Magazine article Science News

Life Found beneath Antarctic Ice Sheet

Magazine article Science News

Life Found beneath Antarctic Ice Sheet

Article excerpt

Pushing the known envelope of life to a new extreme, scientists have found evidence that viable microorganisms populate a gigantic freshwater lake hidden for hundreds of thousands of years beneath the Antarctic ice sheet.

Called Lake Vostok, the near-freezing body of water is locked in perpetual darkness beneath 4,000 meters of ice (SN: 10/2/99, p. 216). No one has yet collected samples of the trapped water, but an international drilling team has bored down to within 120 m of the lake and pulled up samples of the deep ice. According to glaciologists, ice from this level represents lake water that froze to the bottom of the glacial sheet.

"When you take this ice and melt it down, you do find some viable cells," says David M. Karl of the University of Hawaii at Manoa in Honolulu, who reported his results last week at a meeting in Cambridge, England. Originally living in the lake, these organisms became trapped in the lowermost ice as it froze, he says.

Another group, led by John Priscu of Montana State University in Bozeman, also reported observing microbes in the frozen lake water. Priscu's team, however, didn't find evidence that the cells were alive.

Karl and his colleagues used nutrients labeled with radioactive carbon to test for living microbes in the melted ice. By tracking the carbon, they demonstrated that glucose and acetate were broken down to form carbon dioxide. Living cells carry out these same reactions in a process called respiration.

"I think that was a really clever way to look at metabolism. He showed they're viable," says Priscu.

Karl notes that a similar experiment gave a positive result when it flew on the Viking spacecraft in the 1970s. In that case, researchers concluded that no organisms were involved but extreme ultraviolet radiation hitting Mars had broken down the radioactively labeled molecules into carbon dioxide. …

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