Lake Vostok, the largest lake in Antarctica, covers an area of about 5,400 square miles (14,000 square kilometers). It lies in East Antarctica, about 2 1/2 miles (4 kilometers) beneath the surface of the ice that covers the continent. The lake measures about 155 miles (250 kilometers) long and 30 miles (50 kilometers) wide, roughly the size of Lake Ontario in North America. Lake Vostok’s waters reach about 3,000 feet (915 meters) deep at their deepest point. The lake takes its name from Vostok Station, a Russian research facility situated above its southern tip.
Lake Vostok has an average temperature of about 27 °F (–3 °C), lower than the freezing point of water. The lake remains liquid because of the pressure of the overlying ice and heat from the ground below.
Scientists believe that Lake Vostok may have been isolated from the surface for up to 35 million years. However, the lake slowly cycles in new water as the ice moving overhead melts and refreezes. This cycle is thought to take between 55,000 and 110,000 years. Scientists think Lake Vostok’s water may harbor such microscopic life forms as bacteria and viruses that have become extinct elsewhere or developed independently of life on the rest of the planet.
Some scientists believe that Lake Vostok has conditions similar to those on Europa, one of Jupiter’s moons. Europa’s surface consists of ice and may have an ocean of water beneath it. Such an ocean could provide a home for living things. Studies of organisms in Lake Vostok could help scientists understand the types of life that might exist on Europa. But many scientists are concerned that drilling into the lake to take samples may contaminate the water with outside chemicals or organisms.
In the late 1990’s, a team of scientists from Russia, France, and the United States drilled through the ice to within roughly 500 feet (150 meters) of Lake Vostok’s surface. Ice samples taken from the bottom of the hole show evidence of bacteria only found in hot springs. Their presence may indicate an underwater hot spring feeding into the lake. In February 2012, a Russian team completed the drilling, breaking through the ice to the lake water. The pressure of the water in the lake forced water about 100 feet (30 meters) up into the bore hole, freezing the hole shut. The onset of the cold season forced the team to stop short of collecting a sample of the lake water.
In 2012, scientists announced that the first sample, taken from the bottom of the bore hole, revealed no life. However, the analysis of a single sample could not rule out the possibility of life in the lake. In 2013, scientists revealed that a sample from the lake contained evidence of several forms of life. Most of the evidence was for bacteria, but some of it may be from mollusks and fish.
