Clay mineral diversity and abundance in sedimentary rocks of Gale crater, Mars

Creators: Bristow, Thomas F.; Grotzinger, John P.

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Abstract

Clay minerals provide indicators of the evolution of aqueous conditions and possible habitats for life on ancient Mars. Analyses by the Mars Science Laboratory rover Curiosity show that ~3.5–billion year (Ga) fluvio-lacustrine mudstones in Gale crater contain up to ~28 weight % (wt %) clay minerals. We demonstrate that the species of clay minerals deduced from x-ray diffraction and evolved gas analysis show a strong paleoenvironmental dependency. While perennial lake mudstones are characterized by Fe-saponite, we find that stratigraphic intervals associated with episodic lake drying contain Al-rich, Fe^(3+)-bearing dioctahedral smectite, with minor (3 wt %) quantities of ferripyrophyllite, interpreted as wind-blown detritus, found in candidate aeolian deposits. Our results suggest that dioctahedral smectite formed via near-surface chemical weathering driven by fluctuations in lake level and atmospheric infiltration, a process leading to the redistribution of nutrients and potentially influencing the cycling of gases that help regulate climate.

Additional Information

© 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC). Submitted 26 October 2017; Accepted 24 April 2018; Published 6 June 2018. We are grateful to R. Kleeberg who helped develop the CheMin instrument profile model for BGMN and A. Derkowski for informative discussion. S. Hillier and J. Michalski are thanked for constructive reviews. We acknowledge the support of the Jet Propulsion Laboratory engineering and management teams, and MSL science team members who participated in tactical and strategic operations, without whom the data presented here could not have been collected. Some of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. S.G. acknowledges funding from the UK Space Agency (UKSA) (grants ST/J005169/1 and ST/N000579/1). N.M. is funded by the Centre National d'Etudes Spatial (CNES). A.C.M. and B.H. thank NASA's MSL Participating Scientist program for supporting this effort. Author contributions: T.F.B. wrote the manuscript, with corrections, discussions, and/or revised text from coauthors. D.F.B., J.A.C., R.G., J.P.G., P.R.M., D.T.V., and A.R.V. were key in designing instruments and guiding the mission. All authors analyzed data and performed operational roles in data collection. The authors declare that they have no competing interests. Data and materials availability: All data discussed in this manuscript are available from the PDS (https://pds.nasa.gov/) and the CheMin Database (http://odr.io/CheMin). Files and models required to replicate XRD refinements are available upon request.

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