Lake Vostok

Lake Vostok (Russian: Озеро Восток, Ozero Vostok, lit. 'Lake East') is the largest of Antarctica's almost 400 known subglacial lakes.Lake Vostok is located at the southern Pole of Cold, beneath Russia's Vostok Station under the surface of the central East Antarctic Ice Sheet, which is at 3,488 m (11,444 ft) above mean sea level. The surface of this fresh water lake is approximately 4,000 m (13,100 ft) under the surface of the ice, which places it at approximately 500 m (1,600 ft) below sea level. Measuring 250 km (160 mi) long by 50 km (30 mi) wide at its widest point, it covers an area of 12,500 km2 (4,830 sq mi) making it the 16th largest lake by surface area. With an average depth of 432 m (1,417 ft), it has an estimated volume of 5,400 km3 (1,300 cu mi), making it the 6th largest lake by volume. The lake is divided into two deep basins by a ridge. The liquid water depth over the ridge is about 200 m (700 ft), compared to roughly 400 m (1,300 ft) deep in the northern basin and 800 m (2,600 ft) deep in the southern. The lake is named after Vostok Station, which in turn is named after the Vostok (Восток), a sloop-of-war ship, which means 'East' in Russian. The existence of a subglacial lake in the Vostok region was first suggested by Russian geographer Andrey Kapitsa based on seismic soundings made during the Soviet Antarctic Expeditions in 1959 and 1964 to measure the thickness of the ice sheet. The continued research by Russian and British scientists led by 1993 to the final confirmation of the existence of the lake by J. P. Ridley using ERS-1 laser altimetry. The overlying ice provides a continuous paleoclimatic record of 400,000 years, although the lake water itself may have been isolated for 15 to 25 million years. On 5 February 2012, a team of Russian scientists completed the longest ever ice core of 3,768 m (12,400 ft) and pierced the ice shield to the surface of the lake. The first core of freshly frozen lake ice was obtained on 10 January 2013 at a depth of 3,406 m (11,175 ft). However, as soon as the ice was pierced, water from the underlying lake gushed up the borehole, mixing it with the Freon and kerosene used to keep the borehole from freezing. A new borehole was drilled and an allegedly pristine water sample was obtained in January 2015. The Russian team plans to eventually lower a probe into the lake to collect water samples and sediments from the bottom. It is hypothesized that unusual forms of life could be found in the lake's liquid layer, a fossil water reserve. Because Lake Vostok may contain an environment sealed off below the ice for millions of years, the conditions could resemble those of ice-covered oceans hypothesized to exist on Jupiter's moon Europa, and Saturn's moon Enceladus. Russian scientist Peter Kropotkin first proposed the idea of fresh water under Antarctic ice sheets at the end of the 19th century. He theorized that the tremendous pressure exerted by the cumulative mass of thousands of vertical meters of ice could decrease the melting point at the lowest portions of the ice sheet to the point where the ice would become liquid water. Kropotkin's theory was further developed by Russian glaciologist I. A. Zotikov, who wrote his Ph.D. thesis on this subject in 1967. Russian geographer Andrey Kapitsa used seismic soundings in the region of Vostok Station made during the Soviet Antarctic Expedition in 1959 and 1964 to measure the thickness of the ice sheet. Kapitsa was the first to suggest the existence of a subglacial lake in the region, and the subsequent research confirmed his hypothesis.