production, Cold ....................................................................81 Figure 4.6: Volatile Burn-Off .......................................................................................82 Figure 4.7: Production Rates vs. Temperature...............................................................84 Figure 4.8: Iapetus' Transition Region ..........................................................................91 Figure 4.9: Iapetus' Dark Side and IR Spectrum............................................................94 Figure 4.10: Spectrum of Iapetus' Bright Terrain ..........................................................96 Figure 4.11: CO2 Absorption Near Water Sources ........................................................98 Figure 5.1: Si/Mg/Fe ternary diagram and phases .......................................................111 Figure 5.2: BSE image of Murray sample #1 and the 30 regions studied.....................121 Figure 5.3: BSE image of Murray sample #2 and the 11 regions studied.....................122 Figure 5.4: BSE image of Murchison and the 13 regions studied ................................124 Figure 5.5: BSE image of Cold Bokkeveld and the 9 regions studied..........................125 Figure 5.6: BSE image of Nogoya and the two regions studied ...................................126 Figure 5.7: BSE image of Chondrule A of Cold Bokkeveld ........................................128 Figure 5.8: Matrix kamacite grain with schreibersite...................................................129 Figure 5.10: Tochilinite associated with type-I chondrules..........................................131 Figure 5.11: Tochilinite boundary...............................................................................132 Figure 5.12: FESEM image of kamacite/tochilinite alteration boundary......................133 Figure 5.13: Advanced tochilinite alteration ...............................................................135 9 LIST OF FIGURES - Continued Figure 5.14: Tochilinite's stoichiometric parameters, x and n.......................................139 Figure 5.15: Histogram of the Mg/(Mg+Fe) content of tochilinite...............................140 Figure 5.16: Fractured troilite with embedded P sulfide grains....................................141 Figure 5.17: FESEM of P Sulfide ...............................................................................143 Figure 5.18: Murray1, Ch 4 X-ray map BSE...............................................................146 Figure 5.19: Murray1, Ch 4 X-ray map.......................................................................147 Figure 5.20: Murray1, Ch 4 reflected light..................................................................148 Figure 5.21: Cr/Mg Phase...........................................................................................149 Figure 5.22: FESEM TCI ...........................................................................................151 Figure 5.23: Si/Mg/Fe ternary plot for TCI grains.......................................................153 Figure 5.24: Cronstedtite in type II chondrules ...........................................................154 Figure 5.25: Cronstedtite rims on kamacite.................................................................155 Figure 5.26: Oxidized kamacite ..................................................................................157 Figure 5.27: Troilite and tochilinite .............................................................................158 Figure 5.29: Kamacite alteration sequence..................................................................160 Figure 5.30: Plot of tochilinite and P-rich sulfides in Murray......................................163 Figure 5.31: Line scan through Cold Bokkeveld tochilinite grain................................165 Figure 5.32: Depleted P-rich sulfide ternary diagrams ................................................166 Figure 5.33: Volume and alteration of tochilinite and P-rich sulfides ..........................168 Figure 5.34: O/Ni/Fe ternary phase diagram ...............................................................172 Figure 5.35: Magnetite rich dust rim...........................................................................174 Figure 5.36: Indications of parent body alteration .......................................................177 Figure 5.37: Study Region R8I - Indications of parent body alteration ........................178 Figure 5.38: Breccia clast vs. alteration boundary.......................................................181 Figure 5.39: Localized parent body alteration .............................................................182 Figure 5.40: Kamacite near tochilinite ........................................................................185 Figure 5.41: Kamacite and hydrated matrix ................................................................186 Figure 5.42: Nebular alteration of matrix material ......................................................188 10 LIST OF TABLES Table 2.1: Thermal parameters used in the model .........................................................27 Table 2.2: Fraction of CO2 reaching escape velocity as a function of temperature.........33 Table 2.3: Sublimation and movement rates for different sized polar caps. ...................39 Table 3.1: Transport Between Poles of CO2 per Seasonal Cycle. ..................................57 Table 3.2: Predicted Thickness and Mass of a North Polar Cap as a Function of the Latitude of its Edge. ......................................................................................................64 Table 4.1: Production Rates..........................................................................................79 Table 4.2: Volatile Residence Time ..............................................................................87 Table 4.3: Optical Constants and Optical Depth..........................................................103 Table 5.1: Summary of EMPA data (wt%)...................................................................118 Table 5.2: Tochilinite elemental composition (wt%)....................................................137 Table 5.3: Empirical formula for tochilinite.................................................................138 Table 5.4: Empirical formula for P-rich sulfides ..........................................................145 Table 5.5: Cr/Mg phase from Murray #1, chondrule 4 (wt%).......................................150 Table 5.6: Tochilinite/Cronstedtite Intergrowths (TCI) chemistry (wt%).....................151 Table 5.7: Iron oxide distribution.................................................................................156 Table 5.8: Calculated end members (wt%) for tochilinite and P-rich sulfides...............163 Table 5.9: Composition of Cold Bokkeveld tochilinite and P-rich sulfide (wt%)..........164 Table 5.10: Mass balance calculations .........................................................................168 11 ABSTRACT Volatiles are critical in understanding the history of the solar system. We conducted two case studies intended to further this understanding. First, we analyzed the presence of CO2 on Iapetus. Second, we evaluated aqueous alteration in CM chondrites. We studied the distribution, stability and production of CO2 on Saturn's moon Iapetus. We determined that CO2 is concentrated exclusively on Iapetus' dark material with an effective thickness of 31 nm. The total CO2 on Iapetus' surface is 2.3x108 kg. However, CO2 should not be present because it has a limited residence time on the surface of Iapetus. Our thermal calculations and modeling show that CO2 in the form of frost will not remain on Iapetus' surface beyond a few hundred years. Thus, it must be complexed with dark material. However, photodissociation will destroy the observed inventory in ~1/2 an Earth year. The lack of thermal and radiolytic stability requires an active source. We conducted experiments showing UV radiation generates CO2 under Iapetus-like conditions. We created a simulated regolith by mixing crushed water ice with isotopically labeled carbon. We then irradiated it with UV light at low temperature and pressure, producing 1.1x1015 parts m-2 s-1. Extrapolating to Iapetus, photolysis could generate 8.4x107 kg y-1, which makes photolytic production a good candidate for the source of the CO2 detected on Iapetus. We also studied the aqueous alteration of metal-bearing assemblages in CM chondrites. We examined Murchison, Cold Bokkeveld, Nogoya, and Murray using 12 microscopy, electron microprobe analysis and scanning electron microscopy. Alteration on CM meteorites occurred within at least three microchemical environments: S-rich water, Si-rich water and water without substantial reactive components. Kamacite alters into tochilinite, cronstedtite, or magnetite. Sulfur associated alteration can form accessory minerals: P-rich sulfides, eskolaite and schreibersite. Additionally, we determined that there were two alteration events for some CM chondrites. The first formed a hydrated matrix prior to accretion, indicated by unaltered kamacite surrounded by a hydrated matrix. The second occurred after parent body formation. This event is indicated by large regions with consistent alteration features, surrounded by other regions of less altered material. 13 CHAPTER 1 INTRODUCTION The 2006 NASA Strategic Plan identified as the goal for Planetary Science to "advance scientific knowledge of the origin and history of the solar system…." In this work we present two case studies that focus on the history and interactions of volatiles on solar system objects. Ultimately, we attempt to answer the questions of what these objects were like when they formed, and what processes made them like what we see today. Our first case study evaluated the presence of CO2 on Iapetus. Cassini's Visual and Infrared Mapping Spectrometer (VIMS) detected CO2 on Iapetus’ dark side, its leading hemisphere (Buratti et al. 2005). VIMS detected an absorption feature centered at 4.267 um (2343 cm-1), which corresponds to the !3 fundamental asymmetric stretch of CO2 (Sandford and Allamandola 1990a). Preliminary analysis of VIMS data from the Dec 2004 flyby indicated that some CO2 might be in the form of CO2 frost, something not expected. Previous work on the stability of volatiles showed CO2 to be unstable over the age of the solar system at Saturn’s distance from the Sun (Watson et al. 1963; Lebofsky 1975). Lebofsky predicted a rate of loss between 10 and 50 mm year-1 at 0° latitude and between 0.1 and 5 mm year-1 at 60° latitude (1975) for a slow rotating body. However, not only has CO2 been detected on Iapetus, but it has also been detected on other Saturnian satellites: Phoebe (Clark et al. 2005); Hyperion (Cruikshank et al. 2007); Enceladus (Brown et al. 2006); and Tethys, Mimas, Dione, and Rhea (Clark et al. 2008). 14 To address the presence of CO2 in the Saturnian system, we focused on the stability and formation of CO2 on Iapetus. Chapters 2 and 3 describe how long CO2 can reside on the surface of Iapetus before being lost from the system. We expanded the previous studies of the thermal volatility of CO2 by including the effect of gravitational binding energy and Iapetus' obliquity in hopes that it would explain the Cassini observations. We established the effective sublimation rates of CO2, as well as the loss of CO2 due to transport and sequestration in seasonal polar cold traps. Chapter 4 considers the possibility of photolytic production of CO2 from water ice and carbon-rich material. We report the results of laboratory experiments that simulate conditions on Iapetus. We then evaluate the distribution of detected CO2 on Iapetus to constrain production mechanisms. Finally, we calculate the photodissociation rate of CO2 by UV radiation as it relates to the long-term stability of complexed CO2. The second case study evaluates the history of aqueous alteration in the meteorite class CM chondrites. Chapter 5 centers around two major questions of aqueous alteration. First, what are the reactions and products of aqueous alteration? Second, when and where did this alteration occur? We studied four different CM chondrites with different levels of alteration. Meteorites with slight alteration provided a better description of the alteration processes within the early Solar System. We based our study on kamacite, an alloy of 95% Fe and 5% Ni that is very susceptible to alteration by interactions with water. This enabled us to identify regions with limited alteration, identify alteration products, and establish a sequence of alteration. 15 Additionally, we reviewed the distribution and extent of alteration to constrain the history of each meteorite. There are two major regimes where aqueous alteration could occur: pre-accretion and post-accretion. Pre-accreational theories assume that meteoritic materials experienced aqueous alteration in the solar nebula before they accreted into the parent body. Post-accreational theories assume that the aqueous alteration occurred on the parent body with water that accreted concurrently. Our final area of study was to evaluate the extent of alteration in a large number of mineral assemblages in order to determine the applicability of each alteration theory. 16 CHAPTER 2 STABILITY OF CARBON DIOXIDE The chapter was originally published in Icarus as Palmer and Brown (2008). Used with permission. 2.1 Introduction Iapetus is Saturn’s third largest satellite with a radius of 718 km, a bulk density of 1212 kg m-3, and a surface gravity of 0.24 m s-2. Iapetus has dark and bright faces (Morrison et al. 1975). The dark face is hydrocarbon-polymer rich while the bright face is composed mostly of water ice (Buratti et al. 2005). The juxtaposition of two very dissimilar materials on the same planetary surface makes Iapetus an interesting body to study. During the early portion of the Cassini mission at Saturn, the Visual and Infrared Mapping Spectrometer (VIMS) detected CO2 on the dark surface of Iapetus (Buratti et al. 2005). Buratti argues that the CO2 is complexed, either trapped in gaseous, liquid or solid inclusions, bound in clathrates, or adsorbed on regolith grains. Complexed CO2 is very stable and has a long residence time on the surface of Iapetus, but free CO2 ice is still quite volatile at Iapetus’ temperatures, and without a detailed study, it is not clear whether CO2 could exist for long as free ice on the surface of Iapetus. To that end, we have constructed a numerical model of ballistic CO2 transport on Iapetus that takes into account gravitational binding energy and includes detailed calculations of the seasonal and diurnal temperature distribution on Iapetus. Previous work on the stability of volatiles showed CO2 to be unstable over the age of the solar system at Saturn’s distance from the Sun (Lebofsky 1975). Lebofsky 17 predicted a rate of loss between 10 and 50 mm year-1 at the equator and between 0.1 and 5 mm year-1 at 60° latitude (Lebofsky 1975; Watson et al. 1963). Thus, one would expect that CO2 ice could not be stable on Iapetus. Lebofsky’s work neglected the effect of gravity because his study focused on comets with minimal gravity. For larger bodies, however, the effect of gravity becomes important because most of the sublimated material is launched on a ballistic trajectory and eventually impacts the surface. CO2 molecules quite literally hop around the surface until they reach a cold trap, such as the winter pole, or attain escape velocity and leave the system. Here we consider the ballistic transport of CO2 molecules on Iapetus and their eventual capture into semi-permanent cold traps. The questions we address are: - What is the residence time of CO2 ice at mid-latitudes? - How long will CO2 survive on Iapetus when considering gravity? - What is the survival time of a theoretical CO2 polar cap? - What would be the structure of a theoretical CO2 polar cap? - How can CO2 be present today on Iapetus? - How much CO2 must be produced to generate and maintain a polar cap. 2.2 Model To calculate the stability, movement, and distribution of CO2, we create a model that takes into account thermal and sublimation energy balance, and molecular migration across the surface. After determining the appropriate mathematical relationships 18 describing each of these physical processes, we solve the resulting system of equations numerically using a finite-differences approach (Brown and Matson 1987). Below we describe the relevant physics of each of the aforementioned processes. 2.2.1 Thermal Model The thermal model is critical because surface temperature distribution determines the amount of CO2 that sublimates as well as the distribution of speeds of the sublimating CO2 molecules, and thus, the fraction that escapes. As such, careful consideration must be given to the thermal model and its parameters. We modeled three energy transport mechanisms: black body radiation, thermal conduction, and latent heat transport as described in Eq. 2.1, where S (!,f) is the incident solar luminosity, " is latitude, ! is longitude, # is the emissivity, s is the Stefan-Boltzmann ˙ constant, T is temperature, L is the latent heat of sublimation for CO2, M is the mass flux of sublimated material, k is the thermal conductivity, t is time, and z is depth. Specific values for the parameters can be found in table 1. ˙ S( ", # ) = $%T 4 + L M +k dt dz ! (2.1) 2.2.1.1 Insolation ! The incident solar flux is defined by Eq. 2.2, where So is the solar constant of 3.827x10 26 watts, A is the Bond albedo of the surface, and r is the heliocentric distance. ! S( ", # ) = So (1$ A) cos(# sun )cos(# iap ) + sin(# sun )sin(# iap )cos( "sun $ "iap ) 4 %r 2 (2.2) ! 19 The leading side of Iapetus is low-albedo, presumably coated with a carbon rich material, while the poles and trailing side of Iapetus are composed of nearly pure, water ice (Buratti et al., 2005) with an albedo similar to the icy Galilean moons. We used the surface reflectance map generated from the Voyager data (Squyres et al. 1984) to estimate a Bond albedo map. First, we converted his reflectance contours into normal reflectance by using a linear scaling between the two endpoints he suggests, y = 3/5 * x + 1.6. From there, we assume that the normal reflectance is a close approximation to the geometric albedo. To adjust geometric albedo into a Bond albedo, we need the phase integral. Phase functions for neither the bright or dark side on Iapetus are well known. We used Squyres' suggested phase integral of 0.3 for the dark material (1984). We used the phase integral found for Europa, 1.0 (Buratti and Veverka 1983), for the small and very bright region found near the north pole of Iapetus that has an geometric albedo of .65. We scaled linearly between these two end points. Since Iapetus’ south pole was not imaged by Voyager, we used the albedo of the north pole. Finally, we fit a least-squares surface to the contour levels to provide a smooth Bond albedo map. The final Bond albedo map is represented in Fig. 2.1. The photometrically derived albedo map is a good fit for the dark side, but is lower compared to radiometric calculations (Loewenstein et al. 1980; Morrison et al. 1975). The photometrically derived Bond albedo map gives a dark side Bond albedo of 0.04 and a bright side Bond albedo of only 0.39. Radiometery suggests that the bright side of Iapetus has an average albedo of 0.6 (Loewenstein et al. 1980). Additionally, the Voyager IRIS estimates Bond albedo in 20 the range of 0.63 to 0.73 for the other Saturnian satellites (Buratti and Veverka 1984). Figure 2.1: Bond Albedo Map of Iapetus Bond albedo map used for the thermal model based upon the Voyager data (Squyres et al. 1984). Saturn’s orbital semi-major axis is 1.4x109 km and its eccentricity is 0.056 (Lang 1992), resulting in a difference in insolation of about 20% throughout the Saturn year. The sub-solar flux when Saturn is at perihelion is 16.78 W m-2 and is 13.41 w m-2 at aphelion, Eq. 2.2. For simplicity, we assume Iapetus to be orbiting the Sun with Saturn’s orbital elements. Iapetus’ distance from Saturn is 59 Saturn radii, three orders of magnitude smaller than Saturn’s distance from the Sun, thus the approximation is valid for our purposes. 21 The variations in sub-solar latitude during an orbit is of primary importance when considering the effectiveness of polar cold traps. The higher the sub-solar latitude, the more insolation the poles will receive, reducing their effectiveness as a long-term cold trap. Incorporating the variations in latitude of the sub-solar point requires knowledge of the inclination of Iapetus’ equator; the exact value can only be reliably predicted over a span of a few hundred years (Sinclair 1974). Currently, Iapetus has an inclination relative to the equator of Saturn of 15.1°, and to the Sun-Saturn orbital plane of 15.4°, and is decreasing. Due to the perturbations caused by the Sun, Titan, and Saturn’s oblateness, Iapetus’ inclination is not constant relative to the Sun or Saturn, but rather is constant relative to the Laplace plane. The Laplace plane is defined as the plane normal to a satellite’s precessional pole. Near Saturn, the Laplace plane matches Saturn’s equator (obliquity of 26.7°). Further from Saturn where the Sun’s relative influence is greater, the Laplace plane approaches the Sun-Saturn orbital plane. At Iapetus, the Laplace plane is inclined 14.9° relative to Saturn’s equator (Giorgini et al. 1996), and 11.7° relative to Sun-Saturn orbital plane. Iapetus maintains a near-constant inclination of 7.5° to the Laplace plane (Giorgini et al. 1996), but the longitude of Iapetus' ascending node precesses with a period of 3,000 years (Ward 1981). This results in the inclination relative to Saturn’s orbital plane varying between 4.3° and 19.3° over a 3,000-year cycle. Sinclair suggested a polynomial approximation for the inclination relative to the ecliptic, Eq. 2.3, (1974). Time, t, is time in centuries since JD 240 9786.0, and io is 184570. 22 i = io " 0.9555t " 0.0720t 2 + 0.0054t 3 (2.3) Unfortunately, Eq. 2.3 only accurately gives the inclination of Iapetus for several hundred ! years. To estimate the long period variation inclination of Iapetus relative to Saturn’s orbital plane, we set the precession period for the longitude of the ascending node to be 3,000 years. This enables us to describe the long-term temperature trends, though it will be inaccurate for a specific day. Figure 2.2 shows the predicted value by Sinclair, observed values, and our estimated function. 2.2.1.2 Black Body Radiation Black body radiation is calculated using the Stephan-Boltzmann law assuming an emissivity of 0.95, Eq 2.3. Figure 2.3 shows the effect of black body radiation, limiting the maximum temperatures to 108.5K and 128.5K for the bright side and dark side respectively, assuming a circular orbit. 2.2.1.3 Latent Heat Transfer Owing to its high vapor pressure at Iapetus’ temperatures, CO2 will sublimate rapidly. Lebofsky (1975) predicted that CO2 has a sub-solar sublimation rate between 10 and 50 mm year-1 for a slow rotating body with an albedo of 0.5. 23 Figure 2.2: Effective Inclination Iapetus’ inclination varies over a 3,000 year cycle (Sinclair 1974). We assume a constant precession for its longitude of ascending node over a 3,000 cycle giving a sinusoidal variation. Sinclair’s polynomial fit shows good correlation over several 100 years. 24 Figure 2.3: Energy Balance and Temperature The energy lost due to black body radiation and latent heat for a given temperature. Since in equilibrium insolation must balance the heat loss, we can infer the insolation required to achieve a certain temperature. The two horizontal lines show the sub-solar flux based on the different albedos, the dark side of 0.04 and the bright side of 0.5. The effect of conduction is too small to be plotted. 25 To account for both mass and latent heat transport, we use the formulation of Estermann, sometimes known as the free vacuum sublimation equation, Eq. 2.4 (1955). ˙ The mass flux, M , is in grams s-1 m-2, R is the ideal gas constant, T is temperature, P is the partial pressure of the gas (CO2 for our purposes here), and m is the molar mass. ! ˙ M= P m 2"RT (2.4) We use Eq. 2.5 for the saturation vapor pressure of CO2 (Lebofsky 1975) in Torr. ! "1275.62 +0.006833T +8.3071 T P = 10 (2.5) The exponential dependence of sublimation rate on temperature results in an ! effective maximum temperature for pure CO2 ice sublimating into a vacuum since most of the absorbed insolation will go into latent heat loss rather than increasing the surface temperature. Figure 2.4 shows the buffering of temperature by latent heat transport during a diurnal cycle on Iapetus. The individual effect of latent heat transfer with respect to insolation is shown in Figure 2.3. Sublimation is negligible below 70K. If the surface exposure of pure CO2 ice is large enough, the temperature cannot rise over 95K. 2.2.1.4 Thermal Diffusion Many models neglect thermal diffusion for airless bodies because most have a low a thermal conductivity for their surface layers, and thus, conduction has a minimal effect upon the diurnal surface temperatures. We include it here because small 26 Figure 2.4: Buffering Effect of CO2 on Temperature The plot compares two models showing the buffering effect of sublimation on surface temperature. The first model accounts for conduction and blackbody radiation only. The second model considers conduction, blackbody radiation and sublimation. Note, the plateau-like cooling effect of sublimation latent heat near 95 Kelvin. changes in temperature can have large effects on the sublimation rate, especially when considering a high energy flux. To account for thermal energy transport we use the thermal diffusion equation, Eq. 2.6, with a radiative upper boundary, and an insulating lower boundary. Temperature is T, t is time and k is the thermal conductivity. The thermal parameters are given in table 2.1. 27 "T " $ k "T ' = & ) "t "z % #Cp "z ( Table 2.1: Thermal parameters used in the model ! Constant Value Thermal Inertia, $ 30 J m-2 K-1 s-1/2 Heat Capacity, Cp 800 W kg-1K-1 Thermal Conductivity, k 0.0024 J m-1s-1K-1 Thermal Diffusivity, D 6.61 x109 m2/s Regolith Density, H2O 461.13 kg/m3 Solar Flux, So 3.827 x1026 watts Bond Albedo 0.01 to .065 Emissivity, # 0.95 Latent Heat of Fusion 26.3 kg/mol Density of CO2 1718 kg/m3 Diurnal Period Seasonal Period Layer thickness, %z 79.33 Earth days 29.46 Earth years 2.80 cm e(0.07i) (2.6) Ref 1 2 6 6 3 4 5 6 7 8 9 9 6 Number of Layers 40 References: 1 Spencer et al. 2005; 2 Klinger 1980; 3 Keihm et al. 1973; 4 Watson et al. 1963; 5 Morrison et al. 1975; 6 Brown and Matson 1987; 7 Giauque and Egan 1937; 8; Keesom and Koehler, 1934; 9 Lang et al. 1992 We assume that the thermal properties of Iapetus’ surface are similar to those of the Galilean moons. The thermal conductivity and thermal diffusivity can be derived from the thermal inertia, " , using equations 2.7 and 2.8. Heat capacity is defined as Cp, r is the density, and D is the diffusivity. ! (2.7) (2.8) " = #Cpk k "Cp ! D= ! 28 Spencer reported a thermal inertia for Iapetus of 30 J m-2 K-1 s-1/2 (2005), which is similar to the 50 to 70 J m-2 K-1 s "1/ 2 he found for the Galilean moons (Spencer et al. 1999). We assume that the heat capacity and density are independent of depth and ! temperature as described in Table 1. The upper boundary of the diffusion model is a periodic function based upon the insolation absorbed as described in section 2.1.1. The lower boundary is an insulating layer such that dT/dz = 0 at depth. To ensure that the upper layer of the model is thin enough to respond to diurnal heating, we set its thickness to be 1/3 the diurnal skin depth. The diurnal skin depth is the scale length for diurnal thermal diffusion, Eq. 2.9. The skin depth is dz, D is the diffusivity, and t is the time scale of interest. Dt 2" dz = (2.9) We set the top layer to 2.8 cm in thickness and allow the lower layers to have a ! minor exponential increase in thickness, described by dz = e(0.07i) cm, with i being the layer number (Matson and Brown 1989). The required number of layers is such that the total depth over which the thermal solution is obtained is five times the seasonal skin depth, ensuring that temperature cycles are minimal at depth (dT/dt = 0). We use 40 layers, corresponding to a depth of 6.4 meters, exceeding the required depth of 4.95 meters. We do not include thermal conductivity through the CO2 frost itself, but instead use the parameters for a water ice regolith for the conductive layers. To ensure that our equilibrium solution is independent of initial conditions we 29 start from a baseline temperature model that has been run for 50 orbits to allow the layers to reach thermal equilibrium. 2.2.2 CO2 Transport Once we have the temperature of the surface, we calculate the transport of the sublimated CO2. When a CO2 molecule escapes its crystal lattice, we assume that it will take a single sub-orbital ballistic hop. This is a good assumption because near Iapetus’ surface the mean free path is larger than its scale height. The calculation of the where the ballistic trajectory lands requires only the initial speed and direction of a molecule. We neglect the effects of solar radiation pressure upon the molecule. Sublimation into a vacuum produces a half-Maxwell Boltzmann velocity distribution, a distribution with no negative vertical speed component, Eq. 2.10. The temperature of the surface is a major factor in the determination the distribution of speeds as seen in Eq. 10. Velocity is V, f is the fraction of material that has a velocity between V and V+%V, k is the Boltzmann constant, T is temperature, and m is the molecular mass. # m & 2 2 )mV f = 4"% ( V e 2kT $ 2"kT ' 3 2 (2.10) All the CO2 molecules that have velocities greater than Iapetus' escape velocity ! (591 m s-1) will escape from the system regardless of their initial direction, and we assume that they are permanently lost from the system. CO2 molecules that have orbital velocities (above 418 m s-1) are not considered lost to the system since they will not have a stable orbit. Research on asteroid impact 30 ejecta shows that most material ejected at orbital velocities will not reach a stable orbit, but will return to its parent body in a single orbit (Scheeres et al. 2002). The second component of the ballistic flight of CO2 is its direction vector. The angle at which the CO2 leaves the surface is called the angle of trajectory. The radial direction the CO2 takes is called the azimuth. We assume that the CO2 leaves the surface isotropically, analogous to the way a Lambert surface scatters light. Once both the speed and the direction are known, we calculate the suborbital ballistic flight for the CO2 molecules, assuming Iapetus is a perfect sphere. The distance a molecule travels, d, is found using the orbit’s semi-major axis, a, eccentricity, e, true anomaly, f, and flight angle, ", as shown by equations 2.11, 2.12, 2.13 and 2.14. The mass of Iapetus is M, G is the gravitational constant, r is the molecule’s current orbital distance (set to the radius of the moon), and v is the molecule’s velocity. a= 1 2 v2 " r MG (2.11) ! sin 2 (# )r(2a " r) e = 1" a2 f = cos"1 a " ae 2 " r re (2.12) ! (2.13) (2.14) d=(2&-2f)r ! Once we have the initial velocity vector of the CO2, we calculate where it will land. We do this for all variations of speed, direction and source latitude to build a 31 template of distribution. By assuming an isotropic distribution for direction and Maxwell-Boltzmann distribution for the speed, the computation is simplified since the surficial distribution of the mass for a given temperature will be identical from one time step to another except for a scaling factor. As such, we do not need to track each molecule, but can apply the template in bulk without losing accuracy. The validity of our numerically derived templates was confirmed with a Monte Carlo simulation. A cross section of a sample template is shown in Fig. 2.5. One can see that most of the mass travels only a short distance; half the mass falls within 150 km. Nevertheless, the entire moon receives some material, with a minor concentration at the antipode. We use a time step of 1.6 Earth days in the transport model, which is the largest stable time step that ensures the sub-solar latitude does not change substantially before an average CO2 molecule randomly walks to a cold trap. The fraction of sublimated CO2 that reaches escape velocity is strongly dependent on temperature (Eq. 2.10). Table 2.2 shows what fraction of the CO2 will reach escape velocity when it sublimates. The remaining CO2 will make a single ballistic suborbital flight and will stick where it lands. We found that there is no appreciable warming of a polar cap when CO2 condenses because the amount of latent heat transported by the CO2 is small compared to the radiative heat flux. 32 Figure 2.5: Distance of CO2 for a Single Time Step The ballistic distance CO2 travels when sublimated. It assumes a Maxwell-Boltzmann velocity distribution and an isotropic distribution for the angle of trajectory. The distribution shows a single ballistic flight. 33 Table 2.2: Fraction of CO2 reaching escape velocity as a function of temperature. Temperature Fraction 40 K 5.3 x 10-10 50 K 4.8 x 10-8 60 K 9.6 x 10-7 70 K 8.0 x 10-6 80 K 3.9 x 10-5 90 K 1.3 x 10-4 100 K 3.5 x 10-4 110 K 7.9 x 10-4 120 K 1.5 x 10-3 130 K 2.7 x 10-3 140 K 4.3 x 10-3 2.3 Results 2.3.1 Ablation Rate The residence time for CO2 on the illuminated regions of Iapetus is very short. The sublimation rate can be as high as 0.02 g m-2 s-1, such that a thick sheet of CO2 ice cannot survive for long outside of the polar regions. When CO2 sublimates, most of it will land near its source (see Fig. 2.5) whereupon during the next hop, some of the material will return to the source region. As a result, the amount of CO2 removed from a region per unit time is somewhat lower than the sublimation rate, which we will call the ablation rate. The ablation rate is always lower than the sublimation rate. Figure 2.6 shows how fast CO2 can ablate from the surface of Iapetus during a single Iapetus day or 79.3 Earth days. The dark side ablation rate in the equatorial regions can be as high as 13 mm diurnal cycle-1, showing that free CO2 ice cannot remain in the dark region for more even a fraction of a single diurnal cycle on Iapetus. 34 Figure 2.6: Ablation Rate The ablation rate of CO2 for a single diurnal cycle of Iapetus (29.46 Earth days). This uses Iapetus' current effective obliquity of 15.4° and Bond albedos of 0.04 and 0.5. We use a distance of 9.24 AU, the distance Iapetus was from the Sun during the 10 September 2007 fly-by. 35 To characterize the long-term-average ablation rate, we ran several models, determining the ablation rate every 15° in latitude on both dark and bright terrains (0.04 and 0.5 albedo respectively), assuming a sheet of CO2 ice 12 km x 12 km wide and thick enough not to be removed during the run of the model. The eccentricity of Saturn's orbit results in differences in the peak insolation between the north and south poles; thus, we include both poles in our calculation. Figure 2.7 shows the rate of CO2 ice ablation considering both albedo and effective obliquity. The bright regions have a much lower ablation rate, approximately 1/3 less than the dark regions. At mid-latitudes, the effect due to the effective obliquity on the ablation rate is small; however, the ablation rate is greatly affected by effective obliquity near the poles. 2.3.2 Polar Caps As one might expect, CO2 will quickly move from the equator and accumulate at the winter pole, resulting in a polar cap. Once the CO2 falls into a polar cold trap, it will be sequestered until that pole begins its summer. As the polar solar flux increases, the edge of the polar cap will ablate and recede. During the initial stages of the polar summer, approximately 40% of the CO2 liberated in its ablation zone will land on the opposite pole while the remaining 60% will land higher on the source polar cap. This will increase the thickness of the polar cap while its latitudinal extent decreases, such that a thin but wide polar cap will increase in thickness by an order of magnitude just before the highest latitudes start sublimating (Fig. 2.8). 36 Figure 2.7: Long Term Ablation Rates The ablation rate of CO2 from a sheet of CO2 ice at different inclinations, latitudes and Bond albedos. The ablation rates are the average of an entire orbit around the Sun, giving the long term effects. The bright terrain is set at a constant Bond albedo of 0.5 while the dark terrain is 0.04. 37 Figure 2.8: Thickness Evolution of a Seasonal Polar Cap The time evolved thickness and latitudinal extent of a seasonal polar cap. A seasonal polar cap will being as a thin layer of CO2 ice when it is emplaced during the pole's winter season. During the summer season, as the solar flux increases, the edge of the polar cap will ablate with 40% of the ablated material random walking to the opposite pole; however, 60% will land at higher latitudes where there still is a cold trap. The result is a steady thickening polar cap, while its latitudinal extent retreats. 38 Polar caps fall into two categories: permanent and seasonal. If a polar cap is not completely removed during the summer, it is a permanent polar cap; but if it fully sublimates and migrates to the other pole, it is a seasonal polar cap. We can establish the minimum amount of CO2 needed to make a permanent polar cap by tracking how much CO2 a small polar cap would transfer to the other pole in a single season. We created a model with a polar cap that was only six kilometers in radius on the north pole and tracked how much CO2 ended on the south pole over the course of a single orbit. We find that if there is more than 3x107 kg of CO2 on the north pole, then it will not be fully removed over a single seasonal summer, and is thus permanent. Alternatively, if there is less than 3x107 kg of CO2 on the north pole, all of the CO2 will sublimate and be transferred to the opposite pole, and is thus a seasonal polar cap. Additionally, using the same logic and knowing the latitudinal extent of a polar cap, we can predict the minimum amount of CO2 that must be present. To that end we ran a series of models, altering the latitudinal extent of the polar cap and tracking how much CO2 is transferred between poles, (see Table 2.3). Each model provides us with the minimum amount of CO2 that must be present if a polar cap of a given size exists. If the latitudinal extent of a polar cap is known, Table 2.3 then shows how much CO2 must be present. There will be more CO2 in the system, however, because our analysis only considers the permanent portion of the polar cap, and not the CO2 that makes up the seasonal part of the polar cap. 39 Table 2.3: Sublimation and movement rates for different sized polar caps. Extent of Polar Cap (° Latitude) Total Sublimation Kg solar orbit-1 Net Movement Kg solar orbit-1 Percent in Transit 85% 67% 55% 94% 85% 80% 68% 62% 56% 93% 84% 77% 67% 63% 58% Minimum Effective Obliquity 4.3 +89.5 to +90 1.0 x 100 -1 1 +88.5 to +90 1.3 x 10 -1 +87.5 to +90 2.0 x 102 -1 3 +86.5 to +90 2.0 x 10 1.7 x 103 +85.5 to +90 1.5 x 104 1.0 x 104 5 +84.5 to +90 1.1 x 10 6.1 x 104 Current Effective Obliquity 15.4 +89.5 to +90 3.2 x 107 3.0 x 107 8 +88.5 to +90 2.0 x 10 1.7 x 108 +87.5 to +90 7.0 x 108 5.6 x 108 9 +86.5 to +90 1.9 x 10 1.3 x 109 +85.5 to +90 4.3 x 109 2.7 x 109 9 +84.5 to +90 9.4 x 10 5.3 x 109 Maximum Effective Obliquity 19.3 +89.5 to +90 2.9 x 108 2.7 x 108 9 +88.5 to +90 1.9 x 10 1.6 x 109 +87.5 to +90 6.1 x 109 4.7 x 109 9 +86.5 to +90 1.5 x 10 1.0 x 1010 +85.5 to +90 3.0 x 1010 1.9 x 1010 10 +84.5 to +90 5.7 x 10 3.3 x 1010 1 - Transport is less than a monolayer. The aforementioned results are useful to us if we are able to detect a polar cap of a specific latitudinal extent. If we know the size of the permanent cap, we can estimate the minimum amount of CO2 that it must contain. Any less CO2 and the polar cap would not be permanent. The amount of CO2 that can be transported in a season is also dependent on Iapetus, effective obliquity. During periods when Iapetus has a low obliquity, little CO2 is needed to form a permanent polar cap having an ablation rate less than a single 40 monolayer every solar orbit from latitude +90°. However, 1,500 years later, Iapetus will be at its maximum inclination, and the same region would ablate ~0.13 mm of CO2 during a solar orbit. Table 2.3 lists the threshold levels for latitude, but also the minimum, maximum and current effective obliquity. The morphology, behavior, and structure of a permanent polar cap will be defined by the mass of CO2 in the cap and the viscosity of the CO2. During a single orbital cycle, the accumulation of CO2 will generally be even over the entire polar cap; however, the rate of sublimation will be higher at lower latitudes. Over time, this results in a permanent polar cap that thickens more near the pole than at lower latitudes. The thickness of a polar cap will grow until the basal sheer stress exceeds the yield strength of the CO2 ice and it begins to flow. The flow of ice will be away from the pole and into a region with more insolation. The lowest latitude of the polar cap will be determined by the equilibrium point between viscous flow and ablation (Brown and Kirk 1994). This is valid for high-mass polar caps only. Low-mass polar caps will not flow viscously; thus, their shape and structure will be governed solely by the distribution of insolation. Due to the low temperatures and gravitational force on Iapetus, we do not expect there to be any glacial flow. An additional consideration is the difference in insolation between Saturn's aphelion and perihelion, which is approximately 20%. The lower flux incident upon the north pole during its summer allows a north polar cap to persist while a southern polar cap cannot. We find that the south polar cap loses about twice the CO2 than the north polar cap during each season. Table 2.3 provides the sublimation and ablated amounts for a 41 north polar cap only since the north pole sets the lower limit. While permanent polar caps require a large global reservoir of CO2, seasonal polar caps will exist if there is any free CO2 present. The structure of a seasonal polar cap is different than a permanent polar cap; due to the high volatility of CO2, it will only accumulate on the unlit winter pole. Carbon dioxide transported from the summer pole will be deposited just past the seasonal terminator of the winter pole. This will result in a polar cap that extends from the pole to the latitude where the peak diurnal energy flux is less than 1/2 watt m-2 (basically unlit). 2.3.3 CO2 Escape Rates In a closed system, CO2 frost can migrate between the two poles for eternity; however, this is implausible because there are many loss mechanisms for CO2. One process that destroys CO2 on Iapetus is photodissociation by the Sun's UV radiation. We calculate the photochemical time scale using Eq. 2.15, where there absorption cross section for CO2 is denoted as ' defined by (Chan et al. 1993; Lewis and Carver 1983), while the ultraviolet flux is ( (Woods et al. 1998). Summing for all wavelengths between 6nm and 200nm, we calculate a photochemical timescale of 1.7x107 s. "= 1 1 = J %#$ (2.15) Alternatively, we calculate the average time it takes for a molecule to random ! walk to the opposite pole. We use a sublimation temperature of 90K and a launch angle of 45°, giving a Vrms = 225 m s-1 and an average time of flight of 1.7x103 s. Since it takes approximately 350 hops to random walk between the poles, we calculate the 42 average time a CO2 molecule is in motion is 6.0x105 s, more than an order of magnitude less than the photochemical time scale. Carbon dioxide frost can also be sequestered in the regolith, being vaporized by micro-meteorite impact, and adsorbed onto the surface of regolith grains, or bonding with water forming clathrates; however, for this study these effects are neglected. Our primary interest is how quickly CO2 can be lost from the system due to the high velocity tail of the Maxwell-Boltzmann distribution that exceeds the escape velocity. Our model tracks the amount of CO2 lost in this manner and we have calculated rates for three scenarios: 1) a moon totally covered in CO2, 2) permanent polar caps, and 3) seasonal polar caps (Fig. 2.9). When the entire moon is covered in CO2, a large amount of CO2 will escape the system every solar orbit (2x1012 kg solar orbit-1). The subsolar latitude, and thus the effective obliquity, makes no difference in the amount of CO2 that reaches escape velocity as long as the entire surface is covered in CO2. The next regime for escape is when there are large permanent caps. We consider polar caps stretching from the polar regions almost to the equator. As the polar caps shrink, the amount of CO2 that sublimates gets correspondingly smaller. In general, this results in a reduced amount of CO2 escaping from the system. The major factor affecting the CO2 loss rate is the latitudinal extent of any polar caps. Figure 2.9 shows the loss rate of CO2 as a function of the size of the polar cap. 43 Figure 2.9: Long Term Loss Rate of CO2 from Iapetus' Surface The escape rate of CO2 from the surface of Iapetus showing the different regimes of CO2 escape. The maximum escape rate is found when the polar ice sheets do not cover the 30° adjoining the equator. This is because the equatorial regions will be hotter than when they are fully buffered by CO2 ice, allowing for a higher surface temperature and a larger percentage of CO2 being in the high temperature tail of the Maxwell-Boltzmann distribution. 44 Surprisingly, the maximum escape rate for CO2 (3.4x1012 kg solar orbit-1) does not occur when the entire moon is covered in CO2, but rather when large portions of the equatorial region are free of CO2 (about 30 degrees either side of the equator). The reason for the increased escape rate is the effect of the higher temperature of the effectively bare surface. This increases the percentage of CO2 molecules that are in the high velocity tail of the Maxwell-Boltzmann distribution. When the entire moon is covered with CO2, the temperature is buffered to a maximum of 96K, but when the equatorial regions are free of CO2 ice, the surface temperature can reach 130K. When only a small amount of CO2 lands there, the temperature suppression is small, allowing the CO2 to be thermalized close to 130K, rather than 96K. A larger percentage of CO2 will thus reach escape velocity, which can result in more CO2 escaping from the system (see Table 2.2). The last regime we consider is when there is only enough CO2 to make a seasonal polar cap. We believe that this is the most likely case for Iapetus since there are no published detections of a CO2 polar cap. The amount of CO2 that escapes depends primarily on the total amount of CO2 on the surface, and to a lesser extent, the latitudinal extent of the polar cap. For a seasonal polar cap, all the CO2 in the system will sublimate and move between the poles, and the movement between the source and the sink can be seen as a random walk. During this transit across the face of the moon, a typical molecule of CO2 will hop 350 times; many of these hops will be at temperatures much higher than those at the pole from which it came. 45 The cumulative effect is that 6% of the mobilized CO2 will reach escape velocity while moving from the summer pole to the winter pole. Since, to first order, the loss rate is an exponential, we calculate a characteristic time scale for 1/2 the CO2 to be lost from the system to be 5.8 solar orbits, or 170 years. In general, approximately 12% of the CO2 moving between the poles escapes during each solar orbit; however, we find that this is not a constant. Near the limit between seasonal and permanent polar caps, the escape rate is 12% per solar orbit; however, as the total CO2 inventory decreases, the escape fraction increases (Fig. 2.10). This is most likely due to the increasing surface area that is not covered in CO2 allowing for more hops to be made at unbuffered (higher) temperatures. 2.3.4 CO2 Resupply Our previous models predict the evolution of a fixed inventory of CO2. Next, we consider how this picture changes if the CO2 is resupplied, such as photochemically generated or from an active vent. We consider a source region at 30° latitude and vary the production rate of CO2. The actual position of the source region has very little effect on the ultimate distribution of CO2 ice, since CO2 quickly migrates to the winter pole. We find that when starting with no CO2, a seasonal polar cap will form and grow, increasing its size until its escape rate matches the source rate. If the production or liberation rate of CO2 is greater than the loss rate, a permanent polar cap will form. We see this behavior for flux rates higher than 4x106 kg orbit-1, where a small region of the north polar cap that has a Bond albedo of 0.65 will become a permanent polar cap. 46 Figure 2.10: Net CO2 Loss Rate The percent of CO2 lost per orbit as a function of the total amount of CO2 in the system. This graph is based upon an inclination of 15.4° and seasonal polar cap. Typically, 12% of the CO2 escapes per solar orbit; however, as the cap gets smaller, the loss ratio increases and the characteristic time scale for half of the CO2 to escape from the system decreases. 47 We can use the information from Figure 2.9 to determine the size of polar caps that can result from a given resupply rate. Since Figure 2.9 shows how much CO2 will be lost by a polar cap of a given size, we note that with a given a specific escape rate, a polar cap will grow in thickness and extend toward lower latitudes until it reaches steady state, the latitudinal extent depicted in Fig. 2.9. 2.4 Discussion One can see that the long term stability of CO2 is problematic. The first issue to consider whether a CO2 polar cap could be primordial. A strong upper limit to the time polar caps could exist on Iapetus can be estimated by assuming that the entire moon’s primordial inventory of CO2 was emplaced in a single surficial ice sheet. We assume that Iapetus' primordial inventory of CO2 can be extrapolated from the concentration of CO2 found in the plumes of Enceladus of 3% (Hansen et al. 2006). Taking the mass of Iapetus to be 1.88x1021 kg and assuming that 3% of Iapetus' bulk mass is CO2, we get 5.6x1019 kg, or a 5-km-thick sheet of CO2 ice on the moon. To estimate the residence time for this maximum surficial inventory of CO2, we consider extrapolating the loss rate from an Iapetus that is both fully and partially covered in CO2. The loss rate for Iapetus is ~1012 kg solar orbit-1 (Fig. 2.6) until the ice has receded to +60° latitude. Using this loss rate, the entire budget of CO2 can be lost from Iapetus in only 1.6 G.a. While it is likely that all of such CO2 would be removed over the age of the solar system, we cannot rule out that some CO2 would remain today. This estimate is much shorter than what would actually happen because it only 48 considers the CO2 at the poles. In actuality, a large portion of the CO2 from lower latitudes would accumulate in the polar region making the polar cap much thicker than the initial five kilometers. Thus, while unlikely, if the total inventory of CO2 within Iapetus were deposited on the surface when Iapetus was formed, large polar caps would persist to this day. One possible endogenic source of CO2 could be an outgassing fissure similar to the vents on Enceladus (Hansen et al. 2006). Enceladus is outgassing a large amount of volatiles that is the source of Saturn's E ring. Unlike Enceladus, however, any vent on Iapetus is likely to be small with a low outgassing rate for several reasons. First, the surface of Iapetus is heavily cratered with an estimated age of 4.4 G.a. over its entire surface (Ip 2006; Morrison 1982). This would exclude a massive outflow because that would require substantial resurfacing. Second, neither a tenuous atmosphere nor a ring has been observed. Thus, Iapetus cannot be effusing large amounts of gas. Another possible exogenic source for CO2 would be a cometary impact. A hypothetical comet can deposit a maximum CO2 of 1.7x1012 kg on Iapetus, assuming a diameter of six kilometers, a density of 500 kg/m3, a CO2 concentration of 3%, and none of the CO2 lost during impact. We ran a model where we deposited CO2 at the equator and found that approximately 100 years is required for the CO2 to move to the poles where it will form permanent polar caps about 4 degrees in latitudinal extent. These caps will survive on the order of 75,000 years before becoming seasonal polar caps. Finally, once the polar caps become seasonal, they lose ~ 12% of their mass each solar orbit, exhausting the CO2 in an additional 5,000 years. 49 Finally, free CO2 could be photochemically generated from the dark material itself. While the bright regions of Iapetus are clearly H2O dominated, the dark region has not been fully characterized (Buratti et al. 2005). It has been speculated that the dark surface may be: 1) A carbonaceous layer (Smith et al. 1982), 2) CH4 • x H2O and NH3 • H2O embedded in H2O (Squyres et al. 1983), 3) Composed of a nitrogen-rich tholin, amorphous carbon, and a small amount of H2O ice (Buratti et al. 2005). Experiments on Iapetus-like ices have shown that CO2 can be generated via both solar and ion irradiation (Allamandola et al. 1988; Ehrenfreund et al. 1997; Gerakines et al. 1996; Hudson and Moore 2001; Loeffler et al. 2005; Mennella et al. 2004, 2006; Moore and Hudson 1998; Sandford et al. 1990; Strazzulla and Palumbo 1998). Specific laboratory experiments with ultraviolet photolysis of ices composed of H2O, CH3OH, NH3, and CO produced H2CO, CO2, CO, CH4, and HCO (Allamandola et al. 1988). A more recent experiment with mixtures of H2O:NH3:CH4 found that irradiation with 30keV He+ and 60 keV Ar++ results in the formation of C2H4, CO and CO2 (Strazzulla and Palumbo 1998). Buratti et al. (2005) notes that CO2 generated by solar UV radiation will be near the surface and will have a short residence time. She infers that the CO2 must all be complexed due to the short residence times, but we have shown that the gravity binds the CO2. Our model predicts that 94% of photolytically-generated CO2 would move to Iapetus’ poles and later be lost at a rate of 12% per solar orbit. Since the escape 50 percentage is 12% (!=0.12 solar orbit-1), we can use the escape rate (in kg solar orbit-1), to estimate the amount of CO2 that must be on the surface using Eq. 2.16, regardless if it is photolytically generated or primordial. The total number of molecules moving in the system is denoted as No, and the escape rate is dN/dt. Thus, there must be approximately ~8 times as much CO2 moving on the surface as is generated as well as lost. "N = N o# "t The spectra of the three suggested materials do not contain the 4.26-µm (2.16) ! asymmetric stretch absorption feature of CO2 ice. Thus, there must be some CO2 as part of the dark material, most likely complexed due to the volatility of CO2 ice. We assume that this CO2 is being actively produced rather than being primordial. If only complexed CO2 is generated, then its production rate could be small to match the observed CO2 signature. It is more likely, however, that the production of CO2 would generate mostly unbound CO2, which would allow for a higher production rate to match observed values. The unbound CO2 would be free to ballistically move to a polar cold trap, where it might be detected. 2.5 Conclusion In this paper we explored mechanisms for the migration of CO2 on the surface of Iapetus via suborbital, ballistic flight after sublimation. Any CO2 at equatorial and midlatitudes is unstable and quickly migrates to the poles via a random walk process. Once the CO2 reaches the poles, lower energy flux there sequesters it, where the stability of ice in this polar cold trap depends on the effective obliquity of Iapetus. Currently, the effect 51 of obliquity on polar insolation is strong enough to move 3x107 kg of CO2 from a small polar cap of only six kilometers in radius. During the transit between poles, ~ 6% of the CO2 will reach escape velocity and be lost to space, which results in ~ 12% lost every solar orbit (29.46 years). The detection of the 4.26-µm absorption feature requires that some CO2 be present in Iapetus’ dark material, most likely being complexed. It is unlikely that this CO2 is primordial. Since the raw materials for photolytic production of CO2 are present on Iapetus, its production should be ongoing. We assume that most of this new CO2 would be in the form of free CO2, which would end up forming a polar cap. Additionally, due to the large escape rate of CO2 from the surface, any free CO2 ice found on Iapetus implies active production, such as photochemical generation, liberation during an impact, or by an active vent. 52 CHAPTER 3 A POSSIBLE TRACE CO2 POLAR CAP The chapter was originally published in Astrophysical Journal as Palmer and Brown (2007). Used with permission. 3.1 Abstract We model ballistic transport of CO2 on the surface of Iapetus, accounting for gravitational binding energy and polar cold traps. We find that if CO2 is in the form of ice, it has a long enough residence time to be spectroscopically detected. We determine that at mid latitudes, CO2 is volatile, will rapidly ablate and be sequestered in a polar cold trap. Additionally, we find that due to the inclination of Iapetus' orbit, the poles provide only a temporary cold trap, requiring the CO2 to move to the opposite pole at the end of the winter season. During each transit, 5% of the CO2 will reach escape velocity and be lost from the system. Finally, we make a prediction of the latitudinal extent and thickness of a possible CO2 polar cap that could be detected during Cassini's September 2007 flyby of Iapetus. 3.2 Introduction During its orbit insertion, Cassini made a flyby of Iapetus during which the Visual and Infrared Mapping Spectrometer (VIMS) detected complexed carbon dioxide on Iapetus (Buratti et al. 2005). While complexed CO2 is stable over the age of the solar system on Iapetus, free CO2 in the form of frost is not (Lebofsky 1975; Watson, Murray, & Brown 1963). The high volatility of CO2 ice causes it to ablate at a rate of 50 mm/year near the equator (Lebofsky 1975). Because previous work did not consider the effect of 53 the gravitational binding energy and the inclination of Iapetus' orbit relative to the Sun on the stability of CO2 ice on Iapetus, and because inclusion of these factors predict the existence of seasonal cold traps, we explore the conditions under which Iapetus could reveal a seasonal polar cap to Cassini. 3.3 Model To address the main question of this study we created a finite-element model to calculate the stability, residence times, and distribution of CO2 on the surface of Iapetus. We assume an energy balance between insolation, and evaporative cooling, condensation, black body radiation and conduction: Eq. 3.1 (Brown & Matson 1987). The bond albedo ˙ is A, L is the latent heat of sublimation, M the net mass flux, T the temperature, ! is the Stephan-Boltzmann constant, " is the bolometric emissivity, and the thermal conductivity ! is denoted as k. The solar flux, S, is a function of the angle between the surface normal and the line to the Sun, # and $. The effect of conduction is minimal due to the low thermal inertia, which was recently estimated to be 30 J m-2 k-1 s-1/2 (Spencer et al. 2005); while the latent heat of sublimation of CO2 can have a large effect and will buffer the surface temperature of Iapetus to less than 96K where CO2 ice is present. 'T ˙ (1" A)S(#,$ ) = LM +%&T 4 + k 'x (3.1) Embedded in the energy balance equation is the rate of sublimation, which is ! dependent on temperature (Eq. 3.2). It describes the sublimation flux of CO2, denoted as ˙ M Sub [kg m-2 s-1]; the vapor pressure of CO2 is PCO2. The molar mass is !, R is the ideal ! 54 gas constant, and T is the temperature (Esterrmann 1955). We calculate the rate of sublimation by solving equations 3.1 and 3.2 numerically. ˙ M Sub = PCO 2 µ 2"RT (3.2) Once the CO2 ice sublimates, we assume the CO2 molecules will propagate ! isotropically over a hemisphere with velocities that obey a Maxwell-Boltzmann distribution. Their destinations are calculated using a ballistic, suborbital trajectory whereupon they will stick and release their condensation energy into the surface layer. We assume that the flights are collisionless because the sublimation rate in the polar regions is low enough that the mean free path is longer than the atmospheric scale height. We calculate the sublimation and dispersion of the CO2 ice for every element of a onedegree grid (180 x 360 bins). 3.4 Results We found that CO2 has a very short residence time in the mid-latitudes, especially on the dark side of Iapetus, which has an average albedo of 0.04 (Morrison et al. 1975; Squyres et al. 1984). The absorbed solar flux can be as high as 16.8 watts m-2 resulting in a subsolar surface temperature of 130K; or if covered with CO2 ice, 96K with a sublimation rate of 1.8x10-5 kg m-2 s-1. 55 Figure 3.1: Iapetus' Temperature Map The calculated temperature map of Iapetus' north pole during the September 2007 fly-by. Temperature is in Kelvin. 56 The polar regions receive much less solar energy, partly because of their higher albedo of 0.5 (Morrison et al. 1975; Squyres et al. 1983), but more significant is that the effective obliquity of Iapetus relative to the Sun is only 15.4° (Sinclair 1974). This means that the peak temperature at a pole only reaches 74K during the summer. This low temperature generates little sublimation, 1.7x10-9 kg m-2 s-1, which results in negligible cooling due to the latent heat transport. As such, the low insolation for the polar region creates a temporary cold trap that will sequester any CO2 ice for up to half Iapetus' seasonal cycle (15 years), after which, the pole will enter its seasonal summer. The CO2 will then sublimate and ballistically scatter until it reaches the opposite pole. During its transit the average CO2 molecule will make over 350 hops, with many of them occurring in the hot, equatorial region. As a result, 5% of the sublimated CO2 will reach escape velocity as it migrates from one pole to the other. The characteristic time scale for half of the CO2 to escape from the system is approximately 200 years. The total amount of the CO2 in the system determines the size and shape of a polar cap, to include whether the polar cap is seasonal or permanent. If there is less than 4.1x107 kg of CO2 on the surface of Iapetus, then all of the CO2 will sublimate from the coldest portions of the polar cap during a single seasonal cycle; thus, there can be no permanent polar caps with less than 4.1x107 kg. If the amount of CO2 is larger than that, then Iapetus can maintain a permanent polar cap. As the size of a permanent polar cap increases, the amount of CO2 that can move to the opposite pole will increase. Table 3.1 shows the minimum amount of CO2 that is needed to form polar caps of specific sizes. 57 Table 3.1: Transport Between Poles of CO2 per Seasonal Cycle. Extent of Polar Cap1 (° Latitude) Net Movement kg/Saturn yr +89.5 4.1x107 +88.5 2.6x108 +87.5 7.8x108 +86.5 1.7x109 +85.5 3.2x109 +84.5 6.0x109 +83.5 1.1x1010 +82.5 2.0x1010 +81.5 3.6x1010 +80.5 6.3x1010 +79.5 1.0x1011 +78.5 1.5x1011 +77.5 2.2x1011 1 The pole extends from +90° to the listed latitude. The long-term stability and loss rate of any CO2 on Iapetus will be controlled by the effective obliquity of Iapetus relative to the Sun. Currently the effective obliquity is 15.4°, but the orbit of Iapetus precesses around the Laplace Plane every 3,000 years resulting in a sinusoidal variation in the effective obliquity between 4.3° and 19.3°. When Iapetus’ effective obliquity is near its minimum, the stability of CO2 in the polar regions is high. Our model shows that for a small polar cap with a radius of 6.3 km (from +89.5 to +90˚ latitude), only 1.6x10-7 kg m-2 will escape from the system every solar orbit. Nevertheless, 1500 years later the obliquity will be at its maximum, which will greatly increase the amount of CO2 sublimation such that a similarly sized polar cap will have 5.2x10-2 kg m-2 of CO2 escape from the system every solar orbit. 58 3.5 Predictions of a Polar Cap On September 10, 2007, Cassini makes its closest pass of Iapetus at a distance of approximately 1,600 km. This is, so far, Cassini's best opportunity to detect a small CO2 polar cap since the spring season is just starting on Iapetus. The subsolar latitude crossed the equator in April 2007 and will be +1.5° in September 2007 during Cassini's second fly-by. At the time of Cassini's fly-by, the northern region of Iapetus will still be cold, with the northern most latitudes receiving less than 0.5 watt m-2 (see Fig. 3.1). Thus, if a polar cap is indeed present in the north polar regions, much of the polar cap will be pristine, with virtually no sublimation. Most of the CO2 ice on Iapetus’ north pole that collected during the previous winter should remain as a thin layer of CO2 frost. Cassini VIMS will provide spectral data of Iapetus during its fly-by, and the VIMS instrument is capable of detecting the strongly absorbing 4.265-µm fundamentalvibrational transition of solid CO2. The Lambert absorption coefficient for this band is ~1x107 m-1, and as such, VIMS should be able to detect a surface layer of CO2 frost as thin as 1 nm (Brown et al. 2004). We assume that there will only be a seasonal polar cap due to the volatility of CO2. While a northern polar cap can be observed, the CO2 abundance in the southern polar regions must be inferred. The south pole will be in darkness during the flyby so there is little possibility of detecting CO2 that has already moved to the south pole. Nevertheless, our numerical simulations have shown that the south pole will have approximately 25% as much CO2 as the CO2 on the north pole. 59 Once given the extent and thickness of a polar cap, we can estimate the mass of CO2 in the polar cap. We assume that the north polar cap will be of a nearly uniform thickness during Cassini's fly-by. The accumulation that occurs during the north pole's winter season will be sloped, thickest near the pole. However, this non-uniformity is dwarfed by the effects of the early summer when the polar cap is receding and large amounts of CO2 is ablated from the lowest edges of the polar cap and redeposited at higher latitudes. The mean distance traveled by a CO2 molecule is just over 160 km, which is approximately the radius of the cold polar region expected to be seen during Cassini’s flyby. Since the random-walk path-length is almost as large as the cold trap, the CO2 will have an almost isotropic condensation. The result is that the polar cap thickness will increase many times its winter thickness, becoming nearly uniform in thickness. This matches the results from our model where we find the deposition of CO2 on a polar cap to be nearly uniform. Estimating the total CO2 budget of the north polar cap is a simple matter of taking total surface area and multiplying it by the thickness. This assumes a uniform albedo for the region considered. As seen in Voyager data, the dark material on Iapetus extends deep into the polar region (Squyres et al. 1984). As such, the polar cap will be smaller where the albedo is darker. To estimate the volume of an albedo that varies in longitude, one would integrate the mass over longitude. Another way to estimate the amount of CO2 is to observe it while it is in its gas phase after sublimation. This could be done either by using the Ion and Neutral Mass Spectrometer (INMS) on Cassini (Waite et al. 2006) or by using UV absorption 60 spectroscopy during an occultation (Hansen et al. 2006). If we can establish what the flux is at the surface, then we can calculate the polar cap's maximum latitude. Figure 3.2 shows the flux of CO2 in molecules s-1 m-2 that would be able to sublimate from CO2 ice locally when Cassini passes by Iapetus. As time progresses, each latitude ablates more of its CO2 until it is exhausted with lower latitudes ablating faster. The edge of the polar cap will recede, reducing the total sublimation flux. Since the flux is strongly correlated with latitude, we can identify the edge of a polar cap by observing the maximum flux of CO2 and determine how far south a layer of CO2 reaches. In addition, we can calculate the thickness of the polar cap using only its latitudinal extent. We define t0 as the beginning of the accumulation period, e.g., the time when the temperature at a given latitude # drops below the freezing temperature for CO2. We use t1 as the time when CO2 begins to sublimate from latitude f at the start of the summer season. Finally, t2 is when all the CO2 from latitude # has been removed. Figure 3.3 shows the thickness of the polar cap at t2 (when all the CO2 has been removed from latitude #.) The term ho is the thickness of CO2 ice when sublimation began, time t1. The term %h is the increase in thickness due to the condensation of CO2 at latitude # from time t1 to t2. At t2, the thickness of the polar cap is htotal. Using these definitions, the surface mass density, M(#) [kg m-2], is described by ˙ ˙ Eq. 3. The sublimation flux is M sub (",t) [kg m-2 s-1], and MCond (",t) is the condensation flux of CO2 that lands on latitude #, regardless of source region. t2 M(" ) = to $ ! ˙ Cond (",t)dt # M t2 to $ ˙ M Sub (",t)dt ! (3.3) ! 61 Figure 3.2: Flux of CO2 The flux of CO2 from the surface in molecules m-2 s-1. This assumes CO2 coverage over the entire region. As the polar cap recedes, the total flux leaving the surface would also decrease. 62 Figure 3.3: Thickness of Removed CO2 The thickness of the removed CO2, htotal, at latitude # can be described as the sum of two terms: h0, the thickness it has prior to when it began sublimating, and %h, the condensation of CO2 recently sublimated. The condensation of CO2, %h, is approximately isotropic over the polar cap because the mean path length is approximately the same as the width of the polar cap. 63 We have defined t2 to be when there is no CO2 on the surface, thus M(#) = 0. We expand Eq. 3.3 into each of its constituents giving Eq. 3.4. By definition, there will be no sublimation at latitude # from t0 to t1, thus we can eliminate the first sublimation term. After we evaluate the integral, we can divide each term by the density of CO2, which casts them in terms of thickness of CO2. Using the notation from Figure 3.3, we get Eq. 3.5. Equation 3.5 shows that total thickness of CO2 that has been removed from latitude # is the sum of the pre-sublimation thickness plus the additional condensation. t1 to # ˙ M Sub (",t)dt + t2 t1 # ˙ M Sub (",t)dt = t1 to # ˙ MCond (",t)dt + t2 t1 ˙ #M Cond (",t)dt (3.4) (3.5) htotal (" ) = h0 (" ) + #h(" ) ! We combine equations 3.2, 3.4 and 3.5 to get a function of the amount of CO2 that ! has been removed from the region adjacent to the edge of the polar cap, Eq. 3.6. The remainder of the polar cap will have approximately the same thickness because the condensation flux, %h, is nearly isotropic over the entire polar region. Using these relationships, we can identify the thickness of the polar cap using only the maximum extent of the polar cap itself. htotal (" ) = 1 #CO2 % t2 t1 PCO2 µ dt 2$RT(",t) (3.6) Because we know when sublimation began, t1, and we know the time of Cassini ! fly-by, t2, we can calculate the total insolation; and thus, how much CO2 will have been removed, htotal(#) using Eq. 3.6. If Cassini is able to observe the edge of the polar cap, 64 we can calculate the thickness of the polar cap and the mass of the north polar cap. These predictions are tabulated in Table 3.2. Table 3.2: Predicted Thickness and Mass of a North Polar Cap as a Function of the Latitude of its Edge. Latitude1 Thickness2 Predicted Mass of (nm) CO2 in Polar Cap3 (Kg) +84 0.0004 1.1x101 +83 0.0072 3.0x102 +82 0.070 3.8x103 +81 0.60 4.1x104 +80 3.3 2.8x105 +79 15 1.5x106 +78 53 6.4x106 +77 180 2.6x107 +76 530 8.7x107 +75 1,300 2.5x108 +74 3,000 6.5x108 +73 7,000 1.7x109 +72 14,000 3.9x109 +71 28,000 8.4x109 +70 52,000 1.7x1010 1 The amount of CO2 that would be removed above +84° is negligible. 2 The minimal thickness that VIMS can detect is 1 nm, +80 latitude. 3 The total mass assumes a uniform extent of a polar cap. Variations in albedo would require segmenting the polar cap into similar albedo regions and adding their mass. Finally, we use our model to graphically display the width and thickness of a hypothetical CO2 polar cap. Figure 3.4 shows the extent of a polar cap if there were 1x107 kg of CO2 ice on Iapetus. In this model, we expect to see a polar cap with a latitudinal extent from +78 to +90° latitude and a thickness of ~10 nm. 65 Figure 3.4: Polar Cap A depiction of the width and thickness of a hypothetical polar cap as seen during the September 10th, 2007 fly-by of Iapetus. It assumes a total CO2 ice inventory of 1x107 kg. The upper image is the predicted north polar cap that is receding. The lower image is the south polar cap. 66 3.6 Conclusion CO2 at mid latitudes is not stable on Iapetus for more than a few years, and the polar regions provide temporary cold traps for CO2 ice. Every 15 years, however, the CO2 will migrate to the other pole, losing ~5% to space. VIMS can detect CO2 ice at a thickness of 1 nm, and as such, has the capacity to detect a polar cap as small as ~8x104 kg which would stretch from the pole to +80˚. A CO2 budget less than that will be too thin to be detected by VIMS. 67 CHAPTER 4 PRODUCTION OF CARBON DIOXIDE ON IAPETUS 4.1 Abstract Cassini VIMS detected carbon dioxide on the surface of Iapetus during its insertion orbit (Buratti et al. 2005). We evaluated the CO2 distribution on Iapetus and determined that it is concentrated almost exclusively on Iapetus' dark material. VIMS spectra show a 4.26-µm feature with an absorption depth of 24%, which if it were in the form of free ice requires a layer of 31 nm thick. Extrapolating for all dark material on Iapetus, the total observable CO2 would be 2.3x108 kg. Previous volatility studies note that CO2 is unstable at 10 AU over geologic timescales (Lebofsky 1974; Palmer and Brown 2008). It could, however, be stable if trapped or complexed, such as in inclusions or clathrates (Carlson 1996; McCord 1997b). While complexed CO2 has a lower thermal volatility, photodissociation due to UV radiation would still occur at a rate of 4.4x108 kg y-1. Thus, the entire inventory of surface CO2 could be destroyed in less than a single year. The high destruction rate of CO2 requires an active source. We conducted experiments that generated CO2 by UV radiation of simulated icy regolith under Iapetuslike conditions. The simulated regolith was created by flash-freezing degassed water that was crushed into sub-millimeter sized particles and mixed with isotopically labeled amorphous carbon (13C) dust. These samples were placed in a vacuum chamber and cooled to temperatures between 160K and 50K. The sample was irradiated with UV light, and the products were measured using a mass spectrometer. We inferred a production rate of 1.1x1012 13CO2 molecules s-1. Extrapolating to Iapetus, and adjusting 68 for the lower UV intensity and its surface area, we calculate that CO2 production for the entire surface would be 8.4x107 kg y-1, which is close to the photodissociation destruction rate. As such, UV photochemical generation of CO2 is a plausible source of the detected CO2. 4.2 Introduction The Visual and Infrared Mapping Spectrometer (VIMS) detected CO2 on Iapetus’ dark side during the first Cassini-Huygens flyby of the moon (Buratti et al. 2005). VIMS detected an absorption feature centered at 4.267 µm (2343.3 cm-1), which corresponds to the !3 fundamental (asymmetric stretch) of CO2 (Sandford and Allamandola 1990a). Preliminary analysis from VIMS from the Dec 2004 flyby indicated that some CO2 might be in the form of CO2 ice. Cassini VIMS has detected CO2 on Phoebe (Clark et al. 2005), Hyperion (Cruikshank et al. 2007), Enceladus (Brown et al. 2006) Tethys, Mimas, Dione, and Rhea (Clark et al. 2008). Clark et al. (2009) also note that the absorption feature is stronger on the satellites farther from Saturn. Such widespread detection of CO2 in the Saturnian system raises the question of stability because previous work shows that free CO2 would not be stable over geologic timescales on Iapetus (Watson et al. 1963; Lebofsky 1975; Palmer and Brown 2008). The results of the Palmer and Brown study indicate that even with the shelter of polar cold traps, CO2 is still too volatile to remain long on Iapetus as free CO2 for two reasons. First, the sublimation rate can be as high as 13 mm of free ice over the course of a Iapetus day (79.3 Earth days) (Palmer and Brown 2008). As such, a 10-µm layer of free CO2 ice 69 would sublimate within one Earth hour even for the Sun just 10° above the horizon. This makes detecting CO2 as frost highly unlikely. Second, even with the benefit of a polar cold trap sequestering the CO2 for almost 15 years per season, the migration between poles results in a loss of ~6% per migration. Thus, the half-life for CO2 on the surface is only 175 years, making Iapetus an inhospitable place for free CO2. Because of this high loss rate, we test the hypothesis that the detected CO2 is photolytically generated from material on the surface of Iapetus, as suggested by Buratti et al. (2005). Carbon dioxide has been generated in the laboratory via UV photolysis and ion radiolysis (Allamandola et al. 1988; Gerakines et al. 1996; Moore and Hudson 1998; Strazzulla and Palumbo 1998; Hudson and Moore 2001; Mennella et al. 2004, 2006; Loeffler et al. 2005; Hodyss et al. 2008). While these lines of research have shown that CO2 can be formed, the conditions of the experiments may not be directly applicable to Iapetus. Normally, they used thin films of water ice with a wide range of volatiles such as CH3OH, NH3 and CO frozen with the water. The work that is most applicable to Iapetus was done using solid carbon grains to simulate the formation of CO and CO2 in the interstellar medium (Mennella et al. 2004, 2006). They determined that CO and CO2 could be produced from mixtures of water and carbon by energetic ions and UV photolysis. While more relevant than the thin film work, the technique they used may be not directly applicable to UV photolysis on the surface of Iapetus. First, the carbon grains they used were only a few tens of nanometers in size, three orders of magnitude smaller than the expected grain size on outer solar system satellites. Analysis of the spectra of the Jovian satellites indicate that ice grains 70 sizes are between 10 to >100 µm, with 10-50 µm being typical (Hanson and McCord 2004). Secondly, they generated additional hydrogen bonds with the carbon grains by exposing them to a stream of hydrogen gas. Finally, they coated the grains in a very thin veneer of water ice, between 35 and 60 nm. While these conditions may be relevant for the solar nebula, they are not strictly applicable to the surface of Iapetus. The specific exposure to hydrogen and the coating of a thin veneer of water ice are not things we expect to occur on Iapetus. Therefore, we conducted a series of experiments with simple components (crystal water ice and carbon) in a form more likely to be present on the surface of Iapetus. The experiments were performed at a facility in the Lunar and Planetary Laboratory, University of Arizona. 4.3 Method Our experiments were conducted in a cryogenic chamber designed to handle thick samples (up to 10 cm) at low temperatures (20K) and low pressures (10-8 torr) (Fig. 4.1). The chamber has a double vacuum; the outer vacuum chamber provides thermal insulation while the inner chamber contains the working volume. A radiation shield in the outer chamber surrounds the inner chamber. The walls of the inner chamber are thin stainless steel, and the top of the chamber lid is 10 cm from the bottom of the sample chamber, minimizing the thermal conduction. The surface area of the chamber is 9.93 cm2. 71 Figure 4.1: Thick Film Cryogenic Sample Chamber The sample chamber used in our experiments. The chamber is a two vacuum system with the outer vacuum providing thermal insulation for the inner chamber, which is the working area. Temperature probes provide a lower limit to the surface temperature. The pressure is controlled by the turbo pump in the mass spectrometer. The base of the chamber has a cold finger cooled by a closed-cycle helium refrigeration system, CTI Cryodyne, Model 22, capable of cooling to 20K. The cold finger temperature is regulated by a Lakeshore 330 temperature controller with a 50-W heater on the cold finger. A Stanford Research Systems QMS-100 mass spectrometer provides system vacuum and the measurement of gas partial pressures. The system typically operates at pressures of 10-8 torr after a few hours of pumping on a bare chamber. 72 We assume that Iapetus' surface is comprised of a porous regolith of crystalline ice fragments, which is indicated by its low thermal inertia (Spencer et al. 2005). The thermal inertia results in a large thermal gradient such that lower layers of the regolith will be colder than the surface with average basal temperatures less than 70K (Palmer and Brown 2008). Additionally, with such high porosities, volatiles could be produced near the surface and diffuse downward until they reach a cold trap that can hold them on seasonal timescales or longer. Therefore, the typical procedure of growing thin films on a cold substrate in the sample chamber may not be a good simulation of Iapetus' surface. A simulated regolith should be able to trap volatiles, allowing for additional gassurface interactions to occur. Thus, we created particulate samples 1- to 3-cm thick of by crushing the components. This provided a porous and rough surface that could trap volatiles and enhance gas/surface interactions. Unfortunately, we had to generate the components by hand, making it difficult to eliminate all contamination. The primary component of our sample was ultra-pure, degassed water. We removed dissolved gas by pumping a sample of water in a vacuum oven with a mechanical pump and raising the oven's temperature until just below the boiling point of water. When actively pumping on the sample, use used a N2 cold trap to avoid contamination. We held the temperature and pressure at that point overnight, ensuring that most of the dissolved gas had been removed. The system was then pumped down again to remove gasses that had come of out solution. We then backfilled the oven with argon gas, sealed the vessel and moved it to an argon-purged glove box. There we flash froze the water with liquid argon in a pre-cooled mortar and crushed it into fine particles 73 using a mortar and pestle. When observed under a microscope, the particles were all less than 100 µm, with many being much smaller. These particles were not round spheres, but were sharp, angular shards of fractured water ice crystals. The second component of our simulated regolith was amorphous carbon. To ensure that we were only measuring photochemically generated CO2, we used isotopically heavy carbon. This allowed us to focus on mass 45 (13CO2) as the indicator of photochemical reactions and isolated its signature from terrestrial carbon contamination. We used amorphous 13C (Cambridge Isotope Laboratories, Inc, CLM402) and ground it into small particles to increase its surface area. We mixed the carbon grains and water grains together to form our simulated Iapetus regolith. We estimated the albedo of this mixture to be between approximately 0.1 and 0.3 depending on the ratio of carbon to water ice and the particle size of the carbon. We used a carbon to water ratio of approximately 1:500 by mass. An image of the sample is shown in Fig. 4.2a. 74 (a) (b) Figure 4.2: Sample Images a) Freshly mixed sample while still in the mortar. The sample is a dull gray with a water-to-carbon of 500:1. The porosity is approximately 60%. The center of the mixture is slightly darker because the liquid Ar had not fully evaporated. b) The sample in the chamber after undergoing numerous irradiation events. A slight lag deposit has begun to form with the sample albedo becoming darker. 75 After a sample was prepared, it was moved from the glove box and transferred to the sample chamber. The sample was fluidized by suspending it in liquid argon to form a slurry that could be poured without clumping. Once the argon evaporated, the water/carbon mixture became a dry, porous regolith. We measured samples prepared by the same technique to have a bulk porosity of 0.60. The sample chamber was pre-cooled to 60K and purged with argon gas when open to the atmosphere. Once the sample was poured in, the system was sealed with an MgF2 window and pumped down to 10-8 torr. The system temperature was then raised to 120K to remove any atmospheric gases, mostly CO2, that were introduced during sample transfer. Once the system was fully evacuated, the sample was set to the temperature needed for the experiments. The experiments consisted of exposing our sample to vacuum UV photons and measuring the photochemical products. Our source of UV radiation was a 30-watt deuterium bulb (Newport J-59), which emits deuterium Lyman-" photons. The spectrum of the J-59 has two peaks in its photon output, one at 121 nm and a larger peak near 160 nm, dropping off substantially in the visible and IR regions. The factory-measured spectrum is shown in Fig. 4.3. This lamp produced ample vacuum UV photons without a significant thermal radiation. 76 Figure 4.3: Deuterium Bulb UV Flux The J-59 deuterium lamp produces most of its flux in the vacuum UV range. This is the factory-supplied data for a generic bulb. Vertical axis is in arbitrary units. We did not conduct an exact calibration of the absolute UV flux of the lamp, but rather estimated the flux of photoreactive photons by using the photodissociation of water as a proxy. We degassed and froze ultra-pure water in the sample chamber, setting the temperature and pressure to typical experimental conditions. We exposed this sample to our UV light and measured the production rate of hydrogen. Using the ideal gas law, a measured pumping rate of 15 liters sec-1, and assuming that the surface is uniformly illuminated (a good approximation) resulted in a flux of photoreactive photons of 3.2x1017 hydrogen producing reactions per sec per square meter. From the factory data for the lamp, we know that most of these photons have wavelengths of 160nm or less. 77 Our primary tool for data collection was an SRS QMS-100 residual gas analyzer. It provides both system vacuum and the detection of material issuing from the chamber. The system measures the mass to charge ratio of the components that it ionizes and converts this into partial pressures. Because the mass spectrometer can dissociate molecules when it is ionizing them (known as fragmentation), we must correct for this. While baseline fragmentation coefficients are published in the SRS QMS-100 RGA library, we calibrated our system using both degassed ultra-pure water and calibrated air. We used our measured fragmentation coefficients when we applied the fragmentation corrections. We tracked masses 2, 12, 13, 14, 16, 17, 18, 28, 29, 40, 44, and 45. Initial testing showed that these were the only masses present at levels above background. Mass 45 and 29 are the isotopically labeled 13CO2 and 13CO, respectively. Because the system had some terrestrial 12C contamination, we had to correct the amounts of mass 45 and 29 by 1.1% of calculated amount of 12CO2 and 12CO. Because the system has measurable partial pressures for all constituents even without the UV source on, we took background measurements that we subtracted from our experimental data to get the absolute changes in pressure. Our primary background measurements consisted of the 5-30 minutes before we turned on the UV lamp. After long irradiation exposures, we took an additional background measurement that could be averaged with the original measurement to correct for systemic background changes. Increases in partial pressures that were immediate indicated photochemical reactions, while increases that were slow (15 minutes or longer) indicated thermal effects caused by heating of the surface by the UV lamp itself. 78 To convert partial pressure, P, into a mass flux, we used the ideal gas law (Eq. 4.1). We used room temperature, T=300, and the Boltzmann constant, k. We measured the volume flux, dV/dt, of the turbo pump at 15 liters sec-1 by using calibrated leaks (Vacuum Technology, Inc, Accu-Flow Calibrated Leaks). dn P dV = dt kT dt (4.1) 4.4 Results ! We conducted a series of experiments by varying the temperature of the samples (Table 4.1) and exposing them to UV irradiation for short (tens of minutes) to long (hours) periods of time. Mass flux was measured from the pressure increase of the volatiles generated in the sample chamber. We determined that both 13CO (mass 29) and 13 CO2 (mass 45) were consistently produced regardless of temperature, carbon ratio and grain size. The set of experiments that were conducted at lower UV flux rates, similar to the UV flux at Iapetus, produced mass fluxes that resulted in partial pressures below the mass spectrometer's noise level of 10-9 torr. By the end of the irradiation events, we noted the sample surface was darkened with a slight lag deposit (Fig. 4.2b) due to the dissociation and evaporation of water. 79 Table 4.1: Production Rates Experiment Conditions (Temp, Time h:m) 2A 130K, 1:07 2B 50K, 1:10 Volatiles trapped 2E 130K, 2:28 2F 100K, 7:35 2G Low UV flux 2H1 160K, 0:32 2H2 150K, 0:43 2H3 140K, 1:42 2H4 130K, 0:40 2H5 120K, 1:08 2H6 110K, 1:50 2I 100K, 1:47 Outflow lines heated 2J 60K, 7:42 Volatiles trapped 2K 90K, 5:30 CO (molecules s-1) 5.17x1011 3.11x1011 3.12x1011 1.23x1011 2.63x1012 9.50x1011 8.32x1011 3.93x1011 4.76x1011 1.85x1010 5.18x1010 6.30x1010 13 CO2 (molecules s-1) 7.33x1011 1.87x1011 1.12x1012 3.91e1011 1.82x1012 2.37x1012 2.39x1012 1.88x1012 9.10x1011 7.47x1011 3.39x1011 4.58x1011 13 Upon the initial exposure of the sample to UV radiation, there was an immediate rise in the partial pressures of masses 2, 16, 29, and 45, indicating that photochemical reactions were occurring. There also was a gradual rise in mass 18 and 32 as the surface of the sample rose in temperature. A portion of the background of mass 32 may be from contamination, possibly vacuum grease. We did not observe an increase in mass 17 (most likely OH). The lack of mass 17 may be because of its highly reactive nature recombining with hydrogen during its travel along the one-meter line to the mass spectrometer. A representative sample, 2A, was irradiated for one hour at a temperature of 130K, which would be the max sub-solar temperature on Iapetus. We observed an increase of mass 45 (CO2) from a baseline of 4.3x10-9 torr to average pressure of 6.8x10-9 torr. When corrected for fragmentation and terrestrial 13CO2, we calculate a pressure rise 80 from 5.4x10-9 to 6.9x10-9 for a change in pressure of 1.5x10-9 torr. Data from the mass spectrometer is noted in Fig. 4.4. Figure 4.4: CO and CO2 Production, Warm Figure 4.4 shows the data from the mass spectrometer during the warm sample run (2A) that was done at 130K. The data has not had the background removed, but has been smoothed with 4 data points being averaged to improve clarity. Mass 18, H2O, shows an increase over several hours, which is an indication that the sample's surface temperature increased as the deuterium bulb slightly warmed it. The y axis is pressure in torr. The second experiment, 2B, was conducted at a temperature of 50K, similar to the night side of Iapetus (Fig. 4.5). This simulated the reactions that might occur on the night side, assuming that O and OH produced on the illuminated side ballistically travel to the night side. In this experiment, we detected almost no increase in any of the volatile phases except for mass 2 (H2) and mass 16 (O). During this experiment, the temperature 81 of the surface of the sample was close enough to the freezing temperatures of CO and O2 (Brown and Ziegler 1979), that CO, O and O2 may have been frozen to the surface. Figure 4.5: CO and CO2 Production, Cold This shows the mass spectrometer data during the cold sample run (2B) that was done at 50K. The data has not had the background removed, but has been smoothed with 4 data points being averaged to improve clarity. One can see that the increase in mass 29 and mass 45 is much smaller. We note that when the sample is heated, a large amount of volatiles out-gas (Fig. 4.6). The y axis is pressure in torr. In experiment 2J, we verified that photochemistry was actually occurring at low temperatures. Additionally, while the volatiles could be frozen on the surface, we wanted to determine if amorphous solid water (ASW) was trapping the volatiles instead. To do so, after irradiation we heated the sample over the course of five hours to a peak temperature of 170K (Fig. 4.6). We observed a large release of volatiles with all the 82 trapped-volatile species being quasi-simultaneously released. The reservoir was depleted when the temperature reached 125K. Increasing the temperature of the sample further increased only the partial pressure of mass 18 (water) and its fragmentation components. Figure 4.6: Volatile Burn-Off Experiment 2J was conducted at a cold-trapping temperature of 60K. After irradiation, we slowly raised the temperature to drive off trapped volatiles in the regolith or ASW. During the heating cycle, we see a non-species dependent "en mass" removal of volatiles. At 21:00 hours, the bottom temperature probe read 125K, which approaches the temperature for the crystallization phase change of ASW into hexagonal water. Continued heating of the sample shows only sublimation of the water and its effects. Amorphous solid water can trap the volatiles that are generated regardless of their condensation temperatures (Sandford and Allamandola 1990a). For ASW to form in our chamber, H2O molecules must be sputtered from the crystal lattice by UV radiation and eventually stick to a sub-100K surface (McCord et al. 1997b). ASW typically has a relatively low density and, because of its porosity, a large surface area. Volatiles can be 83 entrained in this porous structure and be held until the ASW reaches 130-150 K, when it undergoes a phase change into cubic water ice, ice I (Sandford and Allamandola 1990a; Gálvez et al. 2008). However, experiments show that desorption of trapped CO2 can occur at temperatures as low as 105K (Kumi et al. 2006). Our data are consistent with volatiles being trapped by ASW rather than simply frozen onto the surface. The exact surface temperature is unknown because the temperature probe is at the base of the chamber. The high porosity of the sample creates a thermal gradient between the surface of the sample and the basal temperature probe. Comparing the theoretical vapor pressure of water ice to what is measured at the base of the chamber, we have estimated that the surface temperature is at least 10K higher. The temperature at the base of the sample reached 100K when the peak pressure of trapped volatile release occurred, which we corrected to 110K. This temperature is close to the temperature needed for ASW to release its trapped volatile components, albeit lower than the phase change temperature (Sandford and Allamandola 1990a). 84 Figure 4.7: Production Rates vs. Temperature The mass flux of CO and CO2 appear to be linearly dependent on the temperature of the sample. Temperatures at or below 100K trap volatiles and under-report their actual generation. The nearly linear dependence between production and temperature may be because more CO and CO2 were generated (higher temperature allowing a higher reaction rate), or the regolith may be more capable of trapping volatiles at low temperatures. The final portion of our inquiry was to conduct a systematic observation of the production rate as a function of temperature. We performed a suite of experiments (2H1 to 2H6) and varied the temperature step-wise by 10 degrees from 160K to 110K. We determined that the measured production of CO and CO2 increases with temperature. Figure 4.7 shows all the experimental data including the step-wise experiments. We also see that the production of 13CO2 and 13CO becomes almost undetectable once temperatures of 100K and below are reached. The reason for the lower observed production rates is uncertain. It may be that the lower energy of the surface decreases the amount of produced 13CO and 13CO2. 85 Alternatively, it is possible this only demonstrates that the regolith's ability to trap volatiles increases with lower temperatures. Experimental studies examining the radiation chemistry of H2O and O2 ices also note a dependence on temperature and suggest that it could be due to different energy states (Cooper et al. 2008). 4.5 Discussion 4.5.1 Applicability to Iapetus Due to the constraints of our experimental setup, when a molecule breaks free from its crystal lattice it will collide with the chamber walls many times before it exits. The probability that this molecule exits the sample chamber after any interaction with the chamber is the ratio of the exit hole area to the chamber's total surface area. Using a geometric probability distribution (Casella and Berger 2002), we calculated a mean of ~150 collisions between a molecule and the chamber walls before the molecule is removed. During this time it will impact the surface of the sample ~15 times on average, allowing for gas/surface reactions. Multiple gas/surface reactions are not typically a desired result of this type of experiment, but in our case, it results in a scenario that closely resembles Iapetus. Standard chamber designs that seek to avoid multiple gas-surface interactions are actually less applicable to bodies with non-trivial gravitational binding energies. Iapetus' gravity is strong enough to hold on to most volatile species for some time because the most probable speeds for CO2, H2O, O and OH are lower than Iapetus' escape velocity, 591 m sec-1 (Palmer and Brown 2008). One can use Jeans Escape, Eqs. 4.2 and 4.3, to calculate 86 not only the loss rate of volatiles from the surface, but also derive the number of surface to surface hops molecules make before they are lost. "= GµM rkT (4.2) ! "esc = N 1 2kT (1+ $ )e % $ 2 #µ (4.3) The Jean's escape equation, #esc, provides the flux of molecules where N is the ! number density, k is Boltzmann's constant, T is the temperature, and µ is the molecular mass. Lambda is the ratio of the gravitational binding energy to the thermal energy, where G is the gravitational constant, M is the mass of the object, and r is its radius. Next, we convert the escape flux to a probability of escape. Equation 4.4 is an expression to transpose a mass flux into a number density (Huang 1963) given the most probable speed of the gas, Vp (Eq. 4.5), and the flux of sublimation, #sub. To calculate the probability, p, of a molecule escaping (Eq. 4.6), we take the ratio of the flux that escapes, #esc, to the flux of sublimation, combining Eqs. 4.2, 4.3, 4.4 and 4.5. N= 2 " #sub Vp (4.4) Vp = ! 2kT µ (4.5) p= ! "esc = (1+ #)e $ # "sub (4.6) Finally, we calculate the mean number of hops a molecule would make on the ! surface of Iapetus before it escapes. To do so, we use a geometric distribution that measures the number of trials needed to reach a success (probability p). The average 87 number of trials required before the first success of a geometric distribution is 1/p (Casella and Berger 2002). Thus, the mean number of hops before escape is 1/p. This loss probability and the number of hops only takes into account gravitational effects. Table 4.2 shows the number of hops each molecule makes on the surface of Iapetus before it is lost from the moon. At a surface temperature of 130K, carbon dioxide can make an average of 151 hops before being lost from the system. OH will make only four hops before it is lost to space, assuming that it does not react chemically with the surface first. We note that CO2 has been seen on Hyperion (Cruikshank et al. 2007), a moon with a radius of only 135 km and an escape velocity between 45 and 100 m sec-1 (Thomas et al. 2007). This detection indicates that the generation of CO2 is not exclusively reliant on the moon being able to gravitationally hold onto volatile species for numerous hops. Table 4.2: Volatile Residence Time Species Atomic Number of Weight hops (130K)1 H2 2 1.0 O 16 3.7 OH 17 4.2 H2O 18 4.7 CO 28 16.7 O2 32 28.5 CO2 44 151.0 Number of hops (105K)2 1.1 5.8 6.8 8.0 41.0 81.5 679.0 1 - Subsolar temperature for dark material (Bond albedo 0.04) 2 - Subsolar temperature for bright material (Bond albedo 0.5) 88 4.5.2 Production of CO2 on Iapetus We used our lab experiments to estimate the amount of CO2 that is produced on Iapetus' surface. We adjusted the production rate for Iapetus' lower UV flux and accounted for the surface area of Iapetus. We used sample 2E as a representative production rate of a typical regolith sample. The partial pressure increase for 13CO2 was 2.3 x 10-9 torr, or when converted into a mass flux was 1.13x1012 molecules s-1 using Eq. 4.1. The surface area of the sample in the chamber is 9.93 cm2, which results in a 13CO2 production rate of 1.14x1015 molecules m-2 s-1. The UV flux from the lamp in the lab was much greater than the UV flux on Iapetus so a scaling factor was calculated. The estimated UV flux from our lamp is 3.2x1017 photons m-2 s-1. We calculated that the average flux of Lyman-" photons at Iapetus is 3.6x1013 photons sec-1 m-2 assuming that the flux is a factor of 100 less than the UV flux observed at 1 AU (Woods et al. 1998). However, the total flux of all photons that can drive photo-dissociation of H2O is higher. We consider a photon to be photoreactive if it is has enough energy to remove a single hydrogen atom from a water molecule, a condition met if $ < 242.4 nm (Levine 1985). While CO2 gas is not absorbing past 190nm (Shemansky 1972), studies of water ice indicate photodissociation is relevant at longer wavelengths because the absorption cross-section for ice is 1.6x10-20 cm2 from 190 to 230 nm (Yabushita et al. 2004). Thus, the total flux of all photons that can drive the photodissociation of H2O is 4.9x1015 photons sec-1 m-2. We assumed a quantum yield of unity for photodissociation. Quantum yield for Lyman-" photons is 1.3 (Yi et al. 2007) and 0.1 for 230nm (Yabushita et al. 2004), and as such may overestimate 89 the production of CO2 on Iapetus. We determined that the scaling factor to convert our lab UV flux to Iapetus is 1/65. The composition of the surface material and its distribution on Iapetus will likely have a strong effect on the quantity of CO2 that can be produced. The bright material on Iapetus is well understood. It is composed of crystalline water ice with few impurities (Fink et al. 1976; Clark et al. 1984, 2008; Cruikshank et al. 1998; Buratti et al. 2005). Additionally, Clark notes that there is no indication of ASW on the surface of Iapetus (Clark et al. 2009). The exact composition of the dark material, however, has been more difficult to determine. Proposed theories include hydrated silicates (Veeder and Matson 1980), hydrated silicates mixed with water frost and carbonaceous matter (Lebofsky et al. 1982), a thin carbonaceous layer (Smith et al., 1982), hydrated methane and ammonia frozen in water ice (Squyres and Sagan 1983), and meteoritic organic polymers mixed with hydrated silicates (Bell et al. 1985). More recent spectral analysis suggested that refractory organics, known as Triton tholins, along with amorphous carbon, hematite and H2O were possible matches (Owen et al. 2001). A slight variation to that model included the introduction of HCN polymer to improve the spectral fit (Buratti et al., 2005). The most recent theory is that the dark material is comprised of water ice, nano-phase hematite, metallic iron, carbon dioxide, organic compounds, and trace ammonia (Clark et al. 2009). The nano-phase hematite reduces the albedo of the material without introducing additional features into the spectrum. Finally, VIMS data shows the presence of OH in the spectrum of the dark material (Clark et al. 2009). 90 We assumed that the primary reaction for the formation of CO2 was between oxygen (O and OH) and carbon. Section 4.5.1 demonstrates that O and OH will remain bound to Iapetus for at minimum of three hops, allowing multiple surface reactions. We suggest that O and OH will be generated on the bright material (water ice) and scatter over the surface of Iapetus via a ballistic sub-orbital trajectory. Frequently, the O and OH will land on the dark material, reacting with the carbon-rich material and forming CO and CO2. In most cases, the limiting component for the reaction would be the generation of O and OH from water ice by UV photons with $<242.4 nm. For our production calculations, we used the UV flux on the Iapetus' bright (water rich) material to calculate how much O and OH can be generated. We therefore inferred the surface area of water-rich material from the albedo of Iapetus. Cassini ISS images of Iapetus show that most of the surface of Iapetus is comprised of two distinct phases, a bright, presumably water-rich material and a dark, presumably organic-rich material. These ISS images show that variations in the Voyager low-resolution albedo maps are due to discrete patches of bright material next to patches of dark material, at least down to 10 m (Denk et al. 2008; Giese et al. 2008). This two component areal mix is most clearly seen in the transition region between the bright and dark sides (Fig. 4.8). Using the albedo map from Voyager (Squyres et al. 1984; Palmer and Brown 2008), we estimated the areal coverage of bright material. A pixel with an albedo of 0.6 was assumed to have only bright material while a pixel that has an albedo of 0.04 was 91 assumed to be exclusively dark material. From this, we calculated that roughly 1/3 of the surface is bright material, or 2.1x1012 m2. Figure 4.8: Iapetus' Transition Region ISS image N1568135924, transition region between the dark terrain and the bright terrain. The intermediate albedos detected with Voyager's lower resolution are not due to different material or intimate mixing, but due to the fraction of discrete patches of each material. This has important implications for photochemical reactions. Location -5° latitude, 222° longitude. 92 Extrapolating the lab production rate, scaled for surface area and UV flux, we calculated that 8.4x107 kg y-1 of CO2 can be generated from UV irradiation of the bright material on Iapetus. This amount of CO2 scattered over the dark terrain would result in a layer 11 nm thick. The high volatility of CO2 on Iapetus' surface implies that it will quickly move to the poles unless trapped or bound. 4.5.3 Quantity of CO2 on Iapetus To evaluate if our production rate is reasonable compared with what is observed, we estimated the amount of CO2 present. Cassini VIMS data was used to derive an absorption band depth. We divided Iapetus into three regions to study: dark material (leading side), bright material (trailing side and poles), and transition region. While the single scattering albedos of the bright and dark material are unknown, the low surface reflectivities at 4 µm indicate that multiple scattering events are unlikely. Thus, we assumed that the amount of CO2 could be approximated by a layer of CO2 ice. The thickness of a layer of CO2 on a grain of regolith would be half of the path length, corrected for incidence and viewing angles, which was calculated from the Lambert–Beer law, Eq. 4.7. Because the physical geometry of particles on a rough surface is unknown, we approximated the incident and viewing angle at 45°. "kx( + ) I = e cos# i cos# e Io 1 1 (4.7) The intensity at the depth of the absorption feature is I, and Io is the intensity of ! the continuum. The thickness of the ice is denoted x such that the total path length is the sum of each of the path lengths for incidence and emission, at angles %i and %e, 93 respectively. We solve Eq 4.7 for x by using an absorption coefficient for CO2 at 4.260 µm where k is 3.1x106 m-1 (Warren 1986), which has been resampled to match VIMS resolution of 16.6 nm spectal-1 (Brown et al. 2004). 4.5.3.1 Dark Material (Leading Side) The depth of the CO2 absorption feature is fairly consistent across the center of Cassini Regio, shown by Figure 4.9. For this region we measured an average absorption depth of 24.0% and a standard deviation of 3.6%. The calculated CO2 thickness was 31.1 nm, which can be expressed as .053 g m-2 using a density of 1718 kg m-3 (Keesom and Kohler 1934). To estimate the fraction of Iapetus that is covered in dark material, we again use its Bond albedo map (Palmer and Brown, 2008). Using the same scaling relationship as in section 4.5.2, we calculated an area of 4.37x1012 m2 for dark material on Iapetus. Combining this with our estimate of the concentration of CO2, we calculate roughly 2.3x108 kg of CO2 trapped on the optical surface of the dark material. 94 (a) (b) Figure 4.9: Iapetus' Dark Side and IR Spectrum Data from Cassini VIMS cube CM_1483156810 taken during the December 2004 fly-by. a) The dark side of Iapetus and the region of VIMS pixels averaged for the IR spectrum. b) The 2 to 5 µm region of the dark material's spectrum. The CO2 asymmetric stretch can be seen at 4.26 µm (Buratti et al. 2005). The absorption feature depth is 24.0%. 95 4.5.3.2 Bright Regions (Trailing Side and Poles) Identification of CO2 on Iapetus' bright material has been problematic. Cassini ISS images show that most regions of bright material have small patches of dark material scattered throughout its surface that made it difficult to avoid any dark material at VIMS resolution. Additionally, the low flux of photons from the bright material give a low signal to noise ratio. We used ISS images to help guide image selection and then selected the brightest pixels in VIMS cubes CM_1568129201, CM_1568129331, CM_1568129461 with calibration RC17 (Fig. 4.10a). We used all pixels with an I/F greater than 0.4 at 0.88 µm, selecting 29 pixels out of 2700. We averaged the spectra to increase the signal to noise and were unable to identify a CO2 absorption feature in the spectrum (Fig. 4.10b). The signal to noise measured by peak to trough variations was 28 to 1, which means that a CO2 signature less than 3.6% would be lost in the noise. Thus, it is unlikely that the bright material has any CO2, with a upper limit of 4 nm. 96 (a) (b) Figure 4.10: Spectrum of Iapetus' Bright Terrain a) The Cassini VIMS cube (CM_1568129201) at 0.88 µm denoting which pixels were chosen from this cube. The inset is an ISS image showing the location of the three VIMS data cubes use for the analysis. The brightest pixels were selected to minimize the dark material included in the analysis. b) The averaged spectra of the 29 brightest pixels taken from 3 VIMS cubes. It shows no detectable CO2 absorption feature. An absorption feature of less than 3.6% would not be discernable. Location -43° latitude, 202° longitude. 97 4.5.3.3 Transition Between Bright and Dark Regions The depth of the CO2 absorption feature in the dark material (Clark et al. 2005, 2009) is not consistent across the entire region. A priori, one would expect that CO2 would be most concentrated in the heart of the dark region. Nevertheless, this is not the case. Carbon dioxide is more abundant in the transition region between bright and dark material (Clark et al. 2009). The CO2 absorption feature in the transition region is stronger, approaching 60% (Fig. 4.11). It would require a layer of CO2 98 nm thick to generate an absorption feature of 57.7%. We did not calculate the surface area of all transition regions because the band depth is so variable. As such, we did not calculate a separate amount of CO2 for the transitions regions and simply used the average for leading side's dark material. However, the increase in the absorption feature indicates that the spatial distribution of both bright and dark components may be important in the production of CO2. In the transition regions, there is abundant bright material capable of producing O and OH. Due to the close proximity of both components, O and OH could make a single hop and land in the dark, carbon-rich material, to form both CO and then CO2. It would follow that the production of CO2 would be lower the farther a region is from the bright material, such as in the middle of Cassini Regio, which is observed (Clark et al. 2009). 98 (a) (b) (c) Figure 4.11: CO2 Absorption Near Water Sources The absorption band strength for CO2 in the transition region is much deeper than the global average for Iapetus' dark regions. a) ISS context image where for the VIMS data. b) VIMS cube CM_1568131010 of the transition region. c) The averaged spectrum of the dark material in the boxes in figure 4.11b. Location 2° latitude, 200° longitude. 99 4.5.4 UV Photolysis as the Source of CO2 We consider if UV photolysis can be the reason that CO2 is present on Iapetus. First, we must establish that the CO2 on Iapetus must come from an active source by discussing the complexing CO2 and the effect of photodissociation. Second, we suggest that other mechanisms are less likely to produce CO2, such a radiolytic production. Finally, we highlight that the production and loss rates of CO2 on Iapetus are similar. It is difficult to construct a scenario where primordial CO2 would remain at the observed concentrations over geologic timescales. An active source explains the presence of CO2 without using complex and unidentified mechanisms. Further, an active source of CO2 in the outer solar system has already been suggested to explain the presence of a trace CO2 atmosphere on Callisto (Carlson et al. 1999). It requires the diurnally averaged production of CO2 over the entire moon to be 1.01x107 kg year-1 to maintain the observed atmosphere. 4.5.4.1 Complexed CO2 Regardless of the origin of CO2, it must be complexed to account for the observed thermal stability. The extremely fast sublimation rate of CO2 makes it virtually impossible for CO2 to be in the form of frost on Iapetus. It has been suggested that the increased stability is because of additional interactions between CO2 and the surface. These trapping mechanisms increase the binding energy of the molecules and are known as complexing (Buratti et al. 2005; Clark et al. 2009; Hibbitts et al. 2009). Complexing 100 has been suggested to explain the presence of CO2 and other volatiles on the surface of Jovian satellites (Carlson et al. 1996; McCord et al. 1997a; Hibbitts et al. 2003, 2007). One of the strongest arguments that CO2 is not free ice on Iapetus is that the center of the CO2 absorption feature is shifted toward longer wavelengths. The !3 fundamental of CO2 is centered at 4.2675 µm (2343.3 cm-1) for pure CO2 ice at 80K and 4.2737 µm (2339.9 cm-1) for complexed CO2 at 100K (Sandford and Allamandola 1990a). The shift of the CO2 band to longer wavelengths is mostly due to intermolecular forces that lower the energy needed to excite this vibrational mode. On Iapetus, the CO2 band center is generally near 4.27 µm indicating that the CO2 is most likely complexed. However, there are some areas on Iapetus where the CO2 band centers are closer to 4.26 µm (Cruikshank 2008). Furthermore, variations in the overall shape of the band relative to that of free ice make it difficult to be certain of the physical state of the CO2 in those regions (Clark et al. 2009). It is important to note that both the ratio of water to CO2 and the shape of the substrate can change band centers and shapes (Ehrenfreund et al. 1997). There have been numerous suggestions for the specific mechanisms that can trap CO2, leading to increases in its binding energy. One suggestion is that the volatiles exist in the form of clathrates. Clathrates are an alternate crystal structure of water that has "cages" that can hold volatiles without chemical bonding (Lunine and Stevenson 1985; Blake et al. 1991; McCord et al. 1997b). However, it is unlikely that water ice clathrates are responsible for the stability of CO2 on Iapetus. If clathrates were the main reason that CO2 is present and detected, then the strongest signal for CO2 would be on the water-rich 101 bright material. However, we identify that the opposite is true; the bright material has no detectable CO2. Amorphous solid water has been seen to greatly increase the stability of volatiles (Sandford and Allamandola 1990a). Unfortunately, ASW is not a good candidate as the complexing mechanism for two reasons. First, while the temperatures on the moons' nighttime side are low enough for ASW to be provisionally stable, the ice on Iapetus shows the 1.6 µm crystal absorption feature indicative of crystalline water. There is no indication of amorphous water ice on Iapetus (Clark et al. 2009). Second, if ASW were the key mechanism for trapping CO2, we would again expect to see a higher concentration of CO2 in the bright material, which we do not. Another suggestion is that the volatiles are trapped in gas or fluid inclusions within minerals (McCord et al. 1997b). It has been shown that terrestrial minerals such as basalt, cordierite and apatite can trap CO2 (Fine and Stolper 1986; McCord et al. 1998). However, the formation of these inclusions would be difficult without an atmosphere. Finally, the trapping mechanism could be explained by the adsorption of volatiles onto solid grains, either on water ice or silicates. Adsorption onto ice grains is not a good explanation for the complexing of CO2 for two reasons. First, while experiments have shown that CO2 will adsorb to the surface of water grains, the binding energy increases only modestly, from 2690 K to 2860 K (&Hs/k )(Sandford and Allamandola 1990b). Second, we detect CO2 within the dark material, which lacks a clear ice grain presence. Alternatively, adsorption of CO2 onto silicates does increase its binding energy. 102 Volatiles, specifically CO2, have been seen to adsorb on to clays (Hibbitts and Szanyi 2007) and are stable at temperatures even higher than those in the Jovian and Saturnian system. However, these experiments were conducted at higher pressures than those seen on Iapetus, so further work is needed to define their applicability to satellites that have no atmosphere. 4.5.4.2 Photodissociation Even if all the CO2 on Iapetus were complexed, there would still be problems with its long-term stability. The UV flux at Iapetus would be able to destroy a large amount of CO2 via photodissociation. Equation 4.8 gives the photodissociation rate, J. The solar flux reaching Iapetus' surface is #, and ' is the radiometric cross section for CO2. Both of these parameters are wavelength dependent, $. Integrating from 1nm to 227nm, the calculated photodissociation rate for Iapetus is 6.0x10-8 s-1 (Shemansky 1972; Lewis and Carver 1983; Woods et al. 1998; Chan et al. 1993) J= % "(#)$ (#)d# (4.8) We use the photodissociation rate, along with the number density of CO2 on the ! surface, (, to give us the amount photodissociated, M (Eq. 4.9). The number density for ˙ a layer 31.1 nm thick is (= 7.3x1020 molecules m-2. Summing this destruction rate over ! the effective surface area of dark material yields a total mass loss of 14.0 kg s-1, or 4.4x108 kg year-1. Such a high destruction rate should not be surprising when we consider that the photochemical time scale, 1/J, is 193 Earth days, or just over half an 103 Earth year. Thus, a destruction rate per year that is close to the amount of CO2 on the surface is reasonable. ˙ M = "J (4.9) An issue with this calculation is that the UV light must photochemically react ! with all the CO2 that is also seen by IR light. This assumption is incorrect if IR light can penetrate to depths below the first layer of grains because it would interact with CO2 unseen by UV. We consider the size distribution and possible components to see if this is likely. The size distribution of the grains on Iapetus has not been directly measured, but we can infer the average size by looking at the Jovian satellites. The average size of ice grains in the regolith on Europa has been estimated to be between 20 µm and 50 µm, Ganymede and Callisto's ice grains are even larger (Hansen and McCord 2004). We assume that the dark material's grain size is similar to the ice grains of the Jovian satellites. Table 4.3 shows the required grain thickness for an optical depth of 1 for IR photons. Wavelengths near 4.10 µm were chosen to avoid the CO2 absorption feature at 4.26 µm. Unless there is a layer of small grains (r < 15 µm), it is unlikely that IR light would reach a layer of CO2 that was also protected from UV light. Table 4.3: Optical Constants and Optical Depth Material Wavelength Index of Refraction Type (µm) Real Imaginary H2O1 Carbon2 (ACAR) Carbon2 (BE) 4.10 4.17 4.17 1.35 2.90 3.33 .0111 .0760 1.123 Absorption Coefficient (µm) 0.034 2.292 3.386 Thickness for )=1 (µm) 29.4 0.4 0.3 104 Carbon2 (ACH2) Tholin3 4.17 3.95 1.83 1.64 0.399 0.013 1.203 0.041 0.8 24.2 References: 1-Warren 1984, 2-Zubko et al 1996, 3-Khare et al. 1984 4.5.4.3 Radiolytic Production Due to the high photodissociation rate, it is unlikely that the CO2 is primordial. Thus, it is likely that an active source is continuously generating CO2 on Iapetus' surface. One such source is the radiolytic production of CO2 from ions (Strazzulla and Palumbo 1998; Moore and Hudson 1998; Hudson and Moore 2001; Strazzulla et al. 1998, 2005; Mennella et al. 2004). Observations of the Jovian system have shown that high-energy particles that are trapped in Jupiter's magnetosphere have substantial effects on the generation of volatiles on the surface of its icy moons (Carlson et al. 1999). Radiolytic production on Iapetus is problematic because the flux of ions is not large. Iapetus orbits outside of Saturn's magnetosphere (Dougherty et al. 2005); thus, the ions interacting with Iapetus' surface are only from direct interaction of the solar wind. The solar wind flux of all ions is ~4 x 1010 m-2 s-1 (Lang 1992), three orders of magnitude less than the Lyman-" UV flux at Saturn, and five orders of magnitude less than all photo-reactive UV photons. Comparison of the formation cross-sections of CO2 for UV and 30 keV He+ ions shows that the He+ ions generate three orders of magnitude more CO2 than the UV (Mennella et al., 2004, 2006). If we assume that the solar wind particles impinging on Iapetus surface produce CO2, then ion generated CO2 would be about two orders of magnitude lower than UV derived production. Additionally, similar 105 to cosmic rays, solar wind particles would produce material that would be deep, below the surface and not detectable by Cassini VIMS. Considering the large amount of CO2 detected on the satellites of Saturn and the limited residence time, there must be an active source of CO2. It is reasonable to expect that the system is in steady state, i.e. production equals destruction. If, indeed, CO2 is being destroyed at a rate of 4x108 kg year-1, then we must conclude that there is CO2 production on the order of 4x108 kg year-1. Our lab production rate, when extrapolated to Iapetus, is 8.4x107 kg year-1. This production rate is lower than required, but still substantial. With the errors from lab measurement, the extrapolation to Iapetus, the use of reflectance spectroscopy to get abundances, and the possibility that some CO2 is shielded, UV photolysis is a reasonable mechanism to explain the presence of CO2. 4.6 Conclusion Lab measurement, theoretical calculations and Cassini observations all point to UV photolysis as a plausible source of CO2 on Iapetus. The ease with which CO2 is produced by amorphous carbon and water, both of which are common in the outer solar system, suggests that CO2 may be actively produced on many of the outer planet's satellites and possibly Kuiper Belt objects. Other volatiles present on the Saturnian and Jovian satellites may also be explained by photochemistry rather than being primordial. There is a strong indication that the production of CO2 occurs exclusively in the dark material and not in the bright material. The lack of CO2 on bright water-rich material casts doubt on the suggestions of ice-based complexing mechanisms trapping 106 CO2. Much work remains to determine the complexing mechanism and its accompanying increase in stability. Further, photodissociation appears to be an important contributor to the volatile budget in the outer solar system. If UV light penetrates to the same layer as IR light, then volatiles detected on all the outer solar system satellites have limited residence times and would need to be actively produced. Alternatively, if UV light does not penetrate to the same layer as IR light, it may constrain the particle sizes of the regolith. Much future work is needed to fully characterize the stability and production of volatiles in the outer solar system. One important outstanding question is this: what are the chemical reactions that are taking place to form CO2? These reactions are important for placing constraints on the production of volatiles in the outer solar system, and on Kuiper Belt objects and comets. Additionally, determining the efficiency of gas/surface reactions is an important line of inquiry in understanding non-equilibrium chemical reactions on airless bodies. Finally, the trapping ability of a regolith is not well understood. Because it is likely that all the solar system bodies have a regolith, it is crucial to develop a comprehensive theory of regolith volatile trapping. 107 CHAPTER 5 AQUEOUS ALTERATION OF KAMACITE IN CM CHONDRITES 5.1 Abstract We evaluated kamacite-bearing assemblages in CM chondrites in order to determine the conditions, products and relative timing of aqueous alteration. We examined thin sections of Murchison, Cold Bokkeveld, Nogoya, and Murray using microscopy, electron microprobe analysis and scanning electron microscopy. We identified three separate microchemical environments that create different products depending on the chemistry of altering water. First, we determined that S-rich water alters kamacite to form tochilinite and accessory minerals: P-rich sulfides, eskolaite and possibly schreibersite. We also determined that ~80% of the Fe in kamacite is removed from the alteration region, making it available for the formation of other minerals or Fe-rich aureoles. Second, we determined that Si-rich water alters kamacite to form cronstedtite. Third, we established that water with minimal Si and S alters kamacite to form magnetite. This magnetite retains Ni, which distinguishes it from precipitated magnetite. We also determined that aqueous alteration in Murray and Murchison was caused by two distinct alteration events. The first event created a hydrated clastic matrix by altering anhydrous minerals to form serpentine, cronstedtite, tochilinite and tochilinitecronstedtite intergrowths (TCI), formerly called type-II PCP. Evidence for this event is the high degree of disequilibrium between the hydrated matrix and anhydrous mineral assemblages in Murray and Murchison. The second event of alteration occurred post- 108 accretion. We identified a distinct region that has a consistent degree of alteration surrounded by material with a heterogeneous degree of alteration. The boundary between these regions has no indication of brecciation. Finally, we suggest that parent body alteration on Murray and Murchison occurred as a water-limited process. The amount of water accreted was insufficient to saturate the matrix (and thus, homogenize the water content), allowing for substantial variations in alteration within short distances. 5.2 Introduction CM chondrites are primitive meteorites that have never experienced high temperatures but contain signatures of aqueous alteration (Bunch and Chang 1980). CM chondrites contain approximately 9% water by weight (Rubin, et al. 2007), specifically as hydroxyl components in phyllosilicates, such as serpentine, Mg3Si2O5(OH)4, and cronstedtite, (Fe2+,Fe3+)3(Si,Fe3+)2O5(OH)4, and hydroxides, such as tochilinite, 2Fex-1S • n(Mg,Fe)(OH)2 (McSween 1987, MacKinnon and Zolensky 1984). The distribution and associations of these hydrated phases suggest a history that can provide insight into the role of water in the early solar system. This study of aqueous alteration centers around two major questions. First, what are the reactions and products of the alteration? Second, when and where did the alteration occur? 109 5.2.1 Traditional Alteration Sequence Researchers have proposed an alteration sequence that takes anhydrous primary solar nebula material and alters it into the hydrous minerals seen in CM chondrites today (Fuchs et al 1973; McSween 1979, 1987; Bunch and Change 1980; MacKinnon and Zolensky 1984; Tomeoka and Buseck 1985; Metzler et al. 1992; Browning et al. 1996; Zolensky 1997; Bischoff et al. 1998; Hanowski 1998; Lauretta et al. 2000; Brearley 2004; 2006; Rubin et al 2007). We will briefly review the major alteration stages in the alteration sequence as outlined by Tomeoka and Buseck (1985). The first major stage is the alteration of the iron-nickel alloy, kamacite Fe0.95Ni0.05, into tochilinite by S-rich water (MacKinnon and Zolensky 1984). Tochilinite is an iron-sulfide-hydrate mineral that is characteristic of CM chondrites (Tomeoka and Buseck 1985; McSween 1987). Originally, it was called type-I poorly characterized phase (PCP) due to difficulty with mineral identification (Fuchs et al 1973). Its basic crystal structure is layers of mackinawite, (Fe,Ni)1-xS, interwoven with brucite, (Mg,Fe)(OH)2 (Organova 1974). Due to vacancies within the different layers, the exact composition of tochilinite is best described by the formula 2(Fe,Ni,Cu)1-xS • n(Mg,Fe)(OH)2, where the valid ranges are .09 < x < .29 and 1.58 < n < 1.75 (Gubaidulina et al. 2007). The next major stage in alteration is the conversion of fayalite into cronstedtite (McSween 1979, 1987; Tomeoka and Buseck 1985, Hanowski and Brearley 2001). Cronstedtite is a low temperature phyllosilicate of the serpentine group present in hydrothermal ore veins on Earth (Anthony et al. 2003) and in CM meteorites (Tomeoka 110 and Buseck 1985). The chemical composition of cronstedtite is the same as serpentine 3+ 3+ when there is no Fe+3 present, ((Fe 2+ , Mg) 3"x Fex )(Fex ,Si2"x )O5 (OH) 4 . However, its crystal structure allows for the substitution of Fe3+ for Si (Tomeoka and Buseck 1985; Lauretta et al. 2000; ! Zega and Buseck 2003). The ability for Fe to substitute in for Si provides a stable hydrated silicate mineral that can accept higher ratios of Fe to Si than serpentine. Further aqueous alteration is indicated by an intergrowth between tochilinite and cronstedtite. Original characterization of this phase was called type-II and type-III PCP (Fuchs et al. 1973; Tomeoka and Buseck 1985); however, for this work, we will refer to them as tochilinite-cronstedtite intergrowths (TCI). These TCI grains are usually located in the matrix and fall on a mixing line between cronstedtite and tochilinite (McSween 1987). The formation of TCI grains has been suggested as advanced alteration of tochilinite (Tomeoka and Buseck 1985; Lauretta 2000). As enstatite and forsterite alters, their decomposition releases Si and Mg that can combine with tochilinite, forming TCI (Tomeoka and Buseck 1985; Hanowski and Brearley 2001). The final phase of alteration is the enrichment of cronstedtite with Mg and Si. Initially, additional Mg would result in Mg-rich cronstedtite. Ultimately, the cronstedtite would absorb enough Si that it would become a ferroan serpentine (McSween 1987; Tomeoka and Buseck 1985, 1989; Lauretta et al. 2000). McSween determined that the Mg/Si/Fe ternary diagram could be used to identify the majority of hydrated minerals in this alteration sequence (1987). On this diagram, kamacite's conversion into tochilinite can be seen by a slight increase of Mg (Fig 5.1). 111 Cronstedtite is more Si-rich than tochilinite, plotting near 19 wt% Si, 6 wt% Mg and 74 wt% Fe. TCI is be located on a mixing line between the two phases, typically 75% cronstedtite and 25% tochilinite. Figure 5.1: Si/Mg/Fe ternary diagram and phases The model to describe the hydrated minerals in CM chondrules (McSween et al. 1987). Elements are in wt%. Serpentine grains should fall within the triangle, which is a mixing line for Mg/Fe serpentine and TCI (tochilinite/cronstedtite intergrowth - formerly called poorly constrained phase (PCP) 5.2.2 Location of Alteration In addition to understanding the chemistry of alteration, the question of when and where this alteration occurred is an issue that lacks consensus within the community. There are two major regimes in which aqueous alteration can occur, pre-accretion and post-accretion. The most widely accepted theory is that alteration occurred on the parent body itself, post-accretion (Kerridge and Bunch 1979, McSween 1979, Browning et al. 1996; Hanowski and Brearley 2001, Brearley 2004, 2006). Evidence for alteration on the parent body focuses on veins of minerals crossing mineral assemblages (Lee 1993; 112 Hanowski and Brearley 2000), iron-rich aureoles showing diffusion of Fe (Hanowski and Brearley 2000), homogeneity of the meteorite's composition (Brearley 2004, 2006), diffusion of elements between components (McSween 1979, 1987; Chizmadia and Brearley 2004), a similar degree of alteration among chondrites (Chizmadia and Brearley 2003; Hanowski and Brearley 2001), and a relationship between oxygen isotopes and alteration (Browning et al. 1996). However, there are indications of aqueous alteration occurring before accretion, mostly from textural analysis (Metzler 1992; Bischoff 1998; Cyr et al. 1998; Lauretta et al. 2000). Unaltered glass has been detected adjacent to hydrated minerals in chondrules (Metzler et al. 1992). Also, some anhydrous chondrule silicates are in direct contact with hydrated rim minerals, showing a lack of equilibrium in the chondrule assemblage (Metzler et al. 1992). Finally, the fine-grained rims of chondrites have small grains that have not equilibrated with their surroundings (Metzler et al 1992; Lauretta et al. 2000). These pre-accretional observations have been explained by three theories. The first suggests alteration occurred with the interaction between anhydrous minerals and water vapor directly in the solar nebula (Cyr et al 1998; Lauretta et al. 2000). The second postulates that the alteration occurred in small water-bearing protoplanetary bodies that were catastrophically disrupted and re-accreted (Metzler et al. 1992; Bischoff 1998). The third hypothesis is that silicon-rich dust was hydrated when it experienced shock in an icy region of the solar nebula (Ciesla et al. 2003). The existing theories of alteration establish a strong foundation for deciphering the complex alteration that occurred on CM meteorites. However, there are still many 113 unresolved issues as to the reactions and products. In order to establish a clearer history of alteration, we considered the alteration of kamacite. Kamacite is one of the first minerals to alter. If present, it can be used to identify chondrules and matrix regions that have experienced little alteration. We focused our efforts on identifying and measuring the alteration of kamacite grains, its alteration products, and documenting its context. We used these data to constrain the earliest stages of alteration and infer an expanded alteration history for CM chondrites. 5.3 Analytical Procedure We performed elemental, petrographic and modal mineralogical analysis of four different CM meteorites using an electron microprobe, a field emission scanning electron microscope and a petrologic microscope. We used two separate thin sections of Murray and single thin sections of Murchison, Cold Bokkeveld and Nogoya. These samples were obtained from the meteorite collection at the Lunar and Planetary Laboratory. Basic characterization of our samples was done with both reflected and crosspolarized light. We used a Leica DMLP petrographic polarizing microscope to evaluate the basic mineralogy and alteration context. These results were used to identify metal assemblages and select regions of study. Electron microprobe analysis was conducted at the Lunar and Planetary Laboratory with a Cameca SX-50. The voltage was 15kV with a current of 20nA for individual analyses. We collected microprobe data on the metal grains, any silicate host minerals, the matrix, the dust rims, and surrounding TCI grains. Typically, the microprobe beam was 1-!m for high-resolution detection; however, for sampling the 114 matrix and dust rims, we used a 10-!m beam to gather average values. Microprobe data was the primary tool for estimating the mineralogy of the sample. The microprobe was calibrated with the following standards: spinel for Mg, Al and O; diopside for Si and Ca; chalcopyrite for S and Cu; Indium Phosphide for P; chromite for Cr; albite for Na; and the base metals for Mn, Fe, Ni, Co and Ti. Detection limits are 0.08 wt% for Fe, 0.10 wt% for Ni, 0.04 wt% for S, 0.02 wt% for Ca, 0.04 wt% for P, 0.08 wt% for Co, 0.03 wt% for Cr, 0.02 wt% for Al, 0.03 wt% for Na, 0.03 wt% for Si, 0.03 wt% for Mg, 0.05 wt% for Mn, 0.06 wt% for Ti, 0.12 wt% for Cu, and 0.11 wt% for O. We also used the Cameca's Energy Dispersive X-Ray Spectroscopy (EDS) to quickly identify minerals for further study; however, no data is reported from the EDS measurements. For our EMPA, we included O in the normal analysis rather than relying on stoichiometry, which is the approach used by most other researchers. Measuring oxygen improves the calculation of total oxygen in hydrated samples; however, time constraints prevented us from doing the most accurate oxygen measurements - taking the full area under the spectral curve. Instead, we calibrated the oxygen using chromite or spinel and then used the standard EMPA technique for an element (the peak-to-trough values) to measure the amount of oxygen. Additionally, to allow us to compare our data with previous studies on CM chondrites, we determined O abundances using standard stoichiometry techniques. 115 The measured oxygen technique directly evaluates the actual amount of O present in the sample, including the hydroxyl (OH)-, which the stoichiometry technique does not. Traditional stoichiometric analysis assumes that all oxygen is bound to cations. However, hydrated minerals usually have between two and four hydroxyls, which are 29% of serpentine's molecular mass and 58% of brucite's molecular mass. We estimated the error from our technique by using the variation of O in coherent silicate minerals that have a known stoichiometric value for O. We measured a standard deviation for O of 0.91 at% for olivine, 0.83 at% for enstatite, and 0.62 at% for pigeonite using 79 analyses of Murray #1. Considering the errors introduced by using EMPA on minerals that are both hydrated and mixtures of different phases, the additional error from the peak-to-trough measurement of O is not significant. Elemental X-ray maps were used extensively to determine the petrologic context of altered assemblages. We generated whole meteorite X-ray maps using the following elements: Fe, Si, Mg, S, Ni, O and Ca for all our meteorites, and included Cr, Ti, Al, Co, and K for Murray #1. For 24 specific mineral assemblages, we generated elemental maps using Fe, Mg, S, O, Ni, P and Ca. Eleven of these were wide-field maps, 1.4mm x 1.4mm, to show alteration context, and 13 were high-resolution maps, 150µm x 150µm or smaller, to show the details of alteration structure. Additionally, we generated one large (8 mm x 6 mm) mosaic of a region that displays a transition between unaltered and altered material. To analyze small grains and fibrous structures, we used a field emission scanning electron microscope, Hitachi S-4800 Type II with a ThermoNORAN NSS EDS, at the 116 Department of Material Sciences, University of Arizona. It has a 1-nm resolution at 15 kV, magnification between 20x to 800,000x, a high and low angle backscattered electron (BSE) imaging capability, and an electron dispersive spectrometry (EDS) system. It was run at 20 kV for our data collection. 5.4 Results The primary focus of our study is the alteration of metal grains within CM chondrites. We identified large metal grains and metal-rich chondrules using optical microscopy and whole-meteorite X-ray maps. We analyzed most kamacite grains larger than 20-!m. We included large grains of kamacite isolated in matrix, kamacite blebs within type-I chondrules, sulfide-rich grains associated with type-II chondrules, and matrix troilite-bearing assemblages. Metal grains in CM chondrites are commonly associated with hydrated minerals. Analyses of these phases with the electron microprobe present challenges. The electron microbe is optimized to analyze single-phase, coherent materials. However, hydrated minerals in CM chondrites are seldom present as a single phase. EMPA analyses of these phases often results in low wt% totals because the regions analyzed contain hydrogen, which is not detectable by this technique. Additionally, hydrated minerals can be porous, further lowering the measured total. Because of these complications, we used both the context of Fe-rich grains and a heuristic technique (McSween 1979) to identify minerals as one of three types: tochilinite, cronstedtite, or TCI. We filtered out all hydrated minerals that had a total less than 70 wt% if oxygen was measured. If oxygen was not measured, we accepted analyses with totals greater than 55 wt%. 117 5.4.1 Samples To understand aqueous alteration in CM meteorites, we analyzed the following samples: two sections of Murray, one section of Murchison, one section of Cold Bokkeveld, and one section of Nogoya. The total area of thin section analyzed was 757 mm2. The summary of the elemental composition of each mineral by meteorite is listed in Table 5.1, with a full listing of all collected data points in appendix A. Appendix B gives the summary of each chondrule or mineral assemblage. Our best-sampled meteorite is Murray. It has experienced some alteration, but many chondrules remain unaltered (Rubin et al. 2007). We collected data from 30 study regions on Murray #1 and 11 study regions on Murray #2 (Figs. 5.2 & 5.3). The total numbers of EMPA data points from the two samples are 941. We performed detailed Xray mapping on 18 mineral assemblages, as well as extensive X-ray mapping of a region that appeared to have experienced a low amount of aqueous alteration. Many samples of Murray are brecciated (Rubin et al. 2007). We conducted a careful and extensive study to identify any brecciation features. We searched for sharp boundaries between regions, chemical heterogeneity, and distinct chondrule distributions. Neither of our two samples appears to be a breccia as there are no clear clasts or other characteristics reflecting brecciation in either sample. 118 Table 5.1: Summary of EMPA data (wt%) Hydrated Si Fe Mg Ni S 0.14 (0.14) 3.29 (0.84) 1.22 (2.64) 0.20 (0.18) 1.21 (0.60) 1.46 (1.75) 4.73 (1.45) 1.88 (2.58) 3.28 (1.34) 3.84 (0.98) 2.40 (1.50) 0.78 (0.69) 3.48 (1.13) 2.87 (0.64) 2.19 (0.66) 8.66 (2.96) O Ca Al Mn P Cr Ti Co Cu BDL BDL BDL BDL BDL BDL Total 89.34 (5.97) 93.08 (1.79) 93.98 (4.14) 63.11 (12.89) 83.65 (4.44) 89.73 (5.10) 89.74 (3.98) 94.04 (4.61) 82.50 (5.31) 82.59 (6.88) 87.28 (8.79) 93.76 (1.25) 83.57 (6.07) 83.57 (2.71) 82.82 (6.35) 93.06 (4.01) 63.04 (3.98) 92.38 (46.42) 63.72 (4.36) 96.04 (1.98) 55.97 (2.87) 80.10 89.47 (7.70) 73.28 (12.84) 89.68 (9.75) 91.46 (2.85) Chondrule-Associated Cronstedtite Murray 10.01 39.14 3.17 BDL - Std Dev (0.78) (3.40) (0.79) Murchison 8.26 37.98 3.90 1.44 - Std Dev (1.14) (2.17) (0.92) (0.62) Cold B 9.12 36.58 5.99 0.87 - Std Dev (3.34) (7.01) (1.46) (1.66) Matrix-Associated Cronstedtite Murray 8.38 39.37 3.35 0.55 - Std Dev (1.20) (5.33) (1.46) (0.85) Murchison 9.47 34.74 5.76 0.63 - Std Dev (1.59) (2.87) (1.55) (0.15) Chondrule-Associated Serpentine Murray 11.97 28.11 8.10 0.45 - Std Dev (2.24) (4.22) (2.61) (0.70) Murchison 10.53 28.56 7.56 1.99 - Std Dev (1.43) (4.72) (1.18) (0.41) Cold B 11.28 29.03 9.09 0.74 - Std Dev (2.39) (8.16) (3.39) (0.75) Matrix-Associated Serpentine Murray 11.08 24.57 7.90 1.59 - Std Dev (1.62) (3.79) (1.64) (0.59) Murchison 11.13 25.86 7.77 1.58 - Std Dev (0.99) (3.59) (0.40) (0.20) Cold B 13.01 21.49 10.73 1.42 - Std Dev (1.76) (7.18) (1.72) (0.94) Nogoya 12.29 30.50 8.26 0.14 - Std Dev (0.57) (3.21) (1.48) (0.11) Rim-Associated Serpentine Murray 12.05 23.24 8.66 1.73 - Std Dev (1.76) (4.86) (2.07) (0.85) Murchison 11.77 24.08 8.75 1.71 - Std Dev (0.51) (4.86) (1.19) (0.34) Cold B 14.14 15.43 12.04 1.79 - Std Dev (1.38) (2.49) (2.48) (0.88) Tochilinite/Cronstedtite Intergrowths Murray 5.92 41.68 3.86 1.47 - Std Dev (1.41) (4.32) (1.15) (1.56) Murray (No O) 5.96 41.16 3.98 1.42 - Std Dev (2.08) (5.13) (1.33) (0.81) Murchison 5.11 45.98 3.39 2.99 - Std Dev (6.61) (18.14) (5.34) (1.19) Murchison (No O) 6.13 40.44 5.16 1.21 - Std Dev (2.57) (3.76) (1.89) (1.95) Cold B 8.68 33.88 7.38 1.80 - Std Dev (1.99) (2.59) (1.23) (2.38) Cold B (No O) 10.25 29.23 8.08 1.19 - Std Dev (1.45) (4.19) (1.56) (0.53) Nogoya 10.12 28.19 6.01 0.67 Chondrule-Associated Tochilinite Murray 0.74 40.43 2.08 8.23 - Std Dev (0.63) (5.19) (0.78) (3.09) Murchison 1.31 37.16 2.49 8.12 - Std Dev (1.02) (5.39) (0.37) (3.64) Cold B 1.00 38.43 3.87 7.60 - Std Dev (0.68) (3.85) (0.81) (3.13) Nogoya 0.71 41.99 3.31 4.33 - Std Dev (0.38) (3.46) (0.95) (2.99) 33.41 0.25 2.88 0.13 BDL 0.08 0.07 BDL (5.99) (0.50) (1.78) (0.03) (0.05) (0.06) 35.74 0.32 1.14 0.20 0.20 0.54 BDL BDL (2.52) (0.18) (0.70) (0.09) (0.12) (1.15) 37.18 0.17 1.39 0.26 0.07 1.07 BDL (5.76) (0.11) (0.98) (0.20) (0.14) (2.50) 25.08 0.88 1.22 0.11 0.40 0.08 BDL BDL (1.36) (0.73) (0.04) (0.69) (0.08) 28.58 0.34 0.94 0.26 0.18 1.32 0.36 BDL (3.13) (0.25) (0.30) (0.08) (0.12) (0.73) (0.08) 36.14 0.61 2.31 0.21 0.10 0.29 BDL (4.37) (0.68) (1.38) (0.07) (0.13) (0.23) 33.36 0.20 1.79 0.18 0.11 0.20 BDL (1.74) (0.11) (0.45) (0.02) (0.05) (0.07) 39.27 0.24 1.52 0.23 0.08 0.62 (4.11) (0.23) (1.57) (0.07) (0.11) (0.44) 31.10 (4.02) 29.97 (4.44) 35.99 (4.74) 39.48 (0.78) 0.58 (0.86) 0.50 (0.48) 0.19 (0.22) 0.05 (0.02) 1.30 (0.28) 1.21 (0.18) 1.19 (0.38) 1.61 (0.58) 0.17 (0.04) 0.18 (0.04) 0.20 (0.02) 0.19 (0.03) 0.10 0.32 BDL (0.12) (0.24) 0.11 0.24 BDL (0.06) (0.04) 0.10 0.36 0.06 (0.26) (0.27) (0.02) BDL 0.36 0.06 (0.28) (0.02) BDL 0.09 BDL (0.04) BDL BDL BDL BDL 0.09 BDL (0.03) 0.09 BDL (0.06) BDL BDL 0.08 BDL (0.06) 0.11 (0.05) 0.12 BDL (0.09) BDL BDL BDL BDL 31.74 0.36 1.38 0.20 0.09 0.43 BDL (4.15) (0.34) (0.40) (0.12) (0.06) (0.54) 31.37 0.31 1.40 0.16 0.15 0.24 BDL (0.76) (0.15) (0.23) (0.01) (0.08) (0.07) 34.91 0.45 0.97 0.20 0.08 0.42 BDL (5.49) (0.48) (0.25) (0.04) (0.09) (0.09) 29.65 0.18 1.23 0.11 0.07 0.17 BDL (3.37) (0.39) (0.46) (0.05) (0.27) (0.39) 8.87 0.08 1.27 0.10 BDL 0.09 BDL (3.21) (0.06) (0.48) (0.03) (0.07) 7.85 25.35 0.13 0.86 0.09 0.21 0.22 BDL (3.68) (19.51) (0.30) (0.87) (0.11) (0.14) (0.31) 9.28 (4.30) 6.41 (3.32) 5.24 (2.18) 2.20 16.94 (3.32) 15.86 (2.45) 18.59 (2.72) 16.92 (3.61) 0.05 1.09 0.10 0.10 0.06 BDL (0.02) (0.30) (0.03) (0.10) (0.03) 35.72 0.24 1.28 0.17 0.08 0.32 BDL (3.99) (0.63) (0.39) (0.03) (0.28) (0.25) 0.07 1.49 0.16 BDL (0.04) (0.55) (0.02) 0.13 1.34 0.21 BDL 0.17 (0.18) 0.17 (0.11) 0.13 (0.13) 0.06 (0.04) 0.49 (0.55) 0.88 (0.81) 0.49 (0.16) 0.80 (0.25) 0.08 (0.04) 0.09 (0.06) 0.11 (0.02) 0.17 (0.03) 0.79 (0.62) 0.79 (0.55) 0.47 (0.35) 0.13 (0.19) 0.15 BDL (0.07) 0.17 BDL 1.29 (0.84) 0.48 (0.52) 1.14 (0.47) 0.62 (0.41) BDL BDL BDL BDL 0.10 BDL (0.08) BDL BDL BDL BDL 0.33 (0.20) 0.31 (0.23) 0.15 (0.10) 0.08 (0.11) BDL BDL BDL BDL BDL BDL BDL BDL 30.98 17.82 (3.85) 24.96 (2.76) 19.98 (3.41) 22.27 (2.54) 119 Si Fe Mg Ni 2.07 (2.05) 1.92 (1.33) 5.70 (2.50) 4.02 (3.98) 2.66 Ni S 16.74 (3.62) 16.21 (2.53) 18.95 (1.74) 21.71 (3.55) 18.85 S O Ca Al Mn P Cr Ti Co BDL BDL BDL Cu BDL BDL BDL Total 91.04 (9.28) 80.79 (13.29) 93.57 (6.43) 95.43 (4.22) 94.48 Total Matrix-Associated Tochilinite Murray 1.35 48.85 2.77 - Std Dev (0.92) (4.45) (0.57) Murchison 1.80 47.95 2.92 - Std Dev (0.83) (2.10) (0.63) Cold B 1.62 39.98 5.21 - Std Dev (1.13) (2.92) (0.91) Troilite-Associated Tochilinite Murray 0.75 48.49 2.24 - Std Dev (0.36) (3.11) (0.66) Murchison 0.58 50.38 2.51 Sulfides Si P-rich Sulfides Murray 0.33 - Std Dev (0.56) Murchison 1.48 - Std Dev (2.08) Cold B 0.99 - Std Dev (1.06) Nogoya 1.09 - Std Dev (0.10) Pentlandite Murray 0.43 - Std Dev (0.48) Murchison 0.21 - Std Dev (0.06) Cold B 0.39 - Std Dev (0.58) Nogoya 0.09 Pyrrhotite Murray 0.05 - Std Dev (0.06) Murchison 0.03 - Std Dev (0.01) Cold B 0.03 Troilite Murray 0.09 - Std Dev (0.20) Murchison 0.05 - Std Dev (0.05) Troilite with Oxygen Murray 0.71 - Std Dev (0.60) Nogoya 0.90 Fe 23.74 (4.14) 28.41 (6.82) 30.40 (3.60) 31.53 (0.02) 36.91 (5.03) 34.10 (3.13) 31.12 (2.37) 36.90 Mg 20.96 0.05 1.00 0.06 0.07 0.14 BDL (3.56) (0.05) (0.77) (0.04) (0.23) (0.35) 21.10 0.06 1.16 0.06 0.04 0.13 BDL (2.51) (0.03) (0.61) (0.02) (0.06) (0.31) 21.09 0.15 0.49 0.13 0.19 1.53 BDL (3.48) (0.25) (0.33) (0.02) (0.25) (0.79) 17.20 0.05 0.39 0.06 BDL (4.00) (0.04) (0.15) (0.02) 18.61 0.07 0.44 0.08 BDL O 6.17 (3.50) 7.77 (2.56) 6.81 (4.43) 7.94 (3.01) Ca 0.12 (0.18) 0.40 (0.43) 0.08 (0.14) 0.03 (0.01) Al 0.06 (0.09) 0.20 (0.26) 0.10 (0.09) 0.09 (0.03) Mn BDL P 0.17 BDL (0.03) BDL Cr 0.34 (0.55) 0.51 (0.40) 0.36 (0.38) 0.04 (0.01) Ti BDL BDL BDL BDL 0.17 0.18 (0.22) (0.11) BDL 0.16 Co Cu 0.34 31.92 19.27 (0.55) (6.40) (4.09) 1.16 24.91 16.05 (1.32) (16.46) (11.28) 1.00 25.65 27.01 (1.39) (2.47) (4.42) 1.31 24.59 27.52 (0.40) (1.26) (1.97) 0.33 (0.44) 0.06 (0.02) 0.30 (0.60) BDL 24.06 (4.20) 28.82 (4.37) 31.83 (2.94) 24.95 1.37 (1.38) 1.37 (0.66) 0.54 0.93 (0.91) 0.81 (0.49) 1.38 (1.32) 4.68 Ni 30.88 (3.02) 32.36 (0.81) 32.12 (2.76) 34.36 37.68 (0.57) 37.83 (0.23) 38.94 36.31 (0.58) 36.08 (1.43) 32.11 (2.09) 33.94 S 5.65 (1.88) 0.07 5.11 (0.08) (1.23) BDL 1.85 (0.27) 0.05 1.39 (0.01) (0.08) BDL 1.95 0.13 90.20 (0.97) (0.07) (8.43) 1.41 BDL 84.97 (1.03) (16.71) 0.65 0.14 95.07 (0.22) (0.05) (2.85) 0.70 0.12 96.38 (0.04) 0.00 (0.54) 0.86 (0.25) 1.43 (0.59) 1.08 (0.50) 0.12 BDL BDL BDL BDL 97.42 (4.83) 99.04 (1.99) 98.87 (3.41) 98.09 99.75 (0.38) 100.00 (0.91) 100.16 99.33 (0.98) 98.78 (3.46) 95.50 (6.40) 99.57 Total 99.08 (1.14) 99.64 (0.66) 99.62 (0.83) 3.70 BDL 0.09 BDL (3.46) (0.12) 1.94 BDL 0.02 BDL (0.54) (0.03) 1.72 0.14 0.03 BDL (2.30) (0.52) (0.06) 1.47 0.14 0.02 BDL 0.09 BDL (0.12) BDL 0.06 (0.01) 0.04 0.07 (0.14) (0.07) BDL 0.03 BDL 0.23 BDL (0.41) BDL 0.17 0.11 BDL (0.13) BDL BDL 0.22 BDL (0.27) 0.03 BDL Cr Ti 59.86 BDL (1.29) 60.23 0.00 (1.34) 0.00 60.16 0.00 61.19 0.04 (1.57) (0.24) 61.22 0.12 (1.85) (0.24) 55.56 0.60 (4.86) (0.60) 52.69 1.15 0.40 0.03 0.02 0.06 BDL (0.36) (0.04) (0.02) (0.10) 0.31 BDL BDL BDL BDL (0.04) 0.19 BDL BDL 0.09 BDL 0.52 0.02 0.02 BDL (0.56) (0.02) (0.02) 0.33 0.02 0.02 BDL (0.06) (0.02) (0.03) 4.62 0.08 0.08 BDL (2.19) (0.06) (0.06) 5.75 0.31 0.08 BDL O Ca Al Mn BDL BDL BDL BDL P 0.09 BDL (0.12) 0.14 BDL (0.02) BDL BDL 0.09 BDL (0.10) BDL BDL BDL BDL Co BDL BDL Cu Metals Si Fe Mg Kamacite Murray 0.15 92.32 BDL - Std Dev (0.38) (1.38) Murchsion 0.04 93.26 BDL - Std Dev (0.02) (1.19) Cold B 0.14 90.98 0.19 - Std Dev (0.10) (3.21) (0.41) Oxidized Kamacite Murray 1.03 70.79 0.48 - Std Dev (0.80) (14.05) (0.59) Murchison 0.78 77.21 0.66 - Std Dev (0.68) (13.54) (0.58) Cold B 1.30 58.29 0.98 - Std Dev (0.86) (12.75) (0.71) 5.17 BDL (0.54) 5.03 BDL (0.81) 5.96 BDL (1.46) 4.67 (1.71) 4.90 (1.32) 4.66 (3.02) 0.33 BDL (0.19) 0.32 BDL (0.32) 0.41 BDL (0.42) 0.03 BDL (0.04) 0.02 BDL (0.01) BDL BDL 0.36 0.42 BDL (0.14) (0.27) 0.36 0.25 BDL (0.15) (0.21) 0.87 0.72 (1.16) (0.39) 0.21 BDL (0.06) 0.22 BDL (0.04) 0.27 BDL (0.09) 1.82 14.46 0.15 0.08 0.08 0.56 0.94 BDL (1.39) (10.04) (0.14) (0.09) (0.08) (0.67) (0.62) 1.30 9.64 0.32 0.09 BDL 0.46 0.41 BDL (0.93) (8.07) (0.62) (0.08) (0.16) (0.57) 1.73 27.44 0.25 0.06 0.13 0.32 0.55 BDL (1.86) (8.78) (0.23) (0.06) (0.09) (0.19) (0.46) 0.23 BDL 94.31 (0.12) (4.29) 0.24 0.16 96.22 (0.06) (0.24) (5.42) 0.23 BDL 92.56 (0.22) (10.53) 120 Si Fe Magnetite Murray 1.13 63.50 - Std Dev (2.37) (6.72) Murchison 0.16 68.23 - Std Dev (0.08) (3.06) Cold B 1.07 64.84 - Std Dev (1.69) (7.44) Taenite Murray BDL 73.79 - Std Dev (6.58) Murchsion 0.05 89.24 - Std Dev 0.00 (0.61) Schreibersite Murray 0.27 68.80 - Std Dev (0.51) (10.53) Mg Ni S 2.29 (2.88) 0.07 (0.04) 0.30 (0.49) O Ca Al Mn P Cr Ti Co BDL BDL BDL Cu BDL BDL BDL Total 82.87 (15.64) 93.24 (4.94) 87.73 (16.98) 98.43 (0.14) 99.65 (0.34) 99.36 (1.55) 0.33 0.43 (0.63) (0.48) 0.07 BDL (0.04) 0.61 0.40 (1.01) (0.51) 0.00 0.00 BDL 26.15 0.15 0.11 BDL BDL (4.92) (0.20) (0.23) 24.43 0.06 0.02 BDL BDL (2.42) (0.04) (0.01) 29.85 0.08 0.06 0.10 BDL (3.20) (0.08) (0.10) (0.14) 0.29 BDL (0.04) 0.24 0.00 (0.01) 0.00 1.38 BDL (1.39) 0.09 BDL (0.12) 0.02 BDL (0.01) 0.06 BDL (0.05) BDL 0.06 BDL (0.04) 0.04 BDL (0.02) 0.26 BDL (0.40) 22.78 0.06 (6.22) (0.02) 9.06 BDL (0.11) 12.18 (7.89) 0.17 (0.18) 0.07 (0.03) 0.44 0.09 (0.35) (0.12) 1.34 BDL (0.06) 0.42 BDL (0.13) BDL BDL 0.20 (0.40) 14.95 1.23 (0.81) (0.70) Anhydrous Silicates Si Fe Mg Ni S Orthopyroxene Murray 26.32 1.65 22.49 0.05 0.05 - Std Dev (0.83) (1.88) (1.95) (0.06) (0.10) Muchsion 26.69 1.76 23.06 0.05 0.11 - Std Dev (0.74) (1.21) (0.83) (0.06) (0.21) Cold B 26.96 2.47 22.73 0.08 0.22 - Std Dev (0.48) (1.99) (1.37) (0.08) (0.53) Clinopyroxene Murray 23.81 4.69 11.47 0.03 0.05 - Std Dev (1.54) (6.05) (4.29) (0.04) (0.07) Cold B 22.82 1.98 11.36 0.06 0.07 - Std Dev (1.81) (2.55) (1.45) (0.04) (0.08) Olivine Murray 17.81 14.17 25.27 BDL BDL - Std Dev (1.95) (14.53) (9.53) Murchison 19.36 5.15 31.98 BDL BDL - Std Dev (1.57) (10.78) (7.42) Cold B 18.98 5.28 30.78 0.10 0.13 - Std Dev (1.12) (9.06) (7.00) (0.16) (0.36) Nogoya 19.71 0.50 33.80 BDL BDL O Ca Al Mn P Cr Ti Co Cu Total 48.06 1.00 0.79 0.13 0.01 0.42 0.17 0.01 0.02 101.03 (0.97) (0.80) (0.45) (0.18) (0.01) (0.22) (0.05) (0.01) (0.02) (1.29) 47.26 0.61 0.58 0.09 0.00 0.41 0.10 0.01 0.01 100.65 (0.90) (0.41) (0.21) (0.03) (0.00) (0.14) #DIV/0! (0.01) (0.02) (1.27) 47.13 0.51 0.42 0.15 0.00 0.50 0.02 0.00 101.18 (3.53) (0.37) (0.22) (0.11) (0.00) (0.21) (0.02) (0.01) (2.30) 44.33 (1.96) 45.84 (1.07) 13.07 1.61 0.33 0.03 0.72 (1.54) (0.71) (0.17) (0.08) (0.37) 13.36 3.61 0.39 0.00 0.97 (2.41) (2.16) (0.42) (0.00) (0.29) 0.65 0.01 0.01 99.61 (0.31) (0.02) (0.02) (1.54) 0.02 0.01 100.49 (0.02) (0.02) (0.89) 100.89 (1.69) 101.87 (1.69) 102.20 (1.64) 98.72 42.76 0.23 0.07 0.23 BDL (4.41) (0.17) (0.07) (0.14) 44.48 0.40 0.17 0.09 BDL (3.37) (0.44) (0.22) (0.10) 46.13 0.17 0.11 0.16 BDL (2.67) (0.07) (0.25) (0.10) 44.05 0.23 0.10 0.06 0.00 0.24 BDL BDL BDL (0.10) 0.18 BDL BDL (0.10) 0.33 BDL BDL BDL (0.08) 0.20 0.00 0.00 0.00 121 Figure 5.2: BSE image of Murray sample #1 and the 30 regions studied 122 Figure 5.3: BSE image of Murray sample #2 and the 11 regions studied 123 Murchison is the least altered meteorite that we studied. We studied a single section of this meteorite (Fig. 5.4). We analyzed 13 study regions consisting of both altered and slightly altered material. We collected 271 valid microprobe data points. Additionally, we performed detailed X-ray mapping of four study regions of Murchison. This sample of Murchison has a breccia clast embedded within the host rock. The clast is clearly visible in optical-microscope images, BSE images, and X-ray element maps (different amount of sulfur in the matrix). Of the 13 study regions, 10 are located in the host rock and three study regions are in the breccia clast. The clast is compositionally distinct from the surrounding host material. We were unable to detect any kamacite grains in the breccia clast. There are, however, abundant type-I chondrules with apparent relic kamacite grains. Additionally, the clast has many spherical troilite and pyrrhotite grains in its matrix. Cold Bokkeveld is a meteorite that has experienced substantial aqueous alteration (Rubin et al. 2007). We collected data from nine study regions, resulting in 218 valid EMPA data points. Most of these data are from hydrated minerals, both from chondrules and from the surrounding matrix. Additionally, we performed X-ray mapping of eight study regions to characterize systematic alteration features. Cold Bokkeveld is a brecciated meteorite, and has several clasts in the sample (Fig. 5.5). We identify two clear breccia boundaries, suggesting that it is made up of three separate clasts. These three large clasts have similar matrix and chondrule distributions. Additionally, within the center clast there appears to be an additional small clast (~1 mm2) with both textural and chemical differences. 124 Figure 5.4: BSE image of Murchison and the 13 regions studied The breccia clast is outlined in black. 125 Figure 5.5: BSE image of Cold Bokkeveld and the 9 regions studied The breccia boundaries are outlined in black. 126 Figure 5.6: BSE image of Nogoya and the two regions studied Portions of the middle of the sample were delaminated and unusable. Limited study of this sample was conducted due to the fragile nature of the remaining thin section. 127 The final sample in our study is Nogoya (Fig. 5.6). It is highly altered, similar to Cold Bokkeveld (Rubin et al. 2007). Problems with the mounting of the sample caused the center to become delaminated and unusable. Due to the fragile nature of this sample, we performed only a limited survey of five mineral assemblages within two study regions. We took 18 EMPA data points, 16 of which produced valid results. We conducted no additional X-ray mapping of Nogoya beyond the initial whole-meteorite map. 5.4.2 Kamacite Kamacite is central to our study of aqueous alteration of metal grains in CM chondrites. Our review of kamacite included a total of 61 kamacite grains. 22 kamacite grains were in type-I chondrules and 39 as individual kamacite grains in the matrix. The kamacite grains in the matrix range from as small as a few microns (the resolution limit of the microprobe) to as large as 100 µm. Matrix kamacite grains are typically spherical. They are common in Murchison and Murray, but totally absent from Nogoya. Cold Bokkeveld contains no kamacite with the exception of the small breccia clast mentioned earlier. This small clast has many cracks that are filled with iron oxide, which form veins that stretch between the kamacite grains to the clast boundary (Fig. 5.7). 128 Figure 5.7: BSE image of Chondrule A of Cold Bokkeveld This is one of the few kamacite grains detected in Cold Bokkeveld. Kamacite is only present in a small breccia clast in the middle of our sample. The alterations of the kamacite grains appear to be postbrecciation as well as after most other alteration occurred. The altered kamacite was oxidized with only a trace amount of S. The Fe followed established fracture patterns that formed iron oxide veins. (Cold Bokkeveld, chondrule A) Although there is textural and compositional variation among the meteorites in our samples, the average chemical composition of kamacite falls within expected values for CM chondrites. Our data yield an average composition of Fe.932Ni.050P.007Cr.005Co.002. We also identified small accessory minerals embayed within some of the kamacite grains, including schreibersite (Fig. 5.8), silica, and possibly carbon. The Cr content of the kamacite grains varies substantially from 0.3 wt% in Murchison to 0.7 wt% in Cold 129 Bokkeveld. Cold Bokkeveld kamacite also has higher P, with a concentration of 0.9 wt% vs. the typical 0.3 wt% for the others. However, because Cold Bokkeveld's kamacite is contained in a breccia clast that is texturally different from the rest of the sample, its kamacite values may not be representative of the rest of Cold Bokkeveld. Figure 5.8: Matrix kamacite grain with schreibersite A Fe/P/S element map shows an unaltered kamacite grain. We identified lamellae of schreibersite. (Murray #1, chondrule #13) 130 5.4.3 Tochilinite Tochilinite is an Fe-rich hydrated mineral that is critical to our analysis. While full identification of tochilinite should be done using crystallographic data, we infer its presence using a heuristic technique for mineral identification based on the Si/Mg/Fe ternary diagram (McSween 1979). We considered a mineral to be tochilinite if it fell within 5 wt% of a typical tochilinite composition (0% Si, 95% Fe, and 5% Mg, normalized ternary data, in Murray and Murchison). We excluded points that did not have at least 5 wt% S. We detected Mg-rich tochilinite in Cold Bokkeveld and Nogoya (2% Si, 89% Fe, 9% Mg normalized ternary data). We also plotted the tochilinite's three most abundant elements (O/S/Fe) on a ternary plot and excluded data points that fell outside of acceptable values, based in tochilinite stoichiometry (Gubaidulina et al. 2007). We identified 109 tochilinite grains. Eighty-seven grains of tochilinite were identified in the matrix without association with larger mineral assemblages. We also identified tochilinite in 18 type-I chondrules, two troilite grains, and two isolated kamacite grains. In total, 10 of these tochilinite grains are physically associated with kamacite, usually within type-I chondrules. The larger matrix grains have a texture that is similar to the tochilinite present in type-I chondrules. Application of the chemical filters provided 125 valid tochilinite analyses. The textural characteristics of tochilinite show that it is not a single coherent crystal. In our BSE images tochilinite grains appear as a medium-bright high-Z mineral, but not as bright as kamacite or troilite. The tochilinite has a ragged texture that appears pockmarked (Fig. 5.10). High-resolution imagery indicates that the texture of tochilinite 131 is fibrous and is riddled with bright and dark patches (Fig. 5.11). The small, high-Z patches are discussed in section 5.4.3. While tochilinite typically has a ragged texture, some regions appear to have a smooth texture (Fig. 5.12a). However, when using highresolution images, even grains with a smooth texture reveal regions of high-Z material scattered throughout the tochilinite (Fig. 5.12b & c). Figure 5.10: Tochilinite associated with type-I chondrules Tochilinite is frequently present in type-I chondrules. They have a rounded shape when embayed within the silicate minerals, suggesting relic kamacite. This type-I chondrule has at least three large kamacite grains that have been fully converted into tochilinite. Small kamacite grains that are fully embayed by silicates have not undergone alteration. The dark patches appear to be holes that may indicate grains that were plucked during sample preparation. Mesostases are usually converted into phyllosilicates (Phy). (Murray #1, chondrule B) 132 Figure 5.11: Tochilinite boundary A close up FESEM image shows the boundary between P-rich sulfides, normal tochilinite and an unidentified Cr/Mg mineral. Both tochilinite and the Cr/Mg phase have a fibrous texture. Even at this small scale, tiny P-rich sulfide grains are scattered throughout the tochilinite. (Murray #1, chondrule 4) 133 (a) (b) (c) Figure 5.12: FESEM image of kamacite/tochilinite alteration boundary These three images show that the alteration of kamacite into tochilinite occurs on the exterior of the kamacite grain. (a) Aqueous alteration begins on the outside of kamacite grains, forming a rim the becomes larger as alteration continues. (b) The high-resolution view of tochilinite shows small high-Z streaks that may be the initial formation of the P-rich sulfide grains. (c) Additionally, we do not detect an intermediate alteration phase, even at high resolution. (Murray #1, chondrule 19) 134 Of the 39 type-I chondrules studied, we detected tochilinite in 18 of them. Tochilinite is frequently seen on the outer rim of the chondrule (Fig. 5.10) or within the chondrule itself (Fig. 5.12a). Usually, tochilinite fills a region that has a shape similar to those normally occupied by kamacite blebs. Occasionally, it appears to have expanded into the mesostasis. While many type-I chondrules have only kamacite or tochilinite, we did identify eight type-I chondrules that have both (Fig. 5.12). When kamacite and tochilinite are in contact with each other, the kamacite is normally surrounded by a rim of tochilinite, (Fig. 5.12b). However, we also discovered kamacite grains that had small cavities of tochilinite at their outer edge. These cavities occur as a notch within the general shape of the kamacite grain. These mixtures of kamacite and tochilinite are more frequent in Murray and only occasionally observed in Murchison. We did not locate any such occurrence in Nogoya. Cold Bokkeveld only has kamacite in a single small clast, which is not associated with tochilinite. In some assemblages, threads or ribbons of tochilinite extend beyond the general tochilinite mass (Fig. 5.13a). For some chondrule-associated tochilinite, it cuts through the fine-grained dust rim that surrounds the chondrule and extends into the matrix (Fig. 5.13b). In other occurrences a tochilinite grain extends for 250 µm along the outside edge of the chondrule silicates (Fig. 5.13c). 135 (a) (b) (c) Figure 5.13: Advanced tochilinite alteration Tochilinite grains that have expanded into the surrounding material. Figures 5.13a & b are altered kamacite grains where the newly formed tochilinite has breached the original dust rim. In figure 5.13b, the tochilinite expands 150 µm into the matrix. c) an FESEM image of tochilinite that has also flowed or migrated beyond its original kamacite mineral size. Several fully altered kamacite grains are suggested by the rounded shape filled in with tochilinite. Expansion is required because the volume of tochilinite is twice the volume of the original kamacite, section 5.5.1. P-rich sulfides (Ps) can be noted by the high-Z grains within the tochilinite. (a - Murray #1, chondrule 4; b - Murray #1, chondrule A; c - Murray #1, chondrule H) 136 In addition to characterizing chondrules, we studied high-Z grains in the nearby matrix for comparison. While most of these grains are TCI grains (section 5.4.5), ~25% are tochilinite. We detected 57 such grains that are isolated in the matrix. Most of these grains are small (5 to 20 µm) and do not have fine-grained dust rims. Chemically, they are distinct from the tochilinite associated with chondrules. To evaluate the chemical variations of the different types of tochilinite, we used our data to identify several groups of tochilinite. The first group contains tochilinite that is associated with chondrules, Table 5.2. The second tochilinite group includes grains that are isolated in the matrix. The two groups are compositionally distinct, with the matrix-associated tochilinite having virtually no P and Co, and half the Ni of the chondrule-associated tochilinite. A third tochilinite group is associated with troilite (i.e. tochilinite existing in the fracture channels of troilite grains - section 5.4.8). This troiliteassociated tochilinite is present only in Murray, and the composition of this troiliteassociated tochilinite is similar to the matrix-associated tochilinite. Structurally, tochilinite is comprised of alternating layers of brucite and mackinawite (MacKinnon and Zolensky 1984). However, the ratio of these minerals can vary (Gubaidulina et al. 2007). This variation is reflected in the general tochilinite formula of (Fe,Ni,Cu)x-1 • n (Fe,Mg)(OH)2. The relative amount of brucite (n) varies between 1.58 and 1.75. Additionally, the Fe content of the mackinawite (x) varies between x=.08 to x=.28. 137 Table 5.2: Tochilinite elemental composition (wt%) # Name Si Fe Mg Ni S O Ca Al Mn P Cr Co Cu Total Murray - Chondrule (69)1 Average 0.7 40.4 2.1 8.2 16.9 17.8 0.17 0.49 0.08 0.79 1.29 0.33 BDL 89.5 Std Dev 0.6 5.2 0.8 3.1 3.3 3.8 0.18 0.55 0.04 0.62 0.84 0.20 7.7 1 Murray - Matrix (27) Average 1.4 48.8 2.8 2.1 16.7 21.0 0.05 1.00 0.06 0.07 0.14 BDL BDL 91.0 Std Dev 0.9 4.4 0.6 2.0 3.6 3.6 0.05 0.77 0.04 0.23 0.35 0.05 9.28 1 Murray - Troilite (11) Average 0.8 48.5 2.2 4.0 21.7 17.2 0.05 0.39 0.06 BDL 0.17 0.17 0.18 95.4 Std Dev 0.4 3.1 0.7 4.0 3.6 4.0 0.04 0.15 0.08 0.03 0.22 0.11 4.2 Murchison - Chondrule (9)1 Average 1.3 37.2 2.5 8.1 15.9 25.0 0.17 0.88 0.09 0.79 0.48 0.31 BDL 73.3 Std Dev 1.0 5.4 0.4 3.6 2.4 2.8 0.11 0.81 0.06 0.55 0.52 0.23 10.3 1 Murchison - Matrix (15) Average 1.8 48.0 2.9 1.9 16.2 21.1 0.06 1.16 0.06 BDL 0.13 BDL BDL 94.1 Std Dev 0.8 2.1 0.6 1.3 2.5 2.5 0.03 0.61 0.02 0.31 5.9 1 Cold Bokkeveld - Chondrule (17) Average 1.0 38.4 3.9 7.6 18.6 20.0 0.13 0.49 0.11 0.47 1.14 0.15 BDL 89.7 Std Dev 0.7 3.8 0.8 3.1 2.7 3.4 0.13 0.16 0.02 0.35 0.47 0.10 5.4 Nogoya - Chondrule (4)1 Average 0.7 42.0 3.3 4.3 16.9 22.3 0.06 0.80 0.17 0.13 0.62 0.08 BDL 91.5 Std Dev 0.4 3.5 0.9 3.0 3.6 2.5 0.04 0.25 0.03 0.19 0.41 0.11 2.9 1 - The number in parentheses are the number of tochilinite data points taken. Multiple data points were taken for some tochilinite assemblages. We fit our data to the general tochilinite formula. We allow x and n to be free parameters (Table 5.3). There are small amounts of Si in some of our analyses so we first remove an idealized ferrous serpentine. To avoid skewing the ratio of Fe to Mg, we used the same Fe to Mg ratio as the brucite layer of 4:1, (Fe.80Mg.20)3Si2O5(OH)4. Further, based on the amount of P, we removed a P-rich sulfide phase using the P-rich sulfide composition of Murray, section 5.4.4. Finally, any Al is assumed to be Al(OH)3 and removed (Organova 1974). These corrections improved the fit of our data to the theoretical value of tochilinite. 138 Table 5.3: Empirical formula for tochilinite Name Tochilinite empirical formula 1 Murray, Chondrule (47) 2(Fe66Ni34Cu.6).84S •1.60 (Fe.80Mg.20)(OH)2 Murray, Matrix (12)1 2(Fe93Ni07).88S •1.73 (Fe78Mg22)(OH)2 1 Murchison, Chondrule (2) 2(Fe64Ni36).55S •2.79 (Fe85Mg15)(OH)2 1 Murchison, Matrix (6) 2(Fe92Ni08).93S •1.69 (Fe76Mg24)(OH)2 1 Cold Bokkeveld, Chondrule (26) 2(Fe71Ni29).73S •1.74 (Fe64Mg36)(OH)2 Nogoya, Chondrule (3)1 2(Fe74Ni26).66S •1.88 (Fe74 Mg26)(OH)2 1 - The number in parentheses are the number of tochilinite data points used. Multiple data points were taken for some tochilinite assemblages. The data presented in Table 5.3 and Fig. 5.14 have an additional filter, rejecting points if their n or x value are well outside typical. The average values for tochilinite stoichiometries from most of our samples fall within the valid range of tochilinite (Gubaidulina et al. 2007). Some individual points deviate beyond established parameters (Fig 5.14) with oxygen too high or too low. The largest deviation is Murchison's chondrule-associated tochilinite that has too much oxygen and too little Fe. It is possible that this material is not fully altered, or there may be the inclusion of the Pseudohexagonal Fe(OH)3, which has previously been detected associated with tochilinite (Organova1974). Because Fe(OH)3 has a higher ratio of O to Fe than brucite, this phase can account for the higher ratio of O to Fe seen in these samples. 139 (a) (b) Figure 5.14: Tochilinite's stoichiometric parameters, x and n Plot of all tochilinite and average tochilinite values based on its empirical formula. Tochilinite has the idealized formula of (Fe,Ni,Cu)x-1 • n (Fe,Mg)(OH)2. We plot the two components, 1-x and n, showing the distribution of valid data points. Chondrule based points are circles and matrix points are squares are tochilinite in the matrix. Figure (a) is all the data, and figure (b) is the averages by meteorite. The error bars are one standard deviation. One of the most striking variations between meteorite samples is the ratio of Mg to Fe. We have determined that the Mg content of Cold Bokkeveld and Nogoya is much higher than for Murray or Murchison (Fig. 5.15). The tochilinite grains in Murchison and Murray possess a limited variation in the Mg/(Mg+Fe) ratio, which clusters near 11 at% and has a standard deviation of 3.3. Figure 5.15 displays histograms of the ratios for all of the tochilinite grains that we analyzed in Murray, Murchison, Cold Bokkeveld and Nogoya. The Mg content in Cold Bokkeveld is almost twice as high as for Murray and Murchison, 20.7 at% (3.7). Nogoya's ratio is 15.2 at%. However, the limited data for Nogoya (only four tochilinite grains were sampled) may have introduced a sampling bias. 140 (a) (b) (c) Figure 5.15: Histogram of the Mg/(Mg+Fe) content of tochilinite Histograms for the meteorites: (a) Murray, (b) Murchison, and (c) Cold Bokkeveld and Nogoya. The data for Cold Bokkeveld and Nogoya were combined. The typical Mg/(Mg+Fe) ratio for tochilinite is between 10 and 14 at%. Murchison's average is 12.8% (2.5) and Murray's average is 10.8% (3.3). The tochilinite in Cold Bokkeveld is much more Mg rich, resulting in an average of 20.7% (3.7). Nogoya's average is 15.2% (3.1). Numbers in parenthesis are standard deviation. 5.4.4 P-rich Sulfide and Accessory Phases in Tochilinite We detected many small P-rich sulfides in our samples. These small mineral grains are most likely the unidentified sulfides described in previous works as Q sulfides (Bunch and Change 1980), P-rich Fe,Ni sulfides (Devouard and Buseck 1997), or P-rich 141 sulfides (Nazarov et al. 2009). The largest P-rich sulfide grain in our study, 35 x 25 µm, is embedded within a large troilite grain (Fig 5.16). However, most P-rich sulfide grains are located within tochilinite (Figs 5.18, 5.19 & 5.20). We identified seven type-I chondrules and three matrix grains that have both tochilinite and P-rich sulfides intermixed. We also note that there are an additional eight type-I chondrules and two matrix grains that appear to have both tochilinite and P-rich sulfides, but were not studied. After applying chemical filters, we have a total of 41 valid microprobe analyses of P-rich sulfides. Figure 5.16: Fractured troilite with embedded P sulfide grains A large (150 x 250 µm) fractured troilite grain in Murray. This troilite grain has two large P-rich sulfide grains embedded within its structure that suggests that the P-sulfide and the troilite formed together. We determined that tochilinite fills the fracture channels within the troilite grain, section 5.4.8. (Murray #1, chondrule 3) 142 The correlation between the presence of P-rich sulfides, metallic Fe, and tochilinite was not discussed in previous work (Nazarov et al 2009). They report that Prich sulfides are normally associated with forsterite and pyroxene and with minor components such as chromite [(Fe,Mg)Cr2O4], eskolaite (Cr2O3), barringerite [(Fe,Ni)2P], schreibersite [(Fe,Ni)3P], and daubreelite (FeCr2S4). Nazarov et al. suggest that the tochilinite was formed as an alteration product of the P-rich sulfides, implying at least one occurrence of the two phases coexisting. It is unclear if P-rich sulfides are a coherent single mineral or a mixture of two minerals (Devouard and Buseck 1997). BSE images show that the grains are distinct with clear boundaries. Fractures cross a single grain but do not extend into other grains (Fig. 5.11). Additionally, most of the P-rich sulfide grains do not have any observable textural variability at the 10 µm scale. However, the largest P-rich sulfide grain in our sample set shows numerous small ribbons of high-Z material throughout the grain (Fig. 5.17). Further work with a technique such as TEM is needed to fully characterize the structure of this phase. 143 (a) (b) (c) Figure 5.17: FESEM of P-rich Sulfide Close up FESEM images of a large 35x25 µm P-rich sulfide grain. The primary components are Fe, S, Ni, P, O and Co. The P-rich sulfide phase has not been fully characterized, and it is uncertain if it is a coherent mineral or a mixture of separate phases. In this large grain, there are long ribbons of high-Z material. Fig. 5.16 provides a context image for this grain. (Murray #1, chondrule 3) 144 The P-rich sulfide grains are rich in Fe, Ni, S, O and P, and contain minor amounts of Co. Table 5.4 shows the chemical formula generated by normalizing all components to two Fe atoms. We determine that O is a substantial component of this mineral. More than half of the P-rich sulfides have wt% totals greater than 94%. Finally, the Cr content of most of the P-rich sulfides is below detection limits, but a few grains contain as much as 2 wt% Cr. When we search for Cr using X-ray maps, we see that Cr is absent from the P-sulfide phase. It is likely that the Cr is in a nearby phase (such as eskolaite or daubreelite) that was inadvertently included in the analyzed region. The chemical composition of P-rich sulfides is highly variable between meteorites. The P-rich sulfides in Murchison and Murray have similar elemental compositions (Table 5.4). The average P-rich sulfide composition of Murchison from our data is comparable to the composition reported by Nazarov et al. (2009) with the exception of S, which we observe to be higher. Cold Bokkeveld and Nogoya contain minerals that are similar to P-rich sulfides, but have a lower concentration of P by a factor of five and Co by a factor of three. We will also refer to these minerals as P-rich sulfides. Nazarov et al. observed a similar variation of P concentration within their sample set with a range of 0.57 wt% (ALH 83100) to 8.3 wt% P (EET96016). 145 Table 5.4: Empirical formula for P-rich sulfides Meteorite Empirical Formula Murchison (Nazarov)1 Fe2.0 Ni2.6 S2.1 P0.9 Co0.14 2 Murchison (2) Fe2.0 Ni2.7 S3.2 O1.6 P0.9 Co0.15 2 Murray (32) Fe2.0 Ni2.9 S2.9 O2.0 P1.3 Co0.18 Cold Bokkeveld (5)2 Fe2.0 Ni1.8 S3.3 O0.2 P0.1 Co0.06 2 Nogoya (2) Fe2.0 Ni1.5 S3.0 O0.3 P0.2 Co0.04 1 - Nazarov et al. (2009) collected data on 37 P-rich sulfides in Murchison, but reports a representative value for it. They did not report an O content 2 - Number of data points collected in each meteorite. To determine the composition and distribution of P-rich sulfides associated with tochilinite, we conducted a detailed study of the largest kamacite/tochilinite assemblage in our sample set (Fig. 5.12a). This region has a typical textural and chemical composition for the tochilinite/P-rich sulfide regions present elsewhere. The host chondrule is a type-I chondrule, 400 x 300 µm across, with silicate compositions of Fo95 and En94. The chondrule has altered mesostasis regions composed of cronstedtite. On the side of the chondrule there is a 180 x 100 µm kamacite grain that is surrounded by a tochilinite rim. This rim of tochilinite is as thin as 2 µm on the side away from the matrix and thickens to 30 µm on the side closest to the matrix. We selected the largest portion of the rim for FESEM (Fig. 5.18), high-resolution X-ray maps with the elements Fe, Ni, Mg, S, O, P and Cr (Fig. 5.19) and optical microscopy (Fig. 5.20). 146 Figure 5.18: Murray1, Ch 4 X-ray map BSE A FESEM image showing a small region of the tochilinite resulting from the alteration of a large kamacite grain (see inset image for context). Circles show where EMPA was done, and Figure 5.19 identifies the phases. (Murray #1, Chondrule #4) 147 Figure 5.19: Murray1, Ch 4 X-ray map X-ray map (Fe/P/Cr) of Murray that depicts tochilinite (Toch) and several different accessory minerals, Prich sulfide (Ps), eskolaite (Esk), and schreibersite (Sch). P-rich sulfides are blue-purple and are commonly embedded within tochilinite. Eskolaite can be noted by the bright green Cr-rich minerals on the edge of the tochilinite. Schreibersite is shone as bright purple ribbons streaks. A fibrous phase with ~Cr 6 wt% is unidentified (Cr). One phase labeled with a question mark also remains unidentified. (Murray #1, Chondrule #4) 148 Figure 5.20: Murray1, Ch 4 reflected light A reflected light microphotograph of a kamacite alteration. Scale is similar to Figure 5.19. P-rich sulfide grains can be seen as a slightly darker red/brown in the tochilinite. The sample had a carbon coat present when we took the image. (Murray #1, Chondrule #4) 149 The elemental X-ray maps show a high degree of chemical heterogeneity within the tochilinite region, clearly showing six distinct compositions (Fig. 5.19). We conducted EMPA for representative minerals within this field to provide the mineralogic typing to correlate with the X-ray maps. The two most common phases are tochilinite (red-brown) and P-rich sulfides (blue-purple). Tochilinite is concentrated near the contact with the matrix. The next most common phase is rich in Cr. It has a red-green color in the X-ray map (Fig. 5.19). It also has a similar texture to tochilinite but is slightly darker in BSE images (Fig. 5.11). Compared to tochilinite, this phase has an excess of Cr and O, but is depleted in S (Table 5.5). We have been unable to identify this phase but note a strong correlation between Cr and Mg (Fig. 5.21) with an R2 of 0.93. Figure 5.21: Cr/Mg Phase A plot of the Cr/Mg phase studied in tochilinite. There is a strong correlation between high Mg and Cr. We identified this Cr/Mg phase in one partially altered kamacite grain. 150 Table 5.5: Cr/Mg phase from Murray #1, chondrule 4 (wt%) Si Fe Mg Ni S O P Cr Co Total 1 Tochilinite (13) 0.81 40.83 2.07 8.60 16.09 18.24 0.89 1.60 0.41 90.11 Cr/Mg Phase (14)1 0.38 33.13 4.58 6.24 7.65 25.75 1.02 6.50 0.51 86.34 1 - Number of data points collected. X-ray maps show three additional phases: eskolaite, schreibersite and a third that remains unidentified. We see the highest concentrations of Cr near the contact between tochilinite and silicates. While the mineral grains are too small to be measured using EMPA, we identify them as eskolaite (Cr2O3) because X-ray maps show that only Cr and O are present. The other small mineral is visible as thin bright purple strands in the tochilinite and shows the highest concentration of P in the image. Again these grains are too small for EMPA; however, X-ray maps show they are mostly comprised of Fe, Ni and P, suggesting schreibersite. Both of these phases have been reported as collocated with P-rich sulfides (Nazarov et al. 2009). The final phase has a red-purple color and is marked with a question mark. Its major components are 52.6 wt% Fe, 26.8 wt% O, 6.8 wt% Ni, 4.6 wt % S and a total of 95.7 wt%. We were unable to identify a suggested mineral for this phase. 5.4.5 Tochilinite/cronstedtite intergrowth (TCI) Tochilinite/cronstedtite intergrowth (TCI) grains are one of the most common phases in CM chondrites and are characteristic of this meteorite class. We detected 145 of these Fe and S rich grains throughout the matrix, Table 5.6. After applying chemical filters, 262 valid TCI analyses remained. These TCI grains are typically rounded with 151 lobate edges or irregular shapes, and have a distinct border separating them from the surrounding matrix (Fig. 5.22). Table 5.6: Tochilinite/Cronstedtite Intergrowths (TCI) chemistry (wt%) # Name Si Fe Mg Ni S O Ca Al Mn P Cr Co Cu Murray (187)1 Average 5.9 41.5 3.9 1.5 8.7 29.6 0.15 1.24 0.10 BDL 0.15 BDL BDL Std Dev 1.6 4.6 1.2 1.4 3.0 3.3 0.34 0.46 0.05 0.33 Murchison (25)1 Average 5.43 44.2 4.0 2.4 8.3 25.3 0.11 0.94 0.10 0.17 0.17 BDL BDL Std Dev 2.29 8.4 1.6 2.2 4.1 7.4 0.10 0.45 0.04 0.20 0.30 1 Cold Bokkeveld (50) Average 9.0 32.8 7.5 1.7 6.1 35.7 0.20 1.32 0.17 0.07 0.28 BDL BDL Std Dev 2.0 3.5 1.3 2.1 3.1 4.0 0.56 0.44 0.03 0.25 0.23 1 - Number in parenthesis is the number of observations. Includes both measured O and missing O data. Figure 5.22: FESEM TCI Close up FESEM image of a TCI grain. Even at this resolution, the fibrous nature of TCI is visible. (Murray #1, near Chondrule A) The bulk chemical definition for tochilinite/cronstedtite intergrowth (TCI) grains 152 is not well constrained due to the wide range of possible elemental compositions. McSween noted that TCI fell within a mixing line between tochilinite and cronstedtite on the Si/Mg/Fe ternary diagram, usually with a composition of 75% cronstedtite and 25% tochilinite (McSween 1987). We identified as TCI all minerals that fell within 5 wt% of this mixing line (Table 5.6). Further, we excluded analyses that were more than 2! from the mean on an O/S/Fe ternary diagram. This technique works well for both Murray and Murchison; however, when applied to Cold Bokkeveld and Nogoya it is too restrictive. Many Fe-rich grains were excluded because they were too Mg rich. Comparison of our results to data reported by Rubin et al. (2007), confirmed that our criteria are too restrictive. Rubin considered all large high-Z grains in the matrix to be TCI grains, which resulted in including grains that had less Fe and more Si and Mg than allowed by McSween's heuristic. To maintain consistency with published data, we included high-Fe matrix grains from Cold Bokkeveld and Nogoya (Fig. 5.23). 153 Figure 5.23: Si/Mg/Fe ternary plot for TCI grains This ternary plot displays all TCI grains, plotted on a Si/Mg/Fe ternary diagram (wt%). Red is Murray and Murchison and Cold Bokkeveld is blue. The TCI grains fall along the expected cronstedtite-tochilinite mixing line for Murray and Murchison; however, Cold Bokkeveld's TCI grains are much more Si and Mg rich, suggesting alteration has increased the Si and Mg content (Hanowski and Brearley 2001). 5.4.6 Cronstedtite Cronstedtite was included in our study because it is a common phyllosilicate and assumed to be an alteration product (McSween 1979, 1987; Tomeoka and Buseck 1985). Using McSween's heuristic, we identified a mineral as cronstedtite if it fell within 7 wt% of an ideal cronstedtite composition (19 wt% Si, 74 wt% Fe, and 7 wt% Mg, normalized ternary data). We excluded any points that are outliers when plotted on the O/S/Fe ternary diagram. We also excluded minerals that had more than 5 wt% S because they are likely to be a mixture of cronstedtite and pyrrhotite (Browning et al. 1986). Chondrule- 154 based cronstedtite has virtually no S, while matrix cronstedtite has a higher amount of S (Table 5.1). During our analysis, we identified a total of 28 cronstedtite grains in the matrix, in type-I chondrules and in type-II chondrules. Nine of the matrix cronstedtite grains are not associated with any chondrules or mineral assemblages. Sixteen of the cronstedtite grains are located within type-I chondrules, typically in what appears to be altered mesostasis (Fig. 5.12a). Finally, we identified cronstedtite in 3 of the 6 type-II chondrules that we studied (Fig. 5.24). (a) Figure 5.24: Cronstedtite in type II chondrules (b) Figures 5.24 (a) and (b) show type-II chondrules that have associated cronstedtite grains. It has been suggested that alteration of fayalite occurs preferentially in interior fractures (Hanowski 2001). However, it is unclear if this is the case. (a - Murray #2, Chondrule E2; b - Murchison, F2) We have identified two examples of cronstedtite on the margins of kamacite (Fig. 5.25). In the first occurrence, we identify a 1.5-to-3-µm rim of silicate-rich material surrounding a spherical kamacite grain (Fig. 5.25a). This kamacite grain is unassociated 155 with any other mineral assemblage (i.e. surrounded by only matrix). Chemically, much of the silicate-rich rim matches cronstedtite, but some portions of the rim are slightly more sulfur rich. The second example is a set of kamacite grains in a type-I chondrule (Fig. 5.25b). These kamacite grains have small patches of cronstedtite on their exterior surface, with a 20 µm cronstedtite grain in the middle of the chondrule. (a) Figure 5.25: Cronstedtite rims on kamacite (b) Alteration of kamacite grains into cronstedtite was detected in type-I chondrules. These cronstedtite grains contain a small amount of S. While the S content is much less than that of tochilinite, it is higher that what is typically seen in cronstedtite. (a - Murchison, chondrule F; b - Murchison, chondrule G) 5.4.7 Iron Oxides While most Fe-rich minerals in CM chondrites are kamacite, pyrrhotite or tochilinite, some Fe-rich material in our samples are comprised of mostly Fe and O. Iron oxide is rare in CM meteorites (Brearley 2006), but has been reported previously (Metzler et al. 1992; Nazarov et al. 2009). It is usually assumed to be magnetite that precipitated out of solution (Metzler et al. 1992; Brearley 2006). However, in the 39 iron 156 oxide grains we have identified in our meteorites, the chemistry suggests that there are two different types, pure magnetite and Ni-bearing oxide (Table 5.7). Table 5.7: Iron oxide distribution With Isolated Kamacite Matrix No Ni Ni Murray #1 10 8 3 Murray #2 2 3 1 Murchison 3 3 1 Cold Bokkeveld 2 2 1 One clear division within the iron oxide grains is association with kamacite. We identified 17 kamacite grains that are physically in contact with iron oxide. In these cases, the iron oxide appears as a rim surrounding the kamacite, or as small patches on the kamacite grain's outer surface (Fig 5.26). We determined that all of the iron oxide grains associated with kamacite contain several wt% Ni, usually with a Ni/Fe ratio greater than 1:20. 157 Figure 5.26: Oxidized kamacite The kamacite in this chondrule has not been converted into tochilinite, but small regions are heavily oxidized. EMPA of the altered region detected an increasing amount of oxygen closer to the rim; however, the Ni content remained at 5 at% of the Fe level, indicating oxidized kamacite rather than precipitated magnetite. (Murray #1, chondrule 15) The remaining 22 iron oxide grains are unassociated with kamacite. These grains typically appear as small isolated grains in the matrix. Sixteen of these grains have less than 1 wt% Ni; however, 6 iron oxide grains have Ni contents that are close to the 1:19 Ni:Fe ratio indicative of relic kamacite grains. 5.4.8 Troilite Pyrrhotite is an iron sulfide with the idealized formula of Fe1-xS, where x=0.0 to 0.2. Troilite is a subset of Pyrrhotite when x=0. We used the criteria of x < 0.05 to distinguish between troilite (x<0.05) and pyrrhotite (0.05<x<0.20) in the 47 Fe-S grains in our samples. Twenty-six of the Fe-S grains are typical troilite, but we identified 11 158 pyrrhotite grains with an average value for x=0.09. Additionally, we identified 10 grains of an oxidized troilite that has an oxygen composition between 3 to 9 wt% and a median total of 99.2 wt%. Three of the troilite grains are unusual in several respects. First, these three grains have long fracture channels, something that is not seen in the other 44 Fe-S grains. Second, those fracture channels are filled with tochilinite (Fig 5.27). Finally, upon FESEM analysis of these fracture channels, we observed Ni-rich grains at the center of the fracture channels. The grains are too small for EMPA, and as such, we were unable to determine if they are P-rich sulfides. However, EDS mapping shows a Ni concentration within these grains similar to P-rich sulfides. The troilite grain itself has little Ni, only 0.1 at%, so it is surprising to see such a large amount of Ni concentrated in the middle of the fracture channels. Figure 5.27: Troilite and tochilinite Murray has a large troilite grain that has been altered along fracture lines. Tochilinite has filled the troilite's fractures. In the center of the fracture channels, there are numerous Ni-rich grains that were too small to be identified but might be P-rich sulfides grains. Context image is Fig 5.16. (Murray #1, chondrule 3) 159 5.5 Discussion While much information about the nature of aqueous alteration on chondritic parent asteroids can be obtained by looking at the highly altered meteorites, we have determined that study of partially altered samples (i.e. water-limited alteration) provides us with the ability to identify the precursor material, the alteration processes, and the resultant products. This history of partially altered assemblages is easier to decipher than heavily altered ones because portions of the original state remain. Therefore, we focused our study on kamacite grains that had undergone different degrees of alteration, determined by the differing thicknesses of their tochilinite rims. Using changes in kamacite and other indicators of alteration, we have established an expanded alteration sequence for the CM chondrites and identified signatures of both nebular and parent body alteration. 5.5.1 Proposed Alteration Sequence After reviewing the EMPA data and X-ray maps, we suggest an expanded alteration sequence for kamacite (Fig. 5.29). Agreeing with previous theories (Bunch and Change 1980), we note that most kamacite alteration results in tochilinite. However, we identified a variety of other alteration products including P-rich sulfides, eskolaite, schreibersite, cronstedtite and iron oxide. We suggest that one reason for this variation is the composition of the alteration fluid: S-bearing water forms tochilinite and P-rich sulfides, Si-bearing water forms cronstedtite, and plain water forms iron oxide. Other factors such as fluid pH, temperature, pressure, and duration of alteration also play a role 160 in alteration chemistry. These different regimes are consistent with previous suggestions that alteration is strongly dependent on the microchemical environment in which it occurs (Brearley 2006). Figure 5.29: Kamacite alteration sequence Kamacite alters to form a variety of products depending on the content of the fluid. If there is no S or Si, then iron oxide is formed (Fe3O4). If kamacite alters in the presence of aqueous silica, cronstedtite is formed. However, the most common reaction is for kamacite to react with S-rich water, which forms tochilinite, P-rich sulfides and a few other minor phases (eskolaite, schreibersite and a Cr/Mg rich phase). Eighty percent of the original Fe is removed, suggesting an open chemical system. As tochilinite continues to be subjected to aqueous alteration, its Mg content will increase. The data suggest that, as alteration continues, P-rich sulfides have their P, Co and O leached out and possibly convert to pentlandite. 5.5.1.1 Alteration Products of Water with S It is commonly accepted that tochilinite is formed from the alteration of kamacite by S-bearing water (MacKinnon and Zolensky 1984). Our data support and expand upon this theory. Tochilinite consistently forms a rim around kamacite or along its exterior. When kamacite is not present, we still see indications that kamacite was the precursor to tochilinite. In particular, we consistently identify rounded holes in chondrule silicates 161 with the typical shape of kamacite blebs. These holes are filled with tochilinite and P-rich sulfides. It is possible that some small, isolated matrix tochilinite grains were not formed from kamacite. These matrix-associated tochilinite grains lack inclusions of Ni, P, and Co contents that typify alteration of kamacite. As such, they may have a different petrogenesis. However, these assemblages are outside the scope of this study. We have identified that kamacite alteration goes through several stages. In assemblages with limited alteration there is a relatively homogenous rim of tochilinite around the kamacite (Fig. 5.12a). BSE images from the electron microprobe show a smooth texture. However, under higher magnification, we see that this tochilinite is not homogenous but is riddled with small threads of high-Z material (Figs. 5.12 b & c). We speculate that these small threads are submicron grains of P-rich sulfides. As alteration continues, the S-bearing water fully consumes the kamacite, forming tochilinite interspersed with P-rich sulfides, eskolaite and schreibersite (Fig. 5.19). Mass balance calculations suggest that ~80% of the Fe originally in the kamacite is removed from the assemblage. Finally, at extreme extents of alteration, the Mg content in tochilinite increases. Previous researchers have noted that the Mg content of many phases in substantially altered meteorites is higher (Lauretta et al. 2000; Hanowski and Brearley 2001). We see a similar correlation, as tochilinites in both Cold Bokkeveld and Nogoya have a higher Mg content compared to that in the less altered meteorites Murchison and Murray (Fig. 5.15). 162 In addition to tochilinite, we also detected substantial amounts of P-rich sulfides in rims around altered kamacite. We suggest that these P-rich sulfides formed as an accessory mineral during tochilinite formation. The absence of P and Co from tochilinite indicates that these elements are incompatible with tochilinite. Instead, they combine with Ni, Fe, S and O to form P-rich sulfides. P-rich sulfide appears to be a common product of kamacite alteration, having been identified in all our samples. A detailed study of P-rich sulfides concurrent to this study suggests that P-rich sulfides are not an alteration product (Nazarov et al. 2009). Nazarov et al. suggest that Prich sulfides may be a stable primary phase that formed in the solar nebula after the formation of CAIs. They also point out that trace element data indicate that P-rich sulfides could have formed in the solar nebula by the sulfidization of an unspecified precursor phase (Nazarov et al. 2009). Our data do not support this hypothesis for the Prich sulfides. Our P-rich sulfides are consistently interspersed within tochilinite. In addition, this material is absent from kamacite grains that have experience minimal alteration. Combined, these observations strongly suggest that the P-rich sulfides and tochilinite formed concurrently. Because the tochilinite and P-rich sulfide grains are small and intimately intergrown, it is difficult to analyze individual grains in the alteration rims (Fig. 5.12). To verify that P and Co are incompatible in tochilinite, we performed EMPA on carefully selected tochilinite grains with surface areas large enough to avoid beam overlap with nearby materials. In all of these cases, the abundances of P and Co are below the EMPA 163 detection limits in tochilinite. As such, we assume that any P and Co detected in other analyses of tochilinite are due to beam overlap with small P-rich sulfide grains. We plot Ni against both P and Co individually to determine the relative abundances of tochilinite and P-rich sulfides that contributed to each analysis. There is high correlation between these parameters (R2 is .97 for Ni vs. P and .80 for Ni vs. Co), indicating that the majority of data points are a mixture of these two components (Fig. 5.30). Calculating the compositions of the end members provides the best estimate for the composition of each phase (Table 5.8). Table 5.8: Calculated end members (wt%) for tochilinite and P-rich sulfides P-rich Sulfides Tochilinite Fe 18.31 42.58 Mg BDL 2.41 Ni 40.00 5.00 S 19.90 16.58 O 1.03 20.00 P 7.59 0.10 Co 2.89 BDL Figure 5.30: Plot of tochilinite and P-rich sulfides in Murray Small grains of P-rich sulfides are embedded within tochilinite. As a result, data points may contain variable amounts of both phases. The trend lines provide estimates for the composition of each mineral. 164 While the composition of P-rich sulfides varies strongly among meteorites, a correlation exists between P abundances and the extent of alteration. Data from highly altered meteorites suggest that alteration causes changes in P-rich sulfides even after they form. P-rich sulfides in Cold Bokkeveld and Nogoya are depleted in P, Co and O by a factor of ~10 compared to those in the less altered samples (Table 5.3). Phosphorus and Co depletion of P-rich sulfides in highly altered meteorites is not unique to our data. Nazarov conducted an extensive analysis of P-rich sulfides. His most altered meteorites are the paired group ALH 83100 and ALH 83102 (Grossman 2007), which has an alteration index of CM 2.1 (de Leuw et al. 2009), and Y-82042, which is described as a "CM2 chondrite which is [sic] suffered the highest grade of alteration" (Yanai and Kojima 1987). The P-rich sulfides from these highly altered meteorites have the lowest amounts of P and Co in Nazarov's sample set, less than 1.5 wt% and 0.5 wt% respectively. Alternatively, Murchison is the least altered meteorite in his sample, and its P-rich sulfides have substantial P and Co (5.67 wt% and 2.04 wt%, respectively), in agreement with our data. He does have three meteorites in his sample set whose P-rich sulfides have marginally higher P contents than Murchison (Mighei, Banten and EET 96016). The lack of a consistent aqueous alteration index for CM meteorites makes continuing the correlation difficult, but clearly, "P-rich" sulfide phases in the most altered meteorites have a much lower P and Co content. To understand the composition and petrogenesis of these low-phosphorus "P-rich sulfides", we analyzed P-rich sulfides associated with a matrix tochilinite grain in Cold 165 Bokkeveld (Fig. 5.31). The original kamacite in this assemblage has been fully altered, forming tochilinite with several small P-rich sulfide grains in the core. Because these small grains are embedded within tochilinite, it appears that they were formed in the same way as the P-rich sulfide grains in Murray and Murchison (Table 5.9). Compositionally, they are similar to pentlandite ((Fe,Ni)9 S8) with the exception of having P, Co and O, with a chemical formula of Fe5.0Ni3.6S8 •P0.5O2 Co.01. Table 5.9: Composition of Cold Bokkeveld tochilinite and P-rich sulfide (wt%) # Name Si Tochilinite Average 2.02 Std dev 0.96 P-rich Sulfide Average 0.20 Std dev 0.10 Fe 36.8 2.61 34.2 0.15 Mg 5.63 1.14 0.08 0.12 Ni 5.96 2.97 25.8 0.46 S 17.4 1.38 31.7 0.14 O 21.7 3.12 3.18 0.32 Ca 0.08 0.02 BDL Al 0.30 0.08 BDL Mn 0.16 0.03 BDL P 0.20 0.21 1.8 0.05 Cr 2.64 0.68 0.25 0.02 Co BDL Cu BDL Total 93.4 2.3 97.9 0.3 0.46 0.02 0.17 0.03 (a) (b) Figure 5.31: Line scan through Cold Bokkeveld tochilinite grain X-ray maps of tochilinite with P-rich sulfides. A line scan through a tochilinite grain in the matrix of Cold Bokkeveld shows that the kamacite was converted into two phases, a high-magnesium tochilinite and smaller P-rich sulfide grains. These P-rich sulfide grains are depleted in P and Co. (Cold Bokkeveld, near chondrule H) 166 The P-rich sulfides may not be stable when exposed to intense aqueous alteration. We hypothesize that P, Co and O are leached from the P-rich sulfides as the grains continue to interact with water. While our data are not conclusive, we note that if the removal of P, Co and O continues, the remaining material is similar to pentlandite. We plot all the P-rich sulfides from our meteorites on two ternary diagrams, Fe/Ni/S and O/Ni/P (Fig. 5.32). Both ternary plots show that the highly altered P-rich sulfides fall between normal P-rich sulfides and pentlandite. Figure 5.32: Depleted P-rich sulfide ternary diagrams The Fe/Ni/S phase diagram shows that pentlandite is a separate phase than P-rich sulfides. Pentlandite grains do not have P or Co. The P-rich sulfide grains in Cold Bokkeveld and Nogoya have much less P than Murray and Murchison, < 2 wt%. Cold Bokkeveld and Nogoya's P-rich sulfides may have had most of the P leached from them, which can be seen with a mixing line between pentlandite and P-rich sulfides. It is apparent that the alteration of kamacite into tochilinite and P-rich sulfides does not occur in a closed system. First, O and S must be added to the reaction. Secondly, Fe must be removed from the system because if all the Fe were converted into tochilinite, the volume would increase by a factor of six. While there is indication of a 167 minor volume increase because of the formation of tochilinite, the volume increase is not large enough to account for all the missing Fe. To quantify the loss of Fe, we calculated the mass balance for the conversion of a kamacite grain into tochilinite and P-rich sulfides for a specific assemblage and extrapolate these results to the broader population. Using the partially altered kamacite grain depicted in Fig. 5.33, we measured the area of the remnant kamacite, tochilinite, Prich sulfides and holes. We use these data to estimate the original size of the kamacite. We assumed that alteration was symmetrical, and that the original kamacite was approximately spherical, and that it had the same composition as the unreacted core. We estimated the volume of the kamacite that was altered to be 1.6x10-7 cm3, tochilinite to be 1.4x10-7 cm3, and P-rich sulfides to be 1.86x10-8 cm3. We calculated the molar volume for each element and phase (Table 5.10), and then multiplied the moles per cm3 by the volume to get the number of moles in the alteration region. We determined that 81% of the Fe in the original kamacite was removed during formation of the alteration rim. This process likely occurred via aqueous transport. The liberated Fe may have then been consumed in reactions with Fe-poor minerals or formed Fe-rich aureoles (Hanowski and Brearley 2000). Our calculations show that Ni and P remained in the immediate area. 168 Table 5.10: Mass balance calculations Phase Fe Ni Moles per cm3 Kamacite1 .1327 .0075 2 Tochilinite .0255 .0044 P-rich Sulfide3 .0222 .0314 -9 Total Moles (10 ) Original Kamacite 21.44 1.21 Tochilinite 3.65 0.62 P-rich Sulfide 0.41 0.58 Percent Removed 81.0% -0.1% P .0013 .0109 0.21 0.20 0.20 2.5% 1 - Kamacite density is 7.9 g cm-3 (Anthony 2003). Molecular mass is 55.4 g mol-1 (from Murray #1, chondrule 11) 2 - Tochilinite density is 2.96 g cm-3 (Anthony 2003). Molecular mass is 299.9 g mol-1 (from Murray #1, chondrule 11). Each mole of tochilinite contains 2.59 moles of Fe, 0.44 moles of Ni and no P. 3 - P-rich sulfide density is unknown so pentlandite is used as a proxy, 4.95 g cm-3 (Anthony 2003). Molecular mass is 447.1 g mol-1 (from Murray #1, chondrule 11). Each mole of P-rich sulfide contains 2.0 moles of Fe, 2.83 moles of Ni and .98 moles of P. Figure 5.33: Volume and alteration of tochilinite and P-rich sulfides We measure the area of kamacite, tochilinite, P-rich sulfides and holes in an assemblage from an altered type-I chondrule. We convert the area into an effective radius if the kamacite and alteration products were spheres. Using the modal abundances of each phase, their densities and chemical composition, we calculate the removal of material from the relic kamacite grain. Calculations show that 81% of the original Fe of the kamacite grain is removed from the region, leaving only 19% of the original Fe to form all the tochilinite and P-rich sulfides shown. 169 Another element that forms accessory minerals during aqueous alteration is Cr. It appears that Cr is more mobile than P, Co or Ni. We note that Cr frequently migrates away from kamacite and concentrates near the periphery of the alteration zone (Fig. 5.19). Chromium is not present with either P-rich sulfides or tochilinite and appears to form eskolaite as an accessory mineral, which has previously been identified in CM meteorites (Nazarov et al. 2009). We also see that some of the Cr forms a fibrous Cr/Mg phase, although we have not been able to identify it. Finally, chromite does not appear to form as a product of kamacite alteration. In our samples, chromites have only been detected associated with type-II chondrules. While most of the P that is liberated from kamacite during alteration is consumed in the formation of P-rich sulfides, we also have identified schreibersite in the alteration rim of Murray #1, chondrule 4 (Fig. 5.19). The schreibersite is exposed on all sides, indicating that the original surrounding kamacite has been fully replaced. Our data cannot determine if the schreibersite in Murray #1, chondrule 4 was originally a discrete phase within the kamacite or was formed as an accessory mineral during alteration. We have identified schreibersite as a discrete phase in an unaltered kamacite grain (Fig. 5.9) less than one millimeter away from Murray #1, chondrule 4. Thus, schreibersite may form as Fe and Co are removed from kamacite, enriching the residual metal in P and leading to phosphide formation. Alternatively, it may be present as small inclusions that are concentrated during metal alteration. However, EMPA and EDS measurements failed to identify schreibersite in any other kamacite grains. Additionally, all X-ray maps taken 170 of kamacite do not show any indication of schreibersite, which includes Murray #1, chondrule 4. Thus, it is likely that the schreibersite has formed as an alteration product. 5.5.1.2 Alteration Products of Water with Si While kamacite usually alters in the presence of S-rich water, we determine that S-rich water is not the only microchemical environment on CM meteorites. We propose that the cronstedtite adjacent to kamacite is the result of a Si-rich microchemical aqueous environment. Cronstedtite is not commonly associated with kamacite, but is usually located in type-II chondrules (Hanowski and Brearley 2001). Thus, the detection of cronstedtite associated with kamacite is surprising. Our data show several examples of cronstedtite replacing kamacite (Fig. 5.25). The abundance of Fe in the cronstedtite also indicates a different petrogenesis for the kamacite-associated cronstedtite compared to cronstedtite in type-II chondrules. Ferric iron can substitute for Si in cronstedtite tetrahedral sites. The extent of Fe substitution is described by a variable x in the formula for cronstedtite, 2+ 3+ 3+ (Fe3"x Fex )(Fex Si2"x )O5 (OH) 4 . The average value for x in typical cronstedtite is 0.62. For the cronstedtite-rimmed kamacite grain (Fig. 5.25a) the x value is higher, 0.74. The ! cronstedtite from a type-I chondrule (Fig. 5.25b) has an x value of 0.67, which is still above the average for cronstedtite. The conversion of kamacite into cronstedtite requires the altering fluid to contain aqueous silica (Eq. 5.1). A value for x of 0.66 provides the best match to our observed data and balances the reaction equation. The source of Si to form cronstedtite may be the decomposition of fayalite (Tomeoka and Buseck 1985; McSween 1987). 171 + + 11Fe + 4SiO2 + 19 H 2O ! 3(( Fe 2 + 2.33 Fe.366 )( Fe.366 Si1.33 )O5 (OH ) 4 ) + 13H 2 (5.1) 5.5.1.3 Alteration Products of Water with Limited Reactive Components The final microchemical environment we discuss is one in which the water has neither S nor Si. If kamacite is exposed to water with limited sulfur and silicon, then it will convert into a nickel-bearing iron oxide rather than tochilinite. Such chemical alteration into magnetite was identified previously (McSween 1979; Metzler et al. 1992). As noted in section 5.4.7, Ni is always present when iron oxide is associated with kamacite. Thus, we suggest that iron oxide grains that contain Ni are kamacite grains that have been fully altered. We have also detected iron oxide grains that do not appear to have come from the alteration of kamacite because they lack Ni (Fig. 5.34). It is likely that these grains formed from precipitated Fe, as suggested by Metzler et al. (1992). The Fe that precipitates as magnetite could be generated by the alteration of kamacite to tochilinite (see section 5.5.1.1). Magnetite could also be generated by the serpentinization of fayalite (Eq. 5.2) (Deer et al. 1982). Decomposition of fayalite would also provide Si for cronstedtite-formation reactions. 3Fe2 SiO4 +2H 2O " 2Fe3O4 +3SiO2 +2H 2 (5.2) ! 172 Figure 5.34: O/Ni/Fe ternary phase diagram The O/Ni/Fe phase diagram (in wt%) shows a series of EMPA analysis falling on a mixing line between kamacite and oxygen. Additionally, there is a clustering of iron-oxide grains that contain virtually no Ni, suggesting that they are formed by the precipitation of magnetite. Ni-deficient grains of iron oxide do not always denote formation by precipitation. We analyzed a large chondrule that has a layer of small Ni-deficient iron oxide grains that form a rim around the silicate chondrule (Fig. 5.35). The chondrule and the iron oxide grain rim are encased by a typical fine-grained dust rim that is also Fe-poor. The absence of Ni suggests that these grains are not altered kamacite. Similar oxide grains were detected in the fine-grained rim of Y-791198 (Chizmadia et al. 2008). While Y791198 grains have typical Ni/Fe ratios and are likely to be altered kamacite, ours are severely lacking in Ni with a composition of Fe 59.42 wt% and Ni 0.17 wt% (detection limit: 0.08 wt%). The fine-grained dust rim is compositionally distinct from the matrix. The silicates in the dust rim have 4.1 wt% higher Si, 4.8 wt% higher Mg and 8.0 wt % lower 173 Fe content than the surrounding matrix. The chemical heterogeneity between the matrix and the dust rim indicates that the extent of aqueous alteration was limited for this chondrule. Given these observations, it is difficult to develop a mechanism that would precipitate iron oxide preferentially on the chondrule margin rather than homogeneously throughout the rim. We suggest that the chondrule passed through a region of the solar nebula rich in iron oxide particles that accreted onto its surface. Then the chondrule traveled through a different reservoir containing the typical small-grained dust. We suggest this history because it is unlikely that the iron oxide grains were produced by precipitation from a fluid. 174 Figure 5.35: Magnetite rich dust rim This large chondrule has a large multi-component dust rim. The inner rim is comprised of iron oxide without Ni (magnetite), while the outer rim is a more typical silicate dust rim. It is possible that the chondrule passed through a region where it collected small blebs of magnetite before it passed through the more typical dust that forms its outer dust rim. The large kamacite bleb in the chondrule is embedded with S, but only has trace alteration and has not been converted into tochilinite. (Murray #1, chondrule R6E) 175 5.5.2 Indicators for Post-Accretion Parent-Body Alteration One of the most common theories for aqueous alteration is that it occurred on the parent body after accretion (Kerridge and Bunch 1979; McSween 1979; Hanowski and Brearley 2001; Brearley 2004, 2006). In support of this theory, we see several indicators that there was aqueous alteration after the parent body formed. These indicators include chondrule-associated tochilinite that breaches its dust rim and incises into the matrix, and equilibrium between hydrous phases in chondrules and the matrix. We also have identified chondrules that are asymmetrically altered, a result that could not occur within the solar nebula. 5.5.2.1 Tochilinite growth into matrix The formation of tochilinite produces features that can help establish the relative times of formation or alteration for features surrounding the tochilinite. As kamacite is altered, the resulting tochilinite expands and sometimes forms veins. Anything that these veins react with or cut through must have been present before aqueous alteration. For example, a tochilinite assemblage that breaches its dust rim and extends into the matrix denotes that the matrix was present before alteration. If alteration had instead occurred while the mineral assemblage was free-floating in the solar nebula, the tochilinite would have interacted only with the mineral assemblage and its dust rim. Interaction between mineral assemblages and the matrix is strong evidence that alteration occurred post-accretion. We have identified two kamacite grains that were altered into tochilinite and expanded out of the chondrule, breaching the dust rims and 176 interacting with the matrix (Figs. 5.13a & 5.36). The grain depicted in Fig. 5.36a has a single vein that breaches the dust rim and intrudes into the matrix. Another grain, which is depicted in Fig. 5.36b, has a vein that extends over 150 µm into the matrix, with smaller veins branching out. 5.5.2.2 Regional alteration Another line of evidence that alteration occurred on the parent body is a consistent degree of alteration (Brearley 2006). We identified a clear example of this equilibration in Murray, Study Region R8I, depicted in Fig. 5.37. The altered portion of Study Region R8I, outlined in white in Fig. 5.37, has clear indications of extensive aqueous alteration: the kamacite blebs within all chondrules have been altered into tochilinite, small anhydrous silicate grains in the matrix have been altered into phyllosilicates, and the S content between TCI grains and the matrix has been homogenized. The spatial extent of this advanced alteration is limited in size, about 1 mm2, and has a discernable border. 177 (a) (b) Figure 5.36: Indications of parent body alteration The alteration of kamacite into tochilinite, and the expansion of the resulting tochilinite. Fig. 5.36a is a close up of Fig. 5.13a where tochilinite breached the dust rim and began to extend into the matrix. Fig. 5.36b is a close up of Figure 5.13b and shows a tochilinite grain that has breached its dust rim and cut into the matrix for 150 µm. These tochilinite veins cut into the matrix near TCI grains, with both phases (tochilinite and TCI) remaining discrete. Because these two grains are so close, it is unlikely that they experienced different microchemical environments. This suggests that TCI grains were either not formed from kamacite, or they were formed at a different time and in a different way. (a - Murray #1, chondrule 4, b - Murray, chondrule A) 178 Figure 5.37: Study Region R8I - Indications of parent body alteration The area outlined in white denotes material that has been homogenously alerted. This altered region has all its kamacite blebs converted into tochilinite, the TCI grains have equilibrated with the rest of the matrix, and small matrix grains have been converted into phyllosilicates that are no longer recognizable as individual minerals. The material outside of the white has little to no alteration. This unaltered material has many kamacite grains that are pristine, TCI grains remain distinct from the matrix, and there remain numerous small silicate grains in the matrix. The alteration boundary is not a sharp line, but a lobate flow front, suggesting that it is not the result of brecciation. (Murray #1, R8I) 179 Consistent degree of alteration alone does not exclude nebular alteration because the chondritic material could have been altered prior to accretion. To exclude nebular alteration, we must show that some chondritic material had a lower degree of alteration than it does currently. One method is to look for veins of tochilinite (see section 5.5.2.1). Another method is to evaluate the degree of alteration of nearby material. X-ray maps show that the material surrounding the altered portion of Study Region R8I (the area outside the white line) does not have the same systematic indicators of widespread alteration (Fig. 5.37). There remain numerous unaltered kamacite blebs in chondrules. The matrix has many small silicate grains that have not been altered. The TCI grains maintain their chemical distinction from the matrix, which can be seen by their higher concentration of S. Finally, we have detected several small, unprotected kamacite grains (3 to 6 µm wide) in the matrix that remain pristine. It is therefore highly unlikely that the surrounding material has experienced aqueous alteration on the parent body. The juxtaposition of homogenously and heterogeneously altered regions indicates two things. First, alteration occurred post-accretion for the circled material of Study Region R8I. It is highly improbable that nebular processes would have been able to alter such a selective grouping of material. Second, we note that parent body alteration on Murray and Murchison was not widespread, but focused spatially. Homogenous alteration that is surrounded by heterogeneously alteration indicates that that there was pockets where water was limited and could only homogenize nearby material. 180 Brearley (2006) suggests that microchemical environments play a major role in the alteration processes that occur on CM chondrites. Our data support this theory in regards to both the content and volume of the water. Each pocket of homogenous alteration can be its own microchemical environment. Thus, slightly altered meteorites have many physically separate microchemical environments, which result in high or low alteration depending upon the localized water content. By comparison, highly altered meteorites have alteration signatures that are more consistent among mineral assemblages. These alteration signatures indicate abundant water interacted over large distances and generated homogenous alteration. Such expansive alteration would also have the effect of erasing indications of pre-accretional alteration as suggested by Brearley (2006). We considered the suggestion that the two different degrees of alteration are simply due to brecciation, i.e. the two regions are different clasts that experienced different degrees of alteration. However, in contrast to the sharp boundaries characteristic of breccia clasts (e.g., Murchison, Fig. 5.38a), the alteration boundary in Murray is not sharp and distinct (Fig. 5.38b). The alteration boundary appears like a flow front with lobate edges that wrap partially around mineral assemblages and has a graduated drop off in alteration features over a short distance. The mineral assemblages that are along the alteration boundary are neither fractured nor have broken dust rims. In addition, some have more alteration on the side facing the alteration. We suggest that brecciation is unlikely because the alteration boundary does not have the characteristics that typically define breccia clasts. 181 (a) (b) Figure 5.38: Breccia clast vs. alteration boundary a) A breccia clast in Murchison where its border is clear. There are sharp linear features, the matrix is compositionally and texturally different, and there are chondrules that are fractured along the breccia boundary. b) The alteration boundary (context image Figure 5.37). One can see that the fractured nature is missing. 182 Adjacent chondrules with two different degrees of aqueous alteration in Murray provide additional evidence for parent-body alteration. Chondrule D (left) shows indications of extensive alteration with all its kamacite converted into tochilinite, while Chondrule E (right) has kamacite blebs with different degrees of alteration, including some that are pristine (Fig. 5.39). Differing degrees of kamacite alteration on a single chondrule are unlikely to occur in the solar nebula because all exposed kamacite surfaces would experience the same conditions. These differing degrees of alteration are consistent with parent body alteration where a limited amount of water would convert only the closest kamacite before being consumed. We consider this to be compelling evidence that alteration had to occur on the parent body, that these variations cannot be due to brecciation, and that inhomogeneity of alteration is due to a limited spatial extent of water. Figure 5.39: Localized parent body alteration Chondrule E (right) has several kamacite blebs that are in direct contact with the matrix. One side of the chondrule has a partially altered kamacite grain while the other side is pristine, suggesting that it was not altered in the solar nebula. Also, it indicates that parent body alteration was localized such that there were regions where water was depleted before it homogenously altered the kamacite grains. This is a feature seen only in slightly altered meteorites. (Murray #1, chondrules D&E) 183 5.5.3 Indicators for Pre-Accretion Parent-Body Alteration While there is strong evidence for parent body alteration, there are also observations that are not well explained by that model. Slightly altered meteorites have mineral assemblages with different amounts of alteration that should not coexist if alteration occurred on the parent body. We focus on disequilibrium between components to identify non-parent body alteration. One of the strongest indicators of parent body alteration is homogeneity of alteration. There should be a high consistency in the style and degree of aqueous alteration of components if the alteration occurred on the parent body (Brearley 2006). As such, unaltered kamacite should be surrounded by an anhydrous matrix, or at most, matrix that is only slightly altered. We studied the distribution of tochilinite, TCI, and kamacite to evaluate how homogenous alteration was. Tochilinite is formed from the alteration of kamacite (MacKinnon and Zolensky 1984). TCI grains are suggested to form by further aqueous alteration of kamacite or silicates that are infused with large amounts of Fe (McSween 1979; Tomeoka and Buseck 1985; Lauretta et al. 2000; Brearley 2006). While we used the presence of pristine kamacite near TCI as an indicator of disequilibrium, there are some questions surrounding the petrogenesis of TCI that may invalidate this technique. Zolensky (1993) has suggested that TCI grains may be a byproduct of some other precursor material, rather than kamacite. These hydrous alteration products of kamacite 184 (tochilinite and TCI) should not be present near unaltered kamacite; however, this is not the case in our thin sections. Our data show that every unaltered kamacite grains in close proximity to heavily hydrated surrounding matrix (Fig. 5.40). We conducted a survey of all high-Z grains surrounding a large unaltered kamacite grain to identify all kamacite aqueous alteration products. Within a short distance in every direction, there are grains that are either TCI or tochilinite, with about three times as many TCI grains as tochilinite (Fig. 5.41). To quantify the scope of heterogeneous alteration, we evaluated the average distance between kamacite and TCI grains for 16 mineral assemblages containing pristine kamacite. We chose kamacite surfaces that were exposed to the matrix or dust rim to ensure that coherent silicates did not protect the kamacite from alteration. The average distance was 24.8 µm between an unaltered kamacite surface and the nearest TCI grain. Additionally, out of the 46 individual kamacite surfaces evaluated, 15 were separated from a TCI grain by distances of less than 10 µm. Similar results are obtained even if we exclude TCI and focus on kamacite-derived tochilinite only. Thus, it is clear that the kamacite grains are clearly out of equilibrium with their surroundings. 185 Figure 5.40: Kamacite near tochilinite Image (a) shows a large TCI grain with several small kamacite grains directly adjacent to it. Image (b) shows another region of disequilibrium where the matrix has a large number of TCI grains along with an unaltered kamacite grain. The degree of inhomogeneity suggests that TCI grains formed before final accretion. 186 Figure 5.41: Kamacite and hydrated matrix This BSE image shows several exposed kamacite surfaces that are pristine or have trace alteration on their rims. We analyzed all high-Z grains in the surrounding matrix and identified the hydrated phases in proximity showing anhydrous kamacite is out of equilibrium with the hydrous matrix. The red circles are TCI grains, while the blue circles are tochilinite grains. (Murray #1, chondrule 1) The consistency of hydrous high-Fe phases in the matrix indicates that the matrix was subjected to aqueous alteration while the kamacite grains were not. It is difficult to hypothesize a process that would alter some kamacite into tochilinite (or even further to TCI), while leaving nearby kamacite grains unaltered. It is more likely that the formation of TCI and tochilinite occurred before the final parent body accretion; otherwise, the neighboring kamacite grains would also have been altered. Further, after parent body accretion, the areas surrounding the pristine kamacite did not experience any significant interactions with water. 187 An additional line of evidence for hydration prior to parent body accretion is that tochilinite is commonly in proximity with TCI grains. TCI and tochilinite should not form together in the same microchemical environment. Figure 5.36 shows two different hydrous phases, tochilinite and TCI, that denote different levels of aqueous alteration in proximity with one another. One might suggest that different microchemical environments would be responsible for one kamacite grain altering into tochilinite, while another would become TCI. While different microchemical environments should be expected on the parent body, the proximity of these two phases makes this unlikely. It is more plausible that TCI formed at a different time and place. We rule out the possibility that these variations are due to brecciation. We searched for signs of brecciation to determine if the area around Chondrule 1 was brecciated. Figure 5.42 is an Fe/Ni/S X-ray map of Murray #1, Chondrule 1 and the surrounding matrix. The matrix contains both hydrous minerals (tochilinite and TCI), as well as small anhydrous minerals (kamacite) that are in contact with the matrix. The large number of unbroken dust rims and the lack of either sharp fracture lines or variation in the matrix's bulk chemical makeup indicate that this region is a single, unbrecciated host rock. The area surrounding Chondrule 1 does not appear to have experienced any brecciation after the chondrules and the clastic matrix accreted to form the parent body. From the absence of brecciation, we conclude that such extreme variation in the degree of alteration between the kamacite and the matrix requires that the hydrated materials were altered prior to parent body accretion. 188 (a) (b) Figure 5.42: Nebular alteration of matrix material Image (a) shows numerous kamacite grains that are in direct contact with the matrix. Figure 5.39 shows the large number of hydrated phases that have been confirmed by EMPA. Image (b) has outlined the dust rims for the suite of chondrules in this image. We suggest that this region is not brecciated because that would have disrupted the dust rims. The kamacite is clearly out of equilibrium with its matrix. 189 5.5.4 Model for alteration Because we have strong indicators of both pre-accretional and post-accretional aqueous alteration, we suggest that there were two distinct alteration events. The first episode of alteration created a hydrated clastic matrix, commonly called a regolith breccia. The alteration process began with the formation of type-I chondrules that contain kamacite blebs. Once formed, many of the chondrules were subjected to alteration, forming tochilinite and TCI grains (Tomeoka and Buseck 1985; MacKinnon and Zolensky 1984). This alteration occurred either in the solar nebula or in a precursor planetesimal (Metzler et al. 1992; Bischoff 1998). The conversion of kamacite into hydrated minerals reduced the physical strength of the chondrules, making them susceptible to shattering (Tomeoka and Buseck 1985). It is problematic to have alteration exclusively within the solar nebula because the reaction rates are low at the expected pressure and temperature conditions (Fegley and Prinn 1989; Metzler et al. 1992). Interactions with shock may provide an environment that could drive the alteration reactions (Ciesla et al. 2003). Alternatively, a precursor planetesimal could provide favorable conditions for alteration (Metzler et al. 1992). This planetesimal had to be catastrophically destroyed in order to liberate the hydrated material for re-accretion into the final CM parent body. Regardless of which mechanism alters the material, it is clear that the matrix already contained hydrated clastic minerals when the CM parent body formed. The second episode of alteration occurred after CM parent body formation. This body accreted chondritic material that was a mixture of pristine chondrules, clastic 190 silicate fragments, hydrated matrix (including TCI and tochilinite), and ice. After accretion, the ice melted and interacted with the material around it. Areas where there was abundant water would be saturated and show homogenous features including fully altered kamacite, as seen in Cold Bokkeveld and Nogoya. All traces of pre-accretional alteration would be lost. If instead there was limited water, then there would be a high degree of inhomogeneity of alteration, such as seen on Murray and Murchison (Fig. 5.37). These results are consistent with previous suggestions of multiple alteration events. Clayton et al. (1977) performed oxygen isotope analysis on Murchison, but had difficulty explaining the oxygen isotope distribution in CM chondrites using a simple mixture of matrix and anhydrous material. The oxygen signature in the matrix is different enough from the signature in the chondrules that Clayton et al. (1977) concluded that the matrix could not be formed from the chondrules alone. Clayton and Mayeda (1984) proposed a model that has two different reservoirs and two separate events of alteration. Their data are consistent with a model that contains two fluid-solid interactions, one low temperature and one high temperature. They suggest that the formation of phyllosilicates occurred at low temperature (less than 20° C) and with a high water to rock ratio, at least 44%. This low temperature alteration is consistent with our determination of a highly altered matrix. Also, they suggest another alteration event that alters the anhydrous silicates, which may or may not be the parent body alteration that we detected. Further work is needed to see if the oxygen isotope signatures from parent 191 body alteration, such as tochilinite from type-I chondrules, are consistent with a mixture of hydrous and anhydrous phases. 5.6 Conclusion By using kamacite as an indication of the initial stages of aqueous alteration, we were able to decipher a part of the complex history of CM chondrites. We conclude that alteration on CM meteorites occurred within at least three microchemical environments. These environments can be identified by their products and their textural characteristics (Fig 5.28). The most common alteration microchemical environment is one in which Srich water reacts with kamacite forming tochilinite. Minor elements in kamacite (Cr, P and Co) are not compatible with tochilinite leading to the formation of the following accessory phases: P-rich sulfides, eskolaite and schreibersite. Water that is instead rich in Si will convert kamacite to cronstedtite. We note several examples, typically in type-I chondrules, but also in an isolated kamacite grain. Finally, if water lacks significant S and Si, kamacite corrodes to form magnetite with residual Ni. This residual Ni differentiates this magnetite from magnetite that formed from precipitation of aqueous Fe. We additionally conclude that there were two alteration events on CM chondrites, one that was pre-accretional and one that was post-accretional. The first alteration event is most evident in the less altered meteorites Murray and Murchison. Their clastic matrix is highly altered and out of equilibrium with neighboring anhydrous chondrules. This indicates that the matrix was altered before parent body formation. The observed 192 alteration may have occurred in the solar nebula or on a precursor planetesimal that was disrupted. The second alteration event occurred after the parent body formed. Parent body alteration is indicated by a consistent level of alteration among the chondrules and the matrix. Its effects have erased most traces of previous alteration in highly altered meteorites such as Nogoya and Cold Bokkeveld. Alternatively, on less altered meteorites, alteration is localized. Localized alteration can be identified by regions that are homogenously altered surrounded by less altered material. The juxtaposition of different levels of alteration between two adjacent regions demonstrates two things. First, the alteration occurred on the parent body. Second, the alteration was inhomogeneous resulting from a limited amount of water. The water was heterogeneously distributed and consumed before reaching all components equally. 193 CHAPTER 6 CONCLUSION We pursued NASA's goal of unraveling the history of a few solar system objects. We focused on two case studies that revolved around volatiles in the solar system. We examined CO2 on Iapetus and aqueous alteration in CM meteorites. The recent detection of CO2 on Iapetus is not well explained by previous theories that assume CO2 is primordial. Our expanded analysis of thermal stability was unable to increase the residence time of CO2 frost such that it would remain long enough to be observed. As such, we determined that CO2 must be complexed with the dark material. However, unless shielded, UV photodissociation destroys complexed CO2 at a rate that would deplete the entire observed inventory in just over half an Earth year. Because CO2 is detected in substantial quantity, there must be an active source. The ease with which CO2 is produced by amorphous carbon and water, both of which are common in the outer solar system, indicates that UV photolysis could be the source of CO2. Additionally, the extrapolated production rate is close to the theoretical destruction rate, which is strong evidence that the system is in steady state between the formation and destruction of CO2 by UV radiation. Finally, we suggest that other volatiles, such as O2, CO, H2O2 and O3, may actually be produced in-situ on the Saturnian and Jovian satellites. This is important when evaluating the chemistry of outer solar system surfaces. While the production of CO2 is ongoing, we also studied a process that has been complete for 4.6 Ga. By using kamacite and its alteration products as an indication of the initial stages of aqueous alteration, we were able to decipher a part of the complex history 194 of some CM chondrites. We conclude that aqueous alteration on CM meteorites occurred within at least three microchemical environments: water with S, water with Si and water without substantial reactive components. When kamacite is subjected to interactions with water, it breaks down and forms tochilinite, cronstedtite, or magnetite. We also determined that sulfur associated alteration can form the accessory minerals P-rich sulfides, eskolaite and schreibersite. We additionally conclude that there were two alteration events on some CM chondrites, one that was pre-accretional and one that was post-accretional. The first alteration formed a highly altered matrix prior to accretion. This is indicated by unaltered kamacite in proximity to a hydrous matrix. It remains unclear if the matrix hydration occurred directly in the solar nebula or in a planetesimal that was disrupted. The second alteration event occurred after the parent body formed. We identified a 1mm region in which all components experienced the same degree of alteration, but is surrounded by material that displays a wide range of alteration levels. The juxtaposition of homogenously and heterogeneously altered regions indicates localized parent body alteration. Additionally, it suggests that the localized alteration was due to limited water that was unevenly distributed and consumed before reaching all components equally. 195 APPENDIX A FULL LISTING OF EMPA DATA A.1 Hydrated Chondrule-Associated Cronstedtite Murray 15-n 15-o 16-s 19_c 4_GG_light 4_HH_light 4-4g 4-4j 4-4k1 4-4l 4-4o 4y 6-4c_lt 6-4e 6-4f_lt 6-4l 6b 6b 6e 6m_line 6m_line 6m_line 6m_line 6m_line 6m_line 6m_line 6m_line 6m_line 6m_line 6m_line 8e 8f 8g 8h 8i 9o 9o_2 C-l C-m-dk C-o Mry1-5RA-a Mry1-6RA-a Mry1-6RA-e Mry1-6RF-a Mry1-6RF-b Mry1-Ch11-d8-f Mry1-Ch15-a Mry1-Ch15-b Mry2-ChE-d8-g Mry2-ChE-d8-h Mry2-F-i Mry-A-d Mry-A-j Average Std Dev Murchison Murch-ChF-d8-d Murch-Ch-G-c Murch-Ch-G-e Murch-F-c Murch-F-c Murch-F-f Si Fe Mg Ni S O Ca 10.50 36.22 3.73 0.08 0.21 40.23 0.06 13.03 32.35 3.94 0.05 0.17 40.05 3.09 10.38 39.51 3.98 0.07 0.16 37.24 0.21 9.88 34.38 2.41 0.04 0.19 40.24 0.35 10.26 36.62 3.73 0.06 0.15 41.24 0.26 9.24 40.14 2.53 0.04 0.06 38.35 0.07 9.11 35.26 2.43 0.06 0.14 38.36 0.15 9.21 34.36 2.49 0.21 0.74 40.34 0.17 9.68 39.63 2.76 0.10 0.05 40.29 0.10 9.75 42.19 3.35 0.05 0.02 38.04 0.05 9.79 41.12 2.63 0.06 0.03 40.06 0.10 10.91 38.20 3.11 0.09 28.34 0.55 8.82 34.97 2.62 0.21 0.14 42.97 0.15 9.71 40.00 3.28 0.12 0.04 39.53 0.10 9.31 43.64 2.51 0.00 0.02 38.09 0.06 8.98 42.28 3.30 0.06 0.04 38.45 0.05 10.68 37.30 3.53 0.00 28.72 0.18 9.17 30.60 2.64 0.00 28.87 0.30 9.26 38.52 2.59 0.11 27.55 0.13 9.39 43.22 2.51 0.02 25.86 0.09 9.51 43.45 2.77 0.02 26.41 0.08 10.33 40.47 2.90 0.02 26.74 0.13 10.22 42.26 2.81 0 26.99 0.16 9.81 43.28 3.27 0.02 27.07 0.10 10.22 39.79 3.51 0.00 27.22 0.09 10.12 42.82 3.32 0.02 27.42 0.31 10.09 41.99 3.34 0.00 27.61 0.15 10.51 39.99 3.62 0.00 28.31 0.22 10.83 37.48 3.77 0.01 28.68 0.26 10.64 34.44 3.88 0.01 30.24 0.20 10.15 41.62 2.27 0.03 26.88 0.06 9.92 40.67 2.44 0.00 27.34 0.08 9.81 40.10 2.35 0.06 27.20 0.09 10.39 39.98 3.31 0.00 27.84 0.07 9.65 37.73 2.94 0.03 26.29 0.08 10.06 39.59 3.90 0.04 27.39 0.06 9.12 40.77 3.74 0.1 25.65 0.07 8.99 45.34 1.72 0.04 0.02 38.89 0.04 11.48 35.99 3.35 0.04 0.08 41.75 2.18 9.22 38.54 3.47 0.04 0.42 39.08 0.11 10.49 36.77 3.53 0.02 0.17 27.92 0.13 10.70 38.02 3.92 0.06 0.16 28.37 0.16 10.63 39.03 4.37 0.01 0.04 27.91 0.10 10.98 33.44 4.85 0.00 0.17 30.12 0.30 11.41 33.92 5.09 0.02 0.16 30.15 0.08 8.78 47.92 1.23 0.15 0.05 36.01 0.07 10.11 40.54 2.62 0.10 0.07 38.40 0.07 9.93 38.72 2.89 0.04 0.14 40.76 0.03 9.69 38.38 3.06 0.06 0.20 37.56 0.17 9.99 39.35 2.72 0.00 0.15 38.42 0.35 10.99 38.67 5.35 0.05 0.18 41.35 0.60 9.45 43.41 1.93 0.05 0.03 37.92 0.08 9.31 39.20 3.48 0.02 0.21 37.76 0.20 10.01 39.14 3.17 BDL 0.14 33.41 0.25 (0.78) (3.40) (0.79) (0.14) (5.99) (0.50) Al 3.36 2.67 1.18 6.41 4.15 2.87 6.01 7.26 3.26 0.99 2.56 2.74 7.47 2.41 1.22 0.91 3.63 8.48 4.42 1.05 1.25 1.33 1.31 1.22 1.84 1.25 1.87 2.45 3.13 6.03 1.91 2.92 3.16 2.32 2.65 2.04 1.02 1.01 2.43 2.47 3.10 2.62 1.71 4.77 4.10 0.56 2.83 3.62 3.28 3.02 2.07 1.93 2.25 2.88 (1.78) Mn P Cr Ti Co Cu Total 0.18 0.01 0.03 0.00 0.00 94.59 0.17 0.03 0.06 0.00 0.02 95.63 0.17 0.01 0.15 0.00 0.03 93.10 0.16 0.02 0.10 0.00 0.04 94.21 0.11 0.01 0.09 0.04 0.02 96.87 0.11 0.04 0.07 0.01 0.00 93.65 0.14 0.01 0.11 0.00 0.00 91.79 0.16 0.07 0.16 0.00 0.01 95.17 0.12 0.00 0.09 0.00 0.00 96.08 0.11 0.00 0.09 0.00 0.00 94.64 0.17 0.01 0.08 0.00 0.02 96.62 0.12 0.07 0.12 0.05 84.40 0.17 0.01 0.15 0.00 0.00 97.68 0.12 0.00 0.12 0.00 0.12 95.54 0.14 0.01 0.06 0.01 0.01 95.08 0.07 0.00 0.08 0.02 0.02 94.24 0.14 0.02 0.07 0.12 84.56 0.18 0.05 0.04 0.07 80.64 0.15 0.03 0.11 0.05 83.16 0.10 0.01 0.08 0.06 82.48 0.10 0.02 0.05 0.04 83.84 0.11 0.06 0.04 0.04 82.36 0.13 0.01 0.06 0.06 84.15 0.09 0.04 0.07 0.08 85.17 0.16 0.03 0.08 0.03 83.13 0.10 0.01 0.08 0.10 85.70 0.14 0.02 0.08 0.05 85.43 0.16 0.04 0.06 0.09 85.59 0.16 0.02 0.10 0.06 84.70 0.17 0.03 0.12 0.04 86.05 0.12 0.02 0.09 0.04 83.29 0.10 0.02 0.10 0.00 83.71 0.12 0.00 0.05 0.04 83.11 0.11 0.11 0.05 0.04 84.36 0.12 0.00 0.06 0.07 79.74 0.12 0.04 0.05 0.03 83.45 0.12 0.04 0.02 0.05 80.79 0.09 0.00 0.07 0.00 0.00 96.21 0.12 0.02 0.15 0.00 0.00 97.59 0.11 0.01 0.11 0.00 0.00 93.59 0.11 0.00 0.03 0.03 0.06 82.46 0.11 0.00 0.07 0.03 0.02 84.35 0.09 0.01 0.09 0.04 0.00 84.10 0.13 0.01 0.00 0.32 0.00 85.20 0.16 0.00 0.07 0.17 0.05 85.48 0.10 0.01 0.08 0.05 0.00 0.03 95.02 0.14 0.04 0.03 0.06 0.04 0.00 95.07 0.14 0.02 0.03 0.12 0.00 0.00 96.45 0.17 0.00 0.12 0.10 0.00 0.00 92.77 0.16 0.01 0.03 0.13 0.00 0.05 94.39 0.13 0.04 0.15 0.00 0.00 99.57 0.13 0.01 0.07 0.00 0.00 95.01 0.14 0.03 0.29 0.01 0.00 92.91 0.13 BDL 0.08 0.07 BDL BDL 89.34 (0.03) (0.05) (0.06) (5.97) Si Fe Mg Ni S O Ca Al Mn P Cr Ti Co Cu Total 9.03 36.50 3.37 1.37 3.49 38.22 0.28 0.67 0.18 0.16 0.06 0.03 0.12 0.01 93.47 8.47 35.10 4.72 1.45 3.70 36.87 0.35 0.96 0.27 0.21 0.25 0.02 0.04 0.00 92.41 9.21 37.15 4.05 1.04 1.92 34.66 0.32 2.07 0.21 0.20 0.19 0.00 0.09 0.10 91.21 9.00 41.00 3.00 1.00 3.00 37.00 0.00 1.00 0.00 0.00 0.00 0.00 0.00 94.00 8.64 40.87 2.58 0.96 2.88 37.30 0.24 0.53 0.18 0.13 0.06 0.03 0.06 94.45 6.21 38.75 4.00 2.89 4.39 29.92 0.39 0.55 0.21 0.50 0.85 0.16 0.32 89.15 196 Murch-F-q Murch-F-q-ify Murch-G-d Murch-G-e Murch-G-g Average Std Dev Cold Bokkeveld Cold-C-d Cold-C-f Cold-C-i Cold-C-P Cold-E-w Cold-F-b Cold-F-c Cold-G-c Cold-G-f Cold-G-g_lt Cold-J-a Average Std Dev 6.36 7.22 8.88 9.44 8.41 8.26 (1.14) 41.17 3.05 1.26 37.88 3.24 2.33 36.01 5.45 1.41 36.31 4.67 1.13 37.04 4.76 0.97 37.98 3.90 1.44 (2.17) (0.92) (0.62) 3.80 3.62 3.31 1.84 4.27 3.29 (0.84) 33.06 0.27 35.46 0.29 36.93 0.35 38.53 0.32 35.16 0.76 35.74 0.32 (2.52) (0.18) 0.70 0.60 0.95 1.96 2.50 1.14 (0.70) Al 0.46 0.36 0.36 0.58 2.34 3.24 0.65 1.56 1.44 2.04 2.24 1.39 (0.98) 0.36 0.19 3.95 0.18 0.31 0.15 0.25 0.18 0.21 0.19 0.16 0.17 0.17 0.21 0.09 0.20 0.20 0.54 BDL (0.09) (0.12) (1.15) Mn P Cr Ti 0.32 0.08 0.62 0.41 0.10 0.54 0.30 0.09 0.32 0.79 0.49 8.60 0.12 0.00 0.09 0.12 0.03 0.07 0.20 0.00 0.16 0.17 0.01 0.37 0.15 0.01 0.26 0.15 0.00 0.30 0.16 0.01 0.46 0.26 0.07 1.07 (0.20) (0.14) (2.50) 0.06 0.21 0.19 0.06 0.00 0.04 0.00 0.09 0.02 0.06 BDL BDL 94.45 91.54 93.99 94.80 94.42 93.08 (1.79) Si Fe Mg Ni S O Ca 7.64 40.82 5.91 0.71 0.99 34.92 0.19 4.43 49.44 3.79 0.76 0.76 32.80 0.20 6.01 47.34 4.99 1.34 0.68 34.77 0.19 2.74 30.90 4.51 5.74 9.11 24.48 0.26 11.32 34.57 6.22 0.10 0.23 41.28 0.14 10.87 36.24 4.72 0.31 0.56 39.12 0.43 11.24 35.68 7.35 0.13 0.04 40.23 0.04 11.28 29.47 7.07 0.21 0.34 33.63 0.13 10.96 36.86 5.83 0.10 0.09 40.40 0.11 11.28 34.53 6.68 0.10 0.13 42.25 0.09 12.59 26.56 8.83 0.10 0.44 45.07 0.04 9.12 36.58 5.99 0.87 1.22 37.18 0.17 (3.34) (7.01) (1.46) (1.66) (2.64) (5.76) (0.11) Co Cu Total 0.02 0.00 92.68 0.00 0.00 93.59 0.03 0.05 96.47 0.16 0.03 88.37 0.00 0.04 96.44 0.04 0.02 95.76 0.00 0.00 95.73 0.01 0.00 84.26 0.00 0.04 96.26 0.01 0.02 97.58 0.02 0.07 96.59 BDL BDL 93.98 (4.14) Matrix-Associated Cronstedtite Murray 6j Mry1-6RA-l Mry2-5RA-e Average Std Dev Murchison Murch_A-i Murch-Ch-F-d8-i Murch-Ch-F-d8-j Murch-Ch-F-d8-l Murch-F-i Average Std Dev Si Fe Mg Ni S O Ca 7.22 34.08 4.64 1.53 25.08 2.45 8.32 44.74 1.76 0.06 0.07 0.14 9.61 39.28 3.65 0.07 0.32 0.05 8.38 39.37 3.35 0.55 0.20 25.08 0.88 (1.20) (5.33) (1.46) (0.85) (0.18) (1.36) Si Fe Mg Ni S O Ca 9.24 34.47 4.51 0.55 2.28 24.78 0.11 12.27 29.97 8.34 0.45 0.83 33.49 0.23 8.57 37.00 5.49 0.69 0.89 27.81 0.27 8.80 36.88 5.85 0.60 1.01 28.32 0.30 8.49 35.38 4.59 0.85 1.04 28.52 0.77 9.47 34.74 5.76 0.63 1.21 28.58 0.34 (1.59) (2.87) (1.55) (0.15) (0.60) (3.13) (0.25) Al 0.83 0.77 2.06 1.22 (0.73) Al 1.20 1.32 0.72 0.78 0.68 0.94 (0.30) Mn P Cr Ti Co Cu Total 0.12 1.19 0.18 0.02 77.99 0.07 0.00 0.04 0.06 0.00 0.04 56.08 0.15 0.00 0.03 0.03 0.00 0.01 55.27 0.11 0.40 0.08 BDL BDL BDL 63.11 (0.04) (0.69) (0.08) (12.89) Mn P Cr Ti Co Cu Total 0.12 0.03 0.09 0.01 0.00 77.38 0.29 0.12 2.02 0.28 0.06 0.00 89.68 0.28 0.20 1.59 0.44 0.00 0.00 83.94 0.33 0.18 1.48 0.36 0.00 0.00 84.89 0.26 0.35 1.43 0.00 0.00 82.36 0.26 0.18 1.32 0.36 BDL BDL 83.65 (0.08) (0.12) (0.73) (0.08) (4.44) Chondrule-Associated Serpentine Murray 15-i 16-hh 16-w 17-d 17-f 17-m 9_EE B-e-lt C-i C-j D-d F-ee F-ii F-oo H-g Mry1-ChE-d8-h Average Std Dev Murchison Murch-H-b Murch-H-e Murch-5RA-g Murch-5RA-h Murch-5RA-j Murch-5RA-k-dk Si Fe 15.23 20.27 10.53 30.00 9.77 34.99 12.35 29.15 12.88 27.11 12.46 25.84 11.59 34.31 13.24 26.51 9.62 27.22 9.02 24.57 10.10 31.09 14.90 21.58 15.45 25.70 10.76 32.11 14.51 26.96 9.06 32.40 11.97 28.11 (2.24) (4.22) Mg Ni S O Ca 10.03 0.03 0.75 44.25 0.07 5.06 0.50 2.88 40.00 0.10 8.16 0.31 5.32 33.70 0.30 12.33 0.08 0.28 35.49 0.42 13.51 0.06 0.21 32.11 0.35 7.81 1.83 4.44 34.01 0.28 4.38 0.15 0.26 39.63 6.86 0.04 0.23 41.98 2.34 5.00 0.35 1.22 33.51 0.19 9.25 2.32 1.52 29.01 0.08 7.29 0.07 0.13 34.17 0.04 9.75 0.10 1.09 35.88 0.85 9.47 0.05 0.30 40.82 0.81 5.54 0.05 0.46 31.80 1.38 8.96 0.03 0.04 39.82 1.62 6.23 1.16 4.17 32.12 0.28 8.10 0.45 1.46 36.14 0.61 (2.61) (0.70) (1.75) (4.37) (0.68) Al 1.38 1.79 1.14 2.04 1.26 1.38 3.14 4.02 6.34 1.98 0.80 2.54 3.08 1.99 1.37 2.64 2.31 (1.38) Mn P Cr Ti Co Cu Total 0.22 0.03 0.30 0.04 0.00 92.59 0.19 0.04 1.01 0.01 0.05 92.17 0.28 0.08 0.20 0.00 0.01 94.27 0.32 0.15 0.10 0.00 0.00 92.69 0.38 0.18 0.09 0.00 0.02 88.17 0.15 0.06 0.25 0.06 0.06 88.63 0.17 0.31 0.07 0.00 0.00 94.02 0.21 0.00 0.34 0.03 0.01 95.82 0.16 0.04 0.11 0.00 0.00 83.78 0.14 0.48 0.16 0.05 0.00 78.58 0.13 0.00 0.17 0.00 0.00 83.98 0.19 0.06 0.57 0.00 0.01 87.53 0.20 0.06 0.36 0.00 0.08 96.39 0.17 0.00 0.32 0.00 0.00 84.58 0.22 0.01 0.41 0.00 0.02 93.94 0.19 0.02 0.23 0.05 0.02 0.01 88.57 0.21 0.10 0.29 BDL BDL BDL 89.73 (0.07) (0.13) (0.23) (5.10) Si Fe Mg Ni S O Ca Al Mn P Cr Ti Co Cu Total 10.84 26.52 8.05 1.98 6.47 34.02 0.20 1.12 0.19 0.03 0.20 0.17 0.04 89.83 9.52 35.89 6.06 1.89 2.44 37.88 0.36 2.13 0.16 0.15 0.03 0.07 0.06 96.63 10.31 26.36 7.37 1.83 4.99 32.09 0.11 2.19 0.17 0.08 0.20 0.06 0.02 86.32 8.36 32.71 6.00 2.80 6.63 32.80 0.09 2.39 0.15 0.06 0.20 0.05 0.08 92.73 10.48 24.88 7.90 1.86 5.05 31.85 0.11 1.69 0.20 0.07 0.19 0.04 0.14 85.02 12.37 23.00 8.74 1.65 3.23 32.29 0.12 1.76 0.19 0.07 0.30 0.09 0.08 84.49 197 Murch-5RA-k-lt Murch-5RA-n Murch-5RA-o Murch-5RA-s Average Std Dev Cold Bokkeveld Cold-C-e Cold-C-g Cold-C-w Cold-C-x_dk Cold-C-x_lt Cold-C-x_med Cold-D-c Cold-D-d Cold-D-i Cold-D-p-dk Cold-D-p-lt Cold-E-e Cold-E-f Cold-F-d Cold-F-g Average Std Dev 8.96 10.48 13.10 10.87 10.53 (1.43) 34.52 6.30 2.66 31.95 7.50 1.56 23.88 9.61 1.96 25.93 8.02 1.69 28.56 7.56 1.99 (4.72) (1.18) (0.41) 6.02 4.31 3.14 5.06 4.73 (1.45) 33.00 0.32 32.49 0.13 33.83 0.38 33.30 0.18 33.36 0.20 (1.74) (0.11) 1.50 1.41 1.38 2.33 1.79 (0.45) Al 1.26 0.70 0.63 0.92 0.69 0.57 0.49 6.69 0.69 1.49 1.81 2.23 1.24 2.60 0.72 1.52 (1.57) 0.17 0.19 0.19 0.04 0.16 0.10 0.16 0.00 0.20 0.19 0.29 0.05 0.18 0.12 0.22 0.04 0.18 0.11 0.20 BDL (0.02) (0.05) (0.07) Mn P Cr Ti 0.25 0.12 1.04 0.36 0.10 0.36 0.23 0.17 0.33 0.29 0.03 0.94 0.31 0.04 0.69 0.35 0.08 0.65 0.12 0.02 0.31 0.21 0.00 0.40 0.23 0.44 1.85 0.23 0.01 0.70 0.21 0.03 0.62 0.19 0.00 0.19 0.17 0.02 0.81 0.18 0.10 0.23 0.13 0.00 0.19 0.23 0.08 0.62 (0.07) (0.11) (0.44) 0.12 0.06 0.11 0.07 0.09 BDL (0.04) 94.34 90.77 88.71 88.59 89.74 (3.98) Si Fe 13.96 20.80 10.19 36.93 9.83 38.89 13.98 18.99 10.84 28.19 9.15 37.29 15.94 10.26 11.86 24.26 9.49 32.77 13.46 25.09 12.80 25.82 11.41 32.69 6.78 35.40 10.17 31.07 9.35 36.98 11.28 29.03 (2.39) (8.16) Mg Ni S O Ca 12.69 0.59 0.59 46.17 0.32 9.36 0.75 0.59 42.85 0.14 8.19 1.57 0.69 40.61 0.11 12.28 0.59 1.56 42.25 0.06 8.73 0.60 0.87 37.84 0.09 7.53 0.66 1.14 38.17 0.11 18.60 0.19 0.33 39.43 0.08 7.48 0.08 0.69 41.43 0.17 5.50 1.92 2.29 39.44 0.11 10.52 0.21 1.33 40.45 0.85 9.24 0.14 0.44 35.52 0.61 6.45 0.06 0.27 40.71 0.18 6.45 2.66 10.35 29.10 0.39 6.61 0.60 3.18 41.41 0.40 6.69 0.41 3.93 33.60 0.05 9.09 0.74 1.88 39.27 0.24 (3.39) (0.75) (2.58) (4.11) (0.23) Co Cu Total 0.02 0.04 97.85 0.01 0.00 102.34 0.21 0.04 101.50 0.05 0.20 92.13 0.00 0.11 89.00 0.03 0.05 95.80 0.00 0.01 85.77 0.00 0.00 93.27 0.06 0.03 94.83 0.00 0.05 94.38 0.03 0.00 87.26 0.01 0.00 94.41 0.01 0.06 93.42 0.02 0.00 96.58 0.02 0.03 92.10 BDL BDL 94.04 (4.61) Matrix-Associated Serpentine Murray 12-n 13-i 13-n 1-4g 14-m 1-4o 3-4f 4h 4-h 4-n 4-o 9_Rim5 9_Rim6 9_Rim7 9_Rim9 A-k-dk A-m Mry1-5RA-M1 Mry1-5RA-M2 Mry1-5RA-M4 Mry1-5RA-M5 Mry1-5RA-M6 Mry1-5RA-M8 Mry1-5RA-M9 Mry1-6RA-M13 Mry1-6RA-M4 Mry1-6RA-M6 Mry1-6RA-M7 Mry1-6RE-M1 Mry1-6RE-M2 Mry1-6RE-M3 Mry1-6RE-M6 Mry1-6RE-M7 Mry2-5RB-M1 Mry2-5RB-M2 Mry2-5RB-M3 Mry2-5RB-M4 Mry2-C-r Mry2-C-s Mry2-F-D Mry2-G-h Si Fe Mg Ni S O Ca Al Mn P Cr Ti Co Cu Total 10.47 26.14 6.92 1.08 2.44 37.69 2.30 1.38 0.16 0.77 0.20 0.07 0.08 89.69 14.63 19.16 12.63 0.68 1.86 36.42 0.45 1.13 0.23 0.01 0.35 0.02 0.10 87.67 13.49 22.13 11.98 0.99 2.15 38.84 0.08 1.27 0.18 0.02 0.21 0.05 0.00 91.39 7.64 20.50 5.24 2.07 5.03 19.75 0.78 0.77 0.25 0.06 0.33 0.09 0.07 62.60 13.28 20.90 9.05 2.09 3.49 38.69 0.07 1.36 0.20 0.04 0.37 0.04 0.00 89.59 9.54 26.80 5.70 1.62 3.73 26.23 0.32 1.14 0.16 0.00 0.34 0.05 0.00 75.63 13.60 19.01 11.14 1.87 3.21 33.02 0.10 0.99 0.17 0.09 0.28 0.08 0.07 83.62 10.95 30.49 6.78 1.88 28.70 0.16 2.03 0.14 0.08 0.58 0.04 82.46 9.82 31.68 6.11 1.31 2.26 33.20 0.14 1.91 0.15 0.07 0.66 0.04 0.03 87.38 10.46 29.60 7.38 1.47 2.54 31.13 0.18 1.72 0.16 0.08 0.54 0.05 0.06 85.35 10.07 21.48 9.96 3.14 5.59 26.23 0.15 0.88 0.15 0.16 1.10 0.05 0.19 79.15 11.66 22.93 9.05 1.97 2.98 35.25 0.25 1.44 0.17 0.11 0.23 0.06 0.09 87.05 10.16 26.70 6.84 2.57 3.30 30.74 0.10 1.53 0.16 0.05 0.20 0.06 0.15 83.25 10.88 27.55 8.11 1.50 1.67 33.78 0.13 1.81 0.15 0.13 0.27 0.08 0.01 86.51 11.98 25.72 8.65 1.56 2.95 38.59 0.10 1.60 0.19 0.03 0.16 0.03 0.11 92.36 10.85 26.76 7.56 1.69 2.84 26.70 0.36 1.24 0.19 0.03 0.29 0.07 0.03 78.62 13.44 18.72 10.49 2.17 3.34 31.08 0.10 1.06 0.21 0.18 0.59 0.14 0.01 81.53 11.22 26.64 6.68 1.28 1.83 28.70 0.34 1.25 0.16 0.10 0.25 0.03 0.07 78.98 11.72 25.13 8.79 1.37 2.74 31.13 0.48 1.21 0.15 0.03 0.22 0.03 0.03 83.67 11.81 24.47 6.85 0.98 2.84 30.75 1.72 1.58 0.18 0.05 0.40 0.02 0.03 82.45 11.29 23.26 8.11 1.33 3.61 30.36 0.28 1.01 0.20 0.06 0.24 0.02 0.06 80.56 11.10 23.48 7.43 1.37 2.87 29.21 0.33 1.16 0.19 0.08 0.15 0.05 0.09 78.30 11.07 23.27 7.83 1.23 2.46 29.31 0.80 1.19 0.15 0.18 0.20 0.06 0.09 78.68 9.58 21.81 7.04 3.22 5.11 30.12 0.58 0.98 0.18 0.23 1.09 0.02 0.22 81.13 11.00 28.92 7.07 1.33 3.11 30.79 0.21 1.36 0.15 0.06 0.23 0.04 0.09 85.17 11.38 24.40 8.24 1.17 2.82 30.11 0.23 1.19 0.14 0.04 0.16 0.00 0.05 80.75 11.27 23.36 7.86 1.77 2.78 29.91 0.48 1.21 0.21 0.10 0.28 0.06 0.11 80.22 12.27 21.53 8.59 1.60 3.51 31.85 0.51 1.32 0.19 0.21 0.20 0.01 0.08 82.72 12.05 17.50 9.04 1.76 3.16 30.20 0.48 1.19 0.12 0.06 0.23 0.08 0.09 76.94 8.99 32.89 5.78 1.59 3.42 29.42 0.69 1.50 0.10 0.10 0.16 0.04 0.05 85.39 11.91 22.36 8.84 1.71 3.15 31.65 0.83 1.25 0.22 0.23 0.24 0.06 0.10 83.33 11.32 27.75 6.68 1.03 1.77 29.44 0.50 1.48 0.16 0.19 0.19 0.04 0.03 81.24 11.70 20.85 8.41 1.67 3.62 31.28 0.86 1.16 0.34 0.15 0.89 0.07 0.04 81.73 8.87 26.24 7.15 1.60 5.34 29.68 0.25 1.14 0.14 0.04 0.16 0.02 0.10 81.54 9.51 18.88 6.18 1.13 4.42 28.52 4.89 0.89 0.13 0.14 0.21 0.04 0.04 76.14 10.84 21.69 7.47 1.89 3.26 28.97 0.34 1.21 0.17 0.04 0.20 0.02 0.12 77.00 12.68 21.23 8.85 1.52 3.27 31.73 0.24 1.10 0.18 0.06 0.30 0.04 0.12 82.24 6.96 27.63 6.64 2.60 8.30 21.11 0.64 1.00 0.13 0.11 0.25 0.08 0.04 75.49 11.60 28.39 8.13 1.21 2.18 32.51 0.29 1.17 0.17 0.01 0.20 0.06 0.05 85.99 13.79 27.10 8.46 0.10 0.33 34.61 2.47 1.34 0.12 0.05 0.14 0.13 0.00 0.00 88.63 8.93 28.11 5.86 1.04 4.54 36.73 0.10 1.81 0.13 0.00 0.10 0.07 0.02 87.45 198 Mry2-G-k Average Std Dev 9.72 11.08 (1.62) 28.75 6.34 1.68 24.57 7.90 1.59 (3.79) (1.64) (0.59) 4.72 3.28 (1.34) 32.08 0.12 1.51 0.14 0.02 0.10 31.10 0.58 1.30 0.17 0.10 0.32 BDL (4.02) (0.86) (0.28) (0.04) (0.12) (0.24) Al 1.19 1.52 1.33 1.33 1.14 0.93 1.18 1.10 1.21 (0.18) Al 0.67 0.71 0.57 1.18 1.25 1.38 1.61 1.18 1.75 1.62 1.74 1.41 1.86 1.17 1.41 1.23 0.85 0.90 1.30 0.84 1.63 0.97 0.76 0.95 0.74 1.19 (0.38) Al 1.36 1.20 2.28 1.61 (0.58) 0.09 0.02 BDL BDL 85.29 82.50 (5.31) Murchison Si Fe Mg Ni S O Ca Murch_A-k 11.83 28.98 7.91 1.37 2.28 35.42 0.22 Murch-5RA-M4 11.30 26.66 7.67 1.45 2.37 30.41 0.33 Murch-5RD-d7-a 11.42 29.23 7.68 1.82 4.58 29.61 0.24 Murch-5RD-d7-a 11.42 29.23 7.68 1.82 4.58 29.61 0.24 Murch-5RD-d7-a 10.17 25.96 7.29 1.73 4.44 26.82 0.62 Murch-ChD-d7-aend 9.96 23.38 7.57 1.49 4.23 21.90 0.38 Murch-ChD-d7-astart10.14 18.84 7.69 1.30 4.54 30.30 1.64 Murch-F-g 12.83 24.58 8.65 1.63 3.73 35.70 0.34 Average 11.13 25.86 7.77 1.58 3.84 29.97 0.50 Std Dev (0.99) (3.59) (0.40) (0.20) (0.98) (4.44) (0.48) Cold Bokkeveld Cold-5RA-M4 Cold-5RA-M5 Cold-5RA-p Cold-5RB-M1 Cold-5RB-M2 Cold-5RB-M3 Cold-5RB-M4 Cold-5RB-M5 Cold-A-j Cold-C-A Cold-C-E Cold-C-F Cold-C-j Cold-C-l Cold-C-m Cold-C-N Cold-C-W Cold-C-Y Cold-C-z Cold-D-u Cold-E-m Cold-H-d Cold-H-g Cold-H-p Cold-H-u Average Std Dev Si Fe 14.47 12.35 14.06 11.80 12.75 12.53 14.42 17.31 14.17 19.80 13.60 17.24 14.78 17.48 14.47 21.15 11.56 29.94 10.67 35.33 12.58 27.54 15.61 20.64 11.36 32.37 15.01 19.94 9.38 32.89 15.09 19.09 13.65 19.51 11.69 33.01 14.74 18.67 11.26 15.98 9.60 29.93 13.15 16.80 11.44 25.50 12.04 16.67 13.64 13.79 13.01 21.49 (1.76) (7.18) Mg Ni S O Ca 12.88 1.82 1.84 32.19 0.35 12.36 2.07 1.99 31.36 0.18 12.62 1.92 1.34 29.34 0.09 11.33 1.33 2.09 32.88 0.16 10.63 1.51 2.50 33.35 0.16 10.74 2.06 3.13 32.96 0.18 11.94 1.16 1.88 33.73 0.13 10.28 1.06 1.72 32.75 0.06 9.32 0.36 2.00 42.72 0.10 6.51 0.43 2.03 40.87 0.03 10.07 0.07 1.20 42.35 0.03 13.32 0.20 0.90 47.15 0.03 8.05 0.22 1.82 42.91 0.02 12.36 0.82 1.28 40.01 0.22 8.36 1.80 7.31 35.13 0.09 12.17 1.21 1.35 36.19 0.18 12.69 0.67 1.87 38.60 0.07 8.98 0.62 1.78 38.30 0.34 11.38 1.76 3.60 38.11 0.03 10.86 2.37 3.31 32.17 0.94 8.90 1.36 6.47 39.06 0.11 10.92 2.09 1.94 31.48 0.33 9.66 4.33 2.40 34.66 0.17 10.09 1.73 1.80 30.84 0.11 11.91 2.47 2.42 30.61 0.74 10.73 1.42 2.40 35.99 0.19 (1.72) (0.94) (1.50) (4.74) (0.22) Mn P Cr Ti Co 0.20 0.05 0.23 0.06 0.18 0.19 0.17 0.07 0.05 0.18 0.15 0.26 0.03 0.11 0.18 0.15 0.26 0.03 0.11 0.16 0.13 0.28 0.03 0.10 0.15 0.09 0.25 0.04 0.06 0.15 0.06 0.17 0.01 0.10 0.26 0.03 0.27 0.10 0.18 0.11 0.24 BDL 0.09 (0.04) (0.06) (0.04) (0.03) Mn P Cr Ti 0.21 0.15 0.48 0.07 0.20 0.11 0.46 0.10 0.22 0.05 0.57 0.06 0.21 0.07 0.35 0.05 0.22 0.07 0.25 0.05 0.20 0.06 0.34 0.02 0.22 0.02 0.17 0.07 0.22 0.04 0.18 0.07 0.18 0.02 0.24 0.18 0.07 0.12 0.20 0.01 0.10 0.25 0.03 0.09 0.18 0.05 0.16 0.18 0.03 0.26 0.14 0.02 0.14 0.19 0.03 0.39 0.14 0.02 0.17 0.19 0.00 0.10 0.21 0.02 0.43 0.19 0.14 0.77 0.17 0.01 0.37 0.22 0.09 0.56 0.20 1.31 1.29 0.21 0.02 0.36 0.19 0.08 0.61 0.20 0.10 0.36 0.06 (0.02) (0.26) (0.27) (0.02) Co 0.17 0.17 0.11 0.10 0.10 0.11 0.08 0.02 0.03 0.06 0.00 0.03 0.00 0.08 0.03 0.14 0.03 0.02 0.15 0.12 0.01 0.17 0.22 0.13 0.15 0.09 (0.06) Cu Total 0.01 89.75 82.90 0.04 86.67 0.04 86.67 0.03 78.91 0.03 70.44 0.02 76.13 0.04 89.25 BDL 82.59 (6.88) Cu Total 77.77 75.72 72.35 81.76 84.43 82.43 83.56 83.54 98.32 97.96 95.92 99.68 99.00 91.38 96.77 87.25 88.27 95.93 90.45 78.94 97.61 78.73 91.96 74.99 77.33 87.28 (8.79) 0.11 0.03 0.01 0.00 0.00 0.02 0.05 0.00 0.00 0.00 0.05 0.00 0.00 0.02 0.00 0.03 0.00 BDL Nogoya Si Fe Mg Ni S O Ca Nog-d8R12.81 28.71 9.03 0.06 0.69 40.06 0.03 Nog-d8RA-ChA-f 12.37 28.58 9.19 0.26 1.51 38.60 0.06 Nog-d8RA-ChB-a 11.68 34.20 6.55 0.09 0.14 39.79 0.05 Average 12.29 30.50 8.26 0.14 0.78 39.48 0.05 Std Dev (0.57) (3.21) (1.48) (0.11) (0.69) (0.78) (0.02) Rim-Associated Serpentine Murray 1-4c_dk 1-4c_lt 18-c 18-g 19_n 1-c 1-e 1-f 1-l 2_FF 2-g 2-h 2-j 2-o 2-v Mn P Cr Ti Co Cu Total 0.22 0.01 0.58 0.05 0.00 0.00 93.62 0.19 0.02 0.45 0.08 0.05 0.04 92.59 0.17 0.02 0.04 0.05 0.00 0.03 95.08 0.19 BDL 0.36 0.06 BDL BDL 93.76 (0.03) (0.28) (0.02) (1.25) Si Fe Mg Ni S O Ca Al Mn P Cr Ti Co Cu Total 14.20 23.63 8.82 0.98 2.81 34.66 0.14 1.60 0.24 0.05 0.25 0.07 0.00 87.46 10.68 32.44 6.40 0.90 3.90 36.16 0.10 2.16 0.17 0.05 0.12 0.01 0.02 93.11 7.79 27.55 6.85 2.92 3.55 28.22 0.18 0.93 0.18 0.31 1.59 0.16 0.00 80.22 12.27 16.37 11.95 2.31 3.48 35.97 0.10 0.87 0.22 0.06 0.78 0.14 0.01 84.52 12.85 21.31 9.62 1.97 3.30 34.74 0.09 1.28 0.23 0.05 0.31 0.09 0.06 85.90 11.80 29.89 6.99 1.26 3.95 32.41 0.10 1.65 0.16 0.05 0.23 0.03 0.04 88.57 12.57 23.11 9.31 1.92 3.68 30.01 0.19 1.12 0.18 0.06 0.29 0.03 0.01 82.49 10.87 29.32 8.35 1.18 5.33 30.32 1.62 0.18 0.06 0.16 0.02 0.06 0.06 87.53 11.24 33.63 5.86 1.35 1.64 36.86 1.26 2.01 0.19 0.06 0.32 0.08 0.18 94.68 12.10 22.96 7.73 1.52 3.52 32.05 0.42 1.23 0.80 0.15 2.35 0.05 0.03 86.66 12.32 18.30 8.32 1.11 4.35 25.57 0.28 1.09 0.10 0.12 0.26 0.04 0.03 71.91 15.07 29.05 4.89 0.20 2.67 44.70 0.56 2.08 0.10 0.09 0.07 0.04 0.01 99.53 13.89 20.60 9.54 0.63 5.10 37.63 0.37 0.96 0.12 0.09 0.18 0.04 0.00 89.15 11.36 26.44 4.48 0.81 8.20 25.85 0.66 0.71 0.09 3.08 0.01 0.03 0.00 81.72 12.93 25.70 8.24 2.20 4.94 30.21 0.42 0.75 0.15 0.21 0.26 0.04 0.08 86.14 199 2-w 3-b 3-h 3kk 3ll 3-m 3mm 3mm-1 3-q 3v 4cc 4-cc 4-ccpt2 4ff 4-ff 4gg 4-gg 4-i 4-p 8c 9_Rim1 9_Rim11 9_Rim2 9_Rim3 9_Rim4 9_Rim8 9g Mry1-5RA-M10 Mry1-5RA-M11 Mry1-5RA-M12 Mry1-5RA-M13 Mry1-5RA-M14 Mry1-6RA-M1 Mry1-6RA-M11 Mry1-6RA-M12 Mry1-6RA-M14 Mry1-6RA-M2 Mry1-6RA-M5 Mry1-6RA-M8 Mry1-6RE-M4 Mry1-6RE-M5 Average Std Dev Murchison Murch-5RA-M1 Murch-5RA-M2 Murch-5RA-M3 Average Std Dev Cold Bokkeveld Cold-5RA-M1 Cold-5RA-M2 Cold-5RA-M3 Cold-E-h Cold-F-n Cold-I-e Cold-J-g Cold-J-h Average Std Dev 12.88 8.20 12.21 11.26 13.18 12.47 11.42 12.27 11.86 9.20 11.80 10.87 11.15 11.28 9.70 11.68 10.70 10.28 11.95 12.25 10.44 12.00 12.71 12.82 10.95 11.88 12.68 10.79 13.98 13.08 10.09 15.84 10.67 10.89 11.97 12.33 11.31 16.13 14.33 14.20 17.43 12.05 (1.76) 18.01 24.49 26.41 27.70 18.62 19.20 24.24 22.91 24.20 21.76 26.93 29.42 33.09 23.44 27.70 17.55 19.36 19.73 20.70 25.92 20.75 25.89 20.33 18.48 27.23 25.59 22.16 26.33 16.48 22.60 24.39 12.67 23.68 25.67 23.76 26.37 24.80 11.95 19.20 19.13 12.34 23.24 (4.86) 9.21 0.90 5.41 1.38 8.40 1.88 6.87 1.31 10.30 2.16 11.12 2.31 7.29 1.41 9.03 1.68 10.74 1.41 7.52 2.64 8.03 1.72 7.07 1.61 6.94 1.37 9.30 4.07 7.09 3.72 10.50 2.43 10.49 3.80 9.18 2.19 10.49 4.39 7.89 1.92 8.12 2.07 8.13 2.16 9.70 2.01 10.37 1.89 6.97 1.47 8.10 2.87 10.12 2.08 7.96 1.68 11.41 0.92 7.93 1.58 5.96 1.31 13.27 1.02 6.61 1.29 6.54 1.26 8.19 1.54 7.57 1.22 8.22 1.27 13.31 1.19 10.20 0.89 12.08 0.62 13.84 1.10 8.66 1.73 (2.07) (0.85) 3.79 2.66 2.61 2.01 3.10 3.68 2.49 2.37 2.44 4.39 2.94 2.66 4.99 4.24 3.46 4.93 3.49 3.26 3.21 2.70 2.35 3.66 3.23 3.83 3.04 2.04 3.02 2.03 3.76 3.71 3.15 1.96 3.16 4.53 5.26 2.75 3.48 (1.13) 25.02 0.82 20.16 1.70 31.29 0.14 33.91 0.45 33.56 0.18 31.41 0.13 29.97 0.26 33.69 0.26 30.13 0.13 25.53 29.04 0.12 33.85 0.09 33.19 0.12 29.09 0.55 28.12 0.19 27.87 0.14 26.36 0.38 25.80 0.09 32.08 0.13 28.92 0.12 34.63 0.14 35.45 33.94 0.18 35.69 0.11 33.79 0.12 30.41 29.90 0.15 30.52 0.50 33.88 0.34 31.98 0.12 27.14 0.66 35.98 0.64 27.95 0.68 31.30 0.68 32.32 0.22 32.12 0.17 29.92 0.65 36.31 0.99 35.16 0.53 37.39 0.99 37.54 0.52 31.74 0.36 (4.15) (0.34) 1.12 0.96 1.37 1.57 1.17 0.86 1.69 1.63 1.25 0.75 1.68 1.79 2.00 1.40 1.41 0.94 0.85 0.86 0.87 1.53 1.40 1.50 1.40 1.19 1.71 1.30 1.24 1.11 0.85 1.49 1.69 1.67 1.63 2.42 2.00 1.67 1.54 1.42 0.93 1.72 1.46 1.38 (0.40) Al 1.14 1.53 1.54 1.40 (0.23) Al 0.74 1.01 0.83 0.69 0.98 0.87 1.45 1.18 0.97 (0.25) 0.23 0.10 0.32 0.04 0.16 0.11 0.25 0.12 0.00 0.08 0.22 0.07 0.18 0.15 0.18 0.04 0.17 0.07 0.32 0.08 0.20 0.05 0.34 0.07 0.16 0.06 0.26 0.03 0.21 0.12 0.22 0.04 0.24 0.01 0.22 0.04 0.17 0.08 0.35 0.18 0.04 0.26 0.05 0.19 0.08 0.19 0.07 0.21 0.06 0.19 0.04 0.20 0.09 0.63 0.05 0.14 0.05 0.58 0.06 0.27 0.20 1.05 0.03 0.20 0.33 1.18 0.05 0.19 0.17 1.02 0.05 0.18 0.19 1.00 0.07 0.17 0.06 0.23 0.06 0.18 0.06 0.24 0.04 0.19 0.05 0.37 0.20 0.06 0.40 0.09 0.19 0.05 0.27 0.08 0.15 0.05 0.15 0.05 0.19 0.06 0.29 0.23 0.08 0.37 0.09 0.20 0.04 0.28 0.00 0.19 0.11 0.23 0.05 0.16 0.07 0.17 0.01 0.13 0.16 0.20 0.06 0.21 0.03 0.19 0.04 0.12 0.14 0.20 0.04 0.17 0.20 0.15 0.01 0.16 0.03 0.15 0.03 0.15 0.06 0.21 0.07 0.14 0.14 0.24 0.05 0.19 0.12 0.23 0.02 0.20 0.11 0.33 0.06 0.20 0.04 0.15 0.06 0.23 0.04 0.22 0.05 0.20 0.09 0.43 BDL (0.12) (0.06) (0.54) 0.00 0.13 0.09 0.04 0.16 0.15 0.05 0.05 0.06 0.17 0.03 0.05 0.17 0.21 0.12 0.27 0.09 0.10 0.08 0.10 0.05 0.10 0.03 0.03 0.02 0.11 0.00 0.09 0.04 0.05 0.05 0.12 0.13 0.03 0.09 0.04 0.05 0.03 0.06 0.08 BDL (0.06) 72.44 65.73 84.76 86.42 84.03 81.99 80.04 85.30 82.73 72.60 80.83 88.20 91.07 81.06 83.92 73.35 78.16 73.15 87.26 79.49 82.53 89.13 85.15 84.45 85.70 84.46 80.06 83.65 83.52 83.25 74.42 85.56 75.71 84.09 85.09 85.82 80.91 85.88 87.78 92.50 88.27 83.57 (6.07) Total 81.13 86.49 83.08 83.57 (2.71) Total 79.14 82.07 81.77 74.25 80.98 95.61 87.66 81.10 82.82 (6.35) Si Fe Mg Ni S O Ca 12.32 18.48 10.02 2.09 3.61 31.78 0.17 11.69 27.06 8.56 1.62 2.50 31.84 0.46 11.30 26.71 7.66 1.42 2.51 30.50 0.29 11.77 24.08 8.75 1.71 2.87 31.37 0.31 (0.51) (4.86) (1.19) (0.34) (0.64) (0.76) (0.15) Si Fe 14.35 12.50 14.89 16.31 15.06 14.56 11.80 14.13 12.49 17.88 15.97 12.65 14.66 15.75 13.91 19.64 14.14 15.43 (1.38) (2.49) Mg Ni S O Ca 12.60 2.00 2.31 32.72 0.68 11.93 1.60 1.89 33.24 0.13 12.65 1.87 1.99 33.49 0.20 10.52 2.79 2.47 29.23 1.42 10.62 3.20 3.03 31.61 0.22 17.62 1.24 2.93 43.76 0.11 10.03 0.69 0.98 43.32 0.05 10.35 0.90 1.89 31.90 0.78 12.04 1.79 2.19 34.91 0.45 (2.48) (0.88) (0.66) (5.49) (0.48) Mn P Cr Ti Co Cu 0.17 0.07 0.30 0.01 0.15 0.16 0.23 0.17 0.07 0.11 0.16 0.15 0.24 0.04 0.06 0.16 0.15 0.24 BDL 0.11 (0.01) (0.08) (0.07) (0.05) Mn P Cr Ti Co 0.18 0.26 0.40 0.07 0.11 0.20 0.06 0.44 0.06 0.13 0.19 0.11 0.47 0.02 0.15 0.25 0.15 0.53 0.22 0.21 0.03 0.44 0.24 0.18 0.01 0.26 0.00 0.22 0.03 0.48 0.01 0.13 0.02 0.30 0.06 0.20 0.08 0.42 BDL 0.12 (0.04) (0.09) (0.09) (0.09) Cu 0.04 0.02 0.00 0.00 0.04 BDL Tochilinite/Cronstedtite Intergrowths Murray Si Fe Mg Ni S O Ca Al Mn P Cr Ti (Measured Oxygen) 12-c 8.22 34.81 5.95 1.16 5.90 30.64 0.11 1.31 0.14 0.01 0.14 12-f 4.14 40.88 4.52 2.44 11.03 27.59 0.12 1.18 0.13 0.00 0.12 12-m 6.53 44.24 3.27 1.19 7.10 32.31 0.05 1.02 0.10 0.00 0.06 Co 0.00 0.07 0.00 Cu 0.04 0.02 0.02 Total 88.44 92.22 95.89 200 13-j 13-m 13-o 14-d 1-4d_1 1-4d_2 1-4d_3 1-4d_4 14-h_dk 14-h_lt 1-4i 1-4j 1-4k 1-4m 1-4n 14-n 14-p 15-k 16-ee 16-i 16-jj_dk 16-l 16-p 16-v2 16-v3 18-d 18-e 18-h 19_e 19_k 2-4i 2-4j 2-n 2-t 3-4b 3-4c 3-4d 3-4e 3-n 3w 4_DD 4-4t 4-4u 6-4h 6-4i 6-4m 9_JJ 9_KK 9_QQ_sil1 9_QQ_sil4 9_QQ1 9_QQ2 9_QQ3 9_TT 9u2 A-h A-i A-L-lt C-b C-d C-g D-a-dk F-cc F-j F-t M-h M-i M-j Mry1-6RA-f Mry1-7RE-s 4.38 7.87 9.48 4.45 4.06 6.66 4.64 7.14 6.64 4.93 5.93 6.42 6.51 5.80 6.00 5.78 9.62 4.96 5.14 7.38 4.60 8.13 5.57 6.27 5.44 6.11 6.72 6.12 7.10 5.86 4.32 3.10 6.80 6.31 5.45 6.22 5.11 6.44 5.82 6.02 4.14 3.94 6.01 4.78 6.20 5.65 6.62 5.95 4.05 4.78 4.20 4.85 6.54 6.89 7.88 5.07 3.80 5.26 6.85 7.36 5.97 3.90 7.74 6.60 6.02 6.14 6.98 5.33 6.43 4.93 44.41 37.37 34.40 42.59 42.37 36.02 40.68 37.44 44.73 46.27 35.11 41.09 41.41 38.28 38.61 46.01 33.31 44.45 44.96 35.84 40.77 33.24 32.54 40.99 37.90 37.58 42.99 45.34 39.08 36.35 46.37 48.87 34.10 37.76 46.31 44.66 45.48 45.91 46.28 44.72 46.47 45.13 45.92 45.75 44.33 44.53 45.20 44.41 45.66 45.31 50.35 46.95 45.17 44.95 42.82 46.34 46.88 42.03 44.67 43.84 39.74 35.42 40.90 41.62 39.41 44.20 44.50 47.73 39.85 35.47 4.06 4.84 6.08 4.04 3.44 4.23 3.61 5.37 3.10 2.92 2.17 4.24 4.37 5.64 5.72 3.54 7.87 5.24 3.25 6.83 2.37 7.23 2.09 2.97 3.82 3.60 3.85 3.02 2.17 2.31 3.29 2.27 2.95 5.37 2.98 3.49 3.12 3.20 3.25 3.29 2.85 3.70 3.36 3.57 3.55 3.31 3.30 3.72 2.42 3.35 2.73 3.01 3.18 3.29 4.12 2.98 2.95 3.84 3.30 3.31 2.88 2.55 3.19 4.11 4.99 3.05 3.78 2.73 3.20 3.35 2.23 1.19 1.22 1.79 2.26 1.79 2.06 2.07 0.96 1.65 4.73 1.47 1.60 1.10 1.14 0.46 0.31 0.75 1.08 1.89 1.65 1.50 6.75 1.18 2.02 1.45 1.10 1.08 0.88 2.66 2.07 0.52 0.68 2.22 0.70 0.75 1.44 0.42 0.68 0.68 0.53 0.96 0.41 0.81 0.83 0.83 0.35 0.51 0.86 0.56 0.93 0.39 0.61 0.38 0.49 0.99 1.33 1.67 0.63 0.32 0.74 5.20 0.53 1.64 1.80 0.91 0.66 0.79 1.65 3.77 11.69 6.67 3.97 12.70 11.62 7.25 10.57 9.11 6.23 9.86 5.89 8.32 8.08 9.65 9.28 9.12 1.67 20.07 10.20 9.34 5.49 9.06 9.66 6.91 9.46 6.86 8.22 8.24 3.14 7.27 11.44 7.21 15.95 10.16 9.13 8.30 10.27 7.54 9.68 6.77 9.39 13.68 8.38 10.72 8.35 9.19 6.54 9.15 2.08 7.63 3.11 10.35 7.76 6.25 10.66 3.25 10.26 7.24 5.48 5.63 9.71 4.33 8.68 8.92 8.00 8.22 9.50 5.90 9.60 26.73 30.59 35.36 27.77 28.61 32.26 31.64 33.12 33.20 29.05 36.78 28.67 28.98 27.75 27.14 29.96 39.57 18.65 30.38 31.02 32.69 33.10 31.46 27.91 26.38 23.80 30.86 32.55 35.27 33.52 27.66 32.97 20.53 31.42 29.45 29.30 28.73 31.44 29.77 28.49 27.09 29.04 32.34 28.54 30.74 29.67 32.01 31.77 31.98 30.07 28.86 29.14 32.95 30.09 25.50 29.43 33.35 31.80 32.17 33.90 33.71 21.05 35.12 25.14 30.28 30.99 33.11 29.51 29.85 28.27 0.04 0.29 0.04 0.03 0.19 0.21 0.19 0.28 0.05 0.05 0.53 0.17 0.07 0.15 0.14 0.05 0.04 0.10 0.06 0.12 0.93 0.06 0.76 0.09 0.11 0.21 0.05 0.06 0.42 0.24 0.02 0.04 0.08 0.04 0.34 0.06 0.05 0.05 0.05 0.06 0.16 0.07 0.02 0.04 0.03 0.03 0.04 0.05 0.05 0.04 0.02 0.05 0.02 4.07 0.13 0.09 0.04 0.11 0.05 0.13 0.05 0.11 0.25 0.72 2.27 1.49 1.76 1.25 2.05 1.50 1.63 1.20 1.11 0.82 1.54 1.02 0.90 1.01 1.01 1.30 0.59 1.11 1.49 0.92 1.38 1.15 1.17 1.74 0.86 1.54 1.25 4.25 1.98 0.97 0.64 0.37 1.70 0.97 1.02 1.42 0.83 1.30 1.13 1.64 1.85 0.90 0.90 1.15 1.14 1.09 1.80 0.94 1.04 0.97 1.29 1.14 1.02 1.33 1.36 0.83 1.22 1.13 1.15 0.92 0.88 2.06 0.96 1.06 1.09 1.40 0.86 2.72 0.92 0.08 0.13 0.14 0.06 0.10 0.13 0.09 0.15 0.12 0.07 0.10 0.12 0.10 0.16 0.15 0.08 0.18 0.11 0.05 0.13 0.12 0.16 0.10 0.12 0.11 0.10 0.11 0.07 0.14 0.09 0.08 0.05 0.54 0.13 0.05 0.10 0.07 0.09 0.08 0.10 0.06 0.05 0.08 0.10 0.10 0.07 0.08 0.11 0.05 0.04 0.05 0.08 0.09 0.10 0.11 0.08 0.10 0.06 0.09 0.10 0.08 0.11 0.08 0.13 0.12 0.06 0.10 0.08 0.06 0.09 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.74 0.00 0.03 0.03 0.02 0.01 0.00 0.02 0.02 0.01 0.32 0.02 0.46 0.00 0.01 0.08 0.00 0.00 0.14 0.47 0.02 0.00 0.07 0.02 0.03 0.02 0.01 0.00 0.00 0.02 0.02 0.00 0.01 0.00 0.00 0.01 0.01 0.00 0.10 0.03 0.05 0.00 0.01 0.04 0.02 0.01 0.01 0.02 0.00 0.00 0.03 0.59 0.01 0.01 0.02 0.00 0.00 0.02 0.01 0.03 0.08 0.12 0.15 0.08 0.06 0.13 0.11 0.18 0.06 0.05 1.21 0.12 0.12 0.20 0.23 0.05 0.04 0.19 0.04 0.11 1.41 0.08 0.79 0.09 0.17 0.29 0.13 0.11 0.33 0.61 0.05 0.05 2.23 0.12 0.06 0.07 0.05 0.03 0.04 0.05 0.11 0.09 0.06 0.04 0.04 0.03 0.03 0.06 0.01 0.02 0.04 0.04 0.04 0.06 0.06 0.05 0.04 0.08 0.01 0.05 0.03 1.17 0.11 0.10 0.12 0.04 0.07 0.04 0.10 0.25 0.00 0.02 0.02 0.04 0.04 0.00 0.03 0.01 0.04 0.08 0.00 0.03 0.04 0.12 0.00 0.12 0.08 0.03 0.02 0.48 0.02 0.05 0.02 0.02 0.00 0.00 0.03 0.03 0.03 0.19 0.03 0.43 0.07 0.02 0.02 0.00 0.00 0.00 0.19 0.09 0.00 0.03 0.04 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.04 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.05 0.00 0.00 0.05 0.09 0.00 0.05 0.10 0.00 0.00 0.00 0.00 0.09 0.10 0.01 0.04 0.07 0.02 0.05 0.00 0.00 0.00 0.03 0.12 0.08 0.00 0.05 0.05 0.00 0.00 0.00 0.05 0.06 0.06 0.08 1.54 0.03 0.06 0.08 0.00 0.00 0.06 0.04 0.07 0.00 0.00 0.03 0.00 0.03 0.00 0.00 0.00 0.00 0.10 0.06 0.03 0.02 0.01 0.00 0.01 0.00 0.01 0.00 0.00 0.00 0.03 0.00 0.11 0.04 0.01 0.00 0.00 0.02 0.12 1.98 0.03 0.03 94.60 91.35 92.41 95.39 94.09 90.78 95.23 96.57 96.31 96.00 94.62 92.28 92.33 89.74 89.52 96.07 93.90 95.15 96.36 94.27 91.50 94.07 93.30 87.80 87.25 81.04 95.58 97.84 93.00 91.58 96.45 95.72 84.25 95.37 95.20 94.28 95.78 95.95 96.92 91.58 92.63 98.50 97.62 95.37 95.38 94.51 95.26 97.49 88.53 93.06 91.29 96.10 97.50 93.36 82.69 97.03 92.59 96.31 96.14 95.57 93.83 80.91 94.20 89.09 92.96 94.53 98.96 96.75 90.24 89.02 201 Mry1-8RA-e Mry1-Ch1-d8-a Mry1-Ch1-d8-b Mry1-Ch1-d8-B Mry1-Ch1-d8-C Mry1-Ch1-d8-D Mry1-Ch1-d8-f Mry1-Ch1-d8-G Mry1-Ch1-d8-h Mry1-Ch1-d8-i Mry1-Ch1-d8-J Mry1-Ch1-d8-j Mry1-Ch1-d8-K Mry1-Ch1-d8-k Mry1-Ch1-d8-o Mry1-Ch1-d8-p Mry1-Ch1-d8-q Mry1-Ch1-d8-r Mry1-Ch1-d8-u Mry1-Ch1-d8-v Mry1-Ch1-d8-x Mry1-Ch1-d8-y Mry1-Ch1-d8-z Mry1-ChE-d8-d Mry2-C-aa Mry2-C-bb Mry2-C-cc Mry2-C-ee Mry2-C-z Mry2-E-aa Mry2-E-bb Mry2-E-c Mry2-E-e Mry2-E-gg Mry2-E-l Mry2-E-m Mry2-E-q Mry2-E-s Mry2-E-u Mry2-E-v Mry2-E-w Mry2-E-x Mry2-E-z Mry2-F-A Mry2-F-cc Mry2-F-k Mry2-F-p Mry2-F-q Mry2-F-r Mry2-F-w Mry2-F-x Mry2-F-y Mry2-G-c Mry2-G-e Mry2-G-f Mry2-G-m Mry2-H-h Mry2-H-i Mry2-I-i Mry2-I-j Mry-A-f Mry-A-l Mry-A-p Average Std Dev Murray (No Oxygen) Mry1-5RA-B Mry1-5RA-D 5.86 3.84 4.83 3.91 5.33 3.97 5.00 7.30 6.15 6.99 9.49 6.57 5.04 3.93 4.50 4.19 4.65 4.78 5.09 5.68 4.76 5.64 5.28 3.48 6.82 5.16 9.59 6.78 5.59 6.07 6.45 4.11 4.01 6.27 7.83 5.84 7.16 5.68 8.98 7.38 4.58 4.78 8.89 5.43 6.58 6.53 6.02 6.37 6.55 6.79 7.44 4.65 4.77 7.64 7.41 6.09 3.67 5.45 7.39 4.98 7.73 9.97 4.35 5.92 (1.41) Si 4.21 5.48 41.44 4.40 1.47 41.24 3.32 2.16 47.51 3.02 0.13 41.09 2.97 1.85 40.21 3.63 1.82 45.80 3.70 1.24 43.03 4.98 1.93 42.17 4.95 1.97 40.83 5.93 1.09 42.36 3.78 1.12 31.14 6.33 1.03 45.62 3.22 1.26 37.18 4.52 2.47 42.59 3.56 2.10 46.73 3.37 1.54 42.85 3.85 2.23 43.69 4.78 1.06 45.09 3.68 1.57 44.05 3.70 1.95 42.74 4.43 1.06 41.03 4.08 2.33 40.23 4.53 2.42 40.26 4.35 2.35 36.60 1.88 6.76 40.49 5.94 0.87 41.06 4.30 1.77 29.13 6.38 0.99 44.55 3.55 0.16 44.83 4.15 0.82 40.43 3.03 1.08 37.34 5.21 1.65 34.54 2.21 5.56 44.00 3.65 0.65 38.73 4.99 2.11 40.61 3.20 0.49 42.99 3.12 0.09 40.24 3.58 0.45 44.97 2.68 0.40 36.11 3.88 0.10 37.70 3.24 0.34 45.68 2.54 0.53 44.30 3.08 0.19 35.44 4.54 0.30 36.91 4.19 8.32 40.18 5.52 0.93 41.22 5.25 1.01 44.34 4.91 0.98 42.39 3.93 1.53 42.11 4.14 1.23 40.97 4.60 1.41 41.71 4.45 1.01 44.49 3.72 1.21 45.37 3.19 0.56 46.80 2.00 0.20 45.09 2.72 0.11 42.48 4.18 1.47 45.00 3.81 1.21 42.83 4.88 0.62 43.02 3.27 0.71 44.88 2.99 1.98 42.99 3.64 0.86 35.85 7.48 0.18 23.34 5.86 12.06 41.68 3.86 1.47 (4.32) (1.15) (1.56) Fe 46.29 39.08 Mg 3.01 5.36 Ni 1.98 2.41 9.85 11.51 8.86 11.09 9.10 13.09 13.01 8.43 8.54 6.96 4.53 8.72 11.43 11.72 11.81 12.04 12.59 10.88 10.83 10.43 10.70 9.56 10.16 13.40 7.68 10.18 4.51 5.40 9.69 7.73 8.90 12.99 12.69 11.46 3.20 8.21 9.10 10.50 5.84 7.42 12.78 11.81 8.20 11.39 6.51 6.80 8.34 7.07 6.29 7.28 5.58 10.40 10.04 1.99 3.62 9.20 14.05 9.87 4.35 9.98 4.60 0.73 9.58 8.66 (2.96) S 11.78 10.01 31.25 0.10 29.84 0.20 29.00 0.07 31.89 0.21 32.89 0.15 28.60 0.08 24.86 0.14 28.28 0.32 30.78 0.04 31.21 0.07 26.02 0.43 29.55 0.08 27.76 0.06 29.01 0.03 26.48 0.05 25.16 0.07 27.85 0.05 27.92 0.06 28.27 0.10 29.84 0.16 29.52 0.09 29.19 0.04 29.25 0.14 27.31 0.18 29.68 0.03 28.10 0.07 27.19 0.06 35.36 0.02 27.68 0.03 22.40 0.06 23.40 0.08 26.37 0.76 25.30 0.04 26.41 0.03 27.65 0.21 29.66 0.47 29.38 0.34 26.42 0.37 31.16 0.38 26.97 0.27 25.36 1.23 26.36 0.39 28.10 0.76 29.76 0.12 31.40 0.06 29.87 0.02 32.09 0.02 29.22 0.03 27.78 0.02 28.50 0.03 31.53 0.03 24.59 0.02 32.47 0.05 36.78 0.10 35.58 0.05 33.07 0.09 25.56 0.01 28.66 0.17 31.44 0.16 31.60 0.08 33.73 0.16 38.70 0.04 22.96 0.35 29.65 0.18 (3.37) (0.39) O Ca 0.01 0.05 1.52 1.15 1.12 1.09 1.62 0.91 0.84 0.88 0.81 1.72 1.20 1.27 1.29 1.14 1.12 0.78 1.72 0.94 1.58 1.54 1.29 1.42 0.98 0.35 0.76 0.96 1.71 1.02 1.00 0.93 1.61 1.41 1.00 2.30 0.99 1.45 1.85 1.14 1.80 1.55 0.74 1.50 1.07 0.84 0.94 0.99 1.07 1.16 1.04 1.08 1.09 1.00 1.43 1.16 1.17 1.53 0.95 0.81 0.99 0.94 1.12 1.25 0.41 1.23 (0.46) Al 0.84 0.99 0.14 0.01 0.06 0.00 0.13 0.01 0.12 0.00 0.06 0.03 0.16 0.00 0.04 0.02 0.05 0.00 0.00 0.00 0.11 0.01 0.06 0.00 0.08 0.04 0.11 0.01 0.11 0.00 0.13 0.07 0.12 0.02 0.06 0.04 0.05 0.01 0.14 0.03 0.31 0.00 0.16 0.00 0.14 0.01 0.15 0.04 0.04 0.07 0.14 0.01 0.06 0.00 0.01 0.00 0.09 0.00 0.07 0.05 0.01 0.00 0.15 0.05 0.16 0.04 0.06 0.00 0.09 0.00 0.06 0.02 0.02 0.00 0.13 0.02 0.24 0.01 0.17 0.05 0.12 0.02 0.05 0.02 0.06 0.00 0.07 0.00 0.08 0.04 0.04 0.05 0.12 0.00 0.04 0.03 0.10 0.02 0.06 0.01 0.10 0.00 0.00 0.07 0.09 0.01 0.10 0.02 0.05 0.00 0.10 0.00 0.09 0.04 0.05 0.08 0.14 0.00 0.10 0.04 0.03 0.04 0.12 0.01 0.20 0.03 0.14 0.07 0.10 0.01 0.09 0.04 0.12 0.08 0.12 0.01 0.19 0.02 0.18 0.02 0.13 0.71 0.99 0.03 0.61 0.14 0.12 0.01 0.10 0.05 0.03 0.09 0.00 0.10 0.16 0.00 0.16 0.02 0.15 0.00 0.07 0.09 0.00 0.06 0.02 0.02 0.09 0.00 0.07 0.03 0.00 0.06 0.00 0.06 0.02 0.00 0.14 0.02 0.14 0.11 0.03 0.08 0.54 0.15 0.44 0.14 0.09 0.03 0.06 0.05 0.01 0.17 0.01 0.13 0.05 0.06 0.07 0.00 0.12 0.00 0.00 0.08 0.00 0.04 0.00 0.00 0.10 0.02 0.05 0.00 0.07 0.11 0.01 0.02 0.00 0.02 0.13 0.02 0.03 0.00 0.04 0.12 0.02 0.03 0.00 0.00 0.07 0.16 0.05 0.01 0.02 0.13 0.02 0.01 0.00 0.00 0.20 0.05 0.10 0.03 0.03 0.14 1.42 0.48 0.46 0.02 0.13 0.00 0.09 0.00 0.00 0.08 0.00 0.04 0.02 0.00 0.10 0.02 0.08 0.01 0.00 0.11 0.00 0.08 0.07 0.06 0.12 0.01 0.05 0.00 0.01 0.12 0.01 0.11 0.03 0.09 0.08 0.00 0.09 0.05 0.00 0.06 0.01 0.03 0.07 0.00 0.07 0.00 0.02 0.01 0.00 0.07 0.01 0.05 0.05 0.00 0.08 0.01 0.02 0.01 0.04 0.10 0.00 0.08 0.06 0.01 0.09 0.00 0.05 0.03 0.04 0.11 0.02 0.06 0.01 0.02 0.09 0.00 0.03 0.07 0.02 0.13 0.00 0.04 0.14 0.03 0.11 0.00 0.39 0.00 0.01 0.13 0.00 0.03 0.03 0.03 0.34 2.55 3.24 0.58 0.07 0.11 0.07 0.17 BDL BDL BDL (0.05) (0.27) (0.39) Mn 0.09 0.10 P 0.00 0.00 Cr 0.03 0.23 Ti 0.03 0.01 Co 0.08 0.06 Cu 0.04 0.00 96.24 93.66 94.66 94.39 95.16 97.66 94.43 94.76 94.38 94.44 80.62 96.48 90.37 94.36 95.89 91.50 96.62 95.19 95.92 96.22 94.37 93.49 93.32 92.58 92.60 91.96 79.95 97.02 93.97 81.89 85.06 89.29 91.59 92.72 84.37 91.96 92.35 92.31 88.48 85.03 93.73 92.58 87.70 99.48 92.35 91.83 97.97 92.03 89.33 91.01 93.05 90.25 97.98 96.85 95.91 98.37 94.48 93.50 91.55 97.77 95.35 94.42 85.67 93.06 (4.01) Total 68.38 63.79 202 Mry1-5RA-E Mry1-5RA-F Mry1-5RA-s Mry1-5RA-t Mry1-5RA-u Mry1-5RA-v Mry1-5RA-w Mry1-5RA-x Mry1-5RA-z Mry1-6RA-C Mry1-6RA-CC Mry1-6RA-D Mry1-6RA-EE Mry1-6RA-FF Mry1-6RA-h Mry1-6RA-i Mry1-6RA-j Mry1-6RA-k Mry1-6RA-o Mry1-6RA-q Mry1-6RA-t Mry1-6RA-y Mry1-6RA-z Mry1-6RB-e Mry1-6RB-f Mry1-6RB-g Mry1-6RB-h Mry1-6RB-l Mry1-6RB-n Mry1-6RE-c Mry1-6RE-g Mry1-6RE-h Mry1-6RE-j Mry1-6RE-m Mry1-6RE-n Mry1-6RE-o Mry2-5RA-b Mry2-5RA-d Mry2-5RA-f Mry2-5RA-h Mry2-5RA-i Mry2-5RA-k Mry2-5RB-a Mry2-5RB-b Mry2-5RB-c Mry2-5RB-d Mry2-5RB-e Mry2-5RB-f Mry2-5RB-h Average Std Dev 4.31 5.52 6.97 8.48 5.20 4.84 5.46 9.12 5.81 7.14 4.36 6.79 11.24 11.64 6.88 4.19 4.03 5.86 8.05 5.84 10.12 7.84 3.78 5.73 6.72 7.22 9.19 4.07 2.47 4.88 5.87 3.11 4.86 2.48 3.66 4.79 7.38 5.13 7.11 4.50 3.75 2.82 8.20 7.39 5.33 5.68 7.09 6.22 4.92 5.96 (2.08) 42.42 3.87 3.31 39.30 3.43 1.50 36.85 4.90 1.81 34.78 6.17 2.13 48.19 2.05 0.16 45.59 3.35 0.71 38.15 4.41 2.42 39.88 5.32 0.52 45.23 3.20 0.89 34.71 5.80 1.55 37.48 3.19 1.67 37.27 3.90 2.10 30.14 6.59 0.87 33.44 6.70 0.91 40.16 4.46 1.22 48.02 2.73 1.05 45.64 3.56 1.68 42.34 4.09 1.46 34.87 6.01 1.63 43.48 3.37 1.11 28.58 7.14 1.17 42.21 3.60 0.31 44.41 4.12 2.33 40.72 3.97 1.49 39.40 3.59 0.70 43.31 3.32 0.95 27.91 6.56 2.94 38.77 4.41 1.92 49.72 2.58 1.30 39.86 3.73 2.30 38.21 4.51 1.53 49.70 1.16 1.90 42.25 4.02 2.21 48.31 1.64 2.14 49.43 2.01 0.30 41.48 4.59 2.05 39.39 4.43 0.70 36.38 4.72 2.49 37.93 5.63 1.26 41.53 3.29 2.02 43.63 2.81 1.60 42.90 3.10 3.00 43.21 3.41 0.15 44.61 2.98 0.39 45.29 3.05 0.41 45.72 2.75 0.35 43.90 3.34 0.50 45.02 3.05 0.20 42.26 3.90 0.52 41.16 3.98 1.42 (5.13) (1.33) (0.81) 13.17 8.87 8.43 7.56 9.81 11.14 10.10 3.99 8.55 9.13 9.91 9.32 2.30 2.34 7.67 12.85 12.46 10.52 8.52 8.58 5.50 4.62 14.23 8.05 5.74 6.73 7.74 11.71 14.88 10.26 9.62 12.13 11.09 7.58 1.10 11.62 4.43 11.45 9.00 11.27 12.38 13.73 2.76 5.31 9.97 8.59 6.50 7.51 10.08 8.87 (3.21) 0.01 0.11 0.25 0.24 0.06 0.05 0.05 0.04 0.05 0.11 0.15 0.09 0.15 0.15 0.04 0.05 0.02 0.09 0.11 0.02 0.15 0.06 0.08 0.13 0.05 0.06 0.18 0.09 0.05 0.25 0.04 0.03 0.09 0.03 0.04 0.02 0.11 0.05 0.07 0.06 0.06 0.21 0.04 0.04 0.05 0.04 0.07 0.06 0.05 0.08 (0.06) 0.90 1.71 1.54 1.18 0.65 1.10 1.46 0.77 0.84 1.77 1.23 2.51 1.57 1.58 1.69 0.80 1.17 1.09 1.47 1.49 1.90 1.33 1.30 1.29 1.00 1.37 0.82 1.51 0.74 1.33 1.48 1.01 0.75 2.24 3.20 1.27 1.46 1.45 1.40 0.97 0.88 0.99 1.02 0.78 1.32 0.93 0.94 0.77 0.94 1.27 (0.48) 0.07 0.01 0.11 0.00 0.13 0.03 0.12 0.03 0.09 0.00 0.11 0.00 0.13 0.00 0.09 0.02 0.10 0.01 0.11 0.01 0.09 0.00 0.14 0.01 0.18 0.03 0.17 0.03 0.07 0.00 0.08 0.00 0.11 0.00 0.08 0.00 0.16 0.03 0.05 0.00 0.15 0.02 0.09 0.02 0.08 0.00 0.13 0.01 0.09 0.00 0.05 0.00 0.14 0.03 0.08 0.00 0.07 0.00 0.10 0.01 0.10 0.01 0.03 0.06 0.07 0.00 0.00 0.07 0.05 0.08 0.10 0.00 0.12 0.00 0.08 0.00 0.14 0.00 0.07 0.00 0.08 0.00 0.06 0.00 0.12 0.00 0.08 0.00 0.06 0.01 0.09 0.00 0.11 0.00 0.09 0.00 0.09 0.00 0.10 BDL (0.03) 0.06 0.02 0.05 0.06 0.03 0.01 0.08 0.06 0.13 0.03 0.10 0.00 0.21 0.04 0.09 0.01 0.04 0.02 0.00 0.06 0.08 0.02 0.01 0.00 0.05 0.01 0.11 0.00 0.06 0.02 0.00 0.04 0.05 0.02 0.00 0.05 0.09 0.02 0.10 0.04 0.03 0.02 0.12 0.04 0.11 0.03 0.03 0.03 0.17 0.05 0.05 0.02 0.16 0.04 0.08 0.01 0.08 0.02 0.01 0.00 0.03 0.00 0.00 0.02 0.05 0.01 0.03 0.03 0.09 0.01 0.05 0.00 0.10 0.04 0.04 0.04 0.05 0.03 0.03 0.07 0.28 0.04 0.04 0.02 0.03 0.04 0.01 0.00 0.19 0.03 0.04 0.01 0.13 0.03 0.03 0.06 0.04 0.01 0.00 0.00 0.05 0.02 0.07 0.00 0.33 0.04 0.16 0.00 0.08 0.02 0.11 0.03 0.17 0.02 0.02 0.03 0.22 0.02 0.20 0.01 0.13 0.01 0.06 0.03 0.05 0.02 0.05 0.00 0.05 0.02 0.07 0.06 0.07 0.00 0.04 0.02 0.03 0.01 0.01 0.00 0.06 0.01 0.05 0.00 0.04 0.04 0.08 0.02 0.13 0.03 0.11 0.02 0.07 0.02 0.05 0.00 0.03 0.03 0.05 0.03 0.06 0.02 0.05 0.09 0.21 0.01 0.14 0.00 0.05 0.01 0.05 0.02 0.01 0.01 0.01 0.00 0.05 0.01 0.03 0.07 0.02 0.00 0.00 0.02 0.03 0.02 0.09 0.04 0.00 0.02 0.00 0.00 0.05 0.01 0.01 0.02 0.09 BDL BDL BDL (0.07) 68.27 60.73 61.15 61.05 66.32 67.01 62.35 59.87 64.81 60.58 58.29 62.32 53.35 57.24 62.30 69.84 68.81 65.69 61.09 64.12 55.10 60.16 70.58 61.78 57.34 63.15 56.06 62.81 72.06 63.18 61.60 69.26 65.56 64.62 59.91 66.04 58.19 62.04 62.69 63.85 65.40 67.18 59.03 61.61 65.64 64.20 62.64 62.93 62.87 63.04 (3.98) Murchison Si Fe Mg Ni S O Ca Al Mn P Cr Ti Co Cu Total (Measured Oxygen) Murch_A-f 6.71 40.34 4.53 0.86 6.89 22.40 0.18 1.47 0.08 0.05 0.09 0.00 0.00 83.60 Murch_A-l 7.71 35.88 4.85 5.55 9.38 26.69 0.13 1.02 0.12 0.03 0.17 0.18 0.08 91.80 Murch_I-g 4.97 43.65 3.41 2.21 11.48 27.40 0.11 1.34 0.11 0.00 0.01 0.06 0.06 94.82 Murch_I-i 5.75 43.08 3.69 2.01 10.19 29.53 0.05 1.44 0.09 0.02 0.05 0.02 0.02 95.94 Murch_I-k 5.30 42.93 3.86 1.62 11.03 28.37 0.08 1.64 0.10 0.05 0.05 0.00 0.00 95.04 Murch-5RD-d7-a 1.90 66.41 1.74 4.41 4.95 10.96 0.10 0.23 0.02 0.52 1.45 0.03 0.24 0.16 93.13 Murch-5RD-d7-a 6.25 49.07 5.51 2.71 2.52 20.44 0.42 0.86 0.08 0.63 0.35 0.03 0.16 0.05 89.09 Murch-5RD-d7-a 3.08 40.97 1.96 5.41 13.80 26.69 0.12 0.51 0.09 0.38 0.12 0.02 0.33 0.04 93.50 Murch-8RA-b 3.23 36.91 2.52 7.02 14.31 25.95 0.16 0.42 0.10 0.60 0.59 0.08 0.15 0.37 92.42 Murch-A-e-ify 1.85 65.60 4.51 7.47 0.75 5.78 0.02 0.05 0.00 0.38 0.09 0.00 0.00 86.49 Murch-ChD-d7-c 1.27 61.39 1.20 2.23 3.61 22.85 0.28 0.14 0.02 0.33 0.36 0.00 0.11 0.00 93.78 Murch-ChD-d7-e 5.60 40.78 4.06 2.42 9.37 28.68 0.13 1.22 0.14 0.12 0.15 0.01 0.16 0.00 92.83 Murch-ChF-d8-c 8.33 43.39 2.14 0.72 2.68 34.91 0.18 0.47 0.11 0.07 0.05 0.05 0.06 0.05 93.22 Murch-ChF-d8-f 7.63 40.67 2.97 2.00 4.08 33.25 0.22 0.58 0.19 0.28 0.09 0.03 0.17 0.15 92.32 Murch-F-m 5.87 40.76 4.28 1.47 9.62 29.93 0.00 1.05 0.16 0.02 0.06 0.09 0.03 93.35 Murch-F-o 6.44 45.59 3.20 1.10 8.05 30.34 0.06 1.18 0.08 0.04 0.02 0.01 0.00 96.12 203 Murch-J-f Average Std Dev Murchison (No Oxygen) Murch-5RA-p4 Murch-5RD-f Murch-5RD-h Murch-5RD-i Murch-5RD-j Murch-5RD-k Murch-5RD-l Murch-5RD-n Average Std Dev Cold Bokkeveld (Measured Oxygen) Cold-C-D Cold-ChH-d7-a Cold-ChH-d7-d Cold-ChH-d7-e Cold-C-q Cold-C-r Cold-C-R Cold-C-S Cold-C-X Cold-D-t Cold-D-v Cold-D-w Cold-E-o Cold-E-p Cold-E-q Cold-E-r Cold-E-v Cold-F-i Cold-F-j Cold-F-k Cold-F-l_lt Cold-F-l_med Cold-F-o Cold-G-d Cold-G-j Cold-G-m Cold-H-c Cold-H-e Cold-H-h Cold-H-l Cold-H-q Cold-H-v Cold-I-c Cold-I-d Cold-I-i Cold-I-j Cold-J-i Cold-J-l Cold-J-o Average Std Dev Cold Bokkeveld (No Oxygen) Cold-5RA-b Cold-5RA-e Cold-5RA-g Cold-5RA-l Cold-5RA-m Cold-5RA-n Cold-5RA-r 4.91 5.11 (2.15) Si 4.29 3.45 1.84 8.76 7.98 8.18 7.43 7.12 6.13 (2.57) Si 10.35 8.64 9.24 7.56 6.34 7.42 10.22 9.07 8.82 9.30 11.01 6.79 9.35 10.53 7.14 7.23 3.55 7.81 9.06 9.52 8.35 7.65 9.45 2.37 9.51 7.84 10.89 8.77 7.85 10.63 8.39 9.51 12.39 8.25 10.96 9.06 8.75 6.65 12.49 8.68 (1.99) Si 10.51 10.42 10.52 11.21 7.28 7.85 11.54 44.28 3.24 1.68 10.82 45.98 3.39 2.99 7.85 (9.37) (1.20) (2.14) (4.10) Fe Mg Ni S 26.78 0.05 1.03 0.09 0.01 0.06 25.35 0.13 0.86 0.09 0.21 0.22 BDL (7.40) (0.10) (0.50) (0.05) (0.22) (0.35) O Ca 0.04 0.03 0.08 0.04 0.03 0.06 0.03 0.05 0.05 (0.02) O Ca Al 1.20 0.93 0.41 1.22 1.22 1.26 1.29 1.20 1.09 (0.30) Al 2.09 1.00 1.57 1.18 0.83 0.97 1.20 1.44 0.89 1.72 1.62 1.50 1.39 1.21 1.62 1.44 1.39 1.57 1.23 1.60 0.64 1.48 1.05 0.36 1.66 0.67 1.84 1.52 1.61 0.60 0.88 1.76 0.68 1.58 1.39 1.12 1.02 1.01 1.51 1.28 (0.39) Al 1.32 1.33 1.31 1.91 1.48 0.68 1.86 Mn P Cr Ti 0.00 0.01 0.10 BDL (0.10) Co Cu 92.95 92.38 (3.25) Total 68.92 69.62 67.80 58.53 60.36 60.56 61.66 62.28 63.72 (4.36) Total 95.45 93.63 95.21 93.96 95.41 98.12 99.92 93.69 91.61 94.84 96.55 98.46 98.03 93.76 95.82 96.55 95.24 93.54 96.46 96.08 97.66 95.59 99.34 96.10 95.85 98.10 96.74 96.95 98.41 97.00 99.05 97.47 92.30 94.47 92.82 95.28 96.21 95.81 98.07 96.04 (1.98) Total 56.42 56.45 56.48 57.17 56.88 61.77 54.75 46.69 3.06 0.85 12.63 44.80 5.13 0.99 13.98 40.54 1.91 5.99 16.17 36.19 6.92 0.30 4.76 36.57 7.20 0.39 6.62 37.72 6.69 0.32 6.05 40.91 4.78 0.51 6.43 40.06 5.61 0.35 7.60 40.44 5.16 1.21 9.28 (3.76) (1.89) (1.95) (4.30) Fe Mg Ni S 0.08 0.02 0.01 0.02 0.03 0.01 0.05 0.13 0.07 0.01 0.03 0.00 0.08 0.33 0.11 0.00 0.28 0.07 0.13 0.04 0.06 0.05 0.03 0.02 0.15 0.07 0.04 0.04 0.01 0.03 0.13 0.04 0.04 0.04 0.03 0.01 0.10 0.06 0.06 0.02 0.04 0.00 0.11 0.07 0.06 0.03 0.01 0.00 0.10 0.10 0.06 BDL BDL BDL (0.03) (0.10) (0.03) Mn P Cr Ti Co Cu 34.39 6.86 0.06 1.96 32.37 8.06 1.94 7.67 32.01 7.95 1.32 6.14 35.13 7.26 2.13 8.29 32.77 7.48 0.70 4.96 35.51 6.97 0.51 4.71 35.97 7.09 1.12 4.77 37.86 5.74 0.79 3.18 32.62 8.66 1.72 8.36 33.91 6.53 0.77 4.97 31.22 7.44 0.81 4.68 38.22 6.32 2.23 9.98 35.08 6.63 1.03 4.80 34.19 7.14 1.03 4.21 35.25 7.38 2.19 7.84 34.25 7.57 1.33 6.56 35.14 5.53 3.09 13.75 33.46 7.32 1.73 6.22 30.19 8.77 1.64 7.11 29.33 9.04 1.50 6.33 37.92 6.64 1.54 6.84 34.75 7.64 2.00 6.94 31.25 9.49 2.34 7.57 33.07 4.08 15.60 18.54 29.43 8.96 1.10 6.97 39.15 6.50 1.79 7.61 35.56 5.94 0.50 1.39 31.50 8.36 2.18 8.27 34.95 7.28 1.48 7.78 35.46 7.58 0.74 2.51 34.43 8.02 2.25 8.41 35.84 6.16 1.00 4.57 27.63 11.03 0.67 2.20 32.87 8.01 1.30 5.77 32.75 6.91 0.79 2.67 34.42 7.59 1.87 6.68 33.26 8.09 2.30 8.41 37.67 6.01 3.01 10.10 30.63 7.88 0.16 0.28 33.88 7.38 1.80 6.41 (2.59) (1.23) (2.38) (3.32) Fe 26.72 26.95 26.73 34.36 31.17 36.37 30.30 Mg 9.61 9.45 9.50 6.28 7.30 6.79 7.15 Ni 1.17 1.18 1.30 0.49 1.93 2.01 0.56 S 6.58 6.67 6.66 2.56 7.08 7.61 2.88 39.42 0.02 33.34 0.07 36.25 0.11 31.50 0.13 36.32 3.75 38.92 1.55 39.07 0.07 35.08 0.15 30.17 0.06 36.91 0.11 39.03 0.09 32.66 0.12 38.76 0.41 34.80 0.20 33.66 0.08 37.56 0.09 30.38 0.78 34.79 0.07 37.93 0.05 38.18 0.09 35.42 0.06 34.50 0.07 37.70 0.08 19.27 0.08 37.73 0.04 34.19 0.07 40.25 0.07 35.60 0.16 36.88 0.12 39.13 0.02 36.19 0.09 38.02 0.06 37.30 0.03 36.02 0.05 36.70 0.08 34.07 0.05 33.90 0.05 30.85 0.07 44.64 0.07 35.72 0.24 (3.99) (0.63) O Ca 0.06 0.05 0.06 0.09 0.07 0.07 0.09 0.20 0.02 0.08 0.00 0.00 0.19 0.00 0.32 0.00 0.02 0.02 0.16 0.01 0.43 0.01 0.00 0.02 0.18 0.00 0.52 0.01 0.05 0.00 0.20 1.15 0.73 0.05 0.13 0.17 0.44 0.86 0.04 0.03 0.13 0.02 0.18 0.03 0.05 0.17 0.02 0.18 0.00 0.02 0.14 0.01 0.12 0.03 0.00 0.15 0.01 0.43 0.00 0.03 0.12 0.01 0.47 0.00 0.05 0.13 0.01 0.43 0.00 0.06 0.14 0.01 0.32 0.00 0.10 0.16 0.00 0.29 0.00 0.00 0.21 0.00 0.30 0.06 0.08 0.21 0.01 0.28 0.03 0.00 0.15 0.04 1.38 0.02 0.04 0.19 0.01 0.29 0.04 0.05 0.17 0.00 0.26 0.00 0.04 0.20 0.01 0.25 0.02 0.03 0.14 0.01 0.08 0.00 0.03 0.25 0.00 0.26 0.00 0.06 0.16 0.00 0.25 0.01 0.00 0.08 1.33 0.71 0.49 0.12 0.16 0.01 0.19 0.04 0.06 0.14 0.01 0.10 0.00 0.04 0.13 0.00 0.13 0.04 0.00 0.18 0.00 0.28 0.02 0.08 0.17 0.01 0.20 0.05 0.02 0.15 0.00 0.14 0.01 0.03 0.16 0.00 0.17 0.00 0.05 0.14 0.01 0.34 0.01 0.06 0.21 0.00 0.14 0.01 0.01 0.25 0.00 0.23 0.04 0.10 0.17 0.00 0.34 0.03 0.04 0.14 0.01 0.14 0.07 0.07 0.16 0.00 0.25 0.02 0.01 0.14 0.00 0.17 0.03 0.09 0.17 0.02 0.20 0.01 0.00 0.17 0.08 0.32 BDL BDL BDL (0.03) (0.28) (0.25) Mn 0.17 0.15 0.16 0.14 0.19 0.19 0.15 P 0.00 0.00 0.00 0.00 0.02 0.00 0.00 Cr 0.18 0.15 0.16 0.11 0.23 0.13 0.12 Ti 0.02 0.03 0.03 0.03 0.02 0.03 0.05 Co 0.04 0.02 0.00 0.00 0.04 0.01 0.05 Cu 0.02 0.05 0.06 0.00 0.06 0.05 0.00 204 Cold-5RB-a Cold-5RB-b Cold-5RB-d Cold-5RB-e Average Std Dev 11.55 10.52 11.58 9.72 10.25 (1.45) 20.94 10.29 1.57 31.30 5.93 0.49 29.00 7.29 1.01 27.72 9.31 1.39 29.23 8.08 1.19 (4.19) (1.56) (0.53) 4.75 3.27 2.02 7.59 5.24 (2.18) 0.05 0.17 0.08 0.03 0.07 (0.04) 0.90 2.75 1.36 1.49 1.49 (0.55) 0.16 0.01 0.16 0.02 0.18 0.03 0.16 0.01 0.16 BDL (0.02) 0.19 0.05 0.03 0.04 0.00 0.06 0.02 0.00 0.16 0.05 0.04 0.00 0.25 0.03 0.01 0.06 0.15 BDL BDL BDL (0.07) 50.53 54.69 52.80 57.74 55.97 (2.87) Nogoya Si Fe Mg Ni S O Ca Al Mn P Cr Ti Co Cu Total (Measured Oxygen) Nog-d8RB-ChC-f 10.12 28.19 6.01 0.67 2.20 30.98 0.13 1.34 0.21 0.02 0.17 0.01 0.03 0.00 80.10 Average 10.12 28.19 6.01 0.67 2.20 30.98 0.13 1.34 0.21 BDL 0.17 BDL BDL BDL 80.10 Chondrule-Associated Tochilinite Murray 16-ii1 16-ii2 16-ii3 16-u 19_d 19_f 19_i 19_j 19_m 4_A1 4_B1 4_JJ 4_NN 4_OO 4_q 4-4i 4-4k3 4-dd 4-ee 4-g 4-j 4-v2 6-4k A-a A-b A-c B-a B-c-dk D-a-dk2 D-a-lt D-c-ify D-e D-f D-h D-i E-g F-a F-b F-c F-d-ify F-s H-d1 H-d2 H-e H-f H-h H-i H-l M-k Mry1-Ch11-d8-d Mry1-Ch11-d8-h Mry1-Ch4-d8-i Mry1-Ch4-d8-k Mry1-ChE-d8-c Mry1-ChE-d8-g Si 1.6 1.7 1.3 1.4 1.1 1.0 1.1 0.7 1.1 0.2 0.4 0.4 0.5 0.2 1.0 1.9 1.5 0.2 1.6 0.2 1.4 0.6 0.9 1.8 0.3 0.5 0.3 0.3 0.1 0.2 3.1 0.2 0.1 1.4 0.1 2.1 0.4 0.4 0.4 0.7 0.3 0.4 0.7 0.6 0.3 0.3 0.5 0.4 1.6 0.2 0.3 0.2 0.7 2.4 0.7 Fe 41.8 40.8 41.8 39.8 41.7 55.9 44.0 39.3 31.3 40.6 41.5 44.5 51.5 39.5 41.4 34.3 38.2 33.7 42.0 45.8 42.0 27.3 41.4 35.0 40.6 39.1 37.8 38.1 29.8 37.0 39.7 41.6 46.9 40.0 41.3 39.2 41.5 36.9 43.1 31.1 33.2 38.7 39.5 35.1 43.8 42.8 40.3 43.3 32.2 43.8 45.2 42.9 54.4 40.3 49.7 Mg 1.8 2.1 1.8 1.8 0.9 0.3 0.8 1.0 2.4 2.1 2.5 2.2 1.2 1.7 2.5 2.2 2.2 1.5 3.0 2.3 3.6 1.5 2.4 2.7 2.0 2.2 2.4 4.0 1.6 2.2 3.9 3.7 2.4 2.4 2.0 1.0 2.0 1.9 3.5 1.2 1.1 2.4 2.5 2.3 3.7 2.7 2.5 3.1 2.1 2.4 2.6 2.2 0.8 1.9 2.7 Ni 4.6 5.2 5.5 14.0 7.2 4.5 6.6 8.1 9.8 10.9 8.4 7.5 5.7 12.1 7.8 9.8 6.6 14.1 6.2 5.6 6.7 11.1 9.4 12.7 11.6 12.5 12.0 12.5 11.6 10.0 3.9 8.1 3.8 9.1 10.9 3.8 8.3 11.6 5.9 9.3 19.8 8.2 7.7 11.7 5.8 6.1 6.6 5.9 9.9 8.8 6.3 6.8 5.0 7.9 2.9 S 16.9 17.3 18.2 21.3 14.3 9.7 14.7 15.8 14.5 19.3 18.7 19.3 12.3 17.3 16.9 14.3 16.1 17.8 17.1 18.8 17.4 13.5 18.0 18.4 20.0 19.6 19.1 19.8 16.4 18.1 14.5 20.1 19.4 17.8 19.5 8.1 18.5 19.6 17.9 16.5 20.6 18.3 18.3 18.9 19.6 19.2 18.1 19.7 9.2 19.7 19.2 18.1 9.2 16.2 19.0 O 19.8 21.5 20.3 16.6 24.7 22.2 25.3 27.4 16.0 17.8 19.4 18.4 22.2 20.3 16.8 14.3 13.5 14.3 21.9 17.8 22.7 10.4 16.0 20.1 18.2 16.2 17.5 16.0 10.9 12.9 17.6 18.2 18.8 17.1 15.1 16.7 17.9 14.4 24.1 13.6 14.4 16.0 17.6 15.6 18.5 20.0 18.3 20.1 15.2 17.0 19.1 18.0 25.2 23.3 17.8 Ca 0.1 0.1 0.1 0.0 0.1 0.4 0.1 0.0 0.1 Al 2.1 2.1 2.1 0.4 0.2 0.1 0.2 0.2 0.5 0.2 0.4 0.6 0.4 0.2 0.6 0.5 0.5 0.2 0.9 0.2 0.7 0.1 0.6 0.6 0.4 0.5 0.3 0.6 0.2 0.3 0.8 0.5 0.2 0.3 0.3 0.2 0.5 0.4 0.5 0.2 0.3 0.4 0.5 0.3 0.5 0.3 0.5 0.3 0.2 0.4 0.4 0.2 0.1 0.3 1.0 Mn 0.1 0.1 0.0 0.0 0.1 0.1 0.1 0.1 0.1 0.0 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.0 0.1 0.1 0.0 0.0 0.1 0.1 0.1 0.1 0.1 0.0 0.1 0.2 0.1 0.1 0.1 0.3 0.1 0.1 0.0 0.1 0.1 0.0 0.1 0.2 0.0 0.1 0.1 0.1 0.1 0.1 P 0.10 0.08 0.10 0.01 0.31 0.35 0.40 0.77 1.12 1.07 0.55 0.35 0.71 1.47 0.54 1.01 0.56 2.36 0.33 0.47 0.10 1.55 0.93 1.53 1.01 1.09 1.31 1.17 1.50 1.42 0.32 0.62 0.05 0.95 1.28 0.47 1.09 1.96 0.39 1.37 3.15 0.77 1.06 2.16 0.33 0.09 0.43 0.07 0.70 0.74 0.14 0.37 0.94 0.65 0.01 Cr 0.5 0.4 0.5 0.2 1.0 0.4 1.0 1.3 0.7 2.9 1.8 1.7 1.4 2.2 2.2 0.8 0.2 1.4 1.4 3.4 1.9 1.8 0.3 1.5 1.3 0.9 1.4 0.1 1.1 1.3 0.8 1.3 3.0 1.3 1.3 0.5 1.4 0.8 1.4 2.2 0.8 1.3 1.6 0.9 0.6 2.6 1.0 3.0 2.1 1.0 1.2 3.3 1.2 1.2 0.0 Ti Co 0.2 0.2 0.2 0.5 0.3 0.4 0.3 0.4 0.5 0.4 0.3 0.3 0.4 0.7 0.2 0.3 0.2 0.7 0.1 0.4 0.1 1.1 0.2 0.4 0.3 0.4 0.3 0.3 0.4 0.3 0.1 0.2 0.0 0.2 0.3 0.3 0.3 0.6 0.3 0.3 0.7 0.3 0.3 0.6 0.3 0.1 0.2 0.1 0.1 0.3 0.1 0.4 0.6 0.6 0.1 Cu Total 0.07 89.4 0.13 91.6 0.09 92.2 0.04 96.0 1.77 93.6 0.15 95.5 0.23 94.7 0.17 95.3 0.11 78.2 0.06 95.5 0.08 94.0 0.04 95.2 0.02 96.4 0.06 95.8 0.07 90.0 0.09 79.5 0.05 79.7 0.04 86.4 0.04 94.6 0.06 95.1 0.04 96.7 0.00 68.9 0.09 90.3 0.03 94.6 0.10 96.1 0.06 93.3 0.01 92.6 0.05 92.9 0.12 73.8 0.23 84.1 0.00 84.6 0.10 94.8 0.00 94.7 0.06 90.9 0.05 92.2 0.09 72.7 0.09 92.5 0.05 89.1 0.09 97.8 0.09 77.2 0.04 95.1 0.03 87.0 0.04 89.8 0.08 88.1 0.04 93.5 0.12 94.4 0.08 88.5 0.04 96.1 0.11 73.8 0.00 94.4 0.24 94.8 0.14 92.7 0.01 98.6 0.20 95.2 0.19 94.1 0.1 0.1 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.1 0.1 0.1 0.1 0.1 0.3 0.1 0.1 0.1 0.1 0.1 0.2 0.4 0.5 0.3 0.8 0.5 0.1 0.1 0.1 0.1 0.1 0.0 0.1 0.2 0.0 0.0 0.1 0.4 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 205 Mry1-d8_Ch4_D Mry2-A-a Mry2-A-b Mry2-A-e Mry2-A-g Mry2-A-h Mry2-A-i Mry2-B-d Mry2-C-p Mry2-C-q Mry2-C-w Mry2-H-a Mry2-H-c Mry2-I-f Average Std Dev Murchison Murch-5RA-a Murch-5RA-b Murch-5RA-c Murch-5RA-d Murch-5RA-e Murch-5RA-P8 Murch-5RA-P9 Murch-K-b Murch-K-c Average Std Dev Cold Bokkeveld Cold-5RA-h Cold-5RA-j Cold-C-I-lt Cold-D-b Cold-D-j Cold-D-m Cold-D-o Cold-D-q Cold-D-r Cold-E-a Cold-E-n Cold-G-a Cold-G-h Cold-J-c Cold-J-f Cold-J-p Cold-J-q Average Std Dev 0.2 0.4 0.4 0.5 0.5 0.4 0.7 1.9 0.4 0.4 0.7 0.3 0.7 0.3 0.74 (0.63) Si 0.2 1.1 0.5 0.3 0.4 2.3 2.4 2.3 2.4 1.31 (1.02) Si 1.0 0.8 2.2 0.3 1.2 1.4 1.2 2.0 0.4 0.5 0.2 0.5 0.3 2.4 0.6 0.9 1.1 1.00 (0.68) 35.4 2.5 10.7 15.3 39.5 0.9 4.7 16.1 45.9 1.3 5.3 18.8 47.6 2.3 4.9 19.5 40.8 1.7 9.5 19.5 34.2 1.4 7.9 15.8 40.4 1.9 7.2 17.7 42.0 0.5 7.4 16.4 43.9 1.7 6.4 18.3 44.0 2.0 6.2 18.9 35.8 1.5 8.7 6.7 34.8 1.8 13.1 17.8 41.3 2.5 6.9 17.4 41.1 1.8 5.4 5.3 40.43 2.08 8.23 16.94 (5.19) (0.78) (3.09) (3.32) Fe 17.7 0.1 0.2 0.1 1.31 3.9 0.0 0.6 0.19 15.2 0.3 0.3 0.1 0.32 1.4 0.1 0.05 15.6 0.2 0.3 0.1 0.08 2.8 0.1 0.03 18.3 0.2 0.5 0.1 0.00 1.2 0.2 0.00 19.2 0.6 0.5 0.1 1.30 0.0 0.3 0.04 13.2 0.3 0.4 0.1 1.03 0.7 0.2 0.05 13.7 0.4 0.5 0.1 0.98 0.7 0.2 0.03 18.9 0.9 0.2 0.1 0.77 0.4 0.7 0.31 15.8 0.1 0.3 0.0 0.35 0.8 0.3 0.05 14.7 0.1 0.3 0.1 0.36 1.3 0.2 0.01 5.2 0.2 0.1 0.1 0.42 0.7 0.5 0.00 14.4 0.1 0.6 0.1 1.70 1.1 0.7 0.04 22.3 0.1 0.4 0.1 0.49 1.3 0.2 0.05 24.9 0.1 3.6 0.0 0.87 0.4 0.6 0.00 17.82 0.17 0.49 0.08 0.79 1.29 BDL 0.33 BDL (3.85) (0.18) (0.55) (0.04) (0.62) (0.84) (0.20) Co 0.0 0.0 0.0 0.0 0.0 0.0 0.0 88.0 79.4 90.7 95.1 93.9 75.7 84.4 90.3 88.5 88.5 60.5 86.4 93.4 84.3 89.47 (7.70) Mg Ni S O Ca Al Mn P Cr Ti 41.9 2.2 9.7 20.2 0.0 0.8 0.1 1.01 0.3 35.2 2.6 6.3 15.4 0.2 0.7 0.1 0.45 0.2 32.4 2.0 15.5 18.3 0.2 0.5 0.0 1.73 0.1 30.8 2.6 8.2 15.2 0.1 0.3 0.0 0.83 0.2 32.0 2.1 11.2 16.9 0.1 0.3 0.0 1.15 0.2 41.4 2.5 3.5 16.3 0.0 2.8 0.1 0.01 0.0 34.2 3.0 8.0 14.6 0.3 1.5 0.2 1.23 1.6 45.7 2.4 4.9 12.0 23.0 0.3 0.5 0.2 0.38 0.7 40.9 3.0 5.8 13.8 26.9 0.3 0.5 0.2 0.31 1.0 37.16 2.49 8.12 15.86 24.96 0.17 0.88 0.09 0.79 0.48 BDL (5.39) (0.37) (3.64) (2.45) (2.76) (0.11) (0.81) (0.06) (0.55) (0.52) Cu Total 0.4 0.02 76.8 0.2 0.00 62.5 0.7 0.08 72.0 0.4 0.03 58.8 0.6 0.11 65.0 0.1 0.07 69.1 0.3 0.09 67.4 0.0 0.20 92.6 0.1 0.14 95.3 0.31 BDL 73.28 (0.23) (12.84) Fe Mg Ni S O Ca Al Mn P Cr Ti Co Cu Total 42.6 4.3 3.3 13.2 0.1 0.6 0.2 0.64 0.6 0.0 0.1 0.08 66.7 31.9 2.9 15.2 21.4 0.0 0.3 0.1 1.44 0.9 0.0 0.4 0.08 75.4 43.0 4.4 5.1 18.8 20.1 0.2 0.7 0.1 0.49 0.6 0.2 0.07 95.8 35.6 2.9 12.2 21.2 14.7 0.1 0.3 0.1 0.78 1.6 0.2 0.11 90.0 37.0 4.1 6.2 18.2 20.1 0.1 0.5 0.1 0.65 2.1 0.1 0.01 90.4 38.9 4.2 6.5 18.4 20.4 0.3 0.7 0.1 0.19 1.6 0.1 0.00 92.6 30.4 2.6 5.0 14.0 13.7 0.1 0.8 0.1 0.28 1.2 0.1 0.08 69.4 41.4 5.9 4.6 18.3 22.1 0.1 0.7 0.1 0.00 0.7 0.0 0.10 95.8 39.0 4.5 8.5 21.5 18.9 0.1 0.4 0.1 0.42 1.2 0.2 0.09 95.2 40.7 4.7 5.3 21.3 22.5 0.6 0.4 0.1 0.00 1.5 0.0 0.07 97.7 44.7 4.1 6.2 21.4 18.5 0.2 0.4 0.1 0.00 0.5 0.0 0.09 96.4 37.3 2.8 12.0 18.5 16.8 0.1 0.3 0.1 0.66 0.8 0.3 0.06 90.1 39.4 3.7 8.1 19.1 24.4 0.0 0.3 0.1 0.55 1.6 0.2 0.11 97.8 34.8 4.0 7.1 13.5 25.8 0.2 0.6 0.1 0.54 1.6 0.1 0.14 90.8 41.4 3.7 6.1 20.3 21.7 0.1 0.4 0.1 0.47 0.6 0.2 0.11 95.7 38.9 3.6 9.0 18.4 22.7 0.1 0.5 0.1 0.51 1.5 0.2 0.08 96.6 36.4 3.5 8.8 18.7 17.2 0.1 0.6 0.1 0.45 1.1 0.2 0.11 88.4 38.43 3.87 7.60 18.59 19.98 0.13 0.49 0.11 0.47 1.14 BDL 0.15 BDL 89.68 (3.85) (0.81) (3.13) (2.72) (3.41) (0.13) (0.16) (0.02) (0.35) (0.47) (0.10) (9.75) Co 0.0 0.0 0.0 0.0 Cu Total 0.2 0.15 90.7 0.0 0.00 87.8 0.0 0.10 93.3 0.0 0.09 94.1 0.08 BDL 91.46 (0.11) (2.85) Nogoya Si Fe Mg Ni S O Ca Al Mn P Cr Ti Nog-d8RA-ChA-d 0.6 37.1 2.6 8.3 19.2 20.2 0.1 0.5 0.1 0.41 1.2 Nog-d8RA-ChA-e 0.2 45.3 2.4 1.1 11.6 25.6 0.1 0.8 0.2 0.08 0.3 Nog-d8RB-ChC-a 0.9 42.7 3.9 3.4 17.6 22.8 0.0 1.0 0.2 0.01 0.6 Nog-d8RB-ChC-c 1.1 42.8 4.4 4.5 19.3 20.4 0.0 1.0 0.2 0.00 0.4 Average 0.71 41.99 3.31 4.33 16.92 22.27 0.06 0.80 0.17 0.13 0.62 BDL Std Dev (0.38) (3.46) (0.95) (2.99) (3.61) (2.54) (0.04) (0.25) (0.03) (0.19) (0.41) Matrix-Associated Tochilinite Murray 13-l 14-f 1-4l 15-e 16-k 16-kk 9_LL G-k Si 2.1 0.3 0.6 1.9 1.1 1.0 2.4 0.3 Fe 52.9 53.3 50.8 50.8 48.9 49.1 47.4 49.8 Mg 2.4 2.2 2.6 2.8 3.0 3.5 3.5 2.4 Ni 0.2 1.4 1.9 1.2 3.0 2.2 0.6 0.8 S 25.9 19.5 18.4 15.9 18.2 18.9 13.8 15.8 O 14.6 18.2 16.8 21.6 21.0 20.1 27.3 24.4 Ca 0.1 0.0 0.3 0.0 0.0 0.0 0.1 Al 0.4 1.2 0.2 1.0 0.9 0.7 0.8 1.2 Mn 0.0 0.0 0.2 0.1 0.1 0.0 0.1 0.1 P 0.02 0.01 0.02 0.00 0.01 0.00 0.02 0.02 Cr 0.1 0.0 0.1 0.1 0.1 0.1 0.0 0.1 Ti Co 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 Cu Total 0.05 98.6 0.00 96.3 0.00 91.9 0.08 95.4 0.03 96.3 0.14 95.8 0.06 96.0 0.00 94.9 206 Mry1-Ch1-d8-A Mry1-Ch1-d8-c Mry1-Ch1-d8-F Mry1-Ch1-d8-g Mry1-Ch1-d8-m Mry1-Ch1-d8-s Mry1-Ch1-d8-w Mry2-5RA-a Mry2-5RA-g Mry2-5RA-l Mry2-5RB-i Mry2-C-f Mry2-E-d Mry2-E-ff Mry2-F-j Mry2-G-g Mry2-G-l Mry2-H-j Mry2-H-k Average Std Dev 0.7 0.9 0.3 1.1 0.4 0.5 2.4 2.4 0.5 0.5 2.5 1.5 2.8 0.7 0.5 2.2 3.2 2.5 1.4 1.35 (0.92) 50.1 2.9 2.2 19.6 49.6 2.5 3.2 18.5 48.2 2.5 4.5 20.0 49.7 3.0 2.8 18.6 50.7 3.0 3.0 19.6 49.0 2.7 3.6 19.8 51.7 2.5 0.7 15.9 46.0 2.9 1.1 14.7 39.7 1.9 9.1 18.6 50.6 1.9 0.4 14.4 39.3 3.6 6.5 15.0 41.0 4.2 0.7 12.2 51.1 2.3 0.5 13.6 47.8 2.7 2.7 18.9 62.5 1.6 1.1 6.4 46.7 2.6 0.4 15.1 47.0 2.6 0.8 12.1 46.3 3.6 0.7 15.0 48.8 3.2 0.5 17.7 48.85 2.77 2.07 16.74 (4.45) (0.57) (2.05) (3.62) 18.8 20.5 17.8 19.2 17.8 18.2 21.5 25.8 23.5 15.4 26.4 25.9 23.6 22.0 21.8 20.96 (3.56) 0.0 1.0 0.1 0.00 0.1 0.1 0.7 0.1 0.00 0.1 0.0 1.7 0.0 0.00 0.1 0.0 1.2 0.0 0.01 0.1 0.2 1.1 0.1 0.01 0.1 0.0 1.3 0.1 0.00 0.1 0.1 0.8 0.1 0.02 0.0 0.1 0.8 0.1 0.01 0.1 0.0 0.5 0.1 1.05 1.7 0.1 0.8 0.0 0.00 0.0 0.1 0.7 0.0 0.62 0.8 0.1 4.5 0.1 0.01 0.0 0.1 0.7 0.1 0.00 0.0 0.0 0.8 0.0 0.00 0.0 0.0 0.3 0.0 0.01 0.0 0.1 0.9 0.1 0.00 0.0 0.1 1.1 0.1 0.00 0.1 0.0 0.9 0.1 0.00 0.1 0.0 0.9 0.1 0.01 0.0 0.05 1.00 0.06 0.07 0.14 BDL (0.05) (0.77) (0.04) (0.23) (0.35) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.07 0.1 0.11 0.1 0.04 0.2 0.09 0.1 0.01 0.0 0.00 0.1 0.00 0.1 0.02 0.3 0.13 0.0 0.03 0.2 0.00 0.0 0.00 0.0 0.06 0.1 0.00 0.0 0.00 0.0 0.01 0.0 0.00 0.0 0.05 0.0 0.00 BDL BDL Co 95.5 96.3 95.3 95.9 96.0 95.4 95.7 68.2 73.6 68.8 69.4 90.0 94.7 89.1 98.8 94.1 90.7 91.1 94.5 91.04 (9.28) Murchison Si Fe Mg Ni S O Ca Al Mn P Cr Ti Murch_A-g 2.1 48.9 2.8 1.5 16.9 23.0 0.1 1.9 0.0 0.00 0.1 Murch-5RA-p1 2.3 48.0 2.4 0.8 9.8 0.1 1.1 0.1 0.08 0.0 Murch-5RA-p3 2.3 49.0 2.8 0.8 16.0 0.0 0.9 0.1 0.04 0.0 Murch-5RA-p5 1.3 47.3 2.5 1.8 16.3 0.0 0.9 0.1 0.05 0.0 Murch-5RA-p6 1.5 48.8 2.8 1.0 16.9 0.1 1.1 0.0 0.01 0.0 Murch-5RA-P7 1.1 46.3 2.4 2.9 18.8 0.1 2.4 0.1 0.02 0.0 Murch-5RA-r 2.1 46.9 2.8 0.6 13.6 0.0 0.8 0.1 0.04 0.0 Murch-5RD-c 2.5 42.8 1.9 5.6 14.6 0.1 0.4 0.1 0.25 1.2 Murch-5RD-d 2.6 48.0 4.1 0.6 15.6 0.0 0.9 0.1 0.02 0.1 Murch-5RD-e 1.6 46.5 4.2 1.1 17.0 0.0 1.1 0.1 0.04 0.0 Murch-ChF-d8-e 0.7 48.3 2.7 1.9 19.3 21.3 0.1 2.5 0.0 0.01 0.0 Murch-Ch-F-d8-m 0.9 50.2 2.7 3.3 18.9 19.6 0.1 0.8 0.0 0.01 0.1 Murch-F-j 3.8 47.6 3.7 1.9 13.5 24.8 0.1 0.8 0.1 0.02 0.1 Murch-F-k 0.9 52.5 2.7 2.5 18.1 17.7 0.1 0.7 0.0 0.01 0.1 Murch-F-p 1.2 48.1 3.4 2.6 18.0 20.2 0.1 1.2 0.0 0.01 0.1 Average 1.80 47.95 2.92 1.92 16.21 21.10 0.06 1.16 0.06 0.04 0.13 BDL Std Dev (0.83) (2.10) (0.63) (1.33) (2.53) (2.51) (0.03) (0.61) (0.02) (0.06) (0.31) Cold Bokkeveld Cold-5RA-c Cold-ChH-d7-f Cold-ChH-d7-g Cold-ChH-d7-h Cold-ChH-d7-i Cold-ChH-d7-i Cold-C-Z Cold-D-h Cold-D-s Cold-E-y Cold-H-s Cold-H-t Cold-H-w Average Std Dev Si 0.4 3.2 1.3 0.3 1.6 1.6 2.8 2.5 0.5 0.7 3.4 0.4 2.6 1.62 (1.13) Fe Mg Ni S O Ca Al Mn P Cr Ti 41.0 4.7 4.4 19.8 0.0 0.4 0.1 0.14 1.7 37.4 6.9 5.1 16.6 22.7 0.3 0.5 0.1 0.15 1.0 41.9 5.1 5.7 19.3 18.3 0.1 0.4 0.1 0.03 1.2 42.9 4.7 5.1 19.8 19.5 0.1 0.4 0.1 0.06 2.1 38.8 5.3 5.7 18.4 19.9 0.1 0.3 0.2 0.20 2.4 37.6 5.4 7.8 18.9 21.7 0.1 0.3 0.1 0.36 2.5 43.6 5.5 3.2 18.2 22.6 0.0 1.5 0.1 0.01 0.1 35.5 4.2 12.8 20.8 14.8 0.9 0.4 0.1 0.93 0.6 42.0 4.3 6.1 21.8 18.2 0.1 0.4 0.1 0.31 1.5 42.8 4.6 3.0 19.7 22.3 0.1 0.4 0.1 0.21 1.4 34.8 7.1 4.2 15.3 29.1 0.1 0.4 0.2 0.03 2.8 41.8 4.4 6.1 20.1 21.6 0.1 0.4 0.1 0.06 1.9 39.7 5.7 5.0 17.6 22.5 0.1 0.5 0.1 0.01 0.9 39.98 5.21 5.70 18.95 21.09 0.15 0.49 0.13 0.19 1.53 BDL (2.92) (0.91) (2.50) (1.74) (3.48) (0.25) (0.33) (0.02) (0.25) (0.79) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Cu Total 0.0 0.01 97.3 0.0 0.04 64.7 0.0 0.00 72.0 0.0 0.05 70.4 0.0 0.09 72.3 0.0 0.03 74.2 0.0 0.05 67.1 0.4 0.06 69.8 0.0 0.01 72.0 0.0 0.06 71.7 0.0 0.00 96.9 0.0 0.12 96.8 0.0 0.00 96.3 0.1 0.08 95.5 0.0 0.12 94.9 BDL BDL 80.79 (13.29) Co Cu Total 0.0 0.12 72.8 0.1 0.14 94.0 0.0 0.06 93.5 0.0 0.07 95.1 0.1 0.12 92.9 0.1 0.02 96.4 0.0 0.03 97.6 0.3 0.14 94.0 0.2 0.17 95.6 0.0 0.14 95.4 0.0 0.05 97.4 0.0 0.10 97.1 0.1 0.04 94.8 BDL BDL 93.57 (6.43) 0.0 0.0 0.0 0.0 0.0 0.0 207 Troilite-Associated Tochilinite Murray 3_NN_rim 3-c 3-c2 3cc 3dd 3dd 3-k K-b K-c K-d K-l Average Std Dev Murchison Murch-J-d Average Si 1.0 0.4 0.6 0.7 0.2 0.7 0.5 0.6 1.0 1.5 1.0 0.75 (0.36) Si 0.6 0.58 Fe Mg Ni S O Ca Al Mn P Cr Ti 45.8 1.7 5.7 17.4 11.9 0.0 0.3 0.0 0.09 0.1 52.3 2.6 1.2 20.3 18.5 0.5 0.0 0.00 0.2 50.0 2.5 1.3 21.1 19.5 0.4 0.1 0.00 0.2 49.5 2.5 2.9 20.0 19.2 0.5 0.1 0.00 0.2 45.9 1.1 10.5 25.7 13.2 0.3 0.1 0.03 0.2 47.8 2.3 5.7 20.5 18.8 0.5 0.1 0.02 0.1 43.7 1.8 12.0 23.6 13.8 0.3 0.0 0.02 0.2 53.9 1.8 0.8 29.0 15.3 0.1 0.2 0.1 0.00 0.2 50.9 1.9 0.8 24.4 13.0 0.1 0.3 0.0 0.00 0.2 46.3 3.4 1.4 18.3 23.4 0.1 0.6 0.1 0.00 0.2 47.3 3.0 2.1 18.5 22.7 0.0 0.6 0.1 0.00 0.2 48.49 2.24 4.02 21.71 17.20 0.05 0.39 0.06 BDL 0.17 BDL (3.11) (0.66) (3.98) (3.55) (4.00) (0.04) (0.15) (0.02) (0.03) Mg 2.5 2.51 Ni 50.4 50.38 S O Ca Al Mn P Cr Ti 2.7 18.9 18.6 0.1 0.4 0.1 0.03 0.0 2.66 18.85 18.61 0.07 0.44 0.08 BDL BDL Cu Total 0.3 84.6 0.0 0.10 96.1 0.0 0.16 96.0 0.1 0.22 95.9 0.3 0.40 97.8 0.2 0.24 96.9 0.0 0.8 0.06 96.7 0.0 0.08 101.9 0.0 0.07 92.5 0.1 0.29 95.7 0.1 0.17 95.8 0.17 0.18 95.43 (0.22) (0.11) (4.22) 0.0 0.0 0.0 Co 0.1 BDL Cu Total 0.16 94.5 0.16 94.48 Co Fe 208 A.2 Sulfides P-rich Sulfides Murray Si Fe Mg 14-q 0.76 29.35 1.20 16-q 0.08 29.46 0.00 2-r 1.33 36.52 0.27 3_LL_rim 2.97 19.25 2.51 3_OO_rim 0.12 19.42 0.04 3_PP1 0.75 19.47 0.28 3_PP2 0.60 19.23 0.19 3_PP3 0.23 19.32 0.01 3_PP4 0.30 19.05 0.12 3-e 0.02 24.24 0.00 3-f 0.01 21.17 0.00 3-g 0.02 20.45 0.00 3-z 0.22 23.68 0.00 4_JJ 0.79 24.19 0.83 4-f 0.12 23.44 1.26 6-4a 0.04 22.92 0.01 6-4a2 0.05 21.68 0.04 A-f 0.06 23.74 0.12 A-g 0.96 21.36 0.87 D-g 0.05 25.33 0.05 F-jj 0.19 19.17 0.12 Mry1-Ch11-d8-a 0.02 23.11 0.01 Mry1-Ch11-d8-c 0.08 25.09 1.33 Mry1-Ch11-d8-g 0.09 23.29 0.02 Mry1-Ch-4-d7-d 0.01 14.61 0.05 Mry1-Ch4-d8-b 0.01 24.76 0.03 Mry1-Ch4-d8-d 0.04 23.55 0.21 Mry1-Ch4-d8-e 0.16 29.12 0.91 Mry1-Ch4-d8-g 0.04 24.89 0.00 Mry1-Ch4-d8-j 0.02 22.65 0.00 Mry1-d7RHv_redo 0.35 26.39 0.35 Mry1-d8_Ch4_A 0.01 24.25 0.01 Mry1-d8_Ch4_B 0.03 24.32 0.00 Mry2-F-B 0.76 28.49 1.01 Mry2-F-dd 0.11 27.98 0.06 Mry2-F-s 0.50 29.62 0.24 Average 0.33 23.74 0.34 Std Dev (0.56) (4.14) (0.55) Murchison Murch_I-h Murch-5RD-b Murch-5RD-d7-b Average Std Dev Si Fe Mg 0.41 26.29 0.41 0.16 22.90 0.39 3.88 36.03 2.69 1.48 28.41 1.16 (2.08) (6.82) (1.32) Ni 22.56 26.31 25.58 23.45 39.66 27.75 29.40 33.11 34.58 41.06 42.51 41.76 39.36 26.76 24.92 36.17 33.75 30.79 24.98 35.25 30.01 38.10 30.91 37.27 25.07 36.43 35.60 24.51 36.33 39.88 33.58 35.48 37.04 21.66 28.01 19.58 31.92 (6.40) Ni 35.84 32.91 5.98 24.91 (16.46) Ni 25.77 25.80 21.53 27.42 27.71 25.65 (2.47) Ni 25.48 23.70 24.59 (1.26) S O Ca 18.91 13.01 0.85 26.12 4.33 0.11 27.84 11.23 9.51 11.27 0.20 13.81 3.61 0.00 13.07 10.06 0.02 13.08 10.18 0.03 13.97 9.38 0.00 13.27 6.58 0.00 17.33 3.62 20.96 2.33 20.18 3.23 17.94 3.60 17.12 6.96 15.05 9.87 23.01 2.71 0.01 20.42 2.88 0.01 20.29 6.84 0.30 15.06 5.45 0.13 21.99 3.56 0.19 16.82 5.64 0.42 21.81 2.81 0.00 19.58 9.44 0.10 21.77 2.36 0.00 17.12 4.05 0.00 23.43 2.64 0.03 21.22 3.66 0.00 16.82 12.85 0.14 22.88 2.96 0.00 22.13 2.73 0.00 22.22 6.93 0.06 23.39 2.50 0.06 22.87 2.99 0.02 19.02 10.62 0.22 22.85 8.41 0.22 20.97 10.78 0.32 19.27 6.17 0.12 (4.09) (3.50) (0.18) S O Ca 22.74 5.96 0.07 22.38 0.88 3.03 9.58 0.24 16.05 7.77 0.40 (11.28) (2.56) (0.43) S O Ca 30.22 4.69 0.00 31.74 3.18 0.00 21.62 13.76 0.06 23.18 8.64 0.00 28.27 3.80 0.32 27.01 6.81 0.08 (4.42) (4.43) (0.14) S O Ca 28.91 5.81 0.02 26.12 10.07 0.03 27.52 7.94 0.03 (1.97) (3.01) (0.01) Al 0.23 0.01 0.01 0.40 0.07 0.11 0.06 0.13 0.10 0.02 0.01 0.00 0.00 0.18 0.05 0.05 0.06 0.05 0.20 0.03 0.05 0.00 0.02 0.00 0.02 0.00 0.03 0.06 0.00 0.00 0.07 0.01 0.00 0.23 0.01 0.05 0.06 (0.09) Al 0.09 0.01 0.49 0.20 (0.26) Al 0.03 0.00 0.17 0.20 0.09 0.10 (0.09) Al 0.11 0.07 0.09 (0.03) Mn P Cr Ti Co 0.03 4.00 0.29 0.96 0.03 2.77 0.44 0.52 0.02 1.14 0.16 0.00 0.96 0.06 3.53 0.03 0.00 0.89 0.01 6.40 0.00 0.00 1.53 0.02 4.36 0.00 0.32 1.12 0.02 4.68 0.00 0.32 1.20 0.02 5.47 0.00 0.06 1.32 0.01 5.80 0.04 0.05 1.51 0.04 9.48 0.03 0.00 2.04 0.01 7.98 0.01 0.01 2.32 0.00 7.78 0.03 0.00 1.74 0.04 9.34 0.03 0.02 2.32 0.03 4.68 0.27 1.52 0.05 4.37 2.67 0.01 2.14 0.03 6.91 0.23 3.98 0.03 6.19 0.22 3.71 0.04 5.57 0.59 1.65 0.05 3.41 0.31 1.18 0.03 6.78 0.11 1.27 0.00 5.46 0.11 1.27 0.01 7.12 0.11 0.06 2.18 0.02 5.35 1.40 0.01 2.08 0.00 6.99 0.07 0.01 2.32 0.01 5.81 0.23 0.00 1.78 0.01 6.88 0.45 0.03 3.97 0.05 6.20 1.25 0.00 3.50 0.08 4.00 1.53 0.01 2.63 0.02 6.83 0.28 0.00 2.55 0.02 7.62 0.27 0.03 2.94 0.02 6.36 0.13 0.00 1.44 0.04 6.76 0.50 0.04 4.09 0.02 6.97 0.25 0.01 2.44 0.09 3.08 0.26 1.09 0.08 4.86 0.05 1.51 0.03 2.34 0.06 0.54 BDL 5.65 0.34 BDL 1.95 (1.88) (0.55) (0.97) Mn P Cr Ti Co 0.00 6.15 0.06 1.60 0.06 5.42 0.82 0.01 2.33 0.16 3.75 0.65 0.05 0.29 0.07 5.11 0.51 BDL 1.41 (0.08) (1.23) (0.40) (1.03) Mn P Cr Ti Co 0.01 1.81 0.32 0.04 0.43 0.00 1.80 0.25 0.00 0.46 0.04 1.49 0.12 0.59 0.02 1.93 1.01 0.89 0.01 2.23 0.09 0.88 BDL 1.85 0.36 BDL 0.65 (0.27) (0.38) (0.22) Mn P Cr Ti Co 0.04 1.33 0.05 0.00 0.72 0.06 1.44 0.03 0.00 0.67 0.05 1.39 0.04 BDL 0.70 (0.01) (0.08) (0.01) (0.04) Cu Total 0.06 92.22 0.08 90.27 0.08 105.14 74.92 85.74 78.40 80.03 84.01 82.32 0.09 97.99 0.16 97.48 0.12 95.33 0.05 96.60 0.15 83.47 0.09 84.05 0.07 96.15 0.05 89.09 0.15 90.20 0.14 74.09 0.22 94.86 0.02 79.26 0.19 95.53 0.23 95.63 0.19 94.36 0.07 68.83 0.12 98.80 0.17 95.48 0.15 92.97 0.14 96.93 0.11 98.38 0.08 97.99 0.10 97.25 0.14 97.11 0.16 86.70 0.15 94.29 0.41 85.44 0.13 90.20 (0.07) (8.43) Cu Total 0.09 99.71 0.10 88.37 0.00 66.82 BDL 84.97 (16.71) Cu Total 0.18 97.74 0.17 97.92 0.08 92.27 0.18 92.02 0.11 95.41 0.14 95.07 (0.05) (2.85) Cu Total 0.12 96.76 0.12 96.00 0.12 96.38 0.00 (0.54) Cold Bokkeveld Si Fe Mg ColdB-d8-H-center 0.27 33.74 0.21 Cold-ChH-d7-i 0.20 34.23 0.08 Cold-C-I-dk 2.80 26.57 3.44 Cold-J-k 0.80 27.02 0.73 Cold-J-s 0.90 30.45 0.56 Average 0.99 30.40 1.00 Std Dev (1.06) (3.60) (1.39) Nogoya Si Fe Mg Nog-d8RA-ChA-c 1.02 31.54 1.59 Nog-d8RB-ChC-e 1.16 31.51 1.02 Average 1.09 31.53 1.31 Std Dev (0.10) (0.02) (0.40) Pentlandite Murray 12-l Si Fe Mg Ni S O Ca Al Mn P Cr Ti 1.08 31.91 0.59 28.11 29.49 3.77 0.01 0.20 0.03 0.00 0.06 Co Cu Total 1.49 0.00 96.72 209 12-o 14-o 15-g 15-l 16-d 16-f 16-ff 16-x 9_BB 9_CC 9_YY 9_YY2 D-j G-j K-n Mry1-Ch1-d8-H Mry2-ChE-d8-b Mry2-F-A Mry2-F-aa Mry2-F-C Mry2-F-u Average Std Dev Murchison Murch-A-l-ify Murch-J-c Average Std Dev Cold Bokkeveld Cold-C-b Cold-C-H Cold-C-u Cold-D-a Cold-E-i Cold-F-e Cold-F-f Cold-F-h Cold-F-m Cold-H-a Cold-H-b Cold-H-i Cold-H-j Cold-H-o Cold-I-a Cold-I-line-avg Average Std Dev 1.19 0.33 0.14 0.08 0.49 0.27 0.09 0.04 0.09 1.81 0.28 0.81 0.04 0.20 0.39 0.09 0.05 0.78 0.96 0.02 0.13 0.43 (0.48) 33.19 1.47 33.21 0.17 30.84 0.04 30.74 0.00 37.64 0.93 40.73 0.90 40.52 0.00 42.74 0.00 34.18 0.00 36.29 0.99 42.30 0.07 39.68 0.54 33.13 0.00 33.61 0.07 38.09 0.09 41.52 0.00 39.04 0.00 31.51 0.72 29.67 0.68 47.75 0.00 43.68 0.00 36.91 0.33 (5.03) (0.44) 21.61 30.16 30.42 29.10 23.46 20.62 22.65 21.30 26.27 24.30 20.67 21.61 31.64 27.94 23.99 22.54 25.37 17.34 23.51 15.71 21.06 24.06 (4.20) Ni 25.73 31.91 28.82 (4.37) Ni 30.60 31.03 24.30 34.28 33.74 28.73 33.51 34.38 34.53 34.40 29.19 31.35 34.69 28.68 32.81 33.12 31.83 (2.94) 27.03 32.23 30.76 30.37 29.50 28.02 32.72 33.32 31.73 26.58 33.14 30.13 33.26 30.38 33.03 33.73 34.44 23.83 26.49 34.88 34.37 30.88 (3.02) 9.75 0.04 1.86 0.03 2.79 0.00 3.57 0.00 9.02 0.01 8.75 0.02 0.68 0.00 0.54 0.01 1.55 9.85 2.45 9.05 0.19 0.00 1.42 0.00 1.60 0.00 0.98 0.00 1.10 0.00 5.38 0.00 6.01 0.00 0.34 0.01 0.71 0.01 3.70 BDL (3.46) 0.22 0.04 0.06 0.02 0.27 0.26 0.01 0.02 0.03 0.42 0.02 0.16 0.00 0.00 0.02 0.00 0.00 0.11 0.14 0.00 0.00 0.09 (0.12) 0.02 0.02 0.01 0.00 0.01 0.00 0.02 0.00 0.04 0.04 0.03 0.00 0.02 0.01 0.00 0.03 0.01 0.01 0.02 0.03 0.02 0.02 0.02 0.01 0.04 0.01 0.00 0.01 0.04 0.00 0.02 0.02 0.00 0.01 0.02 0.00 0.05 0.02 0.00 0.03 0.01 0.00 BDL BDL 0.05 0.05 0.06 0.06 0.08 0.07 0.12 0.04 0.11 0.05 0.04 0.05 0.04 0.01 0.05 0.05 0.01 0.11 0.03 0.41 0.11 0.49 0.03 0.02 0.04 0.09 BDL (0.12) 1.02 0.70 1.38 1.11 0.61 0.59 0.79 0.74 1.13 0.57 0.98 0.98 0.90 0.55 0.80 0.66 0.78 0.74 0.95 0.74 0.75 0.86 (0.25) Co 1.01 1.84 1.43 (0.59) Co 0.51 1.62 1.50 1.01 0.67 1.59 1.08 0.76 0.86 2.43 1.33 0.74 0.87 0.62 0.81 0.82 1.08 (0.50) 0.04 0.07 0.03 0.06 0.10 0.01 0.02 0.00 0.02 0.05 0.03 0.00 0.02 0.06 0.01 0.00 0.00 0.00 0.00 0.00 0.00 BDL 95.65 98.88 96.54 95.14 102.19 100.27 97.62 98.77 95.13 100.95 100.02 103.03 99.26 94.24 98.11 99.62 100.93 80.96 88.95 99.52 100.75 97.42 (4.83) Si Fe Mg 0.25 36.31 0.07 0.16 31.88 0.04 0.21 34.10 0.06 (0.06) (3.13) (0.02) Si Fe Mg 0.15 34.53 0.06 0.50 31.41 0.41 1.79 28.25 1.93 0.04 31.37 0.00 0.13 31.71 0.00 1.67 28.27 1.54 0.06 32.62 0.00 0.10 31.01 0.00 0.08 30.86 0.00 0.06 29.64 0.00 0.99 25.30 0.79 0.06 34.19 0.00 0.10 30.96 0.02 0.16 31.75 0.07 0.23 33.34 0.00 0.07 32.64 0.00 0.39 31.12 0.30 (0.58) (2.37) (0.60) S O Ca Al 31.78 2.32 0.00 0.04 32.93 1.56 0.00 0.00 32.36 1.94 BDL 0.02 (0.81) (0.54) (0.03) S O Ca 33.99 0.52 0.00 33.36 3.08 0.10 26.75 7.62 2.10 33.44 0.26 0.00 33.46 0.75 0.00 27.04 4.92 0.00 33.54 0.18 0.00 33.09 0.32 0.00 33.46 0.22 0.00 33.47 0.60 0.00 26.07 5.12 0.02 33.43 0.44 0.00 33.14 0.35 0.00 32.25 2.59 0.02 33.84 0.21 0.00 33.52 0.34 0.00 32.12 1.72 0.14 (2.76) (2.30) (0.52) Al 0.00 0.05 0.16 0.00 0.01 0.18 0.00 0.00 0.00 0.00 0.10 0.01 0.00 0.01 0.00 0.00 0.03 (0.06) Mn P Cr Ti 0.01 0.01 0.05 0.06 0.00 0.06 BDL BDL 0.06 (0.01) Mn P Cr Ti 0.00 0.00 0.03 0.00 0.03 0.05 0.05 0.56 0.09 0.02 0.00 0.01 0.02 0.00 0.09 0.05 0.02 0.17 0.01 0.01 0.09 0.02 0.01 0.01 0.01 0.00 0.06 0.00 0.01 0.03 0.01 0.02 0.28 0.01 0.00 0.02 0.05 0.00 0.06 0.00 0.00 0.05 0.01 0.00 0.03 0.01 0.00 0.01 BDL 0.04 0.07 (0.14) (0.07) Cu Total 0.07 97.63 0.00 100.44 BDL 99.04 (1.99) Cu Total 0.00 100.39 0.00 101.66 0.00 95.10 0.03 100.46 0.07 100.63 0.09 94.26 0.01 101.12 0.00 99.69 0.00 100.08 0.01 100.66 0.00 89.21 0.00 100.25 0.00 100.26 0.05 96.27 0.00 101.29 0.02 100.58 BDL 98.87 (3.41) Nogoya Si Fe Mg Ni S O Ca Al Mn P Cr Ti Co Cu Total Nog-d8RA-ChB-d 0.09 36.90 0.01 24.95 34.36 1.47 0.14 0.02 0.00 0.00 0.03 0.00 0.12 0.00 98.09 Average 0.09 36.90 BDL 24.95 34.36 1.47 0.14 0.02 BDL BDL 0.03 BDL 0.12 BDL 98.09 Pyrrhotite Murray 15-r 9m I-c-ify L-d L-e Mry1-8RA-d Mry2-5RA-j Mry2-H-e Mry-A-k Average Std Dev Murchison Si Fe Mg Ni 0.05 59.02 0.00 0.36 0.01 57.53 0.00 4.68 0.02 61.74 0.00 0.10 0.02 60.18 0.00 1.61 0.02 60.48 0.00 0.99 0.20 58.96 0.13 0.85 0.02 61.02 0.00 0.74 0.05 59.16 0.00 2.12 0.03 60.61 0.00 0.88 0.05 59.86 BDL 1.37 (0.06) (1.29) (1.38) Si Fe Mg Ni S O Ca 38.23 0.20 0.04 36.81 37.63 0.16 0.02 36.95 0.27 0.00 37.44 0.20 0.00 38.37 1.19 0.11 37.60 0.03 37.73 0.44 0.00 38.35 0.31 0.02 37.68 0.40 0.03 (0.57) (0.36) (0.04) S O Ca Al 0.02 0.00 0.08 0.02 0.01 0.02 0.00 0.00 0.02 0.02 (0.02) Al Mn P Cr Ti Co 0.31 0.00 1.26 0.00 0.03 0.00 0.05 0.00 0.38 0.08 0.02 0.42 0.00 0.02 0.00 0.06 0.12 0.00 0.00 0.05 0.05 0.00 0.01 0.08 0.02 0.04 0.02 0.00 0.05 0.00 0.06 0.00 0.02 0.04 0.15 0.05 0.01 0.04 0.00 0.06 BDL 0.23 BDL 0.09 (0.10) (0.41) (0.12) Mn P Cr Ti Co Cu Total 0.01 99.50 0.06 99.56 0.04 100.31 0.11 99.37 0.09 99.32 0.00 99.98 0.03 99.57 0.11 99.81 0.01 100.33 BDL 99.75 (0.38) Cu Total 210 Murch-J-a Murch-J-e Average Std Dev Cold Bokkeveld Cold-C-v Average Troilite Murray 16-a_lt 16-c 16-e 16-t 17-b 17-c 17-e 17-i 2_BB_rim 2_u_core 3-a 3aa 3bb 3ff 3-l 6-4p 6-4q 6-4t 9_FF1 9_FF2 9_FF3 9_FF4 9_FF5 9_GG 9_HH 9_II 9e 9h 9l A-j C-c F-z I-a I-b I-d-ify K-a K-f K-g L-g L-h Mry1-6RB-m Mry1-6RE-k Mry1-6RE-r Mry1-Ch1-d8-I Mry2-5RB-g Mry2-C-x Mry2-C-y Mry2-E-n Mry2-F-E Mry2-G-a Mry2-G-b Mry2-H-g Mry2-I-l Average Std Dev Murchison Murch_I-a 0.02 0.03 0.03 (0.01) 59.28 61.17 60.23 (1.34) 0.00 0.00 0.00 0.00 1.84 37.67 0.90 37.99 1.37 37.83 (0.66) (0.23) 0.33 0.00 0.00 0.01 0.00 0.03 0.28 0.01 0.01 0.06 0.02 0.02 0.31 BDL BDL BDL BDL BDL (0.04) 0.15 0.00 0.12 0.05 0.14 BDL (0.02) 99.36 100.64 100.00 (0.91) Si Fe Mg Ni S O Ca Al Mn P Cr Ti 0.03 60.16 0.00 0.54 38.94 0.19 0.01 0.00 0.09 0.01 0.17 0.03 60.16 0.00 0.54 38.94 0.19 BDL BDL 0.09 BDL 0.17 Co Cu Total 0.01 0.00 100.16 BDL BDL 100.16 Si Fe Mg Ni 0.02 62.26 0.00 0.72 0.03 62.61 0.00 0.37 0.01 62.28 0.00 0.71 0.04 62.19 0.00 0.55 0.07 61.61 0.00 0.77 0.03 61.67 0.00 0.46 0.01 62.07 0.00 0.65 0.02 61.20 0.00 1.27 0.19 57.14 0.06 0.71 0.16 59.64 0.00 0.76 0.01 62.75 0.00 0.14 0.00 61.83 0.00 0.87 0.01 58.45 0.00 4.64 0.04 61.68 0.00 0.15 0.02 62.73 0.00 0.21 0.02 62.12 0.00 0.72 0.03 61.71 0.00 0.82 0.02 61.68 0.00 1.08 0.02 58.99 0.00 3.89 0.02 61.82 0.00 0.97 0.03 60.84 0.00 1.89 0.03 61.28 0.00 1.66 0.03 61.95 0.00 1.02 0.06 60.94 0.00 1.49 0.02 61.61 0.00 1.08 0.06 60.43 0.02 1.42 0.11 61.98 0.00 0.36 0.31 61.96 0.00 0.26 0.02 61.16 0.00 1.42 0.16 61.45 0.04 0.73 0.01 62.16 0.00 0.22 0.02 61.29 0.00 0.74 0.01 61.78 0.00 0.10 0.02 61.79 0.00 0.17 0.07 60.47 0.11 0.18 0.06 61.83 0.00 0.12 0.02 62.05 0.00 0.09 0.01 61.69 0.00 0.51 0.09 59.22 0.00 2.09 0.02 61.48 0.00 0.87 1.45 54.81 1.77 1.33 0.05 62.40 0.03 0.17 0.07 61.87 0.00 0.52 0.28 61.96 0.17 0.16 0.03 62.29 0.00 0.38 0.23 59.23 0.00 3.22 0.02 61.88 0.00 0.68 0.15 60.45 0.00 0.11 0.07 62.68 0.00 0.58 0.05 62.08 0.00 0.67 0.23 56.75 0.09 1.54 0.03 60.94 0.00 1.53 0.06 61.94 0.00 1.30 0.09 61.19 0.04 0.93 (0.20) (1.57) (0.24) (0.91) S O Ca 36.56 0.31 0.00 35.95 0.23 0.01 36.67 0.27 0.03 36.45 0.30 0.03 36.01 0.89 0.01 36.08 0.43 0.04 36.40 0.32 0.05 36.08 0.35 0.01 37.19 1.89 35.76 1.96 36.71 0.14 36.30 0.15 35.85 0.16 36.69 0.74 37.00 0.12 36.87 0.22 0.01 36.78 0.25 0.00 36.47 0.20 0.01 35.86 0.18 36.11 0.22 36.14 0.22 36.43 0.20 36.47 0.19 36.88 0.41 35.90 0.17 35.33 0.65 37.09 36.18 36.77 35.49 0.69 0.00 36.78 0.11 0.00 36.30 0.17 0.01 36.96 0.16 0.00 36.56 0.09 0.02 36.39 1.18 0.01 35.73 1.74 0.01 37.28 0.17 0.00 36.65 0.05 0.01 36.04 0.47 0.01 36.57 0.06 0.00 35.50 0.05 35.84 0.02 36.41 0.05 34.79 1.80 0.03 36.49 0.06 35.60 1.26 0.04 37.16 0.52 0.00 35.59 1.10 0.05 36.56 0.36 0.08 36.60 0.26 0.00 34.58 1.99 0.06 36.32 0.63 0.02 37.16 0.16 0.00 36.31 0.52 0.02 (0.58) (0.56) (0.02) Al 0.02 0.04 0.01 0.02 0.04 0.00 0.00 0.00 0.06 0.05 0.01 0.01 0.03 0.03 0.01 0.03 0.03 0.02 0.02 0.05 0.03 0.02 0.02 0.03 0.03 0.03 0.00 0.01 0.00 0.03 0.04 0.00 0.02 0.00 0.03 0.01 0.02 0.03 0.01 0.02 0.16 0.01 0.01 0.02 0.00 0.01 0.00 0.01 0.00 0.00 0.01 0.01 0.00 0.02 (0.02) Mn P Cr Ti Co 0.00 0.00 0.08 0.06 0.02 0.00 0.08 0.12 0.03 0.00 0.11 0.00 0.00 0.01 0.05 0.03 0.02 0.01 0.06 0.12 0.00 0.00 0.10 0.05 0.02 0.00 0.07 0.07 0.03 0.00 0.06 0.11 0.02 0.08 0.46 0.00 0.00 0.06 0.57 0.04 0.04 0.01 0.24 0.01 0.00 0.03 0.00 0.22 0.00 0.08 0.00 0.20 0.03 0.01 0.00 0.22 0.00 0.03 0.00 0.12 0.02 0.00 0.01 0.00 0.01 0.05 0.03 0.00 0.05 0.11 0.00 0.00 0.00 0.11 0.08 0.00 0.06 0.29 0.06 0.00 0.05 0.08 0.06 0.00 0.05 0.18 0.05 0.00 0.06 0.15 0.05 0.00 0.06 0.09 0.08 0.00 0.07 0.14 0.05 0.00 0.07 0.10 0.06 0.01 0.07 0.12 0.02 0.00 0.02 0.01 0.00 0.04 0.00 0.05 0.00 0.03 0.08 0.00 0.03 0.01 0.18 0.01 0.02 0.08 0.14 0.00 0.00 0.03 0.02 0.02 0.00 0.03 0.05 0.08 0.01 0.44 0.00 0.06 0.00 0.44 0.04 0.05 0.00 0.42 0.00 0.03 0.00 0.16 0.00 0.00 0.00 0.18 0.00 0.09 0.01 0.18 0.01 0.06 0.01 0.03 0.44 0.01 0.00 0.03 0.20 0.03 0.00 0.12 0.02 0.02 0.02 0.00 0.05 0.00 0.05 0.04 0.00 0.05 0.01 0.12 0.01 0.00 0.08 0.00 0.00 0.07 0.00 0.06 0.00 0.23 0.10 0.02 0.06 0.14 0.06 0.00 0.06 0.01 0.03 0.00 0.06 0.00 0.01 0.00 0.05 0.00 0.00 0.06 0.00 0.03 0.09 0.02 0.00 0.06 0.43 0.01 0.01 0.05 0.26 0.03 0.01 0.03 0.25 BDL BDL 0.11 BDL 0.09 (0.13) (0.10) Cu Total 0.08 100.11 0.08 99.54 0.01 100.14 0.00 99.66 0.07 99.68 0.02 98.88 0.03 99.69 0.03 99.17 0.02 97.81 0.07 99.07 0.09 100.16 0.06 99.47 0.06 99.52 0.00 99.58 0.01 100.29 0.00 100.06 0.00 99.83 0.00 99.60 0.37 99.77 0.00 99.38 0.02 99.46 0.09 99.96 0.10 99.97 0.06 100.15 0.01 99.03 0.10 98.31 0.00 99.58 0.00 98.84 0.00 99.67 0.05 98.88 0.00 99.36 0.00 98.64 0.01 99.58 0.02 99.21 0.05 98.96 0.00 99.68 0.03 99.85 0.00 99.23 0.07 98.53 0.03 99.29 0.00 95.25 0.00 98.63 0.03 99.17 0.00 99.31 0.01 99.63 0.01 99.91 0.01 100.41 0.07 97.62 0.03 100.43 0.03 99.88 0.10 95.86 0.11 99.92 0.05 100.98 BDL 99.33 (0.98) Si Fe Mg Ni S O Ca Al Mn P Cr Ti 0.02 61.89 0.00 1.24 36.86 0.31 0.00 0.00 0.02 0.00 0.05 Co Cu Total 0.04 0.00 100.45 211 Murch_I-b Murch_I-j Murch-5RA-q Average Std Dev Troilite with Oxygen Murray 1-4f 16-cc 16-dd 17-n 2_AA_rim 9_PP F-dd F-l K-e K-k Mry2-C-n Mry2-E-y Mry2-F-B Mry2-G-i Average Std Dev 0.03 0.02 0.13 0.05 (0.05) 62.65 0.00 0.63 61.83 0.00 1.17 58.49 0.48 0.20 61.22 0.12 0.81 (1.85) (0.24) (0.49) 36.91 36.59 33.94 36.08 (1.43) 0.01 0.01 0.05 0.33 0.02 (0.06) (0.02) 0.28 0.39 0.01 0.02 0.06 0.02 (0.03) 0.05 0.01 0.05 0.03 0.04 0.04 0.00 0.03 0.16 0.10 0.03 0.00 0.12 0.01 0.02 0.05 BDL BDL BDL BDL BDL BDL 100.69 100.38 93.59 98.78 (3.46) Si Fe Mg Ni 0.56 57.42 0.85 1.10 2.11 53.96 1.98 1.50 0.65 55.78 0.72 2.71 0.40 59.89 0.32 0.53 0.34 57.49 0.27 3.13 0.35 61.01 0.23 0.21 1.94 56.87 1.77 0.46 0.78 49.24 0.16 1.38 0.17 57.56 0.76 0.37 0.39 60.04 0.37 0.17 0.67 42.19 0.18 4.66 0.68 55.37 0.18 1.02 0.11 54.01 0.00 1.88 0.73 56.99 0.59 0.26 0.71 55.56 0.60 1.38 (0.60) (4.86) (0.60) (1.32) S O Ca 34.49 3.50 0.11 29.70 7.17 0.06 33.26 4.55 0.19 34.80 3.36 0.03 32.70 4.54 34.14 2.61 30.85 7.40 0.13 31.29 3.09 0.05 32.45 9.53 0.02 34.87 2.61 0.02 27.90 2.57 0.10 30.84 6.61 0.14 30.41 3.25 0.04 31.88 3.93 0.01 32.11 4.62 0.08 (2.09) (2.19) (0.06) Al 0.22 0.14 0.02 0.00 0.05 0.05 0.13 0.05 0.09 0.04 0.10 0.08 0.02 0.11 0.08 (0.06) Mn P Cr Ti Co Cu Total 0.04 0.06 0.58 0.02 0.04 98.99 0.05 0.01 0.11 0.05 0.05 96.90 0.02 0.11 0.97 0.05 0.03 99.04 0.01 0.00 0.02 0.08 0.15 99.58 0.00 0.16 0.44 0.17 0.03 99.30 0.00 0.00 0.05 0.00 0.00 98.65 0.02 0.05 0.08 0.00 0.09 99.79 0.04 0.05 0.05 0.11 0.00 86.29 0.04 0.00 0.20 0.00 0.13 101.32 0.03 0.00 0.17 0.00 0.00 98.70 0.03 0.00 0.05 0.14 0.00 78.59 0.01 0.09 0.14 0.09 0.00 95.26 0.01 0.01 0.05 0.00 0.08 0.00 89.88 0.01 0.00 0.12 0.03 0.09 94.73 BDL BDL 0.22 BDL BDL BDL 95.50 (0.27) (6.40) Nogoya Si Fe Mg Ni S O Ca Al Mn P Cr Ti Co Cu Total Nog-d8RB-ChC-g 0.90 52.69 1.15 4.68 33.94 5.75 0.31 0.08 0.00 0.00 0.03 0.00 0.04 0.00 99.57 Average 0.90 52.69 1.15 4.68 33.94 5.75 0.31 0.08 BDL BDL 0.03 BDL BDL BDL 99.57 212 A.3 Metals Kamacite Murray Si Fe Mg Ni S O Ca Al Mn P Cr Ti Co Cu Total 12-a 0.03 92.79 0.02 5.53 0.01 0.26 0.00 0.04 0.01 0.28 0.05 0.19 0.02 99.24 12-b 0.05 93.14 0.03 4.72 0.01 0.43 0.00 0.04 0.00 0.30 0.08 0.18 0.11 99.07 13-a 0.02 94.43 0.00 3.70 0.01 0.27 0.00 0.04 0.00 0.38 0.37 0.20 0.04 99.47 13-e 0.03 93.38 0.02 4.12 0.00 0.37 0.00 0.12 0.03 0.37 0.39 0.13 0.19 99.15 1-4a 0.02 91.33 0.00 5.19 0.01 0.25 0.00 0.08 0.00 0.45 0.45 0.15 0.06 97.99 14-a 0.03 91.87 0.02 5.61 0.00 0.27 0.05 0.08 0.02 0.42 0.43 0.22 0.12 99.14 14-b 0.05 91.98 0.00 5.53 0.00 0.26 0.04 0.06 0.03 0.40 0.39 0.18 0.06 98.97 1-4e 0.04 93.28 0.02 5.37 0.02 0.34 0.04 0.12 0.01 0.24 0.19 0.26 0.04 99.97 1-4h 0.03 92.57 0.00 5.02 0.02 0.27 0.03 0.03 0.00 0.39 0.48 0.19 0.06 99.10 14-j 0.04 92.03 0.01 5.63 0.00 0.27 0.02 0.01 0.00 0.40 0.41 0.26 0.00 99.08 14-l 0.17 91.95 0.11 4.79 0.02 0.82 0.03 0.04 0.00 0.39 0.22 0.19 0.05 98.79 15-b 0.10 91.57 0.02 5.52 0.02 0.21 0.01 0.01 0.00 0.53 0.91 0.16 0.05 99.11 15-c 0.11 91.30 0.00 5.39 0.01 0.30 0.02 0.07 0.03 0.52 0.86 0.21 0.03 98.84 15-p 0.07 91.52 0.00 4.89 0.02 0.29 0.02 0.03 0.00 0.46 0.80 0.15 0.02 98.27 15-p2 0.07 92.37 0.01 5.08 0.01 0.22 0.01 0.01 0.05 0.44 0.85 0.19 0.00 99.30 15-v 0.09 90.55 0.01 5.18 0.05 0.95 0.01 0.02 0.00 0.46 0.80 0.25 0.00 98.39 16-m 0.04 91.44 0.00 5.97 0.02 0.24 0.01 0.03 0.00 0.40 0.67 0.24 0.01 99.07 16-o 0.01 92.95 0.01 4.88 0.00 0.27 0.02 0.01 0.00 0.49 0.47 0.17 0.02 99.31 16-y 0.02 92.78 0.00 5.14 0.01 0.27 0.00 0.01 0.01 0.43 0.50 0.19 0.02 99.38 16-z 0.03 92.05 0.00 5.05 0.03 0.35 0.03 0.03 0.04 0.37 0.35 0.15 0.08 98.55 17-a 0.04 92.02 0.01 5.80 0.00 0.30 0.01 0.00 0.00 0.02 0.09 0.26 0.05 98.61 18-a 0.50 92.06 0.00 5.34 0.01 0.23 0.00 0.10 0.02 0.39 1.04 0.24 0.05 100.00 19_a 0.01 92.52 0.00 5.82 0.01 0.22 0.01 0.03 0.01 0.36 0.44 0.23 0.00 99.65 19_h 0.01 93.00 0.01 5.76 0.00 0.24 0.00 0.01 0.01 0.46 0.45 0.19 0.00 100.14 1-a 0.03 93.56 0.00 5.39 0.01 0.17 0.01 0.05 0.46 0.44 0.00 0.16 0.08 100.37 1-k 0.03 93.67 0.00 5.28 0.00 0.20 0.03 0.01 0.28 0.17 0.00 0.19 0.04 99.89 2_CC_Clean 0.05 92.56 0.01 5.02 0.02 0.26 0.04 0.01 0.30 0.21 0.15 0.09 98.72 2_DD_Clean 0.05 92.00 0.00 5.02 0.02 0.29 0.04 0.00 0.09 0.07 0.16 0.09 97.84 2_EE1 0.06 94.31 0.00 5.03 0.01 0.24 0.00 0.13 0.00 0.41 0.79 0.01 0.09 101.11 2_EE2 0.14 92.04 0.00 4.94 0.00 0.25 0.00 0.21 0.01 0.38 0.71 0.02 0.19 98.90 2_EE3 0.14 92.53 0.01 4.85 0.00 0.26 0.01 0.20 0.01 0.38 0.75 0.00 0.20 99.38 2-a 0.06 94.43 0.01 5.08 0.02 0.17 0.00 0.01 0.52 0.80 0.00 0.17 0.00 101.27 4_r 0.65 90.51 0.00 5.79 0.07 0.81 0.01 0.05 0.45 0.66 0.18 0.00 99.19 4-a 0.03 92.45 0.00 5.57 0.03 0.21 0.01 0.00 0.37 0.51 0.00 0.17 0.00 99.35 4-u 0.03 93.60 0.00 4.64 0.03 0.21 0.02 0.00 0.79 0.72 0.01 0.24 0.00 100.29 6-4b 0.08 93.68 0.01 4.88 0.03 0.51 0.03 0.00 0.03 0.49 0.22 0.13 0.12 100.21 E-a 0.01 93.25 0.00 4.79 0.01 0.21 0.01 0.02 0.00 0.42 0.37 0.12 0.08 99.28 E-c 0.03 93.26 0.00 4.62 0.01 0.19 0.01 0.01 0.00 0.56 0.41 0.16 0.00 99.24 E-k 0.04 92.42 0.03 4.83 0.02 0.15 0.03 0.02 0.02 0.26 0.18 0.17 0.02 98.17 F-qq 0.03 91.84 0.02 4.69 0.01 0.21 0.01 0.01 0.00 0.48 0.05 0.42 0.00 97.76 M2-b 2.43 89.62 0.01 5.86 0.00 0.22 0.00 0.01 0.00 0.07 0.12 0.23 0.00 98.58 M-c 1.67 89.50 0.00 5.25 0.00 0.16 0.00 0.05 0.03 0.30 1.03 0.17 0.00 98.16 M-e 1.70 90.50 0.01 5.23 0.00 0.14 0.00 0.01 0.01 0.31 1.02 0.15 0.10 99.17 Mry1-6RA-GG 0.02 92.77 0.00 4.96 0.01 0.04 0.02 0.05 0.39 0.41 0.01 0.19 0.12 98.99 Mry1-6RA-n 0.02 91.95 0.01 5.14 0.00 0.02 0.02 0.01 0.26 0.08 0.00 0.14 0.03 97.67 Mry1-6RA-u 0.15 92.08 0.02 5.78 0.02 0.07 0.00 0.02 0.09 0.18 0.01 0.34 0.00 98.75 Mry1-6RA-v 0.03 92.73 0.02 5.29 0.06 0.02 0.00 0.00 0.00 0.05 0.01 0.31 0.04 98.55 Mry1-6RB-o 0.09 92.12 0.00 4.53 0.03 0.00 0.00 0.00 0.50 0.92 0.00 0.23 0.05 98.49 Mry1-8RA-a 0.03 91.63 0.00 5.94 0.00 0.24 0.00 0.00 0.01 0.46 0.37 0.01 0.31 0.03 99.03 Mry1-8RA-c 0.03 91.97 0.01 4.72 0.03 0.28 0.01 0.00 0.01 0.48 0.63 0.00 0.21 0.10 98.48 Mry1-Ch11-d8-b 0.01 93.38 0.00 5.46 0.02 0.32 0.01 0.01 0.02 0.50 0.42 0.00 0.25 0.00 100.42 Mry1-Ch15-c 0.04 94.67 0.01 3.73 0.01 0.35 0.01 0.01 0.05 0.28 0.12 0.01 0.23 0.00 99.52 Mry1-Ch1-d8-E 0.06 91.71 0.00 4.45 0.01 0.32 0.02 0.01 0.00 0.54 0.73 0.02 0.22 0.08 98.17 Mry1-Ch1-d8-t 0.05 91.36 0.01 5.47 0.01 0.42 0.07 0.00 0.01 0.26 0.15 0.01 0.27 0.14 98.24 Mry1-ChE-d8-a 0.03 93.60 0.00 4.65 0.00 0.34 0.00 0.00 0.00 0.44 0.35 0.00 0.16 0.05 99.63 Mry1-ChE-d8-b 0.07 93.22 0.03 4.81 0.21 0.93 0.03 0.01 0.00 0.37 0.50 0.04 0.26 0.08 100.56 Mry1-ChE-d8-i 0.03 93.16 0.01 4.77 0.00 0.31 0.02 0.00 0.01 0.51 0.41 0.00 0.27 0.03 99.53 Mry1-ChE-d8-j 0.10 92.31 0.02 4.99 0.04 0.55 0.06 0.00 0.02 0.34 0.62 0.00 0.18 0.00 99.21 Mry2-C-b 0.06 94.29 0.01 5.39 0.04 0.41 0.00 0.00 0.00 0.34 0.24 0.23 0.01 101.04 Mry2-C-g 0.04 93.76 0.01 5.11 0.03 0.39 0.00 0.00 0.01 0.18 0.10 0.29 0.00 99.92 Mry2-C-h 0.09 92.85 0.01 4.80 0.04 0.83 0.02 0.00 0.01 0.17 0.07 0.27 0.00 99.18 Mry2-ChE-d8-a_blue 0.05 90.64 0.00 5.07 0.01 0.41 0.00 0.00 0.00 0.39 0.31 0.00 0.20 0.08 97.17 Mry2-C-i 0.11 93.89 0.02 5.42 0.02 0.35 0.02 0.00 0.00 0.09 0.08 0.32 0.00 100.32 Mry2-C-j 0.08 92.68 0.01 6.06 0.09 0.65 0.02 0.01 0.00 0.13 0.06 0.30 0.00 100.08 Mry2-C-t 0.05 94.34 0.03 5.37 0.01 0.27 0.00 0.00 0.00 0.42 0.53 0.25 0.01 101.29 213 Mry2-E-a Mry2-E-cc Mry2-E-t Mry2-I-a Mry2-I-b Mry2-I-d Mry2-I-g Mry2-I-k Mry-A-m Mry-A-n Mry-B-a Mry-B-c Myr2-c-a N-a Average Std Dev Murchsion Murch-5RD-d7-a Murch-5RD-d7-a Murch-5RD-g Murch-8RA-a Murch-8RA-c Murch-A-a Murch-A-c Murch-ChD-d7-b Murch-ChF-d8-a Murch-ChF-d8-b Murch-Ch-G-a Murch-Ch-G-b Murch-D-b Murch-D-d Murch-E-a Murch-E-b Murch-F-a Murch-F-b Murch-F-d Murch-G-a Murch-G-b Murch-K-d Murch-K-f Average Std Dev Cold Bokkeveld Cold-A-a Cold-A-b Cold-C-a Cold-C-p Cold-E-u Average Std Dev Oxidized Kamacite Murray 1-4b 15-p3 15-p4 15-q 15-u 15-w 16-jj_lt 18-b 18-f 1-h E-d F-i F-rr L-a 0.11 0.07 0.24 0.09 0.07 0.04 0.04 0.09 0.06 0.04 0.07 0.04 0.03 0.80 0.15 (0.38) 90.01 0.00 93.71 0.00 86.32 0.06 92.57 0.00 89.82 0.02 91.55 0.00 92.85 0.00 90.38 0.00 92.59 0.01 92.10 0.01 91.35 0.00 93.19 0.00 94.70 0.00 90.46 0.01 92.32 BDL (1.38) 6.04 0.00 5.23 0.03 5.46 0.03 5.34 0.01 6.25 0.03 4.01 0.03 5.95 0.02 5.72 0.05 5.09 0.03 5.15 0.02 6.20 0.00 3.80 0.01 5.30 0.01 5.44 0.01 5.17 BDL (0.54) 0.33 0.01 0.30 0.02 0.92 0.02 0.18 0.00 0.30 0.00 0.38 0.00 0.25 0.00 0.39 0.00 0.23 0.03 0.30 0.00 0.25 0.00 0.32 0.02 0.25 0.02 0.16 0.00 0.33 BDL (0.19) 0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.01 0.01 0.01 0.00 0.01 0.00 0.01 0.03 (0.04) 0.00 0.01 0.02 0.00 0.01 0.00 0.00 0.00 0.01 0.03 0.02 0.00 0.00 0.02 BDL 0.23 0.22 0.20 0.05 0.07 0.17 0.47 0.56 0.30 0.57 0.40 0.28 0.26 0.48 0.20 0.13 0.43 0.32 0.45 0.33 0.26 0.53 0.50 0.17 0.37 0.29 0.50 0.84 0.36 0.42 BDL (0.14) (0.27) 0.24 0.26 0.23 0.27 0.19 0.30 0.26 0.29 0.14 0.17 0.16 0.21 0.31 0.18 0.21 (0.06) 0.02 0.02 0.03 0.08 0.10 0.10 0.12 0.07 0.15 0.06 0.04 0.06 0.01 0.00 BDL 97.22 99.91 93.58 99.59 97.68 97.09 100.23 97.32 99.10 98.68 98.90 98.36 101.28 98.42 99.08 (1.14) Si Fe Mg Ni S O Ca Al 0.04 94.75 0.00 3.99 0.02 0.36 0.04 0.00 0.04 94.75 0.00 3.99 0.02 0.36 0.04 0.00 0.01 95.05 0.00 4.20 0.04 0.05 0.00 0.02 93.04 0.01 5.42 0.00 0.29 0.00 0.00 0.03 92.26 0.01 5.45 0.02 0.41 0.00 0.01 0.03 92.71 0.00 5.28 0.02 0.16 0.03 0.02 0.05 93.48 0.01 4.43 0.01 0.27 0.05 0.05 0.04 94.92 0.00 3.83 0.02 0.28 0.00 0.01 0.02 92.68 0.00 6.45 0.01 0.33 0.00 0.00 0.03 92.93 0.02 4.19 0.02 1.71 0.01 0.01 0.03 92.12 0.00 6.11 0.01 0.27 0.01 0.00 0.03 91.44 0.01 5.97 0.01 0.28 0.01 0.01 0.05 92.80 0.00 4.19 0.00 0.18 0.00 0.02 0.05 93.99 0.02 4.78 0.05 0.23 0.03 0.03 0.07 92.61 0.00 5.22 0.02 0.16 0.00 0.00 0.08 93.16 0.01 5.28 0.03 0.15 0.00 0.03 0.03 94.32 0.00 4.94 0.02 0.20 0.00 0.03 0.04 95.86 0.00 4.01 0.01 0.20 0.00 0.03 0.03 93.38 0.00 4.93 0.01 0.26 0.02 0.03 0.04 91.78 0.00 6.32 0.02 0.23 0.00 0.03 0.03 92.64 0.01 5.84 0.03 0.22 0.00 0.02 0.05 92.18 0.02 5.70 0.01 0.28 0.01 0.01 0.04 92.07 0.01 5.21 0.00 0.27 0.02 0.01 0.04 93.26 BDL 5.03 BDL 0.32 BDL 0.02 (0.02) (1.19) (0.81) (0.32) (0.01) Mn P Cr Ti Co 0.01 0.37 0.10 0.01 0.25 0.01 0.37 0.10 0.01 0.25 0.00 0.36 0.10 0.00 0.20 0.00 0.44 0.26 0.00 0.24 0.01 0.38 0.26 0.03 0.20 0.02 0.58 0.20 0.23 0.00 0.37 0.26 0.24 0.05 0.67 0.57 0.00 0.17 0.01 0.21 0.17 0.00 0.26 0.01 0.41 0.09 0.00 0.27 0.00 0.15 0.07 0.02 0.31 0.01 0.18 0.09 0.00 0.29 0.00 0.54 0.56 0.17 0.01 0.33 0.03 0.20 0.00 0.22 0.48 0.17 0.00 0.19 0.39 0.24 0.00 0.39 0.15 0.25 0.01 0.43 0.13 0.18 0.00 0.43 0.12 0.19 0.00 0.20 0.14 0.21 0.00 0.13 0.08 0.21 0.04 0.37 0.90 0.22 0.00 0.58 0.39 0.22 BDL 0.36 0.25 BDL 0.22 (0.15) (0.21) (0.04) Co 0.24 0.27 0.19 0.24 0.43 0.27 (0.09) Cu Total 0.05 100.01 0.05 100.01 0.05 100.06 0.00 99.73 0.03 99.10 0.12 99.41 0.13 99.36 0.11 100.67 0.00 100.14 0.08 99.78 0.07 99.16 0.00 98.33 0.09 98.60 0.24 99.98 0.12 99.07 0.21 99.78 0.21 100.55 0.22 101.13 0.22 99.60 0.20 99.15 0.13 99.35 0.03 99.82 0.06 98.88 BDL 99.64 (0.66) Cu Total 0.07 100.26 0.05 100.43 0.00 98.40 0.00 99.18 0.00 99.81 BDL 99.62 (0.83) Si Fe Mg Ni S O Ca Al Mn P Cr Ti 0.07 93.00 0.01 5.66 0.02 0.21 0.00 0.02 0.01 0.38 0.57 0.23 92.52 0.01 5.43 0.01 0.21 0.01 0.00 0.03 0.35 1.31 0.08 91.99 0.01 4.68 0.00 0.22 0.00 0.00 0.00 0.38 0.86 0.06 92.11 0.01 5.57 0.02 0.25 0.01 0.00 0.00 0.29 0.62 0.28 85.28 0.92 8.48 0.00 1.15 0.02 0.01 0.03 2.95 0.26 0.14 90.98 0.19 5.96 BDL 0.41 BDL BDL BDL 0.87 0.72 (0.10) (3.21) (0.41) (1.46) (0.42) (1.16) (0.39) Si Fe Mg Ni S O Ca Al Mn P Cr Ti Co Cu Total 2.02 62.20 2.82 4.83 1.85 16.05 0.07 0.35 0.09 0.44 0.64 0.14 0.00 91.48 0.48 77.42 0.24 4.42 1.04 9.38 0.09 0.09 0.09 0.46 1.00 0.17 0.12 94.98 0.98 57.35 0.36 2.35 2.32 27.47 0.18 0.10 0.13 0.64 0.72 0.15 0.06 92.82 0.67 51.88 0.91 2.73 2.45 22.52 0.12 0.31 0.13 1.12 1.83 0.05 0.14 84.86 1.33 46.55 1.50 4.91 3.71 25.86 0.14 0.31 0.09 0.79 2.51 0.49 0.03 88.22 0.08 88.17 0.00 5.70 2.95 1.41 0.02 0.03 0.01 0.03 0.23 0.35 0.11 99.10 0.14 88.93 0.11 4.98 0.75 2.55 0.04 0.06 0.03 0.02 0.46 0.20 0.97 99.23 1.44 48.43 0.48 4.38 2.84 26.54 0.34 0.09 0.21 0.69 0.67 0.22 0.03 86.36 1.16 73.32 0.49 4.64 0.58 10.93 0.08 0.05 0.05 0.40 1.19 0.16 0.00 93.06 0.68 78.86 0.69 4.45 1.44 10.94 0.09 0.02 0.37 0.71 0.02 0.11 0.04 98.43 0.52 79.00 0.49 4.61 1.64 11.18 0.22 0.06 0.03 0.34 0.73 0.13 0.10 99.05 0.43 82.55 0.26 5.71 1.07 4.98 0.04 0.02 0.02 0.53 0.89 0.28 0.00 96.76 0.04 80.75 0.03 6.00 1.08 6.40 0.01 0.01 0.02 0.53 0.04 0.46 0.05 95.44 0.66 63.43 0.55 0.94 3.19 26.02 0.26 0.12 0.08 0.11 1.84 0.04 0.02 97.23 214 L-b-dk M-b M-d M-f M-g M-l Mry1-6RA-p Mry1-6RB-a Mry1-8RA-b Mry1-ChE-d8-k Mry2-E-ee Mry2-I-e N-b Average Std Dev Murchison Murch-5RD-d7-a Murch-8RA-d Murch-A-b Murch-ChF-d8-g Murch-G-h Murch-H-d Murch-K-a Average Std Dev Cold Bokkeveld Cold-5RA-o Cold-A-f Cold-A-h Cold-A-i Cold-A-k Cold-A-n Cold-C-s Cold-C-T Average Std Dev 0.67 61.77 0.80 1.33 2.76 51.04 0.32 3.41 1.74 87.29 0.07 5.12 2.75 51.97 0.17 6.91 1.85 88.71 0.00 4.99 2.39 62.90 0.14 6.54 1.44 69.40 0.88 9.53 0.11 87.56 0.04 4.66 0.96 58.59 0.61 3.17 0.46 71.46 0.73 4.42 0.41 86.88 0.07 5.88 0.24 83.32 0.04 4.48 1.41 71.63 0.11 5.01 1.03 70.79 0.48 4.67 (0.80) (14.05) (0.59) (1.71) 4.86 23.68 0.20 2.88 28.99 0.61 0.16 2.09 0.01 3.21 28.70 0.40 0.07 2.34 0.03 1.64 20.37 0.26 0.61 0.24 0.02 0.02 4.47 24.53 0.17 3.02 14.87 0.17 0.34 2.66 0.06 0.28 3.31 0.03 0.65 7.83 0.15 1.82 14.46 0.15 (1.39) (10.04) (0.14) 0.14 0.04 0.06 0.00 0.00 0.00 0.09 0.00 0.04 0.06 0.03 0.07 0.01 0.08 (0.09) Al 0.03 0.05 0.02 0.17 0.22 0.11 0.03 0.09 (0.08) Al 0.09 0.01 0.03 0.18 0.07 0.04 0.02 0.02 0.06 (0.06) 0.01 0.10 1.50 0.33 0.30 1.70 0.08 0.31 1.08 0.25 0.25 1.69 0.04 0.37 1.10 0.15 0.41 1.50 0.00 3.53 0.15 0.00 0.01 0.35 0.25 0.00 0.19 0.53 0.48 0.08 0.07 0.33 0.84 0.01 0.03 0.24 0.46 0.01 1.48 0.19 0.09 0.41 0.93 0.08 0.56 0.94 BDL (0.08) (0.67) (0.62) 0.13 0.50 0.21 0.33 0.21 0.22 0.20 0.28 0.12 0.25 0.27 0.27 0.16 0.23 (0.12) 0.00 0.00 0.00 0.00 0.02 0.00 0.18 0.00 0.42 0.04 0.00 0.13 0.04 BDL 95.19 92.88 98.22 96.63 99.74 96.52 86.24 93.31 94.36 96.72 97.31 93.85 88.43 94.31 (4.29) Si Fe Mg Ni S O Ca 0.26 78.27 0.37 4.19 1.49 6.73 0.08 0.26 86.19 0.41 5.83 1.72 4.50 0.02 0.52 88.74 0.40 5.55 0.05 1.22 0.05 1.60 73.37 1.82 4.76 1.56 15.84 0.09 1.73 52.00 0.86 2.41 2.73 21.05 1.71 1.06 70.78 0.70 6.45 1.40 16.69 0.26 0.05 91.12 0.03 5.14 0.17 1.47 0.03 0.78 77.21 0.66 4.90 1.30 9.64 0.32 (0.68) (13.54) (0.58) (1.32) (0.93) (8.07) (0.62) Si Fe Mg Ni S O Ca 1.75 57.96 1.52 2.69 1.97 0.34 0.06 40.28 0.46 11.24 5.95 34.47 0.05 0.80 47.28 1.42 6.17 2.38 37.29 0.02 2.68 53.21 2.29 3.76 0.79 29.87 0.18 1.88 58.05 0.95 2.30 0.73 29.54 0.51 1.14 63.19 0.67 3.97 0.40 22.75 0.17 0.43 83.14 0.18 5.17 0.23 10.59 0.05 1.65 63.20 0.38 1.99 1.37 27.58 0.65 1.30 58.29 0.98 4.66 1.73 27.44 0.25 (0.86) (12.75) (0.71) (3.02) (1.86) (8.78) (0.23) Mn P Cr Ti Co 0.00 0.60 0.21 0.00 0.28 0.04 0.47 0.26 0.00 0.25 0.00 0.39 0.20 0.25 0.01 0.43 0.12 0.04 0.21 0.09 0.72 1.67 0.21 0.05 0.26 0.01 0.34 0.01 0.32 0.42 0.15 BDL 0.46 0.41 BDL 0.24 (0.16) (0.57) (0.06) Mn P Cr Ti Co 0.07 0.24 0.27 0.02 0.17 0.04 0.60 1.32 0.73 0.11 0.03 0.17 0.28 0.20 0.23 1.05 0.10 0.30 0.58 0.00 0.05 0.18 0.26 0.67 0.06 0.06 0.25 0.60 0.24 0.11 0.35 0.29 0.19 0.13 0.32 0.55 BDL 0.23 (0.09) (0.19) (0.46) (0.22) Cu Total 0.07 92.58 0.11 100.12 0.69 98.08 0.10 100.12 0.00 85.41 0.02 98.15 0.15 99.10 0.16 96.22 (0.24) (5.42) Cu Total 0.03 67.13 0.12 95.33 0.01 95.98 0.15 94.68 0.06 95.03 0.02 93.52 0.00 100.97 0.05 97.81 BDL 92.56 (10.53) 215 Magnetite Murray 12-j 19_b E-t Mry1-6RA-A Mry1-6RA-B Mry1-6RB-j Mry1-6RB-jsi Mry1-6RB-k Mry1-6RB-ksi Mry1-6RE-b Mry1-6RE-i Mry1-Ch1-d8-L Mry2-5RA-l Mry2-C-c Mry2-H-d Mry-B-e Average Std Dev Si Fe Mg Ni S O Ca 0.69 64.03 0.58 0.75 2.91 27.42 0.14 8.74 49.16 0.16 0.06 0.02 37.16 0.03 0.09 65.94 0.03 0.17 9.19 22.59 0.15 4.98 52.22 2.48 0.22 0.56 0.15 0.12 66.62 0.05 0.12 0.06 0.07 0.06 65.49 0.07 0.63 1.46 0.09 0.07 68.89 0.06 0.58 0.88 21.06 0.09 0.07 65.94 0.09 0.23 7.66 0.10 0.07 67.34 0.10 0.26 5.63 25.33 0.13 0.10 67.13 0.02 0.10 0.03 0.18 0.11 68.26 0.00 0.03 0.02 0.15 0.68 63.56 0.75 0.54 1.73 21.09 0.04 0.66 50.95 0.82 0.45 3.86 0.05 0.09 68.08 0.05 0.68 1.06 26.08 0.11 1.53 61.33 0.09 1.96 1.53 28.63 0.90 0.04 71.00 0.01 0.06 0.02 25.97 0.05 1.13 63.50 0.33 0.43 2.29 26.15 0.15 (2.37) (6.72) (0.63) (0.48) (2.88) (4.92) (0.20) Al 0.11 0.52 0.01 0.16 0.01 0.00 0.00 0.00 0.00 0.01 0.00 0.19 0.80 0.01 0.00 0.01 0.11 (0.23) Al 0.02 0.01 0.01 0.03 0.02 0.03 0.02 (0.01) Al 0.00 0.17 0.01 0.06 (0.10) Mn P Cr Ti Co Cu Total 0.03 0.12 0.16 0.00 0.00 96.95 0.08 0.00 0.05 0.00 0.01 96.00 0.03 0.01 0.08 0.00 0.00 98.28 0.02 0.00 0.04 0.01 0.03 0.00 60.88 0.01 0.01 0.02 0.01 0.00 0.05 67.16 0.04 0.00 0.06 0.01 0.10 0.04 68.05 0.03 0.01 0.06 0.00 0.10 91.99 0.04 0.00 0.03 0.00 0.10 0.05 74.32 0.02 0.00 0.05 0.03 0.11 99.30 0.05 0.00 0.03 0.00 0.00 0.00 67.66 0.03 0.00 0.03 0.01 0.00 0.00 68.62 0.01 0.03 0.07 0.01 0.04 0.01 88.75 0.04 0.00 0.03 0.01 0.01 0.02 57.69 0.03 0.00 0.05 0.04 0.00 96.27 0.19 0.20 0.16 0.22 0.02 96.75 0.01 0.00 0.05 0.00 0.09 97.31 BDL BDL 0.06 BDL BDL BDL 82.87 (0.04) (15.64) Mn P Cr Ti Co Cu Total 0.01 0.03 0.05 0.01 0.01 0.02 87.79 0.00 0.01 0.05 0.01 0.00 0.07 97.85 0.00 0.01 0.05 0.01 0.00 0.07 97.85 0.01 0.04 0.04 0.00 0.03 86.55 0.00 0.01 0.05 0.00 0.00 94.08 0.00 0.06 0.01 0.00 0.01 95.34 BDL BDL 0.04 BDL BDL BDL 93.24 (0.02) (4.94) Mn P Cr Ti Co Cu Total 0.03 0.00 0.02 0.02 0.00 0.00 68.15 0.27 0.12 0.72 0.05 0.04 96.67 0.01 0.01 0.04 0.03 0.06 98.38 0.10 BDL 0.26 BDL BDL BDL 87.73 (0.14) (0.40) (16.98) Murchison Si Fe Mg Ni S O Ca Murch-ChD-d7-agrain 0.22 65.75 0.14 0.07 0.08 21.33 0.03 Murch-ChD-d7-h 0.08 71.43 0.06 0.09 0.02 25.98 0.05 Murch-ChD-d7-h 0.08 71.43 0.06 0.09 0.02 25.98 0.05 Murch-D-c 0.12 64.04 0.02 0.14 0.08 21.99 0.02 Murch-F-l 0.17 69.52 0.05 0.12 0.13 23.91 0.10 Murch-H-g 0.28 67.19 0.09 0.11 0.08 27.36 0.13 Average 0.16 68.23 0.07 BDL 0.07 24.43 0.06 Std Dev (0.08) (3.06) (0.04) (0.04) (2.42) (0.04) Cold Bokkeveld Cold-5RB-c Cold-A-c Cold-C-c Average Std Dev Si Fe Mg Ni S O Ca 0.10 67.79 0.01 0.09 0.02 0.07 3.02 56.38 1.78 0.98 0.87 32.11 0.17 0.08 70.35 0.05 0.12 0.01 27.58 0.01 1.07 64.84 0.61 0.40 0.30 29.85 0.08 (1.69) (7.44) (1.01) (0.51) (0.49) (3.20) (0.08) Taenite Murray 17-h 17-k Average Std Dev Murchsion Murch_B-a Murch-H-a Average Std Dev Si Fe Mg 0.02 69.13 0.00 0.02 78.44 0.00 BDL 73.79 0.00 (6.58) 0.00 Ni S O Ca Al 27.18 0.04 0.32 0.00 0.17 18.38 0.07 0.26 0.01 0.00 22.78 0.06 0.29 BDL 0.09 (6.22) (0.02) (0.04) (0.12) Mn P Cr Ti 0.00 0.00 0.09 0.01 0.01 0.05 BDL BDL 0.07 (0.03) Mn P Cr Ti 0.00 0.69 0.17 0.00 0.19 0.00 BDL 0.44 0.09 (0.35) (0.12) Co 1.38 1.29 1.34 (0.06) Cu Total 0.00 98.33 0.01 98.53 BDL 98.43 (0.14) Si Fe Mg Ni S O Ca Al 0.05 88.81 0.01 8.98 0.01 0.24 0.00 0.03 0.05 89.67 0.00 9.14 0.00 0.23 0.00 0.01 0.05 89.24 BDL 9.06 BDL 0.24 0.00 0.02 0.00 (0.61) (0.11) (0.01) 0.00 (0.01) Co Cu Total 0.32 0.11 99.41 0.51 0.10 99.89 0.42 BDL 99.65 (0.13) (0.34) Schreibersite Murray 13-b 13-c 13-d 6-4n Average Std Dev Si Fe Mg 0.03 73.87 0.00 0.00 74.37 0.00 0.02 73.93 0.00 1.04 53.01 0.80 0.27 68.80 0.20 (0.51) (10.53) (0.40) Ni S O Ca Al 8.26 0.13 1.25 0.00 0.02 8.18 0.10 0.68 0.00 0.04 8.27 0.02 0.22 0.00 0.04 24.01 0.44 3.37 0.02 0.13 12.18 0.17 1.38 BDL 0.06 (7.89) (0.18) (1.39) (0.05) Mn P Cr Ti 0.00 14.81 1.56 0.01 15.14 1.60 0.00 15.89 1.58 0.08 13.94 0.18 BDL 14.95 1.23 (0.81) (0.70) Co Cu Total 0.07 0.00 100.00 0.08 0.03 100.24 0.08 0.10 100.16 0.00 0.01 97.03 BDL BDL 99.36 (1.55) 216 A.4 Anhydrous Silicates Orthopyroxene Murray 12-g 14-e 15-a 15-d 16-j 16-n 16-r 17-g 2-b 3-4g 3hh 4_FF_dark 4-4m 4-4n 4-4r 4bb 4w 8b 9r A-d D-b F-aa F-hh G-b Mry2-C-dd Mry2-E-b Mry2-E-dd Mry-B-b Average Std Dev Muchsion Murch_A-d Murch_I-d Murch-ChD-d7-g Murch-F-h Murch-G-c Murch-H-c Murch-K-e Average Std Dev Cold Bokkeveld Cold-C-J Cold-D-e Cold-D-g Cold-G-k Cold-H-f Cold-H-k Average Std Dev Si 25 26.02 27.27 26.54 26.59 26.24 26.09 25.82 26.26 27.07 25.37 26.58 26.63 26.29 26.83 27.34 26.58 26 27.13 26.18 27.17 25.2 27.65 26.87 24.44 26.05 24.46 27.15 26.32 (0.83) Fe Mg Ni S O Ca Al Mn P Cr Ti Co Cu Total 0.78 24.88 0.03 0.01 48.11 1.41 1.19 0.13 0.01 0.46 0 0 102.01 0.9 22.53 0.04 0.06 47.31 0.38 0.7 0.04 0 0.23 0.02 0.03 98.25 0.72 23.87 0 0 48.9 0.42 0.54 0.04 0.01 0.27 0 0 102.05 0.74 23.76 0.05 0 49.19 0.34 0.77 0.03 0.02 0.26 0.03 0.05 101.79 0.78 23.65 0 0.01 48.79 0.3 0.28 0.06 0.01 0.34 0 0.01 100.83 0.98 23.26 0 0.02 48.34 0.39 0.53 0.11 0 0.31 0 0.02 100.19 3.32 21.02 0.04 0.01 48.04 1.27 0.89 0.27 0 0.77 0 0.03 101.75 2.8 16.3 0.01 0.23 48.11 3.91 2.42 0.25 0.04 0.48 0.03 0.03 100.4 0.6 23.27 0.01 0 48.18 1.45 1.1 0.09 0 0.39 0.16 0 101.5 1.86 23.46 0.02 0 49.06 0.15 0.18 0.04 0 0.39 0 0 102.23 9.3 17.34 0.15 0.01 46.42 1.56 0.68 0.24 0.01 0.46 0.22 0.02 101.81 0.63 22.64 0.04 0.01 48.54 1.32 0.84 0.07 0 0.32 0.11 0.02 101.14 0.56 22.81 0.04 0 48.65 1.45 0.76 0.06 0 0.35 0.02 0 101.33 0.62 22.45 0.02 0 48.56 1.81 1.27 0.09 0 0.39 0 0 101.51 0.68 22.77 0.08 0.01 49.01 1.42 0.57 0.08 0.01 0.37 0 0.09 101.92 0.81 22.82 0.03 48.12 1.56 0.87 0.07 0.01 0.44 0.12 102.19 0.87 21.53 0.02 46.63 1.83 0.78 0.27 0 0.52 0.25 99.3 3.55 19.25 0.05 46.48 1.57 1.67 0.9 0 1.43 0.17 101.08 0.75 23.18 0.09 47.57 0.35 0.81 0.06 0 0.38 0.16 100.48 1.92 23.19 0.23 0.38 47.18 0.46 0.45 0.08 0 0.37 0 0.03 100.5 0.65 24.12 0.1 0.02 48.94 0.4 0.32 0 0 0.33 0.02 0.06 102.12 1.63 22.05 0.12 0.14 46.63 0.38 0.49 0.09 0 0.39 0.02 0 97.14 0.68 23.94 0.02 0.01 49.3 0.37 0.4 0.05 0.01 0.34 0.03 0 102.79 0.85 22.94 0 0 48.37 1.13 0.96 0.01 0.01 0.33 0 0.01 101.47 1.88 23.38 0.14 0.27 46.68 1.06 0.61 0.43 0.02 0.44 0 0.01 99.35 1.3 23.63 0 0.06 49.96 0.37 0.58 0.07 0 0.36 0.01 0.01 102.4 5.4 21.74 0.02 0.05 47.38 0.41 0.68 0.09 0 0.34 0 0 100.56 0.72 24.03 0.04 0 47.14 0.39 0.74 0.05 0 0.37 0.01 0.02 100.66 1.65 22.49 0.05 0.05 48.06 1.00 0.79 0.13 0.01 0.42 0.17 0.01 0.02 101.03 (1.88) (1.95) (0.06) (0.10) (0.97) (0.80) (0.45) (0.18) (0.01) (0.22) (0.05) (0.01) (0.02) (1.29) Si Fe Mg Ni S O Ca Al Mn P Cr Ti Co Cu Total 27.36 0.97 23.63 0.03 0.04 47.55 0.43 0.48 0.1 0 0.33 0 0 100.92 25.99 3.5 21.84 0.04 0.05 48.66 1 0.74 0.16 0 0.68 0 0 102.67 25.46 2.73 22.28 0.17 0.58 45.93 0.33 0.56 0.09 0 0.37 0.1 0 0.03 98.62 26.58 0.62 23.05 0.04 0 47.02 1.37 0.98 0.08 0.01 0.34 0 0 100.09 27.08 2.84 22.71 0.03 0.03 46.55 0.27 0.37 0.07 0.01 0.47 0 0 100.43 26.85 0.9 23.79 0.02 0.01 47.18 0.42 0.49 0.06 0 0.44 0.02 0.03 100.23 27.49 0.76 24.1 0 0.03 47.96 0.43 0.42 0.07 0 0.27 0.02 0.04 101.6 26.69 1.76 23.06 0.05 0.11 47.26 0.61 0.58 0.09 0.00 0.41 0.10 0.01 0.01 100.65 (0.74) (1.21) (0.83) (0.06) (0.21) (0.90) (0.41) (0.21) (0.03) (0.00) (0.14) #DIV/0! (0.01) (0.02) (1.27) Si 26.3 27.37 27.18 27.29 27.2 26.39 26.96 (0.48) Fe Mg Ni S O Ca Al Mn P Cr Ti 4.61 21.64 0.23 1.3 40.1 1.01 0.66 0.23 0.01 0.75 0.78 23.83 0.04 0 49.57 0.38 0.47 0.05 0 0.47 0.66 23.71 0.06 0.02 49.04 0.33 0.32 0.07 0 0.31 1.92 23.7 0.03 0.01 48.82 0.07 0.05 0.15 0 0.26 1.55 22.99 0.01 0 47.5 0.33 0.39 0.08 0 0.45 5.28 20.5 0.08 0.01 47.76 0.92 0.6 0.34 0 0.76 2.47 22.73 0.08 0.22 47.13 0.51 0.42 0.15 0.00 0.50 (1.99) (1.37) (0.08) (0.53) (3.53) (0.37) (0.22) (0.11) (0.00) (0.21) Co Cu Total 0.01 0 96.85 0.02 0 102.99 0.02 0 101.71 0 0.01 102.32 0.02 0.01 100.53 0.05 0 102.7 0.02 0.00 101.18 (0.02) (0.01) (2.30) Clinopyroxene Murray 14-k_lt 16-aa 2_II 6-4f_dk 6k 6m_line 6m_line 9_Rim10 Si Fe Mg Ni S O Ca Al Mn P Cr Ti 24.42 1.08 14.95 0.08 0.01 46.57 11.21 1.78 0.12 0 0.35 22.92 10.03 11.31 0.02 0.17 41.96 11.38 1.8 0.29 0.02 0.42 25.8 0.52 10.51 0 0.01 46.82 12.72 2.97 0.54 0.02 0.61 23.99 1.34 14.24 0.01 0.04 43.57 10.52 2.4 0.28 0.02 0.98 24.93 1.06 13 0 45.05 12.69 1.71 0.58 0.02 1.16 24.73 1.23 12.41 0 45.3 13.58 2.15 0.29 0 1.01 23.74 2.09 10.87 0.02 43.63 13.6 2.04 0.49 0.02 1.4 25.51 2.41 20.34 0.03 0.08 47.92 0.56 0.45 0 0.68 Co 0.41 0.69 1.05 1.13 Cu Total 0.03 100.59 0 100.31 101.08 0 97.39 100.92 101.77 99.07 0.01 0.02 98.01 0 0 0.01 0 217 Mry1-6RA-d Mry1-6RA-II Mry1-Ch11-d8-e Mry2-ChE-d8-f Mry2-C-l Mry2-F-v Average Std Dev Cold Bokkeveld Cold-A-l Cold-D-k Cold-D-l Cold-E-d Cold-E-s Cold-E-x Cold-J-b Average Std Dev 24.12 24.47 24.5 20.22 21.75 22.19 23.81 (1.54) 0.69 13.51 0.02 0.7 10.94 0.01 0.97 13.45 0.1 18.57 4.12 0 14.6 4.65 0.07 10.41 6.21 0.09 4.69 11.47 0.03 (6.05) (4.29) (0.04) 0 0 0.01 0.2 0.03 0.03 0.05 (0.07) 43.18 12.9 0.98 0.24 0.01 0.39 44.58 15.53 2.2 0.61 0.01 1.03 45.28 14.3 0.94 0.09 0 0.34 42.55 11.9 0.63 0.23 0.01 0.3 41.05 14.63 1.15 0.23 0.02 0.41 43.19 14.91 1.26 0.19 0.31 0.98 44.33 13.07 1.61 0.33 0.03 0.72 (1.96) (1.54) (0.71) (0.17) (0.08) (0.37) 0.03 0 0.04 0 0.05 0 0.02 0.05 0 0 0.65 0.01 0.01 (0.31) (0.02) (0.02) 0.46 0.69 0.5 0.24 96.54 100.8 100.52 99.03 98.67 99.78 99.61 (1.54) Si Fe Mg Ni S O Ca Al Mn P Cr Ti 24.29 1.23 12.64 0.08 0.01 45.34 14.04 1.69 0.61 0.01 0.79 22.95 0.55 10.64 0.05 0.01 45.81 15.52 4.9 0.07 0 0.68 19.57 7.62 10.84 0.11 0.21 47.99 8.64 4.44 0.12 0 0.71 24.95 1.02 13.11 0.04 0.01 45.93 12.49 1.29 1.26 0 1.23 22.17 0.57 9.8 0.04 0.08 44.68 15.14 5.53 0.16 0 1.3 21.91 0.65 9.72 0.02 0 46.04 15.07 6.23 0.19 0 1.31 23.92 2.21 12.76 0.11 0.14 45.09 12.6 1.18 0.33 0 0.78 22.82 1.98 11.36 0.06 0.07 45.84 13.36 3.61 0.39 0.00 0.97 (1.81) (2.55) (1.45) (0.04) (0.08) (1.07) (2.41) (2.16) (0.42) (0.00) (0.29) Co Cu Total 0.05 0 100.79 0.02 0.03 101.23 0 0 100.23 0.01 0.04 101.38 0.03 0 99.5 0 0 101.14 0.01 0 99.14 0.02 0.01 100.49 (0.02) (0.02) (0.89) Olivine Murray 13-f 13-k 14-c 14-g 14-k_dk 15-f 15-h 16-b 16-bb 17-l 19_g 19_l 1-b 3_LL_rim-1 4_EE_dark 4-4h 4-4q 6-4d 6-4g 6-4o 6-4r 6-4s 6a 6a 9_DD 9_RR 9_SS 9a 9c 9d 9j 9k 9n 9t 9u1 9v B-d B-g C-h C-n F-bb H-a Mry1-5RA-j Mry1-6RF-c Mry2-ChE-d8-e Si Fe Mg Ni S O Ca Al Mn P Cr Ti 14.83 36.52 10.61 0.08 0.01 36.99 0.23 0.06 0.32 0 0.16 16.07 25.24 17.52 0.03 0 39.62 0.19 0.04 0.26 0 0.18 16.31 25.6 17.94 0.04 0.01 39.3 0.28 0.05 0.26 0.01 0.12 19.1 0.69 34.54 0.04 0.01 49.06 0.16 0.07 0.09 0 0.21 21.32 0.91 31.28 0 0.01 47.92 0.48 0.31 0.1 0 0.28 14.67 40.67 7.77 0.07 0 34.68 0.18 0.04 0.39 0.05 0.35 14.71 41.38 7.28 0.12 0.02 34.97 0.23 0.04 0.41 0.05 0.2 16.42 22.46 19.51 0.09 0 40.82 0.18 0.02 0.49 0 0.25 18.36 1.15 33.71 0.04 0 46.95 0.15 0.03 0.15 0 0.35 15.59 27.19 15.73 0.09 0.01 41.15 0.32 0.06 0.4 0.13 0.22 19.5 1.14 34.01 0.04 0 47.24 0.18 0.04 0.13 0 0.37 19.11 0.92 34.14 0 0 47.82 0.12 0.09 0.12 0 0.39 23.11 1.42 29.94 0 0.01 47.65 0.78 0.29 0.17 0 0.4 19.57 1.96 33.93 0.1 0.05 47.49 0.08 0.01 0.22 0.02 18.94 0.86 33.49 0.05 0.02 46.13 0.16 0.1 0.11 0 0.31 18.95 0.84 34.28 0.06 0 46.67 0.12 0.05 0.17 0 0.36 19.45 0.83 34.53 0 0.01 46.91 0.16 0.11 0.1 0 0.31 18.82 0.96 34.13 0.09 0 46.52 0.13 0.08 0.08 0.01 0.34 19.27 0.85 34.2 0 0 47.03 0.14 0.06 0.12 0.01 0.36 15.94 24.12 19.29 0.05 0 40.19 0.15 0.04 0.24 0.01 0.26 16.92 21.08 21.18 0 0 40.65 0.13 0.05 0.22 0.02 0.31 16.42 25.9 17.65 0.14 0.05 39.3 0.27 0.05 0.26 0.03 0.11 19.32 0.67 33.09 0 44.41 0.39 0.11 0.08 0 0.21 19.74 0.68 33.92 0 45.44 0.36 0.12 0.06 0 0.25 16.28 27.55 16.56 0.12 0.02 41.56 0.04 0.35 0.04 0.09 18.83 2.7 31.72 0.07 0.14 43.11 0.12 0.15 0.31 0.02 0.17 16.15 28.43 16.13 0.05 0 38.48 0.16 0.12 0.29 0.03 0.26 17.75 16.12 24.34 0.08 41.12 0.13 0.03 0.18 0.01 0.17 17.49 17.29 23.06 0.07 40.49 0.15 0.05 0.19 0.01 0.48 16.42 26.48 17.33 0.05 38.09 0.22 0.03 0.37 0.03 0.22 19.89 0.43 34.13 0 45.58 0.31 0.1 0.06 0 0.14 19.56 1.41 34.57 0.03 45.76 0.14 0.02 0.14 0 0.4 19.82 0.92 34.15 0.02 45.66 0.14 0.02 0.24 0 0.38 16.45 27.14 16.63 0.12 38.16 0.54 0.06 0.35 0.15 0.14 16.6 26.18 17.25 0.06 38.13 0.21 0.04 0.31 0.02 0.2 16.77 26.72 16.65 0.06 38.14 0.41 0.01 0.34 0.06 0.1 19.4 0.57 35.37 0.05 0.02 47.56 0.27 0.08 0.05 0 0.14 19.12 0.47 34.51 0 0 45.88 0.19 0.11 0.08 0 0.2 19.07 1.12 34.53 0.02 0.01 47.21 0.14 0.11 0.16 0 0.37 18.71 0.72 34.68 0.04 0 46.92 0.21 0.12 0.03 0 0.23 20.58 8.34 26.28 0.11 0.1 44.62 0.54 0.23 0.22 0.27 0.22 19.95 0.55 35.25 0.01 0 47.21 0.13 0.03 0.13 0 0.25 18.48 1.33 32.89 0.03 0.14 43.56 0.2 0.02 0.17 0 0.34 17.17 23.36 19.73 0.03 0.01 39.57 0.18 0.02 0.29 0.01 0.26 14.05 44.34 6.04 0 0 32.42 0.43 0 0.53 0.06 0.08 Co Cu Total 0.01 0 99.84 0.01 0.01 99.18 0.04 0 99.96 0 0.03 103.99 0 0.06 102.67 0.04 0 98.91 0.01 0 99.41 0 0 100.26 0 0 100.89 0 0 100.9 0.04 0 102.68 0 0 102.71 0.07 0.01 103.87 0 0 103.43 0.04 0 100.23 0.01 0 101.51 0 0.03 102.44 0.05 0 101.23 0 0 102.04 0 0 100.3 0 0.01 100.59 0.01 0 100.18 0.08 98.36 0.06 100.64 0.03 0.03 102.67 0.06 0.04 97.52 0 0 100.11 0.01 99.96 0 99.33 0 99.27 0.05 100.7 0 102.07 0.01 101.36 0 99.82 0.01 99.05 0 99.29 0 0 103.51 0 0 100.57 0 0 102.75 0.02 0 101.7 0.03 0.03 101.57 0.01 0 103.53 0 0 97.19 0.01 0 100.64 0.02 0.08 0 98.06 218 Mry2-C-k Mry2-C-m Mry2-C-o Mry2-E-f Mry2-E-r Mry2-F-c Mry2-F-F Mry2-F-f Mry2-F-G Mry2-F-g Mry2-F-I Mry2-F-t Mry2-H-b Mry2-I-c Mry-A-c Average Std Dev Murchison Murch_B-b Murch_B-g Murch-E-d Murch-F-n Murch-G-f Murch-J-b Average Std Dev Cold Bokkeveld Cold-5RA-k Cold-5RA-q Cold-C-h Cold-C-n Cold-C-o Cold-C-Q Cold-D-f Cold-E-g Cold-E-t Cold-F-a Cold-G-b Cold-G-i Cold-G-l Cold-H-m Cold-I-g Cold-J-e Average Std Dev 18.75 0.79 34.96 0.06 0.01 13.2 42.21 5.76 0.06 0.35 18.77 1.19 34.64 0.06 0 14.78 38.63 10.02 0.1 0.01 19.38 1.22 34.56 0.01 0.06 16.46 25.99 18.3 0.09 0 16.09 30.64 15.04 0.13 0 17.57 16.78 24.47 0.02 0 16.67 27.73 17.16 0.1 0.01 16.52 12.92 23.96 0.06 0 15.78 32.36 13.67 0.14 0.02 16.02 28.66 16.4 0.12 0 19.44 1.01 34.25 0.03 0 18.55 3.07 33.01 0.09 0.09 19.5 0.49 34.32 0 0 17.81 14.17 25.27 BDL BDL (1.95) (14.53) (9.53) 46.46 0.05 0.01 0.26 0 0.19 0.01 0 101.56 34.38 0.98 0.19 0.72 0.05 0.05 0.03 0 98 47.65 0.07 0 0.44 0 0.46 0 0.01 103.29 37.1 0.04 0 0.38 0 0.31 0.05 0.04 101.45 44.9 0.02 0.05 0.11 0.01 0.03 0.02 0 100.35 41.26 0.1 0.02 0.29 0.01 0.32 0.01 0.03 102.88 36.44 0.21 0 0.36 0.05 0.19 0 0.03 0.05 99.22 43.81 0.06 0.02 0.18 0 0.23 0.03 0 103.18 38.35 0.12 0.01 0 0.01 0.2 0 0 0.03 100.39 46.84 0.05 0.01 0.17 0 0.17 0.01 0 100.71 35.42 0.32 0.03 0.41 0.03 0.28 0.02 0.06 0 98.54 39.85 0.16 0.02 0.34 0.01 0.22 0 0.1 101.9 47.48 0.13 0.01 0.16 0 0.36 0 0.06 102.93 46.49 0.18 0.21 0.08 0 0.25 0.02 0 102.07 44.96 0.37 0.11 0.07 0 0.22 0.04 0 100.09 42.76 0.23 0.07 0.23 BDL 0.24 BDL BDL BDL 100.89 (4.41) (0.17) (0.07) (0.14) (0.10) (1.69) Co Cu Total 0.02 0.01 103.18 0 0 103.83 0.02 0.01 99.95 0 0.03 101.7 0 0.01 102.75 0.06 0.01 99.81 BDL BDL 101.87 (1.69) Si Fe Mg Ni S O Ca Al Mn P Cr Ti 21.33 0.56 37.45 0 0.01 43.25 0.24 0.17 0.03 0 0.11 20.1 0.42 33.86 0 0 47.52 1.26 0.59 0 0 0.08 16.6 27.15 17.06 0.08 0 38.28 0.14 0.03 0.27 0.01 0.29 19.6 1.06 34.61 0.04 0.02 45.78 0.16 0.05 0.09 0 0.26 19.59 0.95 34.86 0.03 0.01 46.78 0.16 0.02 0.08 0.02 0.26 18.96 0.74 34.06 0.04 0.02 45.24 0.41 0.13 0.04 0.01 0.08 19.36 5.15 31.98 BDL BDL 44.48 0.40 0.17 0.09 BDL 0.18 (1.57) (10.78) (7.42) (3.37) (0.44) (0.22) (0.10) (0.10) Si Fe 19.71 1.23 19.69 1.03 17.74 11.59 18.17 8.08 19.09 1.05 16.08 32.03 19.67 0.73 19.25 1.45 19.38 1.19 19.85 1.14 19.33 0.87 19.42 0.71 19.77 0.91 17.08 20.95 19.73 0.48 19.66 0.96 18.98 5.28 (1.12) (9.06) Mg Ni S O Ca 34.11 0.04 0.01 45.60 0.13 34.40 0.07 0.01 45.76 0.16 17.00 0.56 1.21 48.18 0.32 27.19 0.40 0.87 42.54 0.08 34.67 0.04 0.01 47.44 0.15 13.99 0.10 0.00 39.31 0.31 34.74 0.00 0.01 47.89 0.14 34.25 0.00 0.00 47.31 0.19 33.93 0.00 0.01 47.26 0.19 34.29 0.12 0.00 47.36 0.16 33.82 0.02 0.00 47.51 0.17 34.41 0.00 0.00 48.05 0.17 34.76 0.06 0.00 47.35 0.17 21.30 0.06 0.00 41.33 0.17 35.22 0.05 0.01 47.73 0.07 34.44 0.03 0.00 47.38 0.13 30.78 0.10 0.13 46.13 0.17 (7.00) (0.16) (0.36) (2.67) (0.07) Al 0.01 0.06 0.95 0.43 0.02 0.03 0.03 0.08 0.05 0.01 0.03 0.01 0.04 0.03 0.00 0.04 0.11 (0.25) Mn P Cr Ti Co Cu Total 0.16 0.00 0.39 0.00 0.02 101.45 0.13 0.01 0.36 0.03 0.00 101.72 0.24 0.13 0.42 0.04 0.00 98.38 0.38 0.04 0.30 0.01 0.00 98.48 0.07 0.00 0.32 0.00 0.01 102.88 0.36 0.02 0.17 0.00 0.04 102.43 0.12 0.02 0.35 0.00 0.00 103.69 0.16 0.00 0.43 0.00 0.00 103.14 0.12 0.00 0.39 0.00 0.02 102.55 0.16 0.00 0.32 0.00 0.00 103.41 0.08 0.00 0.31 0.01 0.00 102.16 0.09 0.00 0.32 0.00 0.00 103.19 0.13 0.01 0.34 0.00 0.00 103.54 0.23 0.00 0.29 0.00 0.00 101.45 0.03 0.00 0.13 0.00 0.04 103.50 0.13 0.00 0.39 0.00 0.03 103.20 0.16 BDL 0.33 BDL BDL BDL 102.20 (0.10) (0.08) (1.64) Nogoya Si Fe Mg Ni S O Ca Al Mn P Cr Ti Co Cu Total Nog-d8RA-ChA-b 19.71 0.50 33.80 0.03 0.03 44.05 0.23 0.10 0.06 0.00 0.20 0.00 0.00 0.00 98.72 Average 19.71 0.50 33.80 BDL BDL 44.05 0.23 0.10 0.06 0.00 0.20 0.00 0.00 0.00 98.72 219 A.5 Other Apatite Murray Mry2-E-p Average Brucite Murray F-u Average Cold Bokkeveld Cold-C-t Average Calcite Murray 1-d 1-g C-e C-f-ify Mry2-I-h Average Std Dev Murchison Murch_I-f Average Cold Bokkeveld Cold-E-b Cold-E-c Average Std Dev Si Fe Mg Ni S O 0.43 1.73 0.28 0.03 0.26 43.83 3.47 6.13 1.99 0.18 1.68 41.85 0.03 0.69 0.00 0.00 0.02 38.64 0.19 1.15 0.02 0.08 0.26 48.00 1.14 4.20 0.77 0.31 1.95 47.51 1.05 2.78 0.61 0.12 0.83 43.97 (1.42) (2.31) (0.83) (0.13) (0.91) (3.93) Ca 44.37 28.33 46.07 42.49 35.86 39.42 (7.31) Al 0.06 0.40 0.02 0.04 0.22 0.15 (0.16) Mn P Cr Ti Co Cu Total 0.06 0.03 0.00 0.01 0.00 91.09 0.12 0.04 0.05 0.00 0.06 84.31 0.00 0.03 0.01 0.02 0.00 85.53 0.00 0.02 0.00 0.00 0.04 92.29 0.03 0.08 0.03 0.00 0.00 92.11 BDL BDL BDL BDL BDL BDL 89.07 (3.84) Co Cu Total 0.00 0.01 86.15 BDL BDL 86.15 Co Cu Total 0.01 0.00 95.78 0.01 0.10 94.14 BDL BDL 94.96 (1.16) Si Fe Mg Ni S O Ca Al Mn P Cr Ti 18.58 12.29 18.33 0.05 0.03 48.66 0.06 1.10 0.21 0.01 0.36 18.58 12.29 18.33 BDL BDL 48.66 0.06 1.10 0.21 BDL 0.36 Si Fe Mg Ni S O Ca Al Mn P Cr Ti 17.92 11.13 16.19 0.14 0.87 49.27 0.05 1.07 0.23 0.02 0.45 17.92 11.13 16.19 0.14 0.87 49.27 0.05 1.07 0.23 BDL 0.45 Co Cu Total 0.00 0.00 99.69 BDL BDL 99.69 Co Cu Total 0.00 0.04 97.38 BDL BDL 97.38 Si Fe Mg Ni S O Ca Al Mn P Cr Ti 0.46 0.99 0.00 0.10 0.17 41.07 41.15 0.01 0.00 7.59 0.00 0.46 0.99 BDL 0.10 0.17 41.07 41.15 BDL BDL 7.59 0.00 Co Cu Total 0.01 0.00 91.54 BDL BDL 91.54 Si Fe Mg Ni S O Ca Al Mn P Cr Ti 1.71 8.29 0.88 0.45 1.97 40.96 31.23 0.41 0.01 0.20 0.02 1.71 8.29 0.88 0.45 1.97 40.96 31.23 0.41 BDL 0.20 BDL Si Fe Mg Ni S O 0.05 0.61 0.00 0.49 0.41 48.06 1.72 0.51 0.00 0.15 0.19 45.21 0.89 0.56 0.00 0.32 0.30 46.64 (1.18) (0.07) 0.00 (0.24) (0.16) (2.02) Ca 45.96 46.17 46.07 (0.15) Ca 38.43 45.53 37.77 40.58 (4.30) Al Mn P Cr Ti 0.00 0.10 0.05 0.02 0.01 0.02 0.03 0.02 BDL 0.06 BDL BDL (0.06) Al 0.14 0.01 0.10 0.08 (0.07) Nogoya Si Fe Mg Ni S O Nod-d8RB-ChC-j 1.85 1.34 2.14 0.12 2.38 50.87 Nog-d8RB-ChC-i 0.17 0.24 0.14 0.03 0.31 44.43 Nog-d8RB-ChC-h 1.58 1.48 1.73 0.09 7.00 45.76 Average 1.20 1.02 1.34 BDL 3.23 47.02 Std Dev (0.90) (0.68) (1.06) (3.43) (3.40) Chromite Murray Mry2-ChE-d8-c Mry2-ChE-d8-d Mry2-ChF-d8-j Mry2-ChF-d8-k Mry2-E-i Mry2-F-J Mry2-F-K Average Std Dev Mg/Cr Unidentified Murray 4_d 4_v_dk 4_v_med Mn P Cr Ti Co Cu Total 0.07 0.05 0.02 0.04 0.00 0.00 97.47 0.22 0.01 0.00 0.00 0.05 0.02 91.17 0.23 0.04 0.04 0.00 0.03 0.00 95.83 0.17 BDL BDL BDL BDL BDL 94.82 (0.09) (3.27) Si Fe Mg Ni S O Ca Al 0.09 25.89 1.24 0.07 0.00 26.30 0.10 4.29 0.09 25.03 1.61 0.11 0.01 26.86 0.04 4.22 0.15 22.47 2.89 0.04 0.02 25.53 0.01 5.07 0.24 20.85 2.35 0.10 0.18 22.92 0.03 4.29 0.12 25.10 1.64 0.08 0.00 28.87 0.05 4.39 0.29 22.33 2.80 0.04 0.07 26.47 0.02 5.31 4.03 23.23 5.83 0.12 0.21 30.93 0.05 4.24 0.72 23.56 2.62 BDL 0.07 26.84 BDL 4.54 (1.46) (1.83) (1.55) (0.09) (2.53) (0.45) Mn P Cr Ti Co Cu Total 0.40 0.01 35.74 0.72 0.08 0.05 95.00 0.46 0.00 37.26 0.45 0.05 0.02 96.19 0.43 0.01 35.67 0.31 0.04 0.00 92.65 0.44 0.01 35.85 0.35 0.05 0.04 87.70 0.46 0.00 36.27 0.00 0.00 96.98 0.44 0.01 34.01 0.00 0.00 0.00 91.77 0.43 0.01 26.71 0.41 0.03 0.00 96.22 0.44 BDL 34.50 0.37 BDL BDL 93.79 (0.02) (3.57) (0.23) (3.31) Si Fe Mg Ni S O Ca Al Mn P Cr Ti Co Cu Total 0.57 31.85 4.17 6.09 5.80 25.22 0.05 0.42 0.08 1.58 5.95 0.03 0.51 83.32 0.49 35.14 6.18 1.96 2.16 29.75 0.67 0.09 0.36 8.06 0.23 0.06 85.15 0.71 38.72 4.49 3.92 2.59 25.71 0.32 0.14 0.81 5.94 0.51 0.04 83.91 220 4-d 4-e 4-k 4-v Mry1-Ch4-d8-a Mry1-Ch4-d8-c Mry1-Ch4-d8-h Mry1-d8_Ch4_C Average Std Dev 0.25 0.25 0.17 0.54 0.48 0.23 0.21 0.24 0.38 (0.18) 34.33 4.77 4.52 7.49 36.15 2.38 10.38 13.99 31.38 3.35 9.83 12.78 32.21 5.65 4.33 2.98 28.71 4.61 5.61 6.22 29.74 5.55 6.47 7.26 34.67 4.03 9.13 14.52 31.50 5.16 6.39 8.38 33.13 4.58 6.24 7.65 (2.96) (1.09) (2.63) (4.44) 27.29 20.06 19.24 28.74 26.58 0.06 29.85 0.02 20.98 0.02 29.79 0.03 25.75 0.04 (3.99) (0.02) 0.35 0.20 0.23 0.36 0.32 0.31 0.30 0.28 0.34 (0.12) 0.08 0.90 7.33 0.03 0.09 1.67 4.05 0.00 0.05 1.34 4.77 0.00 0.19 0.96 7.34 0.02 0.13 1.32 7.54 0.00 0.11 0.06 7.81 0.01 0.10 0.95 5.15 0.01 0.10 1.24 7.58 0.00 0.11 1.02 6.50 BDL (0.04) (0.49) (1.39) 0.35 0.85 0.48 0.68 0.56 0.54 0.41 0.46 0.51 (0.16) 0.01 0.00 0.03 0.07 0.06 0.07 0.04 0.00 BDL 87.71 90.07 83.65 84.05 82.20 88.02 90.52 91.16 86.34 (3.25) 221 APPENDIX B SUMMARY OF ALTERATION Table B.1: Murray #1 Name Ch 1 Ch 2 Ch 3 Ch 4 Ch 6 Ch 8 Ch 9 Ch 11 Ch 12 Ch 13 Ch 14 Ch 15A Ch 15B Ch 16 Ch 17 Ch 18 Ch 19 Ch A Ch B Ch C Ch D Ch E Ch F-A Ch F-B Ch F-C Ch F-D Ch F Ch H Ch I Ch J Ch K Ch L Ch M Ch N Region 5A Alt Rim P-rich 6 Level (um) Sulfide 0 1 - Tr 3 3 2+ - Fa 3 0 0 0 0 - Fa 0 0 0 3+ 4 3 4 4 0-2 3 4 - Tr 1 4 4 - Tr - Tr - Tr 0 0 0 0-1 0 2 24 23 >9 37 N N Y Y Y ? N Y N N N N N N N N N Y N Y Prob N Y Prob N N N Prob N N N N N N N Cron Matrix Iron Oxide Both Toch Cr/Mg Toch Ch Ch Matrix Ch Mag 1 Ox Ka Ch Ox Ka 1 Cr/Mg Toch Ch Both Pent3 2 2 Pent 2 Ta, Fa, Pent Pent Accessory Minerals X-Ray map 1 1 1 1 1 1 1 30 30 34 20 9 20 42 4 42 40 Ox Ka Ox Ka Toch Ox Ka Ox Ka Ox Ka Mag 11 Matrix 1 222 Region 6A 0 Table B.2: Murray #2 Name Ch A Ch B Ch C-1 Ch C-2 Ch E-1 Ch E-2 Ch F-1 Ch F-3 Ch G Ch H Ch I N Mag 1 Alt Rim P-rich Level (um) Sulfide 0 & 3 36 1 0 4 0 - Fa - Fa - Fa - Tr 4 1 >40 3 Prob N Prob N N Y3 N N Prob N Cron Iron Oxide Mag3 Mag Accessory Minerals X-Ray map 2 1 2 2 Fa763 Pent, Chr Pent, Chr, Tr Ch Ch Ox Ka Ox Ka Ox Ka Table B.3: Murchison Name Murch A Murch B Murch D Murch E Murch F Murch G Murch H Murch I Murch J Murch K Murch 5RA Murch 5RD Murch Alt Level 0 0 0 0 0 0 - Tae - Tr -Pyrr 1 4 0&2 1 Rim (um) P-rich Sulfid e N N N N N N N N N N Prob N N Cron Matrix Iron Oxide Ox Ka Mag3 Ch & Matrix Ch Fa413 2 Accessory Minerals X-Ray map Ox Ka3 Ox Ka3 Toch Ox Ka 9 12 6 2 2 2 223 8RA Table B.4: Cold Bokkeveld Name ColdB A ColdB C ColdB D ColdB E ColdB F ColdB G ColdB H-1 ColdB H-2 ColdB I ColdB J ColdB 5RA ColdB 5RB Alt Level -4 - Tr 4 4 4 4 - Fa30 4 - Pent >3 3 - Pyrr >30 >10 Rim P-rich (um) Sulfide N N ? N N ? N N N Trace N N Ch Ch Ch Cron Iron Accessory X-Ray Oxide Minerals map Ox Ka4 Fa50, Pent3 Pent3 2 5 CPX 2 Pent 1 1 Pent 1 Pent 1 Pent 2 Pent 2 3 Ox Pent Ka3 Ch Table B.5: Nogoya Name Region A Region B Region C Region D Region E Region F Alt Level >3 - Pent 4 - Pyrr - Pent - Pent Rim P-rich (um) Sulfide >15 >30 N N N N N N Cron Iron Accessory Oxide Minerals Pent, Pyrr Pent Pyrr Pyrr, Calc Pent Pent XRay map 1 - Fe, Mg, S, O, Ni, P, Ca 2 - Fe, Mg, S, O 3 - Mineral was not part of the assemblage, but near by in the matrix 4 - Possible terrestrial weathering. No tochilinite found. 5 - Clear indication of CPX converting into serpentine 6 - We rated the degree of kamacite's conversion into tochilinite on a scale from 0 (none), 1 (trace), 2 (partial), 3 (significant), and 4 (extensive). 224 REFERENCES Allamandola, L. J., Sandford, S. A., Valero, G. J., 1988. Photochemical and thermal evolution of interstellar/precometary ice analogs. Icarus. 76, 225-252. Anthony, J. W., 2003. Handbook of Mineralogy: Borates, Carbonates, Sulfates. Mineral Data Publishing, Inc. Tucson, Arizona. Bell, J. F., Cruikshank, D. P., Gaffey, M. J., 1985. The composition and origin of the Iapetus dark material. Icarus. 61, 192-207. Bischoff, A., Tomeoka, K., Buseck, P. R., 1998. Aqueous alteration of carbonaceous chondrites: Evidence for preaccretionary alteration. A review Indicators of aqueous alteration in CM carbonaceous chondrites: Microtextures of a layered mineral containing Fe, S, O and Ni. Meteoritics and Planetary Science. 33, 11131122. Blake, D., Allamandola, L., Sandford, S., Hudgins, D., Freund, F., 1991. Clathrate hydrate formation in amorphous cometary ice analogs in vacuo. Science. 254, 548-551. Boctor, N. Z., Kurat, G., O'D. Alexander, C. M., Prewitt, C. T., Sulfide Mineral Assemblages in Boriskino CM Chondrite. Lunar and Planetary Institute Science Conference Abstracts, Vol. 33, 2002, pp. 1534. Brearley, A. J., 1995. Aqueous alteration and brecciation in Bells, an unusual, saponitebearing, CM chondrite. Geochimica et Cosmochimica Acta. 59, 2291-2317. Brearley, A. J., The Action of Water. Meteorites and the Early Solar System II, 2006, pp. 584-624. Brearley, A. J., 2004. Nebular versus Parent-body Processing. In: Davis, A. M. (Ed.) Meteorites, Comets, and Planets Treatise on Geochemistry. Elsevier-Pergamon, Oxford. Brearley, A.J., 2006. The action of water. In: Meteorites and the Early Solar System II. (Eds.) Dante Lauretta, H.Y. McSween Jr. and L. Leshin, Arizona University Press, Tucson, pp. 587-624. Brown, G. N. Jr., Ziegler, W. T. 1979. Vapor pressure and heats of vaporization and sublimation of liquids and solids of interest in cryogenics below 1-atm pressure. In: Timmerhaus, K. D., Snyder, H. A. (Eds.), Advanced Cryogenic Eng 25. Plenum Press, NY 225 Brown, R. H., Cruikshank, D. P., 1997. Determination of the Composition and State of Icy Surfaces in the Outer Solar System. Annual Review of Earth and Planetary Sciences. 25, 243. Brown, R. H., and 21 colleagues, 2004. The Cassini Visual And Infrared Mapping Spectrometer (Vims) Investigation. Space Science Reviews. 115, 111-168. Brown, R. H., and 24 colleagues, 2006. Composition and Physical Properties of Enceladus' Surface. Science. 311, 1425-1428. Brown, R. H., Kirk, R. L., 1994. Coupling of volatile transport and internal heat flow on Triton. Journal of Geophysical Research. 99, 1965-1981. Brown, R. H., Matson, D. L., 1987. Thermal Effects of Insolation Propagation into the Regoliths of Airless Bodies. Icarus. 72, 84-94. Browning, L. B., McSween, H. Y., Jr., Zolensky, M. E., 1996. Correlated alteration effects in CM carbonaceous chondrites. Geochimica et Cosmochimica Acta. 60, 2621-2633. Bunch, T. E., Chang, S., 1980. Carbonaceous chondrites. II - Carbonaceous chondrite phyllosilicates and light element geochemistry as indicators of parent body processes and surface conditions. Geochimica et Cosmochimica Acta. 44, 15431577. Bunch, T. E., Chang, S., Frick, U., Neil, J. M., Moreland, G., 1979. Carbonaceous chondrites. I - Characterization and significance of carbonaceous chondrite /CM/ xenoliths in the Jodzie howardite. Geochimica et Cosmochimica Acta. 43, 17271729. Buratti, B., Veverka , J., 1983. Voyager photometry of Europa. Icarus. 55, 93-110. Buratti, B., Veverka, J., 1984. Voyager photometry of Rhea, Dione, Tethys, Enceladus and Mimas. Icarus. 58, 254-264. Buratti, B. J., and 28 colleagues, 2005. Cassini visual and infrared mapping spectrometer observations of Iapetus: Detection of CO2. Astrophysical Journal. 622, L149L152. Carlson, R., and 39 colleagues, 1996. Near-Infrared Spectroscopy and Spectral Mapping of Jupiter and the Galilean Satellites: Results from Galileo's Initial Orbit. Science. 274, 385-388. 226 Carlson, R. W., 1999. A Tenuous Carbon Dioxide Atmosphere on Jupiter's Moon Callisto. Science. 283, 820. Casella, G., Berger, R. 2002. Statistical Inferences, 2nd ed. Duxbury, Thomas Learning, Australia Chan, W. F., Cooper, G., Brion, C. E., 1993. The Electronic-Spectrum of Carbon-Dioxide - Discrete and Continuum Photoabsorption Oscillator-Strengths (6-203 Ev). Chemical Physics. 178, 401-413. Chizmadia, L. J., Brearley, A. J., 2003. Mineralogy and Textural Characteristics of Finegrained Rims in the Yamato 791198 CM2 Carbonaceous Chondrite: Constraints on the Location of Aqueous Alteration. Lunar and Planetary Institute Science Conference Abstracts, Vol. 34, 2003, pp. 1419. Chizmadia, L. J., Brearley, A. J., 2004. Aqueous Alteration of Carbonaceous Chondrites: New Insights from Comparative Studies of Two Unbrecciated CM2 Chondrites, Y-791198 and ALH81002. Lunar and Planetary Institute Science Conference Abstracts, Vol. 35, 2004, pp. 1753. Chizmadia, L. J., Xu, Y., Schwappach, C., Brearley, A. J., 2008. Characterization of micron-sized Fe,Ni metal grains in fine-grained rims in the Y-791198 CM2 carbonaceous chondrite: Implications for asteroidal and preaccretionary models for aqueous alteration. Meteoritics and Planetary Science. 43, 1419-1438. Ciesla, F. J., Lauretta, D. S., Cohen, B. A., Hood, L. L., 2003. A Nebular Origin for Chondritic Fine-Grained Phyllosilicates. Science. 299, 549-552. Clark, R. N., Steele, A., Brown, R. H., Owensby, P. D., 1984. Saturn's satellites - Nearinfrared spectrophotometry (0.65-2.5 microns) of the leading and trailing sides and compositional implications. Icarus. 58, 265-281. Clark, R. N., and 25 colleagues, 2005. Compositional maps of Saturn's moon Phoebe from imaging spectroscopy. Nature. 435, 66-69. Clark, R. N., and 13 colleagues, 2007. Compositional Mapping of Saturn's Satellite Iapetus with Cassini VIMS and Implications of Dark Material in the Saturn System. AGU Fall Meeting Abstracts. 13, 1426. Clark, R. N., and 11 colleagues, 2008. Compositional mapping of Saturn's satellite Dione with Cassini VIMS and implications of dark material in the Saturn system. Icarus. 193, 372-386. 227 Clark, R. N., and 10 colleagues, 2009. The Composition of Iapetus: Mapping Results from Cassini VIMS. Icarus. Submitted Clayton, R. N., Mayeda, T. K., 1984. The oxygen isotope record in Murchison and other carbonaceous chondrites. Earth and Planetary Science Letters. 67, 151-161. Clayton, R. N., Onuma, N., Grossman, L., Mayeda, T. K., 1977. Distribution of the presolar component in Allende and other carbonaceous chondrites. Earth and Planetary Science Letters. 34, 209-224. Cooper, P. D., Moore, M. H., Hudson, R. L., 2008. Radiation chemistry of H2O + O2 ices. Icarus. 194, 379-388. Cruikshank, D. P., Brown, R. H., Calvin, W. M., Roush, T. L., Bartholomew, M. J., Ices on the Satellites of Jupiter, Saturn, and Uranus. Solar System Ices, Vol. 227, 1998, pp. 579. Cruikshank, D. P., and 30 colleagues, 2007. Surface composition of Hyperion. Nature. 448, 54-56. Cruikshank, D. P., and 23 colleagues, 2008. Hydrocarbons on Saturn's satellites Iapetus and Phoebe. Icarus. 193, 334-343. Cyr, K. E., Sears, W. D., Lunine, J. I., 1998. Distribution and Evolution of Water Ice in the Solar Nebula: Implications for Solar System Body Formation. Icarus. 135, 537-548. Deer, W. A., Howie, R. A., Zussman, J., 1982. Rock Forming Minerals, Volume 1A: Orthosilicates. Longman Group Limited, Burnt Hill, England. Denk, T., Spencer, J. R., Iapetus: A Two-step Explanation for its Unique Global Appearance. Bulletin of the American Astronomical Society, Vol. 40, 2008, pp. 510. Devouard, B., Buseck, P. R., 1997. Phosphorous-rich Iron, Nickel Sulfides in CM2 Chondrites: Condensation or Alteration Products? Meteoritics and Planetary Science Supplement. 32, 34. Dougherty, M. K., and 17 colleagues, 2005. Cassini Magnetometer Observations During Saturn Orbit Insertion. Science. 307, 1266-1270. Ehrenfreund, P., Boogert, A. C. A., Gerakines, P. A., Tielens, A. G. G. M., van Dishoeck, E. F., 1997. Infrared spectroscopy of interstellar apolar ice analogs. Astronomy and Astrophysics. 328, 649-669. 228 Estermann, I., 1955. Gases at low densities. High Speed Aerodynamics and Jet Propulsion, Volume I: Thermodynamics and Physics of Matter 1, 742,744. Fegley, B., Jr., Prinn, R. G., Solar nebula chemistry - Implications for volatiles in the solar system. The Formation and Evolution of Planetary Systems, 1989, pp. 171205. Fine, G., Stolper, E., 1986. Dissolved carbon dioxide in basaltic glasses: concentrations and speciation. Earth and Planetary Science Letters. 76, 263-278. Fink, U., et al., 1976. Infrared spectra of the satellites of Saturn - Identification of water ice on Iapetus, Rhea, Dione, and Tethys. Astrophysical Journal. 207, L63-L67. Fuchs, L. H., Oslsen, E., Jensen, K. J., 1973. Mineralogy, mineral-chemistry, and composition of the Murchison (C2) meteorite. Smithson Contrib Earth Sci. 10, 139. Galvez, Mate, B., Herrero, V. J., Escribano., 2008. Trapping and adsorption of CO2 in amorphous ice: A FTIR study. Icarus. 197, 599-605. Gerakines, P. A., Schutte, W. A., Ehrenfreund, P., 1996. Ultraviolet processing of interstellar ice analogs. I. Pure ices. Astronomy and Astrophysics. 312, 289-305. Giauque, W. F., Egan, C. J., 1937. Carbon Dioxide. The Heat Capacity and Vapor Pressure of the Solid. The Heat of Sublimation. Thermodynamic and Spectroscopic Values of the Entropy. The Journal of Chemical Physics. 5, 45-54. Giese, B., Denk, T., Neukum, G., Roatsch, T., Helfenstein, P., Thomas, P. C., Turtle, E. P., McEwen, A., Porco, C. C., 2008. The topography of Iapetus' leading side. Icarus. 193, 359-371. Giorgini, J. D., Yeomans, D. K., Chamberlin, A. B., Chodas, P. W., Jacobson, R. A., Keesey, M. S., Lieske, J. H., Ostro, S. J., Standish, E. M., Wimberly, R. N., JPL's On-Line Solar System Data Service. Bulletin of the American Astronomical Society, Vol. 28, 1996, pp. 1158. Grossman, J. N., 1994. The Meteoritical Bulletin, no. 76, 1994 January: The U.S. Antarctic Meteorite Collection. Meteoritics. 29, 100-143. Gubaidulina, T. V., Chistyakova, N. I., Rusakov, V. S., 2007. Mössbauer study of layered iron hydroxysulfides: Tochilinite and valleriite. Bulletin of the Russian Academy of Science, Phys. 71, 1269-1272. 229 Hanowski, N. P., 1998. The aqueous alteration of CM carbonaceous chondrites: Petrographic and microchemical constraints. Ph.D dissertation, Univ. of New Mexico. Hanowski, N. P., Brearley, A. J., 2000. Iron-rich aureoles in the CM carbonaceous chondrites, Murray, Murchison and Allan Hills 81002: Evidence for in situ aqueous alteration. Meteoritics and Planetary Science. 35, 1291-1308. Hanowski, N. P., Brearley, A. J., 2001. Aqueous alteration of chondrules in the CM carbonaceous chondrite, Allan Hills 81002: implications for parent body alteration. Geochimica et Cosmochimica Acta. 65, 495-518. Hansen, G. B., McCord, T. B., 2004. Amorphous and crystalline ice on the Galilean satellites: A balance between thermal and radiolytic processes. Journal of Geophysical Research (Planets). 109, 01012. Hansen, C. J., Esposito, L., Stewart, A. I. F., Colwell, J., Hendrix, A., Pryor, W., Shemansky, D., West, R., 2006. Enceladus' Water Vapor Plume. Science. 311, 1422-1425. Hansen, G. B., McCord, T. B., 2008. Widespread CO2 and other non-ice compounds on the anti-Jovian and trailing sides of Europa from Galileo/NIMS observations. Geophysical Research Letters. 35, 01202. Herndon, J. M., Rowe, M. W., Larson, E. E., Watson, D. E., 1975. Origin of magnetite and pyrrhotite in carbonaceous chondrites. Nature. 253, 516-518. Hibbitts, C. A., Klemaszewski, J. E., McCord, T. B., Hansen, G. B., Greeley, R., 2002. CO2-rich impact craters on Callisto. Journal of Geophysical Research (Planets). 107, 5084. Hibbitts, C. A., Szanyi, J., 2007. Physisorption of CO2 on non-ice materials relevant to icy satellites. Icarus. 191, 371-380. Hodyss, R., Johnson, P. V., Orzechowska, G. E., Goguen, J. D., Kanik, I., 2008. Carbon dioxide segregation in 1:4 and 1:9 CO2:H2O ices. Icarus. 194, 836-842. Huang, K., 1987. Statistical Mechanics. Wiley Press, New Jersey. Hudson, R. L., Moore, M. H., 2001. Radiation chemical alterations in solar system ices: An overview. Journal of Geophysical Research. 106, 33275-33284. Ip, W. H., 2006. On a ring origin of the equatorial ridge of Iapetus. Geophysical Research Letters. 33, 16203. 230 Khare, B. N., Sagan, C., Arakawa, E. T., Suits, F., Callcott, T. A., Williams, M. W., 1984. Optical constants of organic tholins produced in a simulated Titanian atmosphere - From soft X-ray to microwave frequencies. Icarus. 60, 127-137. Keesom, W. H., Koehler, J. W. L., 1934. The lattice constant and expansion coefficient of solid carbon dioxide. Physica. 1, 655-658. Kerridge, J. F., Bunch, T. E., Aqueous activity on asteroids - Evidence from carbonaceous meteorites. Asteroids, 1979, pp. 745-764. Klein, C., Hurlbut, C. S., 1999. Manual of Mineralogy, 21st Edition. Klinger, J., 1980. Influence of a phase transition of ice on the heat and mass balance of comets. Science. 209, 634-641. Kumi, G., Malyk, S., Hawkins, S., Reisler, H., Wittig, C. 2006. Amorphous Solid Water Films: Transport and Guest-Host Interactions with CO2 and N2O Dopants. The Journal of Physical Chemistry A. 110, 2097-2105. Lang, K. 1992. Astrophysical Data I. Planets and Stars, X, 937 pp. 33 figs.. SpringerVerlag Berlin Heidelberg New York. Lauretta, D. S., Hua, X., Buseck, P. R., 2000. Mineralogy of fine-grained rims in the ALH 81002 cm chondrite. Geochimica et Cosmochimica Acta. 64, 3263-3273. Lee, M. R., 1993. The petrography, mineralogy and origins of calcium sulphate within the Cold Bokkeveld CM carbonaceous chondrite. Meteoritics. 28, 53-62. de Leuw, S., Rubin, A. E., Schmitt, A. K., Wasson, J. T., Mn-Cr Systematics for the CM2.1 Chondrites QUE 93005 and ALH 83100: Implications for the Timing of Aqueous Alteration. LPSC Abstracts, Vol. 40, 2009, pp. 1794. Lebofsky, L. A., 1975. Stability of Frosts in Solar-System. Icarus. 25, 205-217. Lebofsky, L. A., Feierberg, M. A., Tokunaga, A. T., 1982. Infrared observations of the dark side of Iapetus. Icarus. 49, 382-386. Levine, J. S., 1985. The Photochemistry of Atmospheres Lewis, B. R., Carver, J. H., 1983. Temperature dependence of the carbon dioxide photoabsorption cross section between 1200 and 1970 Angstroms. Journal of Quantitative Spectroscopy and Radiative Transfer. 30, 297-309. 231 Loeffler, M. J., Baratta, G. A., Palumbo, M. E., Strazzulla, G., Baragiola, R. A., 2005. CO2 synthesis in solid CO by Lyman-alpha photons and 200 keV protons. Astronomy and Astrophysics. 435, 587-594. Loewenstein, R. F., Harper, D. A., Hildebrand, R. H., Moseley, H., Shaya, E., Smith, J., 1980. Far-infrared photometry of Titan and Iapetus. Icarus. 43, 283-287. Lunine, J. I., Stevenson, D. J., 1985. Thermodynamics of clathrate hydrate at low and high pressures with application to the outer solar system. Astrophysical Journal Supplement Series. 58, 493-531. MacKinnon, I. D. R., Zolensky, M. E., 1984. Proposed structures for poorly characterized phases in C2M carbonaceous chondrite meteorites. Nature. 309, 240-242. Matson, D. L., Brown, R. H., 1989. Solid-State Greenhouses and Their Implications for Icy Satellites. Icarus. 77, 67-81. McCord, T. B., and 11 colleagues, 1997. Organics and other molecules in the surfaces of Callisto and Ganymede. Science. 278, 271-275. McCord, T. B., and 11 colleagues, 1997. Analysis of NIMS Reflectance Spectra for the Icy Galilean Satellites. Meteoritics and Planetary Science Supplement. 32, 86. McCord, T. B., and 12 colleagues, 1998. Non-water-ice constituents in the surface material of the icy Galilean satellites from the Galileo near-infrared mapping spectrometer investigation. Journal of Geophysical Research. 103, 8603-8626. McSween, H. Y., 1979. Alteration in CM carbonaceous chondrites inferred from modal and chemical variations in matrix. Geochimica et Cosmochimica Acta. 43, 17611765. McSween, H. Y., 1987. Aqueous alteration in carbonaceous chondrites - Mass balance constraints on matrix mineralogy. Geochimica et Cosmochimica Acta. 51, 24692477. Mennella, V., Palumbo, M. E., Baratta, G. A., 2004. Formation of CO and CO2 Molecules by Ion Irradiation of Water Ice-covered Hydrogenated Carbon Grains. Astrophysical Journal. 615, 1073-1080. Mennella, V., Baratta, G. A., Palumbo, M. E., Bergin, E. A., Synthesis of CO and CO2 Molecules by UV Irradiation of Water Ice-covered Hydrogenated Carbon Grains. Astrophysical Journal. 643, 923-931. 232 Metzler, K., Bischoff, A., Stoeffler, D., 1992. Accretionary dust mantles in CM chondrites - Evidence for solar nebula processes. Geochimica et Cosmochimica Acta. 56, 2873-2897. Moore, M. H., Hudson, R. L., 1998. Infrared Study of Ion-Irradiated Water-Ice Mixtures with Hydrocarbons Relevant to Comets. Icarus. 135, 518-527. Morrison, D., 1982. The Satellites of Jupiter and Saturn. Annual Review of Astronomy and Astrophysics. 20, 469-495. Morrison, D., Jones, T. J., Cruikshank, D. P., Murphy, R. E., 1975. 2 Faces of Iapetus. Icarus. 24, 157-171. Nazarov, M. A., Brandstaetter, F., Kurat, G., Carbonaceous Xenoliths from the Erevan Howardite. Lunar and Planetary Institute Science Conference Abstracts, Vol. 24, 1993, pp. 1053. Nazarov, M. A., Kurat, G., Brandstaetter, F., Ntaflos, T., Chaussidon, M., Hoppe, P., 2009. Phosphorus-Bearing Sulfides and Their Associations in CM Chondrites. Petrology. 17, 101-123. Organova, N. I., 1974. Selected-area electron diffraction study of a type II "valleriitelike" mineral. The American Mineralogist. 59, 190. Owen, T. C., et al., 2001. Decoding the Domino: The Dark Side of Iapetus. Icarus. 149, 160-172. Palmer, E. E., Brown, R. H., 2008. The stability and transport of carbon dioxide on Iapetus. Icarus. 195, 434-446. Rubin, A. E., Trigo-RodrÌguez, J. M., Huber, H., Wasson, J. T., 2007. Progressive aqueous alteration of CM carbonaceous chondrites. Geochimica et Cosmochimica Acta. 71, 2361-2382. Sandford, S. A., Allamandola, L. J., 1990. The physical and infrared spectral properties of CO2 in astrophysical ice analogs. Astrophysical Journal. 355, 357-372. Sandford, S. A., Allamandola, L. J., 1990. The volume- and surface-binding energies of ice systems containing CO, CO2, and H2O. Icarus. 87, 188-192. Scheeres, D. J., Durda, D. D., Geissler, P. E., 2002. The Fate of Asteroid Ejecta. Asteroids III. 527-544. 233 Shemansky, D. E., 1972. CO2 Extinction Coefficient 1700-3000 Angstroms. Journal of Chemical Physics. 56, 1582-1587. Sinclair, A. T., 1974. A theory of the motion of Iapetus. Monthly Notices of the Royal Astronomical Society. 169, 591-605. Smith, B. A., and 28 colleagues, 1982. A new look at the Saturn system: The Voyager 2 images. Science. 215, 505-537. Spencer, J. R., Tamppari, L. K., Martin, T. Z., Travis, L. D., 1999. Temperatures on Europa from Galileo PPR: Nighttime Thermal Anomalies The dark side of Iapetus: Additional evidence for an exogenous origin. Science. 284, 1514-1516. Spencer, J. R., Pearl, J. C., Segura, M., Team, C. C., Cassini CIRS Observations of Iapetus' Thermal Emission. 36th Annual Lunar and Planetary Science Conference, Vol. 36, 2005, pp. 2305. Squyres, S. W., Sagan, C., 1983. Albedo asymmetry of Iapetus Voyager photometry of Iapetus. Nature. 303, 782-785. Squyres, S. W., Buratti, B., Veverka, J., Sagan, C., 1984. Voyager photometry of Iapetus. Icarus. 59, 426-435. Squyres, S. W., Sagan, C., 1983. Albedo asymmetry of Iapetus. Nature. 303, 782-785. Strazzulla, G., Palumbo, M. E., 1998. Evolution of icy surfaces : an experimental approach. Planetary and Space Science. 46, 1339-1348. Strazzulla, G., Leto, G., Spinella, F., Gomis, O., 2005. Production of Oxidants by Ion Irradiation of Water/Carbon Dioxide Frozen Mixtures. Astrobiology. 5, 612-621. Thomas, P. C., and 17 colleagues, 2007. Hyperion's sponge-like appearance. Nature. 448, 50-56. Tomeoka, K., Buseck, P. R., 1985. Indicators of aqueous alteration in CM carbonaceous chondrites: Microtextures of a layered mineral containing Fe, S, O and Ni. Geochimica et Cosmochimica Acta. 49, 2149-2163. Veeder, G. J., Matson, D. L., 1980. The relative reflectance of Iapetus at 1.6 and 2.2 microns. Astronomical Journal. 85, 969-972. Warren, S. G., 1984. Optical constants of ice from the ultraviolet to the microwave. Applied Optics. 23, 1206-1225. 234 Waite, J. H., and 13 colleagues, 2006. Cassini Ion and Neutral Mass Spectrometer: Enceladus Plume Composition and Structure. Science. 311, 1419-1422. Warren, S. G., 1986. Optical constants of carbon dioxide ice. Applied Optics. 25, 26502674. Watson, K., et al., 1963. The Stability of Volatiles in the Solar System. Icarus. 1, 317. Ward, W. R., 1981. Orbital inclination of Iapetus and the rotation of the Laplacian plane. Icarus. 46, 97-107. Watson, K., Murray, B. C., Brown, H., 1963. The Stability of Volatiles in the Solar System. Icarus. 1, 317-327. Woods, T. N., Rottman, G. J., Bailey, S. M., Solomon, S. C., Worden, J. R., 1998. Solar EUV Irradiance Measurements During Solar Cycle 22. Solar Physics. 177, 133146. Yabushita, A., Hashikawa, Y., Ikeda, A., Kawasaki, M., Tachikawa, H., 2004. Hydrogen atom formation from the photodissociation of water ice at 193 nm. Journal of Chemical Physics. 120, 5463-5468. Yanai, K., Kojima, H., Japanese Collection of Antarctic Meteorites. Lunar and Planetary Institute Science Conference Abstracts, Vol. 18, 1987, pp. 1114. Yi, W., Park, J., Lee, J., 2007. Photodissociation dynamics of water at Lyman alpha (121.6 nm). Chemical Physics Letters. 439, 46-49. Zega, T. J., Buseck, P. R., 2003. Fine-grained-rim mineralogy of the Cold Bokkeveld CM chondrite. Geochimica et Cosmochimica Acta. 67, 1711-1721. Zubko, V. G., et al., 1996. Optical constants of cosmic carbon analogue grains - I. Simulation of clustering by a modified continuous distribution of ellipsoids. Monthly Notices of the Royal Astronomical Society. 282, 1321-1329. Zolensky, M., Barrett, R., Browning, L., 1993. Mineralogy and composition of matrix and chondrule rims in carbonaceous chondrites. Geochimica et Cosmochimica Acta. 57, 3123-3148. Zolensky, M. E., Mittlefehldt, D. W., Lipschutz, M. E., Wang, M.-S., Clayton, R. N., Mayeda, T. K., Grady, M. M., Pillinger, C., Barber, D., 1997. CM chondrites exhibit the complete petrologic range from type 2 to 1. Geochimica et Cosmochimica Acta. 61, 5099.