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New Map of Antarctica's Lake Vostok Reveals Two Distinct
Parts, With Possibly Differing Ecosystems

A north-south profile of Lake Vostok that measures its depth in meters above sea level. The
  contours of the lake were mapped by estimating the elevation data based on inversion
      gravity date collected while in an airplane. Image credit: Michael Studinger/NSF

Deep in the Antarctic interior, buried under thousands of meters (more than two miles) of
ice, lies Lake Vostok, the world's largest subglacial lake. Scientists believe that the waters
of Lake Vostok have not been disturbed for hundreds of thousands of years, and there are
tantalizing clues that microbes, isolated for at least as long, may exist.

Now, the most comprehensive measurements of the lake — roughly the size of Lake
Ontario in North America — indicate that it is divided into two distinct basins that may have
different water chemistry and biological characteristics. The findings have important
implications for the diversity of any microbial life in Lake Vostok and for how scientists
should study the lake's various ecosystems, if an international scientific consensus is ever
reached to explore the lake.

Lake Vostok is thought to be a very good terrestrial analogue to the conditions on Europa,
a moon of Jupiter thought to hold a large liquid ocean far beneath its frozen surface.
Scientists have argued that if microbial life can exist in Vostok, then it also might thrive on

In a paper published June 19, 2004 in Geophysical Research Letters, a journal of the
American Geophysical Union, scientists from the Lamont-Doherty Earth Observatory of
Columbia University and the University of Tokyo describe the first-ever map of water-depth
in Lake Vostok.

Russia has long maintained a research station at Lake Vostok, and Russian scientists
have previously probed the lake with seismic waves. But these soundings produced
measurements of the water depth only at isolated points. The new measurements are
significant because they provide a comprehensive picture of the entire lakebed and
indicate that, contrary to what scientists had assumed, the bottom of the lake is not one
continuous feature but contains a previously unknown northern sub-basin that is divided
from the southern lakebed by a prominent ridge.

Michael Studinger of Lamont-Doherty, a principal author of the paper, said that the
existence of two distinct regions within the lake would have significant implications for the
kinds of ecosystems scientists could expect to find in the lake and how they should go
about exploring them. "The ridge between the two basins will limit water exchange
between the two systems," he said. "Consequently, the chemical and biological
composition of these two ecosystems is likely to be different."

Using laser altimeter, ice-penetrating radar, and gravity measurements collected by aircraft
flying over the lake, Studinger and Robin Bell of Lamont-Doherty and Anahita Tikku, then
at the University of Tokyo, estimate that Lake Vostok contains roughly 5,400 cubic
kilometers (1,300 cubic miles) of water.

Their measurements also indicate that the lake is divided into two distinct sub-basins
separated by a narrow ridge. The water over that ridge is relatively shallow (200 meters or
650 feet deep), as compared to the rest of the lake, where the water ranges from roughly
400 meters (1,300 feet) deep in the northern basin to 800 meters (2,600 feet) deep in the
southern. The National Science Foundation (NSF) supported the research.

The scientists conclude that the arrangement of the two basins, their separation, and the
characteristics of the meltwater may all have implications for the circulation of water within

the lake. For example, it is possible that if the water in the lake were fresh, the meltwater in
the northern basin would sink to the bottom of that basin, limiting the exchange of waters
between the two basins. The meltwater in the adjacent basin would likely be different. The
two lake basins could therefore have very different bottoms and very different biological
and chemical compositions.

Scientists involved in deciding whether and how to proceed with an exploration of Lake
Vostok have stressed that a great deal of technological development would have to take
place before a device could be deployed to conduct contamination-free sampling.
Currently, there is no scientific sampling of the lake being carried out. The new
measurements also indicate that different strategies would probably have to be developed
depending on the types of lake sediments targeted. The ultimate goal of any sampling
strategy would be to obtain water and sediment samples from the lake bottom.

The lake mapping would help to guide this scientific work. From the observed melting and
freezing patterns of ice moving over Lake Vostok, it is evident that the northern basin
would contain sediments of rock debris carried from land and deposited into the lake. The
southern basin, where water is frozen back to the base of the ice sheet, would not have
these same land deposits, but would more likely contain sediment deposits that recorded
the environmental conditions before the ice sheet sealed off the lake.


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