Scientists Grew Microbes In Mars-Like Conditions – And They Didn’t Just Survive…

Salt-loving microbes kept for months in a lab version of the Martian underground did more than hang on. They grew, according to a study from University of Florida researchers published in the journal Applied and Environmental Microbiology, in what lead author Adam Robinson says adds to “the growing body of evidence suggesting that we should consider the possibility of life on Mars today.”

The microbe is Haloferax volcanii, a salt-loving archaeon found in places like the Dead Sea and Utah’s Great Salt Lake, and a standard stand-in for life that could survive on other planets. According to the Daily Mail, Robinson’s team held it for 180 days in a solution seven times saltier than seawater, with almost no oxygen, a carbon dioxide atmosphere at a small fraction of Earth’s pressure, and either nitrates or perchlorates, chemicals found on Mars that can stand in for oxygen. Cultures given either chemical fed and reproduced; cultures given neither showed no noticeable growth.

Each hazard has been tested alone before, and some studies have shown microbes can cling on for months under several at once. Robinson said “far fewer have been able to combine these conditions together and show that microorganisms can actively grow.” A preprint on what appears to be the same experiment, posted on bioRxiv and summarized by Astrobiology.com, describes 160 days at no more than 24 millibars, a 99.9% CO2 atmosphere and 21 degrees Celsius. It reports growth in every low-pressure treatment, shown by rising optical density and by the microbes breaking down nitrate and perchlorate, and calls it the first demonstration of a halophilic archaeon growing under that combination.

The microbes also appear to have protected their water. They formed biofilms, clumps encased in a slimy protective layer, and lost very little water over the months-long run; the preprint puts water loss below 4%. Growth was far slower than in Earth-like conditions, but the colonies kept growing.

Robinson was careful about what it does not show.

 “I would not say this study suggests there is definitely life on Mars today,” he said.

“However, this work adds to a growing body of evidence suggesting that the shallow subsurface of Mars may still retain environmental conditions conducive to active metabolism and extant life.” 

The lab also did not perfectly recreate every danger Martian life would face, and surviving on Mars is hard because cold, salt, radiation and thin air all hit at once.

Robinson told the Daily Mail that if Mars once hosted life, some organisms may have evolved to tolerate increasingly hostile conditions as the planet changed.

 “If life from Earth can grow under hostile conditions it has never naturally encountered, what might potential life on Mars look like after billions of years of evolution under those conditions?” he asked.