Salt-Loving Microbe Grows in Simulated Mars Conditions
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- Adam Robinson at the University of Florida led a study demonstrating that Haloferax volcanii, an archaeon from the Dead Sea, actively grew in anoxic, low-pressure conditions with perchlorate-laden high-salt media — the first demonstration of growth (not just survival) for salt-loving extremophiles under Mars-like conditions.
- The experiment held the microbes at 21°C, 24 millibar pressure, and 225 grams of salt per litre for 160 days, with growth confirmed by cloudy medium, biological reduction of nitrate and perchlorate, and extensive biofilm visible under scanning electron microscopy.
- Scott Perl of the Los Angeles Natural History Museum said it is surprising any Earth microbe can grow under such low pressure, since nowhere on Earth's surface matches it — but if life evolved on Mars billions of years ago when conditions were more favourable, it would have had time to adapt.
- Sean McMahon at the University of Edinburgh pushed back on the Mars realism, noting that surface pressure is only 6–12 millibar — where liquid water cannot exist — and that at 24 millibar below the surface, temperatures are well below freezing.
- Robinson acknowledged the study's limits: the pressure–temperature combination likely exceeds real Mars conditions, and the yeast extract used as a carbon source would not be found on Mars today, calling the work "a starting point for future experiments."
- The team plans follow-up experiments with cold-loving halophiles at 0–4°C and 7–12 millibar, replacing yeast extract with acetate, and testing salt-loving methanogens that could feed on Mars's atmospheric CO2, which has been linked to detected methane on the planet.
Why it matters: Past Mars missions have avoided potentially habitable zones to prevent Earth-microbe contamination — meaning the most promising areas have never been probed directly. This study reframes the search by showing terrestrial halophiles can actively grow in brine-perchlorate conditions far closer to Mars physics than prior work assumed, putting pressure on the next mission planners to decide whether to risk contamination or keep looking in less promising terrain.
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