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Chemistry, Mineralogy, and Grain Properties at Namib and High Dunes, Bagnold Dune Field, Gale Crater, Mars: A Synthesis of Curiosity Rover Observations

Ehlmann, B. L. and Lapotre, M. G. A. and Stein, N. T. (2017) Chemistry, Mineralogy, and Grain Properties at Namib and High Dunes, Bagnold Dune Field, Gale Crater, Mars: A Synthesis of Curiosity Rover Observations. Journal of Geophysical Research. Planets . ISSN 2169-9097. (In Press)

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The Mars Science Laboratory Curiosity rover performed coordinated measurements to examine the textures and compositions of aeolian sands in the active Bagnold dune field. The Bagnold sands are rounded to subrounded, very fine to medium sized (~45–500 μm) with ≥6 distinct grain colors. In contrast to sands examined by Curiosity in a dust-covered, inactive bedform called Rocknest and soils at other landing sites, Bagnold sands are darker, less red, better sorted, have fewer silt-sized or smaller grains, and show no evidence for cohesion. Nevertheless, Bagnold mineralogy and Rocknest mineralogy are similar with plagioclase, olivine, and pyroxenes in similar proportions comprising >90% of crystalline phases, along with a substantial amorphous component (35% ± 15%). Yet Bagnold and Rocknest bulk chemistry differ. Bagnold sands are Si enriched relative to other soils at Gale crater, and H_2O, S, and Cl are lower relative to all previously measured Martian soils and most Gale crater rocks. Mg, Ni, Fe, and Mn are enriched in the coarse-sieved fraction of Bagnold sands, corroborated by visible/near-infrared spectra that suggest enrichment of olivine. Collectively, patterns in major element chemistry and volatile release data indicate two distinctive volatile reservoirs in Martian soils: (1) amorphous components in the sand-sized fraction (represented by Bagnold) that are Si-enriched, hydroxylated alteration products and/or H_2O- or OH-bearing impact or volcanic glasses and (2) amorphous components in the fine fraction (<40 μm; represented by Rocknest and other bright soils) that are Fe, S, and Cl enriched with low Si and adsorbed and structural H_2O.

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Ehlmann, B. L.0000-0002-2745-3240
Lapotre, M. G. A.0000-0001-9941-1552
Stein, N. T.0000-0003-3385-9957
Additional Information:© 2017 The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. Received 16 JAN 2017; Accepted 19 MAY 2017; Accepted article online 12 JUN 2017. We thank the MSL science, operations, engineering, and management teams for the strategic and tactical planning, execution, and data archiving for the Bagnold dune campaign. We especially thank members, past and present, of the aeolian group for their work to collect this coordinated data set. Special acknowledgement goes to Deirdra Fey and Michael Ravine for assistance with MAHLI image product tracking, processing, and analysis and Jason Van Beek and the Mastcam team at Malin Space Science Systems for their work to acquire images free of shadows and for mosaic production. Thanks to Bob Deen and the JPL OPGS staff for creation of Navcam mosaics. Thanks to Mikki Osterloo and an anonymous reviewer for their comments, which helped us improve this manuscript. B.L.E., A.A.F., R.E.A., V.E.H., and J.R.J. acknowledge the MSL Participating Scientist Program for support. A portion 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. All data used in this study are available online at the NASA Planetary Data System Geosciences Node and can be readily accessed by sol using the Analyst's Notebook tool.
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Subject Keywords:Mars soils; sand dunes; dust; amorphous phase; volatiles; grain size
Record Number:CaltechAUTHORS:20170612-135954084
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Official Citation:Ehlmann, B. L., et al. (2017), Chemistry, mineralogy, and grain properties at Namib and High dunes, Bagnold dune field, Gale crater, Mars: A synthesis of Curiosity rover observations, J. Geophys. Res. Planets, 122, doi:10.1002/2017JE005267
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:78119
Deposited By: Tony Diaz
Deposited On:19 Jun 2017 16:25
Last Modified:12 Dec 2017 19:13

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