"With the refrigerated microscope, we can catch any microbes trapped in liquid veins in their icy habitats," Price said. "This greatly reduces the possibility of contamination. If we just looked in melted ice, we wouldn't know where the bacteria had come from."

Price laid out his reasons for looking in frozen ice for unusual microbes in a paper in the February 1, 2000, issue of PNAS. He argued that ice-loving bacteria, or psychrophiles, could easily live in interconnecting veins of liquid water formed where three ice crystals intersect. Such microbes could survive for hundreds of thousands of years at a temperature just below freezing, metabolizing but probably not multiplying. They would have to endure darkness, 400 times the pressure at the surface, no oxygen, a starvation diet and probably a highly acidic or salty environment.

He estimated that colder ice as old as 400,000 years could still support one cell per cubic centimeter.

Drilling in Antarctic ice, including to within about 100 meters of Lake Vostok, has turned up some bacteria, according to Russian scientists, but all were known before. Bacteria also have been found in ocean ice. Price and other scientists hope to discover new species in solid ice, analogous to the novel thermophiles found in hot seafloor vents living at temperatures above the sea-level boiling point of water (100C or 212F).

All this makes it essential that drills not introduce bacteria into a new environment, whether a sub-glacial lake isolated for half a million years or the ice caps of Mars. No sterile drilling has ever been achieved, Price said, though some drilling under "aseptic" conditions has been claimed. Even the sterilization procedure taken before sending the Voyager spacecraft to M
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Contact: Robert Sanders
rls@pa.urel.berkeley.edu
510-643-6998
University of California - Berkeley
1-Jul-2002