Mars May Be Too Cold For Life

Microbes appear to be dormant in permafrost in a region of Antarctica, which could deal a blow for the search for life in similar regions on Mars.

A group of researchers found negative tests for microbial activity at temperatures below freezing in a region called University Valley, in Antarctica’s McMurdo Dry Valleys. However, in spots just a little above freezing (5 Celsius, or 41 Fahrenheit), the same team found five bacteria and one yeast.

“Detecting activity at this temperature indicates that at least some of the biomass in University Valley soils is viable, and these cells are likely currently dormant and surviving until more favorable conditions come along,” said Jackie Goordial, the principal investigator of the research.

She acknowledged, however, that if only a few cells were active in the permafrost, they could have eluded the detection limits of her instruments. “We also assayed for activity using the same tests we would normally use for other permafrost environments, and which are normally successful,” added Goordial, a postdoctoral fellow in environmental microbiology at McGill University in Montreal, Canada.

McMurdo has been likened to the Phoenix landing site on Mars, which is also at high elevation and at a pole (the north pole, in this case). That said, there have been microbes found in colder temperatures on Earth.

The “champ” is called Planococcus halocryophilus, Goordial said, and it is found in the Ellesmere Island permafrost at the Canadian high Arctic. It reproduces at temperatures down to -15 degrees Celsius (5 Fahrenheit) and can metabolize down to at least -25 Celsius (-13 Fahrenheit). So the new findings come as a bit of a surprise.

We are also hoping to go back to University Valley to obtain more and deeper samples from this site to see if the deeper and older permafrost become truly ‘dead’, which would be our working hypothesis,” said Goordial.

“Our results also indicate that University Valley permafrost soils will be excellent analogues to develop and test life/biosignature detection instruments to be sent if future missions to Mars as well as Europa and Enceladus because of the extremely low biomass present,” she added, referring to icy moons of Jupiter and Saturn (respectively).

McMurdo has been an active region for microbe-hunting. Much of the literature, Goordial said, focuses on lower and mid-elevation areas that have a lot more microbe biomass and diversity. Notable microbial regions include Lake Whillans and Blood Falls, she said.

Even the walls of University Valley have cryptoendoliths (microbes hidden within rocks) that are in regions heated by the sun with humidity traps. Inland and elevated areas tend to have more cold, arid and harsh conditions.

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