Pearce has studied samples from Lake Hodgson, which lies beneath just a few metres of ice in west Antarctica. He says 25 per cent of the genetic sequences he has found do not match anything found in DNA databases. So on its own, having an unusual DNA sequence does not prove that the Vostok bacterium belongs to a new group. There's a long list of systematic tests that will need to be carried out in order to prove that.
The results must also be independently replicated, says Martin Siegert of the University of Bristol, UK, who led an unsuccessful attempt to drill into another Antarctic lake - Ellsworth - last year.
If the bacterium does belong to a new group, it will quickly come under scrutiny. "The next question is, where does it come from?" says Siegert.