Russian scientists have confirmed that they have penetrated Antarctica's Lake Vostok, an event that may "expand the limits of life on Earth," a U.S. scientist says.

At 8:25 p.m. Moscow time on Sunday, drillers hit lake water at a depth of 12,355 feet (3,766 meters)—making them the first ever to probe a subglacial lake, according to a statement provided by Russia's Arctic and Antarctic Research Institute.

Mahlon C. Kennicutt II, a professor of oceanography at Texas A&M University, said that the confirmation appears to be accurate.

That's because the Russian scientists recorded an increase in pressure at the bottom of the borehole—an "obvious clue" that they broke through the ice.

"There's no other reason you would run into a pressure kick like that unless you'd broken into a seal, which would be the surface of the lake," said Kennicutt, who is also the president of the nonprofit Scientific Committee on Antarctic Research.

This "should be celebrated," Kennicutt emphasized. "Fifteen years ago we couldn't imagine the day there would be penetration of one of these lakes."

Indeed, "penetrating Lake Vostok culminates more than a decade of planning," Montana State ecologist John Priscu told National Geographic News by email.

"The success of my Russian colleagues proves, from an engineering standpoint, that we can sample an environment beneath 4,000 meters [13,000 feet] of ice. It also opens the doors for ensuing subglacial science"—including how life might have evolved in such an extreme environment.

Lake Entry May Reveal Microbial Life?

Lake Vostok is the largest of more than 145 subglacial lakes—most of them several kilometers long—that have been discovered under Antarctica in past decades.

The project to probe the Great Lake-size water body, which has been entombed in ice for 25 million years, has been the centerpiece of the Russian Antarctic program. (See 3-D pictures of Antarctica's subglacial "ghost mountains.")

Subglacial lakes may open a new window onto our planet, for example, by offering new insights into climate history or revealing previously unknown life-forms.

Priscu, for instance, has found evidence that microbes could live in the subglacial lake, deriving energy from minerals by "eating rocks," he told National Geographic News in 2007.

"I hope that they can confirm unequivocally that there is indeed microbial life in the lake," Priscu said today.

"This has been the center of much debate in the past that can only be resolved with actual sample return. If they can confirm there is life in the lake, it will transform our view of Antarctica."

Clean Technology Paid Off

The hole above the drill site has had been kept open for 30 years with kerosene and antifreeze. But as drillers neared the ancient lake, the team started taking careful steps to ensure the project won't contaminate the lake water.

For example, the team used a hot-water drill during the last few meters to prevent any foreign material from entering the lake environment, Texas A&M's Kennicutt said.

Such clean technology seems to have paid off, he said. According to the Russian statement, water from the lake rose up into the borehole upon impact, so the likelihood that anything went down into the lake is low.

The scientists, however, can conduct research at the lake only during Southern Hemisphere summer, from November to February, so they plan to keep the hole open until they can return during the next research season.

At that time, the Russian scientists will be able to start sampling the lake water that's come up and frozen inside the borehole.

However, Kennicutt said, there's a lingering concern with that approach: Bringing up the ice samples could contaminate them, since the Russian team isn't using clean technology in the upper part of the borehole.

"Good Times to Be a Polar Scientist"

In general, Kennicutt cautioned that the Russian entry into Lake Vostok is only a first step-it may take decades more before scientists can get a full picture of what's happening under the Antarctic ice.

Meanwhile, other research teams are preparing to make their own forays into the subglacial world.

For instance, "the U.S. and U.K. have subglacial projects and plan to penetrate two lakes that lie beneath the West Antarctic Ice Sheet next year," Montana State's Priscu said.

Martin Siegert, head of the U.K.'s Subglacial Lake Ellsworth Program, said in a statement, "We are very much looking forward to working with Russian scientists next year when they retrieve 'lake samples' from the frozen lake water within the borehole."

"In particular, we will want to compare direct measurements and samples from Lake Ellsworth with the Lake Vostok material, to understand biodiversity and environmental conditions beneath the ice sheets in Antarctica," he said.