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Habitability and Biosignature Formation in Simulated Martian Aqueous Environments

Macey, Michael C; Ramkissoon, Nisha K; Cogliati, Simone; Toubes-Rodrigo, Mario; Stephens, Ben P; Kucukkilic-Stephens, Ezgi; Schwenzer, Susanne P; ... Olsson-Francis, Karen; + view all (2023) Habitability and Biosignature Formation in Simulated Martian Aqueous Environments. Astrobiology , 23 (2) pp. 144-154. 10.1089/ast.2021.0197. Green open access

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Abstract

Water present on early Mars is often assumed to have been habitable. In this study, experiments were performed to investigate the habitability of well-defined putative martian fluids and to identify the accompanying potential formation of biosignatures. Simulated martian environments were developed by combining martian fluid and regolith simulants based on the chemistry of the Rocknest sand shadow at Gale Crater. The simulated chemical environment was inoculated with terrestrial anoxic sediment from the Pyefleet mudflats (United Kingdom). These enrichments were cultured for 28 days and subsequently subcultured seven times to ensure that the microbial community was solely grown on the defined, simulated chemistry. The impact of the simulated chemistries on the microbial community was assessed by cell counts and sequencing of 16S rRNA gene profiles. Associated changes to the fluid and precipitate chemistries were established by using ICP-OES, IC, FTIR, and NIR. The fluids were confirmed as habitable, with the enriched microbial community showing a reduction in abundance and diversity over multiple subcultures relating to the selection of specific metabolic groups. The final community comprised sulfate-reducing, acetogenic, and other anaerobic and fermentative bacteria. Geochemical characterization and modeling of the simulant and fluid chemistries identified clear differences between the biotic and abiotic experiments. These differences included the elimination of sulfur owing to the presence of sulfate-reducing bacteria and more general changes in pH associated with actively respiring cells that impacted the mineral assemblages formed. This study confirmed that a system simulating the fluid chemistry of Gale Crater could support a microbial community and that variation in chemistries under biotic and abiotic conditions can be used to inform future life-detection missions.

Type: Article
Title: Habitability and Biosignature Formation in Simulated Martian Aqueous Environments
Location: United States
Open access status: An open access version is available from UCL Discovery
DOI: 10.1089/ast.2021.0197
Publisher version: https://doi.org/10.1089/ast.2021.0197
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Microbiology, Simulation, Sulfate reduction, Biosignature, Habitability
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/10177523
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