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Radar plumbs buried Antarctic lake for life
Water in the freshwater lake buried 4 kilometers (2.5 miles) beneath the Antarctic ice sheet is constantly refreshed with nutrients, scientists conclude in today's issue of Nature. They believe Europa may contain similar nutrients necessary for life.
"Our results indicate that ice melts in one place and freezes in another," said Martin Siegert, a glaciologist at the University of Bristol in England. "It is a mechanism by which nutrients can be input to the lake."
To reach their conclusions, Siegert and colleagues used radar data that reveals how the ice sheet flows over Lake Vostok. The data also shows a cross-section of the ice sheet along the line of flow.
"As ice flows across the lake, deep within the ice sheet, the internal layers diverge from the ice base in the south of the lake and converge to the ice base in the north," said Siegert. "Thus, ice must be added to the ice base in the south and taken from it in the north."
The melting point of ice in environments such as Lake Vostok is related to the thickness of the ice above the water. The melting point is colder under thicker ice, as it is at the northern end of the lake.
The water that melts at the northern end will thus be colder and less dense than water at the southern end. "The density contrast between these waters will cause the circulation," said Siegert.
Previous research based on ice cores taken from about 11,800 feet below the surface of the ice sheet and 495 feet above Lake Vostok shows that glacial ice has lots of impurities but the refrozen ice has none.
"This means that (glacial) ice melts, leaves the gas hydrates and sediment in the lake, and then freezes as H2O," said Siegert.
This process is likely to infuse the nutrients and gases essential to support life in Lake Vostok, concludes Charles Bently, a geophysicist at the University of Wisconsin, in an accompanying article in Nature.
Scientists have yet to acquire a water sample from Lake Vostok out of concern that they might contaminate one of the most pristine ecosystems on Earth.
However, the Scientific Committee on Antarctic Research will hold meetings over the next several months to hatch a plan for exploration of the lake. Similar plans will be used for the exploration of Jupiter's moon, Europa.
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