Lake Vostok
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Lake Vostok is a subglacial lake in Antarctica . It is located at 77° S 105° E, beneath Russia's Vostok Station, 4,000 meters (13,000 feet) under the surface of the central Antarctic ice sheet. It is 250 kilometers long by 50 kilometers 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 metres (650 feet) deep, compared to roughly 400 metres (1,300 feet) deep in the northern basin and 800 metres (2,600 feet) deep in the southern. Lake Vostok covers an area of 14,000 square kilometers (5,400 square miles). It has an estimated volume of 5,400 cubic km (1,300 cubic miles) and consists of fresh water. In May 2005 an island was found in the center of the lake.
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 kilometers-deep 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.)
The average water temperature is around −3 °C, below normal freezing point because of ice pressure. Heat from the Earth's interior (geothermal) warms the bottom of the lake. The ice sheet itself insulates the lake from cold temperatures on the surface.
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 3,623 meters (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 meters (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 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 form of some 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.
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.
Lake Vostok is an oligotrophic extreme environment, one that is supersaturated with oxygen, with typically 50 times higher oxygen levels than those 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 be unstable if brought to the surface.
Due to this fact, if water is released from Lake Vostok due to drilling, it could gush like a popped carbonated (fizzy) drink can and, if not contained, open the lake to possible contamination and pose a potential hazard to scientists.
No other natural lake environment on Earth has this much oxygen. Organisms in Lake Vostok are believed to be capable of overcoming very high oxygen stress. They 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 Europa, a moon of Jupiter, confirming that life can survive in Lake Vostok might strengthen the argument for the presence of life on Europa.
In April 2005, German, Russian and Japanese Researchers found that the lakes has tides. Depending on the position of the sun and the moon, the surface rises between 1 and 2 centimeters. The researches 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.
External Links
Lake Vostok information page, updated often (http://www.70south.com/news/989352796/index_html)de:Wostoksee es:Lago Vostok fr:Lac Vostok nl:Vostokmeer ja:ボストーク湖 pt:Lago Vostok fi:Vostok (järvi) ru:Восток (озеро)