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Studies of the Gusev Crater Spirit Landing Site and Plagioclase Feldspar Compositions on Mars

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Studies of the Gusev Crater Spirit Landing Site and Plagioclase Feldspar Compositions on Mars University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Doctoral Dissertations Graduate School 8-2007 Mapping the Martian Geologic Record: Studies of the Gusev Crater Spirit Landing Site and Plagioclase Feldspar Compositions on Mars Keith Alan Milam University of Tennessee - Knoxville Follow this and additional works at: https://trace.tennessee.edu/utk_graddiss Part of the Geology Commons Recommended Citation Milam, Keith Alan, "Mapping the Martian Geologic Record: Studies of the Gusev Crater Spirit Landing Site and Plagioclase Feldspar Compositions on Mars. " PhD diss., University of Tennessee, 2007. https://trace.tennessee.edu/utk_graddiss/246 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 Keith Alan Milam entitled "Mapping the Martian Geologic Record: Studies of the Gusev Crater Spirit Landing Site and Plagioclase Feldspar Compositions on Mars." 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 requirements for the degree of Doctor of Philosophy, with a major in Geology. Harry Y. McSween, Jeffrey E. Moersch, Major Professor We have read this dissertation and recommend its acceptance: Larry A. Taylor, John B. Rehder 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.) To the Graduate Council: I am submitting herewith a dissertation written by Keith Alan Milam entitled “Mapping the Martian Geologic Record: Studies of the Gusev Crater Spirit Landing Site and Plagioclase Feldspar Compositions on Mars.” 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 requirements for the degree of Doctor of Philosophy, with a major in Geology. Harry Y. McSween, Jr. Major Professor Jeffrey E. Moersch, Major Professor We have read this dissertation and recommend its acceptance: Larry A. Taylor John B. Rehder Acceptance for the Council: Carolyn R. Hodges, Vice Provost and Dean of the Graduate School (Original signatures are on file with official student records.) Mapping the Martian Geologic Record: Studies of the Gusev Crater Spirit Landing Site and Plagioclase Feldspar Compositions on Mars A Dissertation Presented for Doctor of Philosophy Degree The University of Tennessee, Knoxville, Keith Alan Milam August, 2007 Dedication This dissertation is dedicated to Kerry and the rest of my family, whose patience, love, understanding, and support, have allowed me to follow my dream. iii Acknowledgments This journey would not have been possible without the encouragement and support of Harry Y. McSween, Jr. (“Hap”) during my time at the University of Tennessee. Hap has taught me what it means to be a professional and polished scientist. He is the academic standard by which I judge myself. Both Hap and Jeff Moersch have made it possible for me to sail to Mars and back on several missions . every boy’s dream. Thanks also to my other committee members Larry Taylor and John Rehder for their support and mentoring along the way. I really appreciate the Larry’s “tough love” – it was just what the doctor ordered for the overly confident undergrad that walked through the front door of the geology department several years ago. I also want to thank those currently or formerly at the University of Tennessee upon whose shoulders I have rested. To Mike Wyatt, my academic sibling, I have been and continued to be inspired by the quality of your research and appreciate all you have done for me. Karen Stockstill, we spent a great deal of time in the trenches together. To Bill Deane, our friendship and mutual interest in caving and impact cratering has been one exciting adventure. I appreciate the friendship and laughter that I experienced with others along the way: Dan Britt, Josh Cahill, Tabbatha Cavendish, Josh Chamot, Mike DeAngelis, Tasha Dunn, Jonathan Evenick, Heather Gastineau, Amitabha Ghosh, Eddy Hill, Linda Kah, Penny King, Nick Lang, Pascal Lee, Rachel Lentz, Rhiannon Mayne, Jeff Nettles, Jen Piatek, Kathy Ocker-Stone, Michael Rampey, Valerie Reynolds, Patrick Schunneman, Cara Thompson, Livio Tornabene, Tomohiro Usui, Chris Whisner and so many others who are too numerous to mention. I am deeply grateful to “the girls” in the office who, over the years, have taken great care of me and all of my fellow graduate students: Melody Branch, Teresa Parrott, Diane Pealor, and Denise Stansberry. Your concern, care, and help have made this an easier experience. And to Ray Mowry and the staff at “Ray’s Place”: not only do you provide the best cup of sweet tea on the hill, but your iv friendship and friendly conversation have always brightened many a dreary day. To my many friends in Knoxville outside the university: thanks for opportunity to have a life beyond campus. My family and I will miss you all: Tom, Lisa, Emily, Nick, Noah, Luke, Mitzi, A.C., Robert, Lisa, Tim H., Becky, Phoenix, John, Joel, Shonda, Joe, Hanna, Mike, Caleb, Josh, Diane, Hunter, Carolyn, Tim W., Alaura, Sarah, Alicia, J. C., and Mildred. I hope that our paths cross many times again. To my boys, the Cub Scouts: grow up strong and well and continue to “do your best”. Make yourselves, your family, and community proud of who you are and the things you do. Last but most definitely not least, I would not have made it this far without the love and support of my family. To my beautiful wife, Kerry, I really could not have done this without you. I appreciate your patience and understanding through the ups and downs of graduate school. I am glad you were there to share in my triumphs and were willing to listen to my problems. You are everything a Kentucky girl is and should be. I love you babe. To my son, Zacary, I have enjoyed our adventure so far. I am glad you share my enthusiasm in science and “doing experiments” and cannot wait to see what’s around the corner for you. If you keep your nose to the grindstone, you’ll go far. To my baby girl Emily, you’re the apple of your daddy’s eye. Keep those hugs and giggles coming. v Abstract The flurry of activity involved in the scientific study of Mars has resulted in multiple new data sets from several missions (Mars Global Surveyor (MGS), Mars Odyssey (MO), Mars Exploration Rovers (MER), Mars Reconnaissance Orbiter (MRO), and Mars Express) that provide information for unlocking the planet’s geologic and climatic history. This three part study utilized both orbital data and laboratory experiments to examine Mars for morphologic and mineralogic evidence of aqueous activity and magmatic evolution. The first study examined Gusev Crater, landing site for the Spirit MER rover. This work began during final landing site selection and was published just prior to Spirit’s January 2004 landing. In this work, I examined the paradigm that Gusev once held a paleolake and that it contains detrital sediment from the northern highlands. Analyses involved using the most current data then available. I produced thermophysical, morphological, and surface unit maps showing the spatial distribution and stratigraphic relationships of materials on the floor of Gusev. Orbital analyses found no unambiguous evidence of paleolake deposits. This study offered alternative hypotheses explaining floor units, one of which, volcanic deposition, has since been verified by Spirit on the ground. The second and third studies address our ability to accurately derive plagioclase compositions on Mars and to use thermal emission spectroscopy to map vi the distribution of plagioclase compositions on Mars. Plagioclase is the most abundant mineral in the martian crust and may provide information about the igneous evolution and subsequent alteration of the Martian surface. The second study focuses on mixtures more complex in nature than the two-component (composition) plagioclase sand mixtures used in previous work. Linear deconvolutions of laboratory spectra from mixtures involving additional components and phases were used to calculate average plagioclase compositions whose accuracies were found to be comparable to previous studies. The final project carried results from previous laboratory studies one step further to map the global distribution of plagioclase compositions on Mars. Maps reveal a world dominated by labradorite and bytownite, with lesser amounts of other plagioclase. Localized variations are difficult to discern at the scale of individual MGS Thermal Emission Spectrometer (TES) observations. vii Table of Contents Part 1: Introduction 1 1. Overview 2 2. Characteristics of the MER-A (Spirit) Gusev Crater Landing Site 2 3. Multi-Component and Multi-Phase Plagioclase 4 4. The First Plagioclase Compositional Maps of Mars 7 5. Summary 8 6. References 10 Part 2: THEMIS Characterization of the MER Gusev Crater Landing Site 13 Abstract 14 1. Introduction 15 2. Methods 17 3. Identification of Units 20 3.1. Unit Nomenclature 20 3.2. Thermophysical Properties 20 3.3. Morphological Characteristics 24 3.31. Unit Descriptions 24 3.32. Morphologic Unit Contacts 28 3.33. Layering Within Morphologic Units 29 4. Discussion 30 4.1. Proposal of Surface Units 32 4.2. Surface Unit Elevations and Thicknesses 32 4.3. Crater Densities 32 4.4. Gusev Crater Stratigraphy 33 4.5. Comparisons to Previous Work 38 4.6. Depositional Models 40 4.7. MER Testable Hypotheses 45 viii 5. Summary 49 Acknowledgments 51 References 52 Appendix for Part 2 55 Tables 56 Figures 58 Part 3: Plagioclase Compositions Derived From Thermal Emission Spectra of Compositionally Complex Mixtures: Implications for Martian Feldspar Mineralogy 86 Abstract 87 1.
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