DRILLING into Lake Vostok, the giant lake trapped under thousands of metres of Antarctic ice, could trigger a violent explosion of water, according to scientists who have calculated that the levels of gases dissolved in the lake are as high as in a can of soda.
Lying 4 kilometres beneath the Russian Antarctic field station, with a surface area of around 14,000 square kilometres, Lake Vostok is the largest and deepest subglacial lake ever found. It has been completely sealed off from the surrounding environment for at least a million years. 快猫短视频s hope to discover unique life forms in the water that could hint at what kind of life may be lurking in ice-covered bodies of water elsewhere in the Solar System, such as those on Jupiter鈥檚 moon Europa.
A Russian, French and US team has already drilled to within around 100 metres of the water鈥檚 surface, and plans to break through into the lake by 2005. In the meantime, the researchers have been analysing ice cores from the bore hole to work out the chemical composition of the lake.
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Results suggesting that high levels of gases are dissolved in the lake water spurred NASA scientist Chris McKay to investigate further. He and his colleagues found that levels of gas in the water entering the lake from the overlying ice sheet are much higher than in layers of ice that have frozen back out of the lake, suggesting that the lake is accumulating gas over time (Geophysical Research Letters, vol 30, p 1702). 鈥淭he lake must be pumped full of gas,鈥� he says. 鈥淲e calculated 2.5 litres of gas for every litre of water.鈥�
He says this could put people drilling into the lake at risk, as the built-up pressure could explode in a dangerous 鈥渂low-out鈥�. Teams that drill for oil avoid this by filling the bore hole with fluid that is at higher pressure than the oil they are drilling into. But in this case the fluid in the bore hole will have to be at lower pressure, to avoid contaminating the lake. John Priscu, co-author of the recent study and a geobiologist at Montana State University at Bozeman, says this may not be enough to prevent a blow-out. 鈥淚f the water rushes up too high it will start degassing and spewing.鈥�
But Russian Antarctic scientist Vladimir Lipenkov says plans to drill into Vostok will go ahead, with the pressure of the fluid in the bore hole as close as possible to that in the lake. 鈥淣obody was going to access the lake water in the same way that a thirsty teenager would open a bottle of Coca Cola,鈥� he says.
He is more interested in what the gas results mean for any life under the ice. The oxygen concentration in Vostok is thought to be about a thousand times higher than in the ocean, so any organisms in the lake must have evolved mechanisms to cope with such an extreme environment. Cynan Ellis-Evans of the British Antarctic Survey is hopeful that unique life forms will be found. 鈥淚 would suggest that many microbes will tolerate subglacial lake environments,鈥� he says. 鈥淚f these environments have been around long enough, substantial evolutionary adaptation will have occurred, creating novel organisms and processes.鈥�
Priscu studies microorganisms that have been collected from ice cores above the lake. He is now trying to culture these bacteria to see if they have higher than normal levels of molecules that can neutralise free radicals, the highly reactive molecules formed by oxygen.
