Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars

Abstract

Establishing the presence and state of organic matter, including its possible biosignatures, in martian materials has been an elusive quest, despite limited reports of the existence of organic matter on Mars. We report the in situ detection of organic matter preserved in lacustrine mudstones at the base of the ~3.5-billion-year-old Murray formation at Pahrump Hills, Gale crater, by the Sample Analysis at Mars instrument suite onboard the Curiosity rover. Diverse pyrolysis products, including thiophenic, aromatic, and aliphatic compounds released at high temperatures (500° to 820°C), were directly detected by evolved gas analysis. Thiophenes were also observed by gas chromatography-mass spectrometry. Their presence suggests that sulfurization aided organic matter preservation. At least 50 nanomoles of organic carbon persists, probably as macromolecules containing 5% carbon as organic sulfur molecules.

Indigenous Organic‐Oxidized Fluid Interactions in the Tissint Mars Meteorite

“…Thiophenes were also detected in samples of mudstone from Gale crater (Eigenbrode et al, 2018) and are routinely identified in extraterrestrial samples (Bandurski & Nagy, 1976;Komiya et al, 1993;Simmonds et al, 1969). Thiophenes were also detected in samples of mudstone from Gale crater (Eigenbrode et al, 2018) and are routinely identified in extraterrestrial samples (Bandurski & Nagy, 1976;Komiya et al, 1993;Simmonds et al, 1969).…”

“…Organic matter is also expected on the surface of Mars due to meteoritic input (Flynn, 1996;Flynn et al, 2004) but has so far proven difficult to detect in situ Leshin et al, 2013;Ming et al, 2014) with only a limited range of putative indigenous organics being detected (Eigenbrode et al, 2018;Freissinet et al, 2015). This is due to not only the limits of landed scientific payloads but also the confounding effects of oxidizing minerals, especially perchlorate salts, initially discovered by the Phoenix ©2019.…”

Perchlorate‐Driven Combustion of Organic Matter During Pyrolysis‐Gas Chromatography‐Mass Spectrometry: Implications for Organic Matter Detection on Earth and Mars

“…Organic compounds concentrate in sediments in lacustrine depositional environments on Earth similar to those proposed for the formation of these mudstones and perchlorate content of these Martian sediments could be expected to be low owing to the aqueous environment in which they were deposited. It has been suggested that the survival of organic molecules in the Murray mudstone may have been higher (than in the Sheepbed) allowing its detection (Eigenbrode et al, ). However, it is also possible, based on the findings of the current study, that the organic matter contents of the two units are similar and that it is the decreased level of perchlorate in the lower Murray mudstone that has facilitated the detection of more complex, nonchlorinated, organic molecules.…”

“…However, it is also possible, based on the findings of the current study, that the organic matter contents of the two units are similar and that it is the decreased level of perchlorate in the lower Murray mudstone that has facilitated the detection of more complex, nonchlorinated, organic molecules. The lower Murray mudstone samples, which yielded the complex organic matter detection (Eigenbrode et al, ), have around 10 times less perchlorate than the Sheepbed mudstone samples which only yielded simple organochlorines (Freissinet et al, ; Sutter et al, ).…”

Radiolysis of Macromolecular Organic Material in Mars‐Relevant Mineral Matrices

“…The Sample Analysis at Mars instrument onboard the Mars Science Laboratory (MSL) Curiosity Rover detected chlorinated hydrocarbons indigenous to the ~3.5‐Ga lake sediments at Yellowknife Bay, Gale crater (Freissinet et al, ). Other aliphatic, aromatic, and sulfur‐bearing hydrocarbons that were detected in lake sediments studied at Pahrump Hills are thought to be derived from larger macromolecular structures that aided their preservation (Eigenbrode et al, ). Other potential indications of indigenous organic matter are indirect and are observed as thermal evolution of CO 2 and CO observed during Sample Analysis at Mars' evolved gas analysis and are in part attributed to decarboxylation and decarbonylation of organics in samples from diverse rocks and aeolian sediments in Gale crater (Ming et al, ; Sutter et al, ), which may also explain CO 2 observed by the Viking GCMS (Biemann et al, ).…”