One of the world's largest lakes is buried almost 2.5 miles under the icy surface of Antarctica and has been sealed from the air for 15 million years.
But scientists, who have spent years drilling down to Lake Vostok's subglacial surface, are hopeful the recent discovery of complex organisms may point to a richer ecosystem than previously thought.
The genetic material from ice near the lake's surface is commonly associated with known organisms such as mollusks, crustaceans and even fish. Still researchers cautioned the material may come from past contamination, or possibly carried into the lake from the ocean via Antarctica's network of subglacial rivers.
The study, published in the PLoS One journal, examined RNA genetic material found in the ice. An overwhelming majority -- 94 percent -- of the RNA matched to known sequences of bacteria, while six percent of the sequences matched with multi-cellular organisms.
Some of the bacteria even matches the kinds that thrive in hot water, like volcanic hydrothermal vents. If such vents existed in Lake Vostok, they could provide nutrients that might sustain more complex lifeforms.
Locked in the bitter cold, under extreme pressure and without any light, the lake would seem inhospitable to life. Moreover, the water may also contain toxically high levels of oxygen, leading some researchers to believe the lake could be sterile.
Still, the new findings leave scientists with hope.
"We found much more complexity than anyone thought," said Scott Rogers, a biologist at Bolwing Green State University involved in the project. "It really shows the tenacity of life, and how organisms can survive in places where a couple dozen years ago we thought nothing could survive."