Lake Vostok - Traits

Traits

The lake water is estimated to have been sealed off under the thick ice sheet about 15 million years ago. 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. 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 replaced every 13,300 years—its effective mean residence time.

The coldest temperature ever observed on Earth, −89 °C (−128 °F), was recorded at Vostok Station on 21 July 1983. The average water temperature is calculated to be 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 may warm the bottom of the lake. The ice sheet itself insulates the lake from cold temperatures on the surface.

Lake Vostok is an oligotrophic extreme environment, one that is expected to be supersaturated with nitrogen and oxygen, measuring 2.5 l (0.088 cu ft) of nitrogen and oxygen per 1 kg (2.2 lb) of water, that is 50 times higher than those typically found in ordinary freshwater lakes on Earth. The sheer weight and pressure around 345.60 bars (5,012.5 psi) of the continental ice cap on top of Lake Vostok is believed to contribute to the high gas 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.

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 about 12 mm (0.47 in). The lake is under complete darkness, under 354.60 bar (5,143.0 psi) of pressure, and expected to be rich in oxygen, so there is speculation that any organisms inhabiting the lake could have evolved in a manner unique to this environment. There is a 1 microtesla magnetic anomaly on the east coast of the lake, spanning 105 by 75 km (65 by 47 mi). Researchers hypothesize that the anomaly may be caused by a thinning of Earth's crust in that location.

Living Hydrogenophilus thermoluteolus micro-organisms have been found in Lake Vostok's deep ice core drillings; they are an extant surface-dwelling species. This suggests the presence of a deep biosphere utilizing a geothermal system of the bedrock encircling the subglacial lake. There is optimism that microbial life in the lake may be possible despite high pressure, constant cold, low nutrient input, potentially high oxygen concentration and an absence of sunlight. Jupiter's moon Europa and Saturn's moon Enceladus may also harbor lakes or oceans below a thick crust of ice. Any confirmation of life in Lake Vostok could strengthen the prospect for the presence of life on icy moons.