MOSCOW - Opening a scientific frontier miles under the Antarctic ice, Russian experts drilled down and finally reached the surface of a gigantic freshwater lake, an achievement the mission chief likened to placing a man on the moon.
Lake Vostok could hold living organisms that have been locked in icy darkness for some 20 million years, as well as clues to the search for life elsewhere in the solar system.
Touching the surface of the lake, the largest of nearly 400 subglacial lakes in Antarctica, came after more than two decades of drilling, and was a major achievement avidly anticipated by scientists around the world.
"In the simplest sense, it can transform the way we think about life," NASA's chief scientist Waleed Abdalati told The Associated Press in an email Wednesday.
The Russian team made contact with the lake water Sunday at a depth of 12,366 feet (3,769 meters), about 800 miles (1,300 kilometers) east of the South Pole in the central part of the continent.
Scientists hope the lake might allow a glimpse into microbial life forms that existed before the Ice Age and are not visible to the naked eye. 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 believed to be found under the ice crust on Mars, Jupiter's moon Europa and Saturn's moon Enceladus.
Valery Lukin, the head of Russia's Arctic and Antarctic Research Institute, said reaching the lake was akin to the Americans winning the space race in 1969.
"I think it's fair to compare this project to flying to the moon," said Lukin, who oversaw the mission and announced its success.
American and British teams are drilling to reach their own subglacial Antarctic lakes, but Columbia University glaciologist Robin Bell said those are smaller and younger than Vostok, which is the big scientific prize.
"It's like exploring another planet, except this one is ours," she said.
At 160 miles (250 kilometers) long and 30 miles (50 kilometers) wide, Lake Vostok is similar in size to Lake Ontario. It is kept from freezing into a solid block by the more than two-mile-thick crust of ice across it that acts like a blanket, keeping in heat generated by geothermal energy underneath.
Lukin said he expects the lake to contain chemotroph bacteria that feed on chemical reactions in pitch darkness, probably similar to those existing deep on the ocean floor but dating back millions of years. "They followed different laws of evolution that are yet unknown to us," he said.
Studying Lake Vostok will also yield insights about the origins of Antarctica, which is believed by many to have been part of a broader continent in the distant past.
And the project has allowed the testing of technologies that could be used in exploring other icy worlds. "Conditions in subglacial lakes in Antarctica are the closest we can get to those where scientists expect to find extraterrestrial life," Lukin said.
Drilling through the ice crust in the world's coldest environment brought major technological challenges.
Temperatures on the Vostok Station on the surface above the lake have registered the coldest ever recorded on Earth, reaching minus 128 degrees Fahrenheit (minus 89 degrees Celsius). Conditions were made even tougher by its high elevation, more than 11,000 feet (3,300 meters) above sea level.
The effort has drawn fears that the more than 60 tons of lubricants and antifreeze used in the drilling may contaminate the lake's pristine waters. Bell said the Russian team was doing its best "to do it right" and avoid contamination, but others were nervous.
"Lake Vostok is the crown jewel of lakes there," said University of Colorado geological sciences professor James White. "These are the last frontiers on the planet we are exploring. We really ought to be very careful."
Lukin said Russia had waited several years for international approval of its drilling technology before proceeding. He said that, as anticipated, lake water under pressure rushed up the bore hole, pushing the drilling fluid up and away, then froze, forming a protective plug that will prevent contamination of the lake.
Russian scientists will remove the frozen sample for analysis in December when the next Antarctic summer season comes. They reached the lake just before they had to leave at the end of the Antarctic summer, when plunging temperatures halt all travel to the region.
Lukin, who made numerous trips to Antarctica, said the physiological challenges of extreme cold and thin oxygen were aggravated by isolation.
"If something happens to you or your colleague, there is no one to help," he said. "It's actually easier to help an astronaut in space."
Martin Siegert, a leading scientist with the British Antarctic Survey, hailed reaching Lake Vostok as "an important milestone ... and a major achievement for the Russians."
The British are trying to reach another subglacial lake, Lake Ellsworth.
"The Russian team share our mission to understand subglacial lake environments and we look forward to developing collaborations with their scientists and also those from the U.S. and other nations, as we all embark on a quest to comprehend these pristine, extreme environments," Siegert said in an email.
Americans scientists are drilling at Lake Whillans, west of the South Pole.
Some voiced hope that studies of Lake Vostok and other subglacial lakes will advance knowledge of Earth's own climate and help predict its changes.
"The clues to how Earth may respond to the continuing impact of humans, particularly fossil fuel emissions and related climate change, are housed in the records of past climate change in Antarctica," said Mahlon Kennicutt II, Texas A&M University professor of oceanography, who leads several Antarctic science groups.
"A view of the past gives us a window on our planet's future," he said.
Russian researchers plan to continue exploring with robotic equipment that will 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 at the end of the 19th century by Russian scientist and anarchist Prince Pyotr Kropotkin. Russian geographer Andrei Kapitsa noted 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.
Drilling in the area began in 1989 and dragged on slowly due to funding shortages, equipment breakdowns, environmental concerns and severe cold.
The lake's crystal-clear water may make entrepreneurs sweat just thinking of its commercial potential, but Lukin shot that idea down.
He said his team had no intention of selling any Vostok water samples, but would eventually share the results of their work with scientists from other nations.
AP Science Writer Seth Borenstein reported from Washington.