Habitability and Biosignature Formation in Simulated Martian Aqueous Environments

作者：Michael C. Macey, Nisha K. Ramkissoon, Simone Cogliati, Mario Toubes-Rodrigo, Ben Stephens, Ezgi Kucukkilic-Stephens, S. P. Schwenzer, V. K. Pearson, Louisa J. Preston, Karen Olsson‐Francis · 发表于：Astrobiology · 年份：2022 · DOI：10.1089/ast.2021.0197 · 被引用次数：12 · 研究领域：Planetary Science and Exploration、Spaceflight effects on biology、Microbial Community Ecology and Physiology

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 ...