Dr Ben Tatton - The Open University

Dr Ben Tatton

High-altitude Andean lakes as analogues for Noachian-Hesperian Mars

Geomorphological evidence places liquid water at the Martian surface through the Noachian-Hesperian transition (3.7 - 4.2 Ga), under an arid, low-O2, high-UV climate warmed by transient pulses of reducing gases. To find a terrestrial match, global ecoregion-scale climate and UV-B data were resampled and combined with thermochemical models of crater-lake fluid chemistry constrained by orbital and rover datasets. This identified Laguna de Antofagasta, a volcanically influenced freshwater lake in the Argentinian Puna.

Sediment cores were characterised by mineralogical, physicochemical, and genome-resolved metagenomic analysis, and used to inoculate anaerobic microcosms containing a Mars regolith simulant. Communities partitioned along redox and salinity gradients, and recovered MAGs included sulfur- and nitrogen-cycling chemolithoautotrophs with complete dissimilatory sulfate reduction pathways. In live microcosms nitrate was depleted, sulfate modified and iron drawn down by one to two orders of magnitude, while major ions were unaffected, indicating biological control of redox geochemistry, with implications for biosignature target selection.