A Review of Sample Analysis at Mars-Evolved Gas Analysis Laboratory Analog Work Supporting the Presence of Perchlorates and Chlorates in Gale Crater, Mars

Abstract

The Sample Analysis at Mars (SAM) instrument on the Curiosity rover has detected evidence of oxychlorine compounds (i.e., perchlorates and chlorates) in Gale crater, which has implications for past habitability, diagenesis, aqueous processes, interpretation of in situ organic analyses, understanding the martian chlorine cycle, and hazards and resources for future human exploration. Pure oxychlorines and mixtures of oxychlorines with Mars-analog phases have been analyzed for their oxygen (O2) and hydrogen chloride (HCl) releases on SAM laboratory analog instruments in order to constrain which phases are present in Gale crater. These studies demonstrated that oxychlorines evolve O2 releases with peaks between ~200 and 600 °C, although the thermal decomposition temperatures and the amount of evolved O2 decrease when iron phases are present in the sample. Mg and Fe oxychlorines decompose into oxides and release HCl between ~200 and 542 °C. Ca, Na, and K oxychlorines thermally decompose into chlorides and do not evolve HCl by themselves. However, the chlorides (original or from oxychlorine decomposition) can react with water-evolving phases (e.g., phyllosilicates) in the sample and evolve HCl within the temperature range of SAM (<~870 °C). These laboratory analog studies support that the SAM detection of oxychlorine phases is consistent with the presence of Mg, Ca, Na, and K perchlorate and/or chlorate along with possible contributions from adsorbed oxychlorines in Gale crater samples.

Oxidized and Reduced Sulfur Observed by the Sample Analysis at Mars (SAM) Instrument Suite on the Curiosity Rover Within the Glen Torridon Region at Gale Crater, Mars

“…Laboratory sulfide purity was determined by X‐ray diffraction (Wong et al., 2020). Chlorine phases were chosen due to the observations of chlorides and (per)chlorates on Mars (J. Clark et al., 2021; Glavin et al., 2013). The phyllosilicate nontronite was chosen because evidence of similar phyllosilicates has been observed in several samples (e.g., Bristow et al., 2015, 2018; McAdam et al., 2022; Thorpe et al., 2022).…”

Manganese Mobility in Gale Crater, Mars: Leached Bedrock and Localized Enrichments

“…Thus, a strong oxidant is necessary to induce precipitation of Mn as an oxide. Oxychlorine species are strong oxidants and have been identified in Gale crater bedrock (Clark, Sutter, et al., 2021; Ming et al., 2014; Sutter et al., 2018) and by the Wet Chemistry Laboratory on Phoenix (Kounaves et al., 2010, 2014). Specifically, perchlorate ($${{\mathrm{C}\mathrm{l}\mathrm{O}}_{4}}^{-}$$) and chlorate ($${{\mathrm{C}\mathrm{l}\mathrm{O}}_{3}}^{2-}$$) were detected by SAM (Sutter et al., 2018).…”

Constraining Alteration Processes Along the Siccar Point Group Unconformity, Gale Crater, Mars: Results From the Sample Analysis at Mars Instrument

“…Similar to the Gm, samples limited to undetectable nitrate and oxychlorine has also affected over ∼325 m of stratigraphically lower samples that span the GT trough, the VRR, down to the Oudam sample below the VRR (J. Clark et al, 2021;J. V. Clark et al, 2020;McAdam et al, 2020).…”