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Understanding Martian Alteration Processes by Comparing In-Situ Chemical Measurements from Multiple Landing SitesCharacterizing the history of aqueous activity at the martian surface has been an objective of the Mars Exploration Rovers (MER) and the Mars Science Laboratory (MSL). Although the geologic context of the three landing sites are different, comparisons across the datasets can provide greater insight than using data from one mission alone. The Alpha Particle X-ray Spectrometer (APXS) is common to all three rovers (Spirit at Gusev crater, Opportunity at Meridiani Planum, and Curiosity at Gale crater) and provides a consistent basis for these comparisons. Soil and Dust: Fine grained basaltic soils and dust are remarkably uniform in chemical composition across multiple landing sites. These similarities in the concentrations of major, minor, and a few trace elements (Fig. 1) are indicative of planet-wide consistency in the composition of source materials for the soils. S and Cl vary by a factor of two in the soil and dust, but there is no clear association with any bulk cation (e.g., no correlation between S and total Ca, Mg, or Fe in soils). These volatile elements, however, are clearly associated with the nanophase-ferric iron component in the soil established by Mössbauer spectroscopy [1,2]. S and Cl likely originated as acidic species from volcanic out-gassing and subsequently coalesced on dust and sand grain surfaces, possibly with an affinity towards Fe3+ sites. Importantly, given the mobility of S and Cl in aqueous exposures, soil samples maintaining the typical molar S/Cl ratio of ~3.7:1 indicate minimal interactions with liquid water after the addition of S and Cl. In contrast to this well-established baseline, soil samples have been discovered at all three landing sites with atypical S/Cl ratios (e.g., subsurface soils), indicative of a more complex aqueous history.
Document ID
20190027719
Acquisition Source
Johnson Space Center
Document Type
Conference Paper
Authors
Yen, A. S. (Jet Propulsion Laboratory (JPL) Pasadena, CA, United States)
Gellert, R. (University of Guelph Guelph, Ontario, Canada)
Morris, R. V. (NASA Johnson Space Center Houston, TX, United States)
Ashley, J. W. (Jet Propulsion Laboratory (JPL) Pasadena, CA, United States)
Berger, J. A. (University of Guelph Guelph, Ontario, Canada)
Clark, B. C. (Space Science Institute (SSI) Boulder, CO, United States)
Cohen, B. A. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Ming, D. W. (NASA Johnson Space Center Houston, TX, United States)
Mittlefehldt, D. W. (NASA Johnson Space Center Houston, TX, United States)
O’Connell-Cooper, C. D. (University of New Brunswick Saint John, New Brunswick, Canada)
Salvatore, M. (University of Northern Arizona Flagstaff, AZ, United States)
Schmidt, M. E. (Brock Univ. Saint Catherines, Ontario, Canada)
Schröder, C. (Stirling Univ. United Kingdom)
Thompson, L. M. (University of New Brunswick Saint John, New Brunswick, Canada)
VanBommel, S. J. (Washington Univ. Saint Louis, MO, United States)
Date Acquired
July 24, 2019
Publication Date
July 22, 2019
Subject Category
Lunar And Planetary Science And Exploration
Report/Patent Number
JSC-E-DAA-TN70395
Meeting Information
Meeting: International Conference on Mars
Location: Pasadena, CA
Country: United States
Start Date: July 22, 2019
End Date: July 25, 2019
Sponsors: Universities Space Research Association (USRA)
Distribution Limits
Public
Copyright
Public Use Permitted.

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