Lake Vostok (Russian: восток, "east") is the largest of more than 140 subglacial lakes found under the surface of Antarctica. It is located beneath Russia's Vostok Station, 4,000 meters (13,000 ft) under the surface of the central Antarctic ice sheet.
No other natural lake environment on Earth is as rich in oxygen and it is speculated that any organisms inhabiting the lake would have needed to evolve special adaptations to survive. These adaptations to an oxygen-rich environment, might include high concentrations of protective enzymes.
Due to the lake's similarity to the Jupiter moon Europa and Saturn's moon Enceladus, any confirmation of life living in Lake Vostok would strengthen the prospect for the possible presence of life on Europa or Enceladus.
Earth Institute Article
(after doing this post, I realized there was an original post here, however it's a year and a half old, and this is really nifty, so I think people newer to the community would get a kick out of seeing it)