Abstract EANA2025-69

Evidence of hydrological activity on Mars during the Noachian (4.1–3.7 billion years ago, Ga) and Hesperian (3.7–3.0 Ga) periods is abundant (1). However, the transition from the Noachian to Hesperian has been suggested to have been a turbulent period in Mars' history as conditions transitioned from a warmer, wetter environment to the colder, more arid conditions of the middle to late Hesperian (2). Low-energy lacustrine environments, such as those found in Gale Crater and Jezero Crater, are considered ideal for preserving biosignatures in sedimentary material (3). The discovery of phyllosilicates and hydrated secondary minerals in both paleolakes confirms the prolonged presence of liquid water, prompting questions about past habitability and endemic microbiomes (4,5).

High-altitude Andean lakes (HAALs) within the Central Andean Puna are subjected to poly-extreme conditions, experiencing high ultraviolet radiation (UV) levels, large diurnal temperature fluctuations, negative water balances, and seasonal ice cover (6). These environments provide an opportunity to study microbial communities influenced by geological and physicochemical conditions similar to those predicted for crater lakes during the Noachian-Hesperian transition.

Water and 30 cm long sediment core samples were collected from five points around a previously uncharacterised HAAL, Laguna de Antofagasta (LDA; -26.111148, -67.407338), situated in the Catamarca province of Argentina. Samples were transported to the Open University, UK, at 4 °C. DNA was extracted using the XS buffer method (7) and sequenced with a metagenome shotgun sequencing approach. The taxonomic composition and functional potential of microbiomes in water and lake sediment samples were analysed using genome-resolved metagenomic methods.

A non-redundant set of 19 metagenome-assembled genomes (MAGs) was produced. Genes associated with the oxidation of inorganic sulfur compounds, nitrate reduction, dissimilatory nitrate reduction to ammonia (DNRA), and hydrogen and carbon monoxide oxidation were identified. The range of metabolic strategies displayed within the LDA microbiome suggests that metabolic flexibility may be essential for coping with the permutations of highly dynamic, poly-extreme environments. These findings offer insights into metabolic strategies that may have been employed within crater lakes during the Noachian-Hesperian Transition and can inform biosignature selection in future life detection missions. 

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