An unmapped reservoir of briny liquid chemically similar to sea water, but hidden under an inland Antarctic glacier, appears to support microbial life in a cold, dark, oxygen-poor environment a most unexpected setting to be teeming with life.
The McMurdo Dry Valleys of Antarctica are devoid of animals and complex plants and scientists consider them to be one of the Earth's most extreme deserts. The Valleys receive, on average, only 10 cm (3.93 inches) of snow each year. Despite the lack of precipitation, during the Antarctic summer, temperatures rise just enough for glaciers protruding into the valleys to begin melting. The meltwater forms streams that enter lakes covered by ice that is two-to-three-stories thick.
Even less forgiving are the conditions found below the Taylor Glacier, an outlet glacier of the East Antarctic Ice Sheet in the otherwise ice-free Dry Valleys. The lack of light beneath the glacier makes the process of photosynthesis improbable, causing researchers to wonder how organisms found below the glacier could survive.
The research, which appears in the April 17 issue of Science, suggests that over the past 1.5 million years the microbes adapted to manipulate sulfur and iron compounds to survive. In place of photosynthesis, the microbes converted Fe(III) to Fe(II) to create food and energy.
The study was led by Jill Mikucki, a National Science Foundation-funded researcher at Dartmouth College. Mikucki and a team of researchers based their analysis on samples taken at the ominously, but aptly named Blood Falls, a water-fall-like feature at the edge of the glacier that flows irregularly, but often has a strikingly bright red appearance in stark contrast to the icy background.
The key piece of data supporting the hypothesis that the microbes were in fact surviving by turning Fe(III) to Fe(II) came from samples analyzed by Ariel Anbar, one of the authors of the study and an associate professor at
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Arizona State University