University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Doctoral Dissertations Graduate School 8-2012 Formation and Alteration of Basaltic Soils on Mars Ian Oliver McGlynn [email protected] Follow this and additional works at: https://trace.tennessee.edu/utk_graddiss Part of the Geochemistry Commons, Geology Commons, and the Sedimentology Commons Recommended Citation McGlynn, Ian Oliver, "Formation and Alteration of Basaltic Soils on Mars. " PhD diss., University of Tennessee, 2012. https://trace.tennessee.edu/utk_graddiss/1397 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 Ian Oliver McGlynn entitled "Formation and Alteration of Basaltic Soils 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. Christopher M. Fedo and Harry Y. McSween, Jr., Major Professor We have read this dissertation and recommend its acceptance: Jeffrey E. Moersch, Carol P. Harden 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.) Formation and Alteration of Basaltic Soils on Mars A Dissertation Presented for the Doctor of Philosophy Degree The University of Tennessee, Knoxville Ian Oliver McGlynn August 2012 Copyright © 2012 by Ian O. McGlynn ii All rights reserved. Acknowledgements iii Results from this research have only been possible with the guidance, support, and patience of my co-advisors Dr. Christopher M. Fedo and Dr. Harry Y. McSween, Jr. I am immensely grateful for the opportunity they have provided to explore the desolate and arid plains of Mars with the twin Mars Exploration Rovers Spirit and Opportunity. I am also grateful to the committee members, Dr. Jeffrey E. Moersch and Dr. Carol P. Harden, whose time and effort has improved the quality of this dissertation. I am grateful to the MER operations and development trams and to the scientists and engineers at NASA and JPL who sent two explorers out into the unknown. Specific contributions were provided from the following individuals: D. M. Burr (Tennessee), R. Gellert (Guelph), K. E. Herkenhoff (USGS), O. Karahayit (OSU), R. Li (OSU), H. W. Nesbitt (Western Ontario), A. Patchen (Tennessee), A. D. Rogers (Stony Brook), E. Simpson (Kutztown), and R. J. Sullivan (Cornell). To Karina my martian partner in crime, thank you for keeping the wonder and enthusiasm. We walk upon a world not of our own and ponder the differences, yet it is the similarities that are most striking. Wispy clouds high above in an atmosphere so thin and fragile, against a brilliant sky with a billion stars looking down, and grains of sand roll steadily in the breeze. Let’s dream and explore together. I am forever indebted for the enduring support from family through the long days and nights, for kindling the spark and sustaining the ambition. Finally, I am appreciative for the mentorship of Dr. Gregory S. Okin (UCLA), Dr. John M. Hanchar (MUN), and Dr. Lin H. Chambers (NASA LaRC) who showed the way forward. Abstract iv The current surface of Mars is an arid inhospitable environment, dominated by aeolian processes, composed of largely volcanic rocks that have little apparent indication of pervasive aqueous chemical weathering, and blanketed by dust. Rocks are composed of basalts and the “soil” sediments appear to be largely basaltic-derived, and are chemically similar on a global scale. If the climate was once warmer and wetter during the Noachian period, with environmental conditions favorable to the development of life, physically weathered remnants, such as large quantities of phyllosilicate minerals, should remain. Basaltic soils provide a crucial constraint on chemical and physical weathering processes, and are critical for determining the environmental and climatic history of Mars. To understand the origin of sediments, this dissertation investigated the (1) textures of sedimentary grains at Gusev Crater, (2) the chemical and mineral compositions of sediments at the Mars Exploration Rover landing sites in Meridiani Planum and Gusev Crater, and evaluated the potential chemical alteration from weathering, and (3) applied mineral fractionation experiments of analog basalt sediment with implications for interpreting the sorting of sediments on Mars. Textural results indicate that soils are continuously transported and modified by aeolian conditions, and originate primarily from comminuted impacted bedrock. Soil chemical compositions resemble unaltered basalt but mixing of sulfates and phyllosilicates is permissible. Comminuted and grain size sorted basalt analog sediments demonstrate the potential for significant compositional variations imposed by hydrodynamic sorting, an important determinant of soil compositions on Mars. Combined, these results show that soils on Mars are heterogeneous mixtures of comminuted locally derived rocks that have been minimally altered by chemical weathering from olivine dissolution, and are mixed with dust containing older phyllosilicates and sulfates. Table of Contents v Chapter 1 Introduction .................................................................................................................... 1 1. Soil Sediments on Mars .......................................................................................................... 2 2. Mechanisms of Sediment Production ..................................................................................... 3 3. Composition and Alteration of Sediment ............................................................................... 4 4. Aeolian Reworking and Sorting.............................................................................................. 6 5. Implications of Results ........................................................................................................... 6 References ................................................................................................................................... 8 Chapter 2 Origin of Basaltic Soils at Gusev Crater, Mars, by Aeolian Modification of Impact- Generated Sediment .................................................................................................................. 11 1. Introduction ........................................................................................................................... 13 2. Methodology ......................................................................................................................... 15 2.1. Sample Selection ........................................................................................................... 15 2.2. Textural Parameters ...................................................................................................... 18 2.3. Grain Size Distribution ................................................................................................. 21 3. Textural Characteristics of Gusev Soils ................................................................................ 24 3.1. Dark Soil ....................................................................................................................... 25 3.2. Bed Form Armor ........................................................................................................... 33 3.3. Lithic Fragments ........................................................................................................... 36 3.4. Bimodal Mixed Soil ...................................................................................................... 39 3.5. Excavated Subsurface Soil ............................................................................................ 43 4. Soil Formation in Gusev Crater ............................................................................................ 49 4.1. Step 1: Surface Formation ............................................................................................ 49 4.2. Step 2: Comminution .................................................................................................... 51 4.3. Step 3: Aeolian Modification ........................................................................................ 53 5. Conclusions ........................................................................................................................... 54 6. Acknowledgments................................................................................................................. 55 References ................................................................................................................................. 56 Appendix ................................................................................................................................... 63 Chapter 3 Soil Mineralogy at the Mars Exploration Rover landing sites: An Assessment of the Competing Roles of Physical Sorting and Chemical Weathering ................................................ 65 1. Introduction ..........................................................................................................................