After more than a decade of stop-and-go drilling, Russia pierced through Antarctica's frozen crust last year and took back samples of water from a vast lake that has lain untouched for at least 14 million year.
Scientists say the icy darkness of Lake Vostok, under some 12,139 feet of ice, may provide a glimpse of the planet before the Ice Age and clues to life on other planets.
"After excluding all known contaminants, bacterial DNA was found that does not match any known species in world databases," Sergei Bulat of the St Petersburg Nuclear Physics Institute told RIA.
"If it (the bacteria) had been found on Mars, then without a doubt we would have said there is life on Mars - but this is DNA from Earth," he said. "We are calling this life form unidentified or unclassified."