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Nature and Degree of Aqueous Alteration of Outer Main Belt Asteroids and CM and CI Carbonaceous Chondrites University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Doctoral Dissertations Graduate School 5-2013 Nature and Degree of Aqueous Alteration of Outer Main Belt Asteroids and CM and CI Carbonaceous Chondrites Driss Takir [email protected] Follow this and additional works at: https://trace.tennessee.edu/utk_graddiss Part of the The Sun and the Solar System Commons Recommended Citation Takir, Driss, "Nature and Degree of Aqueous Alteration of Outer Main Belt Asteroids and CM and CI Carbonaceous Chondrites. " PhD diss., University of Tennessee, 2013. https://trace.tennessee.edu/utk_graddiss/1783 This Dissertation is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a dissertation written by Driss Takir entitled "Nature and Degree of Aqueous Alteration of Outer Main Belt Asteroids and CM and CI Carbonaceous Chondrites." I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Doctor of Philosophy, with a major in Geology. Harry Y. McSween Jr., Joshua P. Emery, Major Professor We have read this dissertation and recommend its acceptance: Jeffery E. Moersch, Michael W. Guidry Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) Nature and Degree of Aqueous Alteration of Outer Main Belt Asteroids and CM and CI Carbonaceous Chondrites A Dissertation Presented for the Doctor of Philosophy Degree The University of Tennessee, Knoxville Driss Takir May 2013 Copyright © 2013 by Driss Takir All rights reserved. ii Dedication In memory of my father iii Acknowledgements This dissertation would not been completed without the guidance of my advisors, Dr. Joshua P Emery and Dr. Harry Y McSween Jr. I feel lucky to have worked on fascinating and exciting projects with leading experts in planetary sciences. Josh and Hap both taught me what a professional scientist should be. I would especially like to thank them for their generous financial support during my time at the University of Tennessee that allowed me to attend conferences and do research in various places in the US and around the world. I also wish to thank Dr. Jeffery E Moersch and Dr. Michael W Guidry (my committee members) for their helpful comments improving this dissertation, Roger Clark (USGS) and Karl Hibbitts (APL) for allowing me to use their laboratories to measure meteorite spectra, NASA IRTF staff for their excellent assistance with asteroid observations, and Earth & Planetary Sciences department staff, students, and faculty for their support and encouragement. I also owe a great deal of gratitude to my family, especially my mother and my wife. This dissertation would not been possible without their moral support through the years. iv Abstract CM (Mighei-like) and CI (Ivuna-like) carbonaceous chondrites are primitive meteorites that consist of some of the most pristine matter known in the Solar System. They are thought to be genetically related to outer Main Belt asteroids (C-, D-, G-, F-, T-, and B-types) that span the 2.5 < a < 4.0 AU region. They are also thought to be the source that might have delivered water and organics to terrestrial planets during their accretion. The goal of this dissertation is to develop reliable 3-m [micron] spectral indicators that can place constraints on the degree and location of aqueous alteration in the outer Main Belt region, and on the nature of phyllosilicate mineralogy on the surface of these asteroids. To that end, we have undertaken combined petrologic, geochemical, and spectroscopic analyses of CM and CI chondrites and outer Main Belt asteroids. Using the SpeX spectrograph/imager at NASA Infrared Telescope Facility (IRTF), we measured near-infrared (NIR: 0.7-4.0 m) spectra of 40 outer Main Belt asteroids that allowed the identification of four 3-m spectral groups, each of which presumably reflects a distinct surface mineralogy. We also measured spectra of 9 CM chondrites (in addition to the CI chondrite Ivuna) in the laboratory under asteroid-like conditions. These measurements revealed three spectral groups of CM chondrites, all of which are distinct from the spectrum of Ivuna on the basis of the 3-μm band center and shape of spectra, showing that distinct parent body aqueous alteration environments experienced by different carbonaceous chondrites can be distinguished using reflectance spectroscopy. All CM and CI chondrites in the present study are found to be similar to the group of asteroids that are located in the 2.5 < a < 3.3 AU region and exhibit a sharp 3-µm feature, attributed to OH-stretching in hydrated minerals. However, no meteorite match was found for asteroids with a rounded 3-µm feature that are located farther from the Sun (3.0 < a < 4.0 AU), or for groups with distinctive spectra like 1 Ceres or 52 Europa. v Table of Contents Introduction…………...…..…………………………………….……………………………......1 References…….………………………………………………………………………......4 Chapter 1: Outer Main Belt asteroids: Identification and distribution of four 3-µm spectral groups….………………………………………………………………………………..5 Abstract…………………………………………………………………...………………6 1.0 Introduction…...……………………………………………………………………..8 2.0 Methodology……………………...………………………………………………...10 3.0 Results……..………………………………………………………………………..16 4.0 Discussion…………………………………………………………………………..18 5.0 Conclusions…………………………………………………………………………26 References…….…………………………………………………………………………29 Appendix A…………………………………………………………………………...…39 Chapter 2: Nature and degree of aqueous alteration in CM and CI carbonaceous chondrites………………………………………………………………………………………..61 Abstract……………………………………………………………………………….…62 1.0 Introduction………………………………………………………………………...64 2.0 Methodology………………………………………………………………………..66 3.0 Results…………………………………………………………………………..…..72 4.0 Discussion…………………………………………………………………………..74 5.0 Conclusions…………………………………………………………………………82 References……………………………………………………………………………….85 Appendix B1…………………………………………………………………………….97 vi Appendix B2..………………………………………………………………………….116 Appendix B3..………………………………………………………………………….118 Chapter 3: Implications of Aqueous Alteration in CM and CI Carbonaceous Chondrites for Outer Main Belt Asteroids………...……………………………………………………...120 Abstract………………………………………………………………………………...121 1.0 Introduction……………………………………………………………………….122 2.0 Methodology……………………………………………………………………....124 3.0 Results…………………………………………………………………………......126 4.0 Discussion………………………………………………………...……………….129 5.0 Conclusions………………………………………..………………………………134 References……………………………………………………………………………...136 Appendix C…………………………………………………………………………….141 Conclusion…………...….……………………………………………………………………..156 VITA..………………………………………………………………………………………….159 vii List of Tables Chapter 1 Table A1. Physical properties. Source: http://ssd.jpl.nasa.gov/sbdb.cgi.......................................40 Table A2. Observing parameters for asteroids observed with the LXD mode of SpeX………...41 Table A3. Observing parameters for asteroids observed with the prism mode of SpeX………..42 Table A4. Results………………………………………………………………………………..43 Chapter 2 Table B1. Carbonaceous chondrites analyzed in this study……………………………………..98 Table B2. Estimated chemical formulae of average CM matrix serpentines for nine CM chondrites and Mineralogical Alteration Indices (MAI) of Browning et al. (1996)……..99 Table B3. Tochilonite compositions (wt. %) in CM chondrites……………………………….100 Table B4. Diagnostic characteristics of progressive alteration in CM chondrite petrologic subtypes of Rubin et al. (2007)……………………………………………………........101 viii Table B5a. The 3-μm feature parameters for meteorite spectra measured in dry conditions and the 2.3-μm and 0.7-μm parameters for meteorite spectra measured in ambient conditions…………………………………………………………………………..…...102 Table B5b. The 3-μm feature parameters for cronstedtite, the three Mg-serpentine polymorphs, and saponite…………………………………………………………………………… 103 Chapter 3 Table C1. Observing parameters for asteroids observed with the LXD mode of SpeX at NASA IRTF………………………………..………………………………………………..….142 Table C2. Criteria used to classify the shape of the 3-µm feature……………………………..143 Table C3a. Meteorite analyses………………………………………………………………....144 Table C3b. Asteroid analyses……………………………………………………………....….145 Table C4. Chi-squared (2) test results for all meteorites and asteroids with the 3-µm sharp band…………………………………………………………………………………..…146 ix List of Figures Chapter 1 Figure A1. Uncorrected spectrum of 10 Hygiea with thermal models, using different values of the beaming parameter (η)………….……………………………………………………44 Figure A2. Spectrum of 10 Hygiea uncorrected and corrected, using thermal model of a beaming parameter η = 0.92……………………………………………………………………….45 Figure A3. The band depth is calculated by using a regression line across the K-band of the spectrum of 52 Europa. The band depth at 3.00 µm is: 11.48 ± 0.99 %. The dashed line shows the band depth at 3.00 µm…………………..........................................................46 Figure A4. Determination of the best fit for the rounded 3-µm feature of 361 Bononia. The calculated chi-squared of the second order polynomial fit (in gray) across the 2.85- 3.25-µm region has a lower value than one
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