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Even in the harshest environments, microbes always seem to get by. They thrive everywhere from boiling-hot seafloor hydrothermal vents to high on Mt. Everest. Clumps of microbial cells have even been found clinging to the hull of the International Space Station (SN: 08/26/20). 

There was no reason for microbial ecologist Noah Fierer to expect that the 204 soil samples he and colleagues had collected near Antarctica’s Shackleton Glacier would be any different. A spoonful of typical soil could easily contain billions of microbes, and Antarctic soils from other regions host at least a few thousand per gram. So he assumed that all of his samples would host at least some life, even though the air around Shackleton Glacier is so cold and so arid that Fierer often left his damp laundry outside to freeze-dry.

Surprisingly, some of the coldest, driest soils didn’t seem to be inhabited by microbes at all, he and colleagues report in the June Journal of Geophysical Research: Biogeosciences. To Fierer’s knowledge, this is the first time that scientists have found soils that don’t seem to support any kind of microbial life.

The findings suggest that exceedingly cold and arid conditions might place a hard limit on microbial habitability. The results also raise questions about how negative scientific results should be interpreted, especially in the search for life on other planets. “The challenge comes back to this sort of philosophical [question], how do you prove a negative?” Fierer says.

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