Lake Vostok

Lake Vostok
When imaged from space by radar, Lake Vostok can be seen as a flat area within the ice sheet. (NASA GSFC)
Lake type subglacial rift lake
Basin countries (Antarctica)
Max. length 250 km
Max. width 50 km
Surface area 15,690 km²
Average depth 344 m
Max. depth 1,000 m
Water volume 5,400 ± 1,600 km³
Residence time 13,300 yrs
Islands 1 (found May 2005)
Settlements Vostok Station

Lake Vostok (Russian: восток, "east") is the largest of more than 140 subglacial lakes found under the surface of Antarctica. It is located beneath Russia's Vostok Station, 4,000 metres (13,000 ft) under the surface of the central Antarctic ice sheet. It is 250 kilometres (160 mi) long by 50 kilometres (31 mi) 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 (660 ft), compared to roughly 400 metres (1,300 ft) deep in the northern basin and 800 metres (2,600 ft) deep in the southern. Lake Vostok covers an area of 15,690 square kilometres (6,060 sq mi). It has an estimated volume of 5,400 cubic kilometres (1,300 cu mi) and consists of fresh water. The average depth is 344 metres (1,129 ft). In May 2005 an island was found in the center of the lake.

Contents

Discovery

Radar imaging

Airborne ice-penetrating radar data first showed lakes beneath the Antarctic ice-sheet in the late 1960s and early 1970s. The existence of Lake Vostok was first noted in 1973 by scientists of the Scott Polar Research Institute, but not named by them.[1]

Russian and British scientists delineated the lake 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 large amounts of liquid water under the more than three-kilometer thick icecap, promising to be the most unspoiled lake on Earth. The lake has at least 22 cavities of liqued water, avarging 10km each.[2]

The lake water is undoubtedly very old. Initially, it was thought that the same water had made up the lake since the time of its formation, giving a residence time in the order of one million years.[3] Later research by Robin Bell and Michael Studinger from the Lamont-Doherty Earth Observatory of Columbia University suggested that the water of the lake is continually freezing and being carried away by the motion of the Antarctic ice sheet, while being replaced by water melting from other parts of the ice sheet in these high pressure conditions. This resulted in an estimate that the entire volume of the lake is frozen and removed every 13,300 years—its effective mean residence time.[4] In comparison, the similarly sized Lake Ontario has a residence time of six years, which is typical for a lake of that size.

Temperature

The average water temperature is around −3 °C (27 °F); 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

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 metres (11,886 ft) long. Ice samples from cores drilled close to the top of the lake have been analyzed 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 100 metres (300 ft)[5] above the suspected boundary where the ice sheet and the liquid waters of the lake are thought to meet. This was to prevent contamination of the lake from the 60 ton column of freon and aviation fuel Russian scientists filled it with to prevent it from 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.[6]

Environment

Ecosystems

Since Lake Vostok 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.

Pressure and oxygen

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.[3]

Life

The lake is rich in oxygen and there is speculated that any organisms inhabiting the lake would have needed to evolve special adaptations to survive. These adaptations to an oxygen-rich environment might include high concentrations of protective enzymes.

Microorganisms have been found in ice core drillings, but they are extant surface dwelling species. Since the ice core drilling stopped before they reached the water, to limit contamination, it is postulated that lower down there still may be unique microorganisms still to be found.[7]

Due to the lake's similarity to the Jupiter moon Europa and Saturn's moon Enceladus, any confirmation of life living in Lake Vostok would strengthen the prospect for the possible presence of life on Europa or Enceladus.[8]

Tidal forces

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 a pumping effect that keeps the water circulating, which would promote the productivity of microorganisms if there are any.

Research

To probe the waters of Lake Vostok for life, without contamination, plans were initiated in 2001 by the Jet Propulsion Laboratory 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.[9][10]

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.

In early 2010 the head of the Russian Antarctic Expedition, Valery Lukin, announced that a team of Russian scientists had only 100 meters of ice left to drill in order to reach the water. According to Lukin, new equipment had been developed by researchers at the St. Petersburg Nuclear Physics Institute that would ensure the lake remains sterile upon intrusion. The scientists expect to reach the lake in 2010-2011.[11]

It is suspected that the Antarctic subglacial lakes may be connected by a network of subterranean rivers. CPOM glaciologists Duncan Wingham (University College, London) and Martin Siegert (University of Bristol, now University of Edinburgh) published in Nature in 2006 that many of the subglacial lakes of Antarctica are at least temporarily interconnected. 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.[3]

See also

References

  1. ↑ Oswald, G. K. A.; Robin, G. de Q. (1973). "Lakes beneath the Antarctic Ice Sheet". Nature 245 (5423): 251–254. doi:10.1038/245251a0. 
  2. ↑ Dieter Fütterer; Georg Kleinschmidt (2006). Antarctica: contributions to global earth sciences : proceedings of the IX International Symposium of Antarctic Earth Sciences Potsdam, 2003. Birkhäuser. pp. 138–. ISBN 9783540306733. http://books.google.com/books?id=PcJcEvPFpT4C&pg=PA138. Retrieved 30 July 2010. 
  3. ↑ 3.0 3.1 3.2 Siegert MJ (2000). "The identification, examination and exploration of Antarctic subglacial lakes". Sci Prog 83 ( Pt 3): 223–42. PMID 11077478. 
  4. ↑ "Columbia University Scientists Present Long Sought Opportunities to Safely Explore Life Within Earth's Most Ancient and Inaccessible Ecosystem". The Earth Institute at Columbia University. March 21, 2002. http://www.earthinstitute.columbia.edu/news/2003/story08-27-03.html. Retrieved March 31, 2010. 
  5. ↑ Jouzel J, Petit JR, Souchez R, Barkov NI, Lipenkov VY, Raynaud D, Stievenard M, Vassiliev NI, Verbeke V, Vimeux F (1999). "More than 200 meters of lake ice above subglacial Lake Vostok, Antarctica". Science 286 (5447): 2138–41. doi:10.1126/science.286.5447.2138. PMID 10591641. 
  6. ↑ Priscu JC, Adams EE, Lyons WB, Voytek MA, Mogk DW, Brown RL, McKay CP, Takacs CD, Welch KA, Wolf CF, Kirshtein JD, Avci R (1999). "Geomicrobiology of subglacial ice above Lake Vostok, Antarctica". Science 286 (5447): 2141–4. doi:10.1126/science.286.5447.2141. PMID 10591642. 
  7. ↑ Alan T. Bull (2004). Microbial diversity and bioprospecting. ASM Press. pp. 139–. ISBN 9781555812676. http://books.google.com/books?id=cDeuY0ON6RQC&pg=PA139. Retrieved 30 July 2010. 
  8. ↑ "Mystery of Antarctica's 15-Million Year-Old Lake". The Daily Galaxy. 2007-12-04. http://www.dailygalaxy.com/my_weblog/2007/12/secret-life-o-1.html. Retrieved 2007-12-05. 
  9. ↑ Ice Explorer Conceived for Other Worlds Gets Arctic Test
  10. ↑ Robot to Explore Buried Ice Lake
  11. ↑ Russians Close to Reaching Lake Vostok The St. Petersburg Times Retrieved on March 09, 2010

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