Cultivation of halophilic archaea in shallow subsurface Martian conditions has implications for extant life on Mars.

Haloferax volcanii actively grew for 160 days under Mars-relevant low pressure (24 mbar), high salinity, anoxia, and nitrate or perchlorate, with biofilm formation and persistent carotenoid biosignatures.

• Why it matters: Demonstrating metabolism, not just survival, under combined Martian surface-to-subsurface stressors is needed to assess whether localized shallow brines could be habitable.
• What they did: Anoxic, CO₂-enriched cultures were incubated for 160 days at 24 mbar in hypersaline media supplemented with nitrate or perchlorate, with growth tracked by optical density and nitrate/perchlorate reduction.
• The result: Growth occurred in all low-pressure treatments, Raman signals showed carotenoid biosignatures after prolonged incubation, and liquid loss stayed below 4%, supporting active metabolism in Mars-relevant brines.

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