A team of scientists that recently investigated the levels of dissolved gases in the remote Antarctic lake found the concentrations of gas in the lake water were much higher than expected, measuring 2.65 quarts (2.5 liters) of nitrogen and oxygen per 2.2 pounds (1 kilogram) of water. According to scientists, this high ratio of gases trapped under the ice will cause a gas-driven "fizz" when the water is released.

"Our research suggests that U.S. and Russian teams studying the lake should be careful when drilling because high gas concentrations could make the water unstable and potentially dangerous," said Dr. Chris McKay of NASA's Ames Research Center in California's Silicon Valley. McKay is lead author of a paper on the topic published in the July issue of the 'Geophysical Research Letters' journal.

"We need to consider the implications of the supercharged water very carefully before we enter this lake," said Dr. Peter Doran, a co-author and associate professor of Earth and Environmental Sciences at the University of Illinois at Chicago.

Lake Vostok is a rich research site for astrobiologists, because it is thought to contain microorganisms living under its thick ice cover, an environment that may be analogous to Jupiter's moon, Europa. Europa contains vast oceans trapped under a thick layer of ice. Russian teams are planning to drill into Lake Vostok's 2.48 mile (four kilometer) ice cover in the near future, and an international plan calls for sample return in less than a decade.

An important implication of this finding is that scientists expect oxygen levels in the lake water to be 50 times higher than the oxygen levels in ordinary freshwater lakes on Earth. "Lake Vostok is an extreme environment, one that is supersaturated with oxygen," noted McKay. "No other natural lake environment on Earth has this much oxygen."

The research also suggests that organisms living in Lake Vostok may have had to evolve special adaptions, such as high concentrations of protective enzymes, in order to survive the lake's oxygen-rich environment, the researchers say. Such defense mechanisms may also protect life in Lake Vostok from oxygen radicals, the dangerous byproducts of oxygen breakdown that cause cell and DNA damage. This process may be similar to that of organisms that scientists theorize may once have lived on Europa, whose ice layer and atmosphere are thought to contain radiation-produced radicals and oxygen.

"We expect to find that the organisms in Lake Vostok are capable of overcoming very high oxygen stress," said co-author Dr. John Priscu, a geo-biologist at Montana State University in Bozeman. Priscu heads an international group of researchers that will deploy a remote observatory at Lake Vostok within three years and return samples within 10 years.

The team also determined the ratios of gases in the lake. The scientists discovered that the air-gas mixture there, besides dissolving in the water, also is trapped in a type of structure called a 'clathrate'. In clathrate structures, gases are enclosed in an icy cage and look like packed snow. These structures form at the high pressure depths of Lake Vostok and would be unstable if brought to the surface.

Lake Vostok is located 2.48 miles (four kilometers) beneath the East Antarctic Ice Sheet. The lake, and more than 70 other lakes deep beneath the polar plateau, are part of a large, sub-glacial environment that has been isolated from the atmosphere since Antarctica became covered with ice more than 15 million years ago. Scientists theorize that Lake Vostok probably existed before Antarctica became ice covered, and may contain evidence of conditions on the continent when the local climate was subtropical.

For images and further information about plans to return research samples from Lake Vostok, go to:

http://salegos-scar.montana.edu/

The paper's authors also include K.P. Hand, Stanford University and Dr. D.T. Andersen, the SETI Institute.

The research was jointly funded by NASA and the National Science Foundation.