Abstract
Sediments in the hyper-arid core of the Atacama Desert are a terrestrial analog to Mars regolith. Understanding the distribution and drivers of microbial life in the sediment may give critical clues on how to search for biosignatures on Mars. Here, we identify the spatial distribution of highly specialized bacterial communities in previously unexplored depth horizons of subsurface sediments to a depth of 800 mm. We deployed an autonomous rover in a mission-relevant Martian drilling scenario with manual sample validation. Subsurface communities were delineated by depth related to sediment moisture. Geochemical analysis indicated soluble salts and minerology that influenced water bio-availability, particularly in deeper sediments. Colonization was also patchy and uncolonized sediment was associated with indicators of extreme osmotic challenge. The study identifies linkage between biocomplexity, moisture and geochemistry in Mars-like sediments at the limit of habitability and demonstrates feasibility of the rover-mounted drill for future Mars sample recovery.
Highlights
The surface of Mars is dry, cold, and exposed to high levels of ionizing radiation
The hyper-arid core of the Atacama Desert in Chile is widely regarded as a tractable Mars analog in the field of astrobiology
Our chemical analysis focused on geochemical reservoirs readily available and relevant to biological communities and using methodology that was comparable with other microbial ecology studies
Summary
The surface of Mars is dry, cold, and exposed to high levels of ionizing radiation. data accumulated over the past few decades by orbital and landed missions have demonstrated that early in its history the planet may have been habitable for microbial life with abundant sources of energy, carbon, nutrients, and shelter (Cabrol, 2018). Surface sediment and subsurface horizons displayed patchy recovery with low yields of quantifiable DNA in the range 0.067–6.5 ng/g sediment, indicating extremely low standing biomass (Supplementary Tables S3, S5).
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