Deep, dark and mysterious, Lake Vostok is one of the largest subglacial lakes in the world.
Once a large surface lake in East Antarctica, Lake Vostok is now buried under more than 2 miles (3.7 kilometers) of ice near Russia's Vostok research station. Covered with ice for millennia, cut off from light and contact with the atmosphere, Lake Vostok is one of the most extreme environments on Earth. "The lake has been ice-covered for at least 15 million years," said Brent Christner, a Louisiana State University biologist who has examined ice cores collected above the lake.
In the 1990s, Christner was part of an international team that discovered microbes in frozen lake water collected above Lake Vostok's liquid surface, called accretion ice. The top half-inch (1 centimeter) of the lake surface freezes onto the flowing ice sheet above the lake, scientists think.
Analysis of the life forms suggests Lake Vostok may harbor a unique ecosystem based on chemicals in rocks instead of sunlight, living in isolation for hundreds of thousands of years. "The types of organisms we found suggested they derived their energy from minerals present in the lake and sources from the underlying bedrock," Christner said. More recent studies of genetic material in Vostok's accretion ice revealed snippets of DNA from a wide variety of organisms related to single-celled creatures found in lakes, oceans and streams. These "extremophiles" could mimic life on other moons and planets, such as Jupiter's icy moon Europa. [Image Gallery: Alien Life of the Antarctic]
Despite several attempts, no teams have successfully retrieved pristine samples of lake water with evidence of life. A Russian team is currently analyzing water samples collected in 2012 for signs of microbial life. In 2013, scientists exploring Antarctica's subglacial Lake Whillans reported the presence of microbial life in water retrieved from a buried lake. There are nearly 380 subglacial lakes in Antarctica.
Below the surface
Lake Vostok is one of the largest lakes on Earth in size and volume, rivaling Lake Ontario in North America. Its only water supply is meltwater from overlying ice sheet, Christner said. "To my knowledge, there is no evidence for influx or efflux of water from Lake Vostok," he said. This constant replenishment from melting ice means the water in the lake may be relatively young, just thousands of years old, according to ice core studies. But the true age of the lake water is unknown.
Researchers have mapped Lake Vostok's shape with remote sensing techniques, such as seismic soundings and ice-penetrating radar. Lake Vostok is much shallower on one end than the other, with the two basins separated by a ridge. Some scientists think the ridge could be a hydrothermal vent, similar to the ocean floor black smokers that teem with tubeworms. The long, narrow lake may lie in a rift valley, similar to Lake Baikal in Russia.
Geothermal heat from the Earth keeps the temperature of the lake water hovering around 27 degrees Fahrenheit (minus 3 degrees Celsius), scientists believe. The weighty pressure of the overlying ice keeps the lake liquid despite its below-freezing temperature.
The lake itself is 143 miles (230 km) long, 31 miles (50 km) wide and as much as 2,625 feet (800 meters) deep. Lake Vostok sits near the South Pole in East Antarctica. The presence of a large buried lake was first suggested in the 1960s by a Russian geographer/pilot who noticed the large, smooth patch of ice above the lake from the air. Airborne radar experiments by British and Russian researchers in 1996 confirmed the discovery of the unusual lake.
"Lake Vostok is one of the easiest subglacial lakes to detect due to its size," Christner said. "[Yet] I believe most of its secrets remain."
- Guide to Antarctica (Infographic): A map of Antarctica's notable features and facts.
- Antarctica's subglacial lakes: An overview of Antarctica's lakes written by a glacial scientist.
- WISSARD: The home of an ongoing and successful effort to drill into Antarctica's Lake Whillans.