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Traces of life discovered in 2000 in a lake of the Antarctic started again the debate on extraterrestrial life. Europa, a satellite of Jupiter, also conceals liquid water under an ice layer. The discovery took place in one of the most bizarre sites of our planet. An unvisited place, well hidden, which was a good candidate to shelter life forms still completely unknown. The place is lake Vostok, a huge stretch of water lying under the ices of East Antarctic, an ecosystem isolated from the atmosphere and light since at least a million years. For the astronomers, this small invisible sea is a sample of what is expected to be the conditions on Europe, one of Jupiter's small moons, where it is suspected with more and more reasons that an ocean of liquid water exists under a crust of ice.
In 1993, a radar of the European earth observation satellite ERS1 revealed the presence of a large stretch of water almost twice as large as Corsica buried under some 3750 meters of ice near the Vostok Russian station, where the lowest temperatures of the sphere were recorded (down to -89°C). With a surface of 14000 square kilometres and a volume of water estimated of 1800 cubic kilometers, it is obviously the largest and the deepest of the some 80 Antarctic lakes already listed under the icecap.
In 1998, a Russian, French and American collaboration carried out a sample taking campaign in Vostok, down at -3623 meters, stopping within 120 meters above the immense natural basin, in order not to contaminate the lake. This sample, the deepest ever taken out, allowed paleoclimatology laboratories to reconstitute the history of the climate during the last 400000 years. "But by studying this sample," tells Jean-Robert Petit, researcher at the Laboratory of Glaciology and Geophysics near Grenoble in France, "we realized that at about -3540 meters and down to -3750 meters, we had drilled a layer of particular ice, which obviously had melted then frozen again. We are now certain that this frozen water passed through the lake." Without violating the purity of the lake, the scientists had now hands on a witness of the Vostok mysteries. "This refrozen ice contains elements of the lake, salts and probably microbes," continued Jean-Robert Petit. These microbes, this extreme life hoped by all, were the object of analysis on behalf of two American teams directed by John Priscu of the University of Montana and David Karl of the University of Hawaii.
On December 10, 2000, two teams of American biologists announced in the scientific magazine Science that they have important clues proving that life thrives in the lake. The discovery immediately suggested that this had some relevance as for the search of extraterrestrial life.
Under the electronic microscopes and in incubation vats, the promise was held. Bacteria were listed per hundreds by the two teams. Bacteria which indicate that life literally thrives in lake Vostok. David Karl's team counted 200 to 300 microbes per gram, while John Priscu's team advanced the figure of 1000 to 10000 microbes per gram.
