The team of Russian scientists trying to uncover the prehistoric Lake Vostok miles beneath a surface of Antarctic ice are not lost, according to American Antarctic explorer John Priscu.

"I can assure you that they are not lost or out of contact," he wrote in an email. "I never said the Russians were lost."

Fox News reported that the team hadn't been heard from for more than five days.

"What I can tell you is that they are doing something that has never been done before—think of it, sampling a lake under 2.5 miles of ice at a location that is the highest, driest and coldest desert on our planet," he adds.

What the Russian team is trying to do is unprecedented—the waters of Lake Vostok have been left untouched beneath more than two miles of ice for more than 15 million years. Lake Vostok has been called the "most alien lake on earth," and scientists believe microscopic "extremophiles" that can survive in very low temperature and light situations might live in the water.

The drilling expedition started more than a decade ago, in 1998, and the team was expected to hit water any day as the unforgiving Antarctic winter approaches. Vostok Station, the Russians' headquarters, has recorded the lowest temperature ever seen on earth: -129 degrees. In recent days, temperatures have dipped below -40 degrees Fahrenheit.