¹E.Das,¹J.F.Mustard,^1,2J.D.Tarnas,¹A.C.Pascuzzo,¹C.H.Kremer
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114720]
¹Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI 02912, United States of America
²NASA Jet Propulsion Laboratory, California Institute of Technology, United States of America
Copyright Elsevier

The Olympia Undae sand sea contains the largest known deposit of gypsum discovered on the surface of Mars. The origin of this gypsum, a hydrated sulfate mineral requiring liquid water for its formation, remains largely unconstrained. We examine the hypothesis that gypsum was derived from the early-Amazonian aged Basal Unit, which is suggested to contain hydrated sulfates. Previous attempts to detect hydrated sulfates in the Basal Unit using CRISM and OMEGA data have been largely inconclusive. In this paper, we characterize the hydrated sulfate mineralogy of the Basal Unit using the Guided Endmember Extraction (GEEn) method which can detect target mineral spectra in mixed environments that obscure absorptions characteristic of certain minerals. In this paper, we outline a novel workflow for the application of GEEn to a set of CRISM images from the Olympia Cavi region and present spectral evidence for the presence of polyhydrated sulfates in the Basal Unit. We validate the applied GEEn workflow using CRISM data from various regions on Mars where sulfates have previously been detected. Non-linear mixture modeling is used to determine that spectra of the Basal Unit are best modeled as a spectral mixture of water-ice, sand/dust, mafic dune material, gypsum, and polyhydrated magnesium sulfate⁎. These sulfate detections could indicate the presence of liquid water in the polar region during the Amazonian.1

¹A. A. Simon,¹H. H. Kaplan,²E. Cloutis,³V. E. Hamilton,⁴C. Lantz,¹D. C. Reuter,⁵D. Trang,^6,7S. Fornasier,⁸B. E. Clark,⁹D. S. Lauretta
Astronomy & Astrophysics 644, A148 Link to Article [DOI https://doi.org/10.1051/0004-6361/202039688]
¹Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, MD, USA
²Department of Geography, University of Winnipeg, Winnipeg, Canada
³Southwest Research Institute, Boulder, CO, USA
⁴Institut d’Astrophysique Spatiale, Université Paris-Saclay, CNRS, 91405 Orsay, France
⁵Hawai’i Institute of Geophysics and Planetology, University of Hawai’i at Manoa, Honolulu, HI, USA
⁶LESIA, Observatoire de Paris, Université PSL, CNRS, Université de Paris, Sorbonne Université, 5 place Jules Janssen, 92195 Meudon, France
⁷Institut Universitaire de France (IUF), 1 rue Descartes, 75231 Paris Cedex 05, France
⁸Department of Physics and Astronomy, Ithaca College, Ithaca, NY, USA
⁹Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA

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^1,2S.Fornasier et al. (>10)
Astronomy & Astrophysics 644, A142 Link to Article [DOI https://doi.org/10.1051/0004-6361/202039552]
¹LESIA, Observatoire de Paris, Université PSL, CNRS, Université de Paris, Sorbonne Université, 5 place Jules Janssen, 92195 Meudon, France
²Institut Universitaire de France (IUF), 1 rue Descartes, 75231 Paris Cedex 05, France

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¹Conel M.O’D. Alexander,^1,2Jonathan G. Wynn,¹Roxane Bowden
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13746]
¹Earth and Planets Laboratory, Carnegie Institution for Science, 5241 Broad Branch Road, NW, Washington, District of Columbia, 20015 USA
²Division of Earth Sciences, National Science Foundation, 2415 Eisenhower Avenue, Alexandria, Virginia, 22314 USA
Published by arrangement with John Wiley & Sons

The bulk S elemental abundances and δ34S values for 83 carbonaceous chondrites (mostly CMs and CRs) and Semarkona (LL3.0) are reported. In addition, the S elemental abundances and δ34S values of insoluble organic material (IOM) isolated from 25 carbonaceous chondrites (CMs, CRs, and three ungrouped) are presented. The IOM only contributes 2–7% of the S to the bulk meteorites analyzed and exhibits no systematic variations. The average group bulk S abundances are similar to previous measurements. In-group variations likely reflect variations in matrix abundances, as well as parent body processes and weathering. The S and C abundances are roughly correlated and scatter about a mixing line between CI-like matrix and C-free and S-depleted chondrules. Systematic deviations from this mixing line may indicate different degrees of heating of matrix material in the nebula. There are no systematic variations in average group δ34S values, in contrast to what is seen for the volatile chalcophiles Zn, Te, Se, and Ag, as well as the less volatile siderophile Cu. Renormalization of the elemental and isotopic compositions indicates that the elemental and isotopic fractionations of Zn, Te, and Ag were controlled by the same process, whereas Se is intermediate in its behavior between these three elements and S. The isotopic fractionations could be associated with diffusion of volatile chalcophiles into sulfide at the end of chondrule formation. Copper appears to be distinct in its behavior from the chalcophiles, perhaps because it is more refractory and more siderophile.