After more than 20 years of drilling, Russian scientists have finally opened a vertical channel to Lake Vostok, an ancient freshwater lake sealed for at least 15 million years under more than two miles of polar ice. Here's what you should know about one of Earth's best-preserved time capsules:

Hold on. They drilled for two decades?
You read that right. Drilling began in 1989 — before scientists could even confirm the 160-mile-long lake's existence — and "dragged on slowly due to funding shortages, equipment breakdowns, environmental concerns, and severe cold," says Vladimir Isachenkov for the Associated Press. So it was only a few days ago, says Andrea Mustain at Scientific American, that the "team's ice-coring drill broke through the slushy layer of ice at the bottom of the massive ice sheet and reached fresh, liquid lake water."

Is the lake dramatically cold?
Surprisingly not. Surface temperatures at the Vostok station, where researchers work, are among "the coldest ever recorded on Earth," reaching negative 128 degrees Fahrenheit, says Isachenkov. But the underwater lake itself is believed to be warm, thanks to the "giant pressure of the ice crust and geothermal energy underneath." 

What makes this lake so valuable?
It's all about the prospect of finding untouched life. If anything is alive in the lake, it's been sealed off from the rest of the world for millions of years. "It's like exploring another planet, except this one is ours," Columbia University's Robin Bell tells the AP. Indeed, the drilling could be a valuable precursor to potential mining operations on other planets, and has been a "gold mine for learning about possible conditions on Jupiter's moon Europa or Saturn's moon Enceladus," which are also covered in thick layers of ice, says Marc Kaufman at The Washington Post.

So there's a consensus that this was a worthwhile project?
Not necessarily. "The long effort has met with controversy over some of the chemicals and techniques used in the drilling," says Kaufman. Some scientists are concerned that a "pristine" Lake Vostok could be contaminated with some of the chemicals used in the drilling, including kerosene and Freon. 

What now?
Scientists are heading back to Russia, and won't return to Antarctica until the "harsh winter" ends,  says Amber Acker at But they'll have plenty of work to keep them busy back home: "Jubilant Russian scientists are carrying home 40 liters of relic water," says "Lake Vostok's treasury is ready to reveal its millions-year-old secrets."

Sources: ABC News, Al.comAssociated Press, RT.comScientific AmericanWashington Post