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by Aaron L. Gronstalfor Astrobiology Magazine
Moffett Field CA (SPX) Mar 15, 2013
Last week, reports began to emerge that Russian scientists had discovered a previously unknown species of bacteria in samples of lake water from one of Antarctica's most famous subglacial lakes. Word quickly spread throughout the blogosphere, sparking questions about what the mysterious bacteria could be. However, it is important to note that no peer-reviewed study concerning this research has been published as of yet.
Lake Vostok is the largest suglacial lake yet discovered in Antarctica. In the late 1950s, geographer Andrey Kapista became the first to suggest that a lake might exist below the ice. His theory was based on seismic data collected by the Soviet Antarctic Expeditions. Conveniently for Russian scientists, this lake was located underneath Russia's newly established Vostok station.
Lake Vostok has an average depth of 344 meters and an estimated volume of 5,400 km3. It's a big lake, but that's not what makes it so special. Lake Vostok's fresh water lies underneath 4000 meters of ice, and 500 meters below sea level). Many scientists think that Vostok's cold, dark water has been trapped under the ice for a very long time (some estimates are in the range of 15 million years).
The environment in the lake itself is nothing short of extreme. Sunlight cannot penetrate the thick ice sheet. Pressures are as high as 354.6 bar (compared to the roughly 1 bar of pressure we feel at the surface). The water is thought to be rich in oxygen (which at really high concentrations, can actually be dangerous for living organisms). Anything living in Lake Vostok would've had to evolve some interesting survival strategies in order to eek out a living in this unique subglacial world.
Breaking Through to the Other Side
It was a struggle, but in 1998, Russian, French and American scientists drilled to within 100 meters of the lake's surface. They stopped in order to prevent contaminating the lake with drilling fluid. This is because the drill-hole was filled with Freon and kerosene to prevent the hole from collapsing or freezing shut.
At the bottom of the 1998 core, scientists identified bacteria frozen in the ice. Their theory was that this ice at the bottom of the core came from frozen lake water - and that the bacteria were evidence of a microbial ecosystem in Lake Vostok.
In 2011, the Russians drilled to within 50 m of the lake, then switched to a cleaner drilling method that used a thermal drill head and silicon oil fluid. They stopped just short of the lake's surface, not actually breaking into the water.
When the drill was removed from the borehole, the lower pressure of the hole allowed water to flood upward. This lakewater then froze, capping the hole and providing freshly-frozen lake water that could be sampled. In 2012, the team returned and then drilled back down to the surface of the lake to collect samples.
In a report by the Russian news agency RIA Novosti, Sergey Bulat of the Laboratory of Eukaryote Genetics at the St. Petersburg Nuclear Physics Institute seemed to claim that the bacterium was not the result of contamination because its DNA did not match any of the species identified as contaminants in the drilling fluid.
In the RIA Novosti report, Bulat was quoted as saying, "After excluding all known contaminants...we discovered bacterial DNA that does not match any known species listed in global databanks. We call it unidentified and 'unclassified' life."
However, the head of the St. Petersburg Nuclear Physics Institute, Vladimir Korolev, quickly cautioned that contamination from the kerosene could not be ruled out (see this report from the Russian Times:) Then, on Saturday March 9, Korolev confirmed to Russia's Interfax News Agency that further examination proved the bacteria to be nothing more than contaminants.
It's a disappointing result, but the story of life's potential in Lake Vostok is not over. The most important thing to note is that none of this work has appeared in publication yet, so the stories surrounding any life in Lake Vostok are pure speculation. Only future work in the laboratory will determine whether or not the Vostok samples hold anything of scientific interest worth publishing.
This year, the Russian team continued to collect fresh samples (retrieving some as recently as March 1st). The new samples will soon make their way across the ocean on a ship bound for St. Petersburg. When the fresh water samples arrive in May of this year, maybe they will help clear up the story of life's potential in the waters of Lake Vostok.
Plying Icy Waters on Earth and Beyond
They have already indicated that microbes were present in the water, although they have yet to perform the analysis necessary to identify their species.
The Brits are also hoping to grab sediments from the bottom of Lake Ellsworth, but are currently working to improve their hot-water-drilling method.
Life that survives in extreme environments can help astrobiologists understand life's potential on other worlds in the Universe where the conditions aren't as generally cozy as Earth. Any life found in Lake Vostok, and similar subglacial lakes in Antractica, could provide invaluable information about the strategies microorganisms might use to inhabit sub-surface oceans on icy worlds like Jupiter's moon Europa, or Saturn's moon Enceladus.
"These two moons are covered in ice, yet beneath their icy shells we have strong evidence that vast, global liquid water oceans exist," says Kevin Hand, Deputy Chief Scientist for Solar System Exploration at NASA's Jet Propulsion Laborator (JPL), "The subglacial lakes of Antarctica provide us with an interesting window into the extremes of life here on Earth and help inform our understanding of how life elsewhere could adapt to comparable environmental conditions."
JPL and NASA have recently completed a study of mission options for investigating Europa's ocean. The results of those reports can be found on the Outer Planets Assesment Group website here.
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