Lake Vostok

Lake Vostok is the largest known subglacial lake in Antarctica. It is about the size of Lake Ontario in North America but has been continuously buried under the ice of East Antarctica for at least fifteen million years. Researchers have been studying the lake to see how living creatures have adapted and survived in such harsh conditions. However, the only access to the lake that scientists have is through boreholes drilled through the ice, but these have allowed them to examine ice core samples, including the lowest layer of ice, which is at the lake’s surface. Though the water temperature of Lake Vostok is below freezing, geothermal energy from Earth’s crust prevents it from freezing, and the 2.4-mile- (4-kilometer)-thick ice layer provides insulation.

Though Lake Vostok is trapped beneath the ice, the water within it is not stagnant. Very slowly, over thousands of years, it is replaced by water from melted ice. The lake takes its name from Vostok Station, a Russian research station that was established in 1957 and located over the then-undiscovered lake. The station was named for the Vostok, the lead ship of the First Russian Antarctic Expedition.

Background

Antarctica is Earth’s fifth-largest continent. Almost its entire landmass, which covers the South Pole, lies under a sheet of ice. It is the coldest, driest, highest, iciest, and windiest continent. Encompassing about 5.5 million square miles (14.2 million square kilometers), most of East Antarctica is a high plateau, while West Antarctica is mostly an ice sheet that engulfs an archipelago of mountainous islands.

About three billion years ago, Antarctica was part of the landmass that became the southern continents. The landmass slowly broke apart and was significantly divided about seventy million years ago, though some land mammals were able to traverse it during migration. At that time, it was still mostly forested with a combination of southern conifers and ferns. Between forty-nine million and seventeen million years ago, Antarctica was isolated, as the Drake Passage between it and South America widened. The closer it moved to the South Pole, the cooler Antarctica became. Eventually, it became glaciated. The ice covering the continent sealed in hundreds of freshwater lakes and rivers, freezing and receding, until about fourteen million years ago, when it remained frozen.

British and Russian expeditions discovered Antarctica in 1820. In the 2020s, life at the South Pole existed along the edges of the continent and in the waters below the ice. The only humans in the region were scientists in research stations and occasionally tourists.

The existence of the lake was unknown until later in the twentieth century. Russian polar scientist Andrei Kapitsa noted the unusually smooth terrain in 1957 and speculated that a huge lake could be beneath the ice. Aerial radio echo surveys in 1974 confirmed his suspicion, and satellite measurements taken in 1993 provided further evidence.

Overview

Lake Vostok is one of the largest bodies of freshwater on Earth. Its surface area is 4,826 square miles (12,500 square kilometers), and it is more than 980 yards (900 meters) deep. The lake exists in darkness and complete isolation from the surface.

Researchers wondered whether life could have survived in such cold and dark waters. In most water habitats, microscopic animals eat algae that use the sun to make food using photosynthesis. In a dark and isolated body of water, they wondered what a food web might look like.

Russian researchers were the first to drill through the ice to reach Lake Vostok in December 2012. They angered many in the scientific community by using kerosene drilling fluid that was contaminated by bacteria from the surface. This prevented scientists from having reliable data about organisms that were in the lake. They could not be certain that the organisms they discovered were not introduced by the drilling process. The Russians would not agree to follow a sterile protocol while drilling to protect potential ancient microorganisms.

In January 2013, an expedition funded by the United States reached Lake Whillans in West Antarctica using sterile drilling techniques. They discovered that microbes called chemolithoautotrophs, bacteria that eat rocks, are the base of the ecosystem of the subglacial lake. They produce a basic carbon source for other organisms in the food web. These microorganisms were later discovered in another subglacial Antarctic lake, leading researchers to theorize that they are likely to be found in Lake Vostok as well.

Researchers believe that Lake Vostok is located in a generally north-south bedrock depression. It is about 155 miles (250 kilometers) long and about 30 to 50 miles (50 to 80 kilometers) wide. The freshwater of the lake lies below sea level, and a ridge runs approximately down the middle. It is replenished by meltwater from the ice sheet, which is its only source of new water; however, researchers do not know how old the water is. The water in the lake is about 27 degrees Fahrenheit (-3 degrees Celsius) at all times.

Ice core samples collected during the 1990s have produced many varieties of bacteria, fungi, and other organisms from just above the lake’s surface, where the freshwater freezes in a layer of new ice on the underside of the glacier. In a study published in 2013, Bowling Green University researchers examined ice core samples collected by the US Geological Survey from the southern main basin and near a bay in the southwestern part of the lake. They found 3,507 unique gene sequences. These included bacteria that are usually found in digestive systems of fish and other creatures; fungi; and two species of single-celled organisms called archaea that live in extreme environments. They also found psychrophiles, organisms that live in extreme cold, as well as thermophiles, which live in extreme heat. The presence of thermophiles supports the theory that hydrothermal vents are located in the deepest parts of Lake Vostok. Many other species were not identified. The majority of species were found in the samples from the bay. Other studies have identified a well-known species of rock-eating chemolithoautotroph in ice samples taken from lake water that flowed into the Russian borehole. In 2020, scientists further studied the lake, finding additional bacteria and eukaryotes. They also found a genetic sequence from a rock cod, a fish species commonly found along the Antarctic coast. This was the first report of a fish possibly inhabiting Lake Vostok.

In addition to learning about living creatures in the lake, researchers have eyed Lake Vostok and other subglacial lakes of Antarctica as possible practice grounds for discovering life on other planets. The environment in the lakes is considered so inhospitable that it might mimic conditions on other celestial bodies on which it seems nothing could live.

Bibliography

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