Russian scientists have reached the surface of a gigantic freshwater lake hidden under kilometres of ice for some 20 million years.
After more than two decades of drilling in Antarctica, reaching Lake Vostok is a major discovery.
Scientists around the world believe it may allow a glimpse into microbial life forms, not visible to the naked eye, that existed before the Ice Age.
It may also provide precious material that would help look for life on the ice-crusted moons of Jupiter and Saturn or under Mars' polar ice caps where conditions could be similar.
"It's like exploring another planet, except this one is ours," Columbia University glaciologist Robin Bell told The Associated Press.
According to a statement Valery Lukin, the head of Russia's Arctic and Antarctic Research Institute, which is in charge of the mission, said his team reached the lake's surface on Sunday.
He had previously compared the Vostok mission to the space race to the moon, and had promised that Russia would not lose to the US this time around.
"There is no other place on Earth that has been in isolation for more than 20 million years," said Lev Savatyugin, a researcher with the AARI. "It's a meeting with the unknown."
While temperatures on the Vostok Station on the surface have registered the coldest ever recorded on Earth, reaching -89C, the water in the lake is warmed by the giant pressure of the ice crust and geothermal energy underneath.
The Russian team reached the lake just before they had to leave at the end of the Antarctic summer season.
Although far from being the world's deepest lake, the severe weather of Antarctica and the location's remoteness made the project extremely challenging.
Lake Vostok is 250 km long and 50 km across at its widest point, similar in area to Lake Ontario. It lies about 3.8 km beneath the surface and is the largest in a web of nearly 400 known subglacial lakes in Antarctica.
However the project has drawn strong fears that 66 tonnes of lubricants and antifreeze used in the drilling may contaminate the pristine lake.
The Russian researchers have insisted the bore would only slightly touch the lake's surface and that a surge in pressure will send the water rushing up the shaft where it will freeze, immediately sealing out the toxic chemicals.
Scientists will only remove the frozen sample for analysis in December when the next Antarctic summer comes.
Scientists believe that microbial life may exist in the dark depths of the lake despite its high pressure and constant cold -- conditions similar to those expected to be found under the ice crust on Mars, Jupiter's moon Europa and Saturn's move Enceladus.
“In the simplest sense, it can transform the way we think about life," NASA's chief scientist Waleed Abdalati told Associated Press.
Scientists in other nations hope to follow up this discovery with similar projects.
American and British teams are drilling to reach their own subglacial Antarctic lakes, but those lakes are smaller and younger than Vostok, which is the big scientific prize.
Some scientists hope that studies of Lake Vostok and other subglacial lakes will advance knowledge of Earth's own climate and help predict its changes.
In the future, Russian researchers plan to explore the lake using an underwater robot equipped with video cameras that would collect water samples and sediments from the bottom of the lake, a project still awaiting the approval of the Antarctic Treaty organization.
The prospect of lakes hidden under Antarctic ice was first put forward by Russian scientist and revolutionary, Prince Pyotr Kropotkin at the end of the 19th century.
Russian geographer Andrei Kapitsa pointed at the likely location of the lake and named it following Soviet Antarctic missions in the 1950s and 1960s, but it wasn't until 1994 that its existence was proven by Russian and British scientists.
The drilling in the area began in 1989 and dragged on slowly due to funding shortages, equipment breakdowns, environmental concerns and severe cold.
