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The origin and implications of clay minerals from Yellowknife Bay, Gale crater, Mars

Bristow, Thomas F. and Grotzinger, John P. and Ehlmann, Bethany L. (2015) The origin and implications of clay minerals from Yellowknife Bay, Gale crater, Mars. American Mineralogist, 100 (4). pp. 824-836. ISSN 0003-004X. PMCID PMC5548523.

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The Mars Science Laboratory (MSL) rover Curiosity has documented a section of fluvio-lacustrine strata at Yellowknife Bay (YKB), an embayment on the floor of Gale crater, approximately 500 m east of the Bradbury landing site. X-ray diffraction (XRD) data and evolved gas analysis (EGA) data from the CheMin and SAM instruments show that two powdered mudstone samples (named John Klein and Cumberland) drilled from the Sheepbed member of this succession contain up to ~20 wt% clay minerals. A trioctahedral smectite, likely a ferrian saponite, is the only clay mineral phase detected in these samples. Smectites of the two samples exhibit different 001 spacing under the low partial pressures of H_2O inside the CheMin instrument (relative humidity <1%). Smectite interlayers in John Klein collapsed sometime between clay mineral formation and the time of analysis to a basal spacing of 10 Å, but largely remain open in the Cumberland sample with a basal spacing of ~13.2 Å. Partial intercalation of Cumberland smectites by metal-hydroxyl groups, a common process in certain pedogenic and lacustrine settings on Earth, is our favored explanation for these differences. The relatively low abundances of olivine and enriched levels of magnetite in the Sheepbed mudstone, when compared with regional basalt compositions derived from orbital data, suggest that clay minerals formed with magnetite in situ via aqueous alteration of olivine. Mass-balance calculations are permissive of such a reaction. Moreover, the Sheepbed mudstone mineral assemblage is consistent with minimal inputs of detrital clay minerals from the crater walls and rim. Early diagenetic fabrics suggest clay mineral formation prior to lithification. Thermodynamic modeling indicates that the production of authigenic magnetite and saponite at surficial temperatures requires a moderate supply of oxidants, allowing circum-neutral pH. The kinetics of olivine alteration suggest the presence of fluids for thousands to hundreds of thousands of years. Mineralogical evidence of the persistence of benign aqueous conditions at YKB for extended periods indicates a potentially habitable environment where life could establish itself. Mediated oxidation of Fe^(2+) in olivine to Fe^(3+) in magnetite, and perhaps in smectites provided a potential energy source for organisms.

Item Type:Article
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URLURL TypeDescription ItemSupplementary Data CentralArticle
Bristow, Thomas F.0000-0001-6725-0555
Grotzinger, John P.0000-0001-9324-1257
Ehlmann, Bethany L.0000-0002-2745-3240
Additional Information:© 2015 Mineralogical Society of America. Open access: Article available to all readers online. Manuscript received June 4, 2014. Manuscript accepted September 20, 2014. Manuscript handled by Janice Bishop. We are grateful to R. Kleeburg for help with modeling XRD patterns and to D. Deocampo and J. Cuadros for thoughtful reviews. Support from the engineers and staff of NASA Mars Science Laboratory Mission are gratefully acknowledged. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Deposit item AM-15-45077, Table 1, Appendix Figure 1, and Methods section. Deposit items are stored on the MSA web site and available via the American Mineralogist Table of Contents. Find the article in the table of contents at GSW ( or MSA (, and then click on the deposit link.
Funding AgencyGrant Number
Subject Keywords:Mars, Yellowknife Bay, clay minerals, CheMin, XRD, habitability
Issue or Number:4
PubMed Central ID:PMC5548523
Record Number:CaltechAUTHORS:20150501-103431979
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Official Citation:Thomas F. Bristow, David L. Bish, David T. Vaniman, Richard V. Morris, David F. Blake, John P. Grotzinger, Elizabeth B. Rampe, Joy A. Crisp, Cherie N. Achilles, Doug W. Ming, Bethany L. Ehlmann, Penelope L. King, John C. Bridges, Jennifer L. Eigenbrode, Dawn Y. Sumner, Steve J. Chipera, John Michael Moorokian, Allan H. Treiman, Shaunna M. Morrison, Robert T. Downs, Jack D. Farmer, David Des Marais, Philippe Sarrazin, Melissa M. Floyd, Michael A. Mischna, and Amy C. McAdam The origin and implications of clay minerals from Yellowknife Bay, Gale crater, Mars American Mineralogist, April 2015, v. 100, p. 824-836, doi:10.2138/am-2015-5077CCBYNCND
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:57144
Deposited By: Ruth Sustaita
Deposited On:01 May 2015 17:58
Last Modified:06 Nov 2020 16:57

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