Motion of ice across Lake Vostok revealed. (Earth Science).

Lake Vostok, a vast freshwater lake locked in perpetual darkness beneath 4 kilometers of glacial ice in Antarctica, nevertheless harbors life. New measurements of the movement of the lake's overlying ice sheet could help scientists determine where to drill to get the freshest samples of that life without contaminating the lake.

Scientists have drilled to within 120 meters of the lake's surface and found microbes in ice samples (SN: 10/9/99, p. 230). Those organisms lived in the lake but were trapped in ice as lake water froze onto the ice sheet passing overhead, the researchers propose.

Earthquakes in the region suggest there may be hydrothermal vents on the lake bottom that could host more-complex forms of life (SN: 3/3/01, p. 139). No one has drilled all the way down to the lake itself for fear of introducing organisms from Earth's surface into an ecosystem that's been isolated for many millennia.

That's where the new measurement of ice flow can help. Recent Global Positioning System readings indicate that the ice sheet is moving southeastward across and beyond the broad lake at about 3 m per year, says Michael Studinger, a geophysicist at the Lamont-Doherty Earth Observatory in Palisades, N.Y. At that rate, the overlying ice would traverse the lake in 16,000 to 20,000 years. He and his colleagues report their findings in the March 21 Nature.

The team's results suggest that future drilling through the ice sheet southeast of the lake could extend all the way to the bedrock without worry of contaminating the lake's ecosystem. --S.P.