Posted on February 04 2015
Original Image: Christopher Michel
When we think of coldness on Earth, it doesn’t get much more frigid than Antarctica. In some places there the thickness of the ice is measured in miles. Amazingly, though, at a depth of over two miles, liquid Lake Vostok has sat unseen for perhaps 35 million years. The discovery of liquid lakes under the ice has been made possible by the use of radio echo-sounding technology deployed from aerial surveys. The differing densities of ice and water reflect radio waves at different speeds and produce a picture showing the lakes. Lake Vostok is the biggest of these sub-glacial lakes; at almost 150 miles long, 30 miles wide and a mean depth of over 1,000 feet, it is the 15th largest by area and the seventh largest by volume, in the world. Researchers have also located hundreds of other sub-glacial lakes and there’s no reason to think there aren’t more as yet undiscovered. Water melts and forms these lakes as glaciers ride over the rough terrain in certain areas of bedrock, creating enormous friction. The resulting heat melts some of the ice. There is also speculation that geologic vents may conduct heat from Earth’s interior to the bedrock surface.
As old as these lake basins are, the water in them is not of the same age. The water may change out annually or even more frequently in some lakes. It can flow to other lakes along the bedrock surface or through conduits in the ice itself. Some of it freezes to the ice “roof” over the lake and is carried away by glacial movement. Most of the water remains liquid despite its temperature below freezing because it is under tremendous pressure from the overlying ice. Lake Vostok’s rate of water changeover is estimated to take 13,000 years, but the water circulating into and out of the lake is 400,000 years old. So while the water circulates to some degree, these systems are sealed off from the surface, and scientists feel they may contain very ancient life forms. Russian researchers have been drilling through the ice above Lake Vostok for years, creating concerns that once they reached the water, biological contamination of the long-isolated waters could result. There is also the danger of contamination by the harsh chemical fluids used to keep the drill bit and pipe from freezing and seizing up. They finally reached lake water, or at least the less dense ice just above it, in 2013, but found no new microbes. If such new life forms are someday discovered, they will lend weight to the argument that similar organisms could exist in the harsh polar environments found on Mars, or on Europa, one of the moons of Jupiter.