Searching for the Glen Torridon-Sulfate-Bearing Unit transition in Gale Crater, Mars: Results from the Mars Science Laboratory Sample Analysis at Mars-Evolved Gas Analyzer (SAM-EGA) - INSU - Institut national des sciences de l'Univers Accéder directement au contenu
Communication Dans Un Congrès Année : 2021

Searching for the Glen Torridon-Sulfate-Bearing Unit transition in Gale Crater, Mars: Results from the Mars Science Laboratory Sample Analysis at Mars-Evolved Gas Analyzer (SAM-EGA)

Résumé

The Curiosity rover started exploring the phyllosilicate-bearing Glen Torridon (GT) region in Gale crater, Mars in early 2019 and is now driving towards a stratigraphically higher sulfate-bearing region (based on orbital spectral data). This phyllosilicate-sulfate transition represents an ancient environmental/climatic change from a wet, near-neutral pH Mars to a drier and possibly more acidic planet. The Sample Analysis at Mars-Evolved Gas Analyzer (SAM-EGA) on board Curiosity analyzed three sedimentary rock samples Nontron (NT), Bardou (BD), and Pontours (PT) in the upper Glen Torridon region as of July 2021 in order to constrain their volatile chemistry and support mineralogical interpretations. NT was drilled in a rubbly unit close to the base of the Mount Mercou cliff, BD was drilled at the top of the cliff, and PT was drilled 25 m stratigraphically above BD. SAM-EGA detected H2O, SO2, CO2, CO, HCl, and limited NO in all three samples. No O2 evolutions were observed. NT evolved H2O comparable to samples in the underlying GT region, consistent with Fe-rich dioctahedral smectites (e.g., nontronite). BD evolved less H2O than NT, but still showed evidence for Fe-rich smectites. PT did not evolve H2O at temperatures indicative of phyllosilicates. All three samples evolved broad SO2 releases consistent with Fe sulfates, which have been observed throughout the mission. One subsample of NT (NT2) and PT evolved SO2 above 700 °C, which was interpreted as originating from an amorphous Mg sulfate. The CO2 and CO evolutions detected by SAM were highly variable and suggestive of varying contributions from adsorbed CO2, carbonates, oxidized organic C, and instrument background. Evolved NO was very low and varied between samples, likely due to different nitrate salt abundances. The lack of O2 detections suggested that (per)chlorates were either absent or only present at very low abundances. HCl releases were similar to previous samples and suggested the presence of chlorides. Overall, SAM-EGA results from the upper Glen Torridon region in Gale crater were consistent with the decrease in phyllosilicates and presence of Mg sulfates indicated by orbital spectral data of the region. Additionally, SAM-EGA results indicated the presence of Fe sulfates, chlorides, possible trace nitrates, and oxidized carbon compounds.
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Dates et versions

insu-04507899 , version 1 (17-03-2024)

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Joanna Clark, Greg Wong, Amy Mcadam, James Lewis, Brad Sutter, et al.. Searching for the Glen Torridon-Sulfate-Bearing Unit transition in Gale Crater, Mars: Results from the Mars Science Laboratory Sample Analysis at Mars-Evolved Gas Analyzer (SAM-EGA). AGU Fall Meeting 2021, Dec 2021, New Orleans, United States. pp.id. P24A-08. ⟨insu-04507899⟩
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