Antarctic microbes and the search for aliens? How are they related?

Even in the harshest environments, microbes always seem to survive. They thrive everywhere, from hydrothermal vents on the boiling seafloor to the top of Mount Everest; Clusters of microbial cells have even been found attached to the hull of the International Space Station. There would be no reason for a study by a microbial ecologist Noah Fierer, where 204 soil samples were collected near the Shackleton Glacier in Antarctica, to be any different.

A typical soil sample could easily contain billions of microbes, and Antarctic soils in other regions harbor at least a few thousand per gram, so it was assumed, in the study, that all samples would have at least some life in them despite the air around Shackleton Glacier being so cold and arid.

But to the intrigue of the ecologist, some of the coldest and driest soils did not appear to be inhabited by microbes, and it is the first time that soils free of any type of microbial life have been found. This can only suggest that extremely cold and arid conditions impose a strict limit on microbial habitability, but it also leads scientists to ask questions about how they should interpret negative results, especially in the search for life on other planets. These results are notoriously difficult, because no measurement is perfectly sensitive giving the possibility that a well-executed experiment will miss something that is actually there.

If there were some undetected microbes in the soil, this does not subtract from the evidence that cold and arid conditions pose a serious challenge to life. The combination of multiple very challenging environmental conditions restricts life to more than one acting on its own.

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