Sedimentary Organics in Glen Torridon, Gale Crater, Mars: Results From the SAM Instrument Suite and Supporting Laboratory Analyses

Abstract

The Sample Analysis at Mars (SAM) suite instrument on board NASA's Curiosity rover has characterized the inorganic and organic chemical composition of seven samples from the Glen Torridon clay-bearing unit. A variety of organic molecules were detected with SAM using pyrolysis (up to ~850°C) and wet chemistry experiments coupled with evolved gas analysis (EGA) and gas chromatography-mass spectrometry (GCMS). SAM EGA and GCMS analyses revealed a greater diversity and abundance of sulfur-bearing aliphatic and aromatic organic compounds in the sediments of this Gale crater unit than earlier in the mission. We also report the detection of nitrogen-containing, oxygen-containing, and chlorinecontaining molecules, as well as polycyclic aromatic hydrocarbons found in Glen Torridon (GT), although the sources of some of these organics may be related to the presence of chemical reagents in the SAM instrument background. However, sulfur-bearing organics released at high temperature (>600°C) are likely derived from martian sources (e.g., igneous, hydrothermal, atmospheric, or biological) or exogenous sources and consistent with the presence of recalcitrant organic materials in the sample. The SAM measurements of the GT clay-bearing unit expand the inventory of organic matter present in Gale crater and is also consistent with the hypothesis that clay minerals played an important role in the preservation of ancient refractory organic matter on Mars. These findings deepen our understanding of the past habitability and biological potential of Gale crater.

Evolved Gas Analyses of Sedimentary Rocks From the Glen Torridon Clay‐Bearing Unit, Gale Crater, Mars: Results From the Mars Science Laboratory Sample Analysis at Mars Instrument Suite

“…OCS and CS 2 evolved coincident with the high temperature CO and SO 2 in the GE1 run also support this idea of reduced C present and available to react with S species. These sorts of associations between organics and sulfates have been discussed as possibilities for past samples analyzed by SAM (e.g., Eigenbrode et al., 2018; Freissinet et al., 2019) and sulfur‐bearing organics detected in SAM GCMS runs of GT samples, including GG and GE, may also indicate associations or interactions between sample reduced organic compounds and sulfates or SO 2 evolved during their decomposition (Millan et al., 2022).…”

“…SAM pyrolysis GCMS and wet chemistry experiments also detected reduced organic compounds in several GT samples, and the reader is referred to Millan et al. (2022) for a detailed discussion of those results.…”

“…Trace abundances of oxidized carbon compounds such as oxalate salts may be indicated by CO and some CO 2 evolution during EGA of several GT samples. SAM pyrolysis GCMS and wet chemistry experiments also detected reduced organic compounds in several GT samples, and the reader is referred to Millan et al (2022) for a detailed discussion of those results.…”

“…% tetramethylammonium hydroxide in methanol). These analyses indicated a diversity of organic compounds (Millan et al., 2022; Williams et al., 2021). While some of the organic molecules detected are related to SAM’s wet chemistry experiment reagents and related background, it is also likely that some sulfur‐containing organics evolved from samples at high pyrolysis temperatures are indigenous to the sample.…”

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

“…Alternatively, it is possible that the sulfur was delivered from a sulfide‐containing basaltic source that underwent minimal or partial alteration (McAdam et al., 2014). The observation of mixed sulfur oxidation states could also be due to multiple sources of sulfur, such as sulfates (crystalline and/or amorphous) and preserved reduced sulfur in organic molecules (Eigenbrode et al., 2018; Millan et al., 2022). Regardless of source, the presence of both oxidized and reduced sulfur has interesting implications toward the habitability of the GT region.…”