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Lake Vostok

2007 Schools Wikipedia Selection. Related subjects: Geography of Asia

                       Lake Vostok
   Lake Vostok - Location within Antarctica (NASA)

                     Location within Antarctica ( NASA)

   Coordinates  77° S 105° E Coordinates: 77° S 105° E
   Lake type    subglacial
   Max-length   250 km
   Max-width    50 km
   Surface area 14,000 km²
   Water volume 5400 km³
   Islands      1 (found May 2005)

   Lake Vostok (the name comes from the Russian word for "east") is the
   largest of more than 140 subglacial lakes found under the surface of
   Earth's southern-most continent— Antarctica. It is located at 77° S
   105° E, beneath Russia's Vostok Station, 4000 metres (13,000 feet)
   under the surface of the central Antarctic ice sheet. It is 250 km long
   by 50 km wide at its widest point, thus similar in size to Lake
   Ontario, and is divided into two deep basins by a ridge. The water over
   the ridge is about 200 m (650 feet) deep, compared to roughly 400 m
   (1,300 feet) deep in the northern basin and 800 m (2,600 feet) deep in
   the southern. Lake Vostok covers an area of 14,000 km² (5,400 mi²). It
   has an estimated volume of 5400 km³ (1,300 cubic miles) and consists of
   fresh water. In May 2005 an island was found in the centre of the lake.

Discovery

Radar imaging

   Russian and British scientists discovered the lake's existence in 1996
   by integrating a variety of data, including airborne ice-penetrating
   radar imaging observations and spaceborne radar altimetry. It has been
   confirmed that the lake contains plenty of liquid water under the more
   than three-kilometre thick icecap, promising to be the most unspoiled
   lake on Earth. Its water is very old, with a mean residence time in the
   order of one million years (as compared with six years for Lake
   Ontario, which is typical for lakes of that size).
   Lake Vostok is visible from space as the ice sheet above it is flat.
   (NASA GSFC)
   Enlarge
   Lake Vostok is visible from space as the ice sheet above it is flat. (
   NASA GSFC)

Average water temperature

   The average water temperature is around −3  °C; it remains liquid below
   the normal freezing point because of high pressure from the weight of
   the ice above it. Geothermal heat from the Earth's interior warms the
   bottom of the lake. The ice sheet itself insulates the lake from cold
   temperatures on the surface.

Ice core research

   Researchers working at Vostok Station produced one of the world's
   longest ice cores in 1998. A joint Russian, French, and U.S. team
   drilled and analyzed the core, which is 3623 m (11,886 feet) long. Ice
   samples from cores drilled close to the top of the lake have been
   analysed to be as old as 420,000 years, suggesting that the lake has
   been sealed under the icecap for between 500,000 and more than a
   million years. Drilling of the core was deliberately halted roughly
   120 m (400 feet) above the suspected boundary where the ice sheet and
   the liquid waters of the lake are thought to meet to prevent
   contamination of the lake from the 60 ton column of freon and aviation
   fuel the Russians filled it with to prevent it freezing over.

   From this core, specifically from ice that is thought to have formed
   from lake water freezing onto the base of the ice sheet, evidence has
   been found, in the form of microbes, to suggest that the lake water
   supports life. Scientists suggested that the lake could possess a
   unique habitat for ancient bacteria with an isolated microbial gene
   pool containing characteristics developed perhaps 500,000 years ago.

An extreme environment

Likely two separate ecosystems

   Since it has been discovered that it consists of two separate basins
   divided by a ridge, it has been suggested that the chemical and
   biological compositions of these two ecosystems are likely to be
   different.

High pressure and high oxygen concentration

   Lake Vostok is an oligotrophic extreme environment, one that is
   supersaturated with oxygen, with oxygen levels 50 times higher than
   those typically found in ordinary freshwater lakes on Earth. The sheer
   weight of the continental icecap sitting on top of Lake Vostok is
   believed to contribute to the high oxygen concentration. Besides
   dissolving in the water, oxygen and other gases are 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 become
   unstable if brought to the surface.

   Due to this high-pressure extreme environment, if water were to be
   released from Lake Vostok (from drilling, for example), it could gush
   like a popped carbonated drink can and, if not contained, open the lake
   to possible contamination and pose a potential hazard to scientists.

Speculation on possible life and comparisons to Europa

   No other natural lake environment on Earth has this much oxygen. Any
   organisms in Lake Vostok must be capable of overcoming very high oxygen
   stress. Some have speculated that such organisms may have had to evolve
   special adaptations, such as high concentrations of protective enzymes,
   in order to survive the lake's oxygen-rich environment.

   Due to the lake's similarity to a moon of Jupiter, Europa, confirmation
   that life can survive in Lake Vostok might strengthen the argument for
   the presence of life on Europa.

Tidal forces in Lake Vostok

   In April 2005, German, Russian, and Japanese Researchers found that the
   lake has tides. Depending on the position of the Sun and the Moon, the
   surface of the lake rises between 1 and 2 cm. The researchers assume
   that the fluctuation of the lake surface has the effect of a pump that
   keeps the water circulating, which would be necessary for the survival
   of microorganisms if there are any.

Recent research

   In January 2006, Robin Bell and Michael Studinger, Geophysical
   researchers from Columbia University, announced in Geophysical Research
   Letters the discovery of two smaller lakes under the icecap, named 90
   Degrees East and Sovetskaya.

   It is also suspected that the Antarctic subglacial lakes may be
   connected by a network of subterranean rivers. Glaciologists Duncan
   Wingham ( University College, London) and Martin Siegert (University of
   Bristol) published in Nature in 2006 that many of the subglacial lakes
   of Antarctica are at least temporarily interconnected. Obviously
   because of varying water pressure in individual lakes, large,
   sub-surface rivers may suddenly form and then force large amounts of
   water through the solid ice.

   To probe the waters of Lake Vostok for life without contamination,
   plans were initiated by JPL to start with a melter probe- the so-called
   "cryobot" - which melts down through the ice over Lake Vostok,
   unspooling a communications and power cable as it goes. The cryobot
   carries with it a small submersible, called a "hydrobot", which is
   deployed when the cryobot has melted to the ice-water interface. The
   hydrobot then swims off and "looks for life" with a camera and other
   instruments.

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