BioEd Online

Plans to drill into Lake Vostok, an underground Antarctic lake thought to have been isolated for 20 million years, could be revised after researchers revealed that it may contain two distinct ecosystems.

The first detailed map of Vostok's bed shows that the 240 km-long lake comprises two deep basins divided by a ridge¹. If the ridge stops water flow between the basins, each could host different organisms, as research on Lake Bonney, another Antarctic lake with two basins, has shown.

The news, released last month, has now made researchers rethink their plans to enter the lake. Many believe that Lake Vostok's waters harbour unique life.

"We need to sample both basins," says microbiologist John Priscu of Montana State University in Bozeman, part of an international team working on plans to drill into Vostok. Priscu want to make two holes or survey the lake with an autonomous submarine, an idea that tallies with suggestions made by other experts. He plans to discuss the ideas when the team meets later this month.

Michael Studinger, an Earth scientist at Lamont-Doherty Earth Observatory in New York, and his colleagues made the map by measuring the gravity above Vostok. The Earth's pull is weaker over deep water, because water has less than half the density of rock. By criss-crossing the lake in a plane - flying a total of 21,000 km - the team pieced together a map of the lakebed.

The work revealed Vostok's dimensions. Studinger estimates that the lake holds about 5,400 cubic kilometres of water - equivalent to 5% of the world's freshwater surface lakes. Lake Vostok has a similar area to Lake Superior, the largest of North America's Great Lakes, but is far deeper, in parts more than a kilometre deep.

Extreme environment

Collecting the readings was not easy. Studinger spent four weeks camped above the lake with the map-making team, at times in an unheated tent. "Only your nose can stick out of your sleeping bag," he recalls.

The temperatures, typically -30 to -40 ºC, are not the only thing that makes living at Vostok tough. The base is at 3,500 metres above sea level; oxygen levels are reduced even at lower altitudes in Antarctica. One research student developed altitude sickness, and was airlifted out by a Hercules plane equipped with skis, despatched from the nearby US McMurdo research base.