Lake Vostok – Australian Science

Lake Vostok: life beneath the ice

Kevin Orrman-Rossiter — Fri, 26 Jul 2013 00:09:44 +0000

Imagine, Lake Vostok is covered by more than 3,700 metres of Antarctic ice. Devoid of sunlight, it lies far below sea level in a depression that formed 60 million years ago, when the continental plates shifted and cracked. Few nutrients are available. Yet scientist, led by Scott Rogers, a Bowling Green State University professor of biological sciences, have found a surprising variety of life forms living and reproducing in this extreme environment. A paper published June 26 in PLOS ONE details the thousands of species they identified through DNA and RNA sequencing.

What lies sealed beneath the glacial ice?

Antarctica, 35 million years ago, had a temperate climate and was inhabited by a diverse plants and animals. About 34 million years ago, a huge drop in temperature occurred and ice covered the lake, when it was probably still connected to the Southern Ocean. This lowered the sea level by about 100 metres, which could have cut off Lake Vostok from the ocean. The ice cover was intermittent until a second big plunge in temperature took place 14 million years ago, and sea level dropped even farther.

As the ice crept across the lake, it plunged the lake into total darkness and isolated it from the atmosphere, and led to increasing pressure in the lake from the weight of the glacier. While many species probably disappeared from the lake, as indicated by Rogers’ results, some seem to have survived.

Rogers and his colleagues examined core sections from the ice above Lake Vostok that were extracted in 1998. At the time, no one had reached the actual lake, a feat that was achieved only last year. But the drilling had gone deep enough to reach a layer of ice at the bottom of the sheet that formed as lake water froze onto the bottom of the glacier where it meets the lake. The team sampled cores from two areas of the lake, the southern main basin and near an embayment on the southwestern end of the lake. The embayment appears to contain much of the biological activity in the lake.

By sequencing the DNA and RNA from the ice samples, the team identified thousands of bacteria, including some that are commonly found in the digestive systems of fish, crustaceans and annelid worms, in addition to fungi and two species of archaea, or single-celled organisms that tend to live in extreme environments. Other species they identified are associated with habitats of lake or ocean sediments. Psychrophiles, or organisms that live in extreme cold, were found, along with heat-loving thermophiles, which suggests the presence of hydrothermal vents deep in the lake. Rogers said the presence of marine and freshwater species supports the hypothesis that the lake once was connected to the ocean, and that the freshwater was deposited in the lake by the overriding glacier.

These results, however, are not without controversy.

Other claims and other lakes

Long before he began using these techniques to study the ice, Rogers and his team had developed a method to ensure purity. Sections of core ice were immersed in a sodium hypochlorite (bleach) solution, then rinsed three times with sterile water, removing an outer layer. Under strict sterile conditions, the remaining core ice was then melted, filtered and refrozen.

Sergey Bulat has doubts about the results, despite the careful sample preparation. Bulat, a Lake Vostok expert at the Petersburg Nuclear Physics Institute in Gatchina, Russia, is quoted as saying, “that it is very probably that the samples are heavily contaminated with tissue and microbes from the outside world.”

Quirin Schiermeier has noted in Nature News:

Bulat and Rogers have both studied Vostok ice samples taken in the 1990s by a consortium of Russian, French and US Antarctic researchers. In the past, the pair pondered a close collaboration. But their scientific relationship broke over enduring disagreement about the level of contamination of samples.

In March, Bulat himself faced criticism over an unknown species of bacterium his team had discovered in a Lake Vostok ice core drilled last year. Sceptics said that this finding was due to contamination from drilling fluid.

The two researchers’ claims are probably the first in what will no doubt be an interesting period of discovery in Lake Vostok and other Antarctic lakes. The first samples of water from Lake Vostok itself, collected in early 2013 are currently being analysed. The Russian team has said that it hopes to have results within the next year. Bacteria, of known species, have been recovered from the smaller Antarctic Lakes, Whillans and Vida. Lake Vida has been sealed off for around 2,800 years. Ice cores drilled in 2005 and 2010 have recently revealed life, but at about one-tenth of the abundance usually found in freshwater lakes in moderate climate zones. Similarly in Lake Whillans the bacteria levels were roughly one-tenth the abundance of microbes in the oceans.

These results are glimpses into the the sub-glacial world of Antarctica. Glimpses that may change how we not only view this continent but also providing clues to how extra terrestrial life may exist on icy moons such as Jupiter’s Europa and Saturn’s Enceladus.

Cite this article:
Orrman-Rossiter K (2013-07-26 00:09:44). Lake Vostok: life beneath the ice. Australian Science. Retrieved: Apr 27, 2024, from http://australianscience.com.au/science-2/lake-vostok-life-beneath-the-ice/

test

The post Lake Vostok: life beneath the ice appeared first on Australian Science.

Lake Vostok and the search for extraterrestrial life

Sharon — Mon, 25 Mar 2013 00:17:53 +0000

When Russian geographer and Antarctic explorer Andrey Kapitsa travelled to Vostok Station in 1959 he was looking for evidence of a subglacial lake that was first proposed by Russian scientist Peter Kropotkin at the end of the 19th century. Whilst Kropotkin was not able to specify the location of subglacial lakes, he theorised that masses of fresh water could be trapped far below the Antarctic ice sheets. He believed that the massive pressure of thousands of meters of solid ice would mean that temperatures at the bottom of the ice sheet would be high enough to create isolated water lakes.

Lake Vostok (Image courtesy of the National Science Foundation)

During expeditions to the region around Vostok Station in 1959 and 1964 Kapitsa took numerous seismic readings of the thickness of the Antarctic ice sheet. When Kapitsa analysed his measurements he was able to confirm that he had found a subglacial lake – just as Kropotkin predicted.

It wasn’t until the 1970s that further tests were conducted on Lake Vostok. British scientists performed numerous tests including airborne ice-penetrating radar surveys over the site. Results confirmed the presence of a liquid, freshwater lake far below the icy surface. In the 1980s and 1990s subsequent studies confirmed the details of the lake and revealed that it was the largest of 140 known Antarctic subglacial lakes (about 400 subglacial lakes exist worldwide). Measurements showed that the lake was more than 250km long, 50 km wide, about 400m deep, and was submerged more than 4km under the surface. In 2005 it was discovered that Lake Vostok had a number of islands, and that it’s likely that Lake Vostok is connected to other Antarctic subglacial lakes by a series of subglacial rivers. Unfortunately, scientists are still unsure how water might travel between the lakes, however it appears that the water in Lake Vostok may have been trapped under the ice for 15 – 25 million years. Lake Vostok is interesting to astronomers and astrobiologists, who theorise that if life exists somewhere in the cold murky depths of the lake, then perhaps it could also survive in the cold icy moons of our outer solar system.

Since 1989 there have been various efforts to drill down into the lake to obtain samples to test for microbes. However, drilling Lake Vostok has proven to be a very difficult exercise due to the remote location, freezing temperatures (the coldest recorded temperatures on Earth were recorded at Lake Vostok at -89 degrees Celsius), and long dark winters that reduce drilling times. Samples were taken from an ice core that reached within 100m of the lake in 1998, 2011 and 2012 but these results were inconclusive.

Black Smoker Hydrothermal Vent (Image Courtesy University of Victoria)

Recently researchers announced that they had penetrated the ‘surface’ of Lake Vostok and had analysed samples taken from the drill head in the borehole. Results indicated a type of bacteria that was ‘unknown’ – a result that initially excited scientists. However, the next day, it was announced that the bacteria in the sample was found to use kerosene as an energy source. This was problematic for the team, as they use significant amounts of kerosene and freon at the site to stabilise the borehole (54 tonnes over the last few years). This result pointed to a likely contamination of the sample. Researchers advised they would be conducting further tests in order to collect ‘clean’ samples.

So – why are we so interested in Lake Vostok?

Until the mid 1980s we had a very narrow idea of where life could survive on our planet. We essentially applied the ‘Goldilocks’ theory; in order to foster ‘life’ the environment had to be not too hot, not too cold, must have water, sunlight etc… In the 1980s and 1990s, scientists discovered that microbial life has an amazing ability to survive in what we would consider extreme environments, niches that are blisteringly hot, dry, acidic, or even extremely cold. The discovery of these microbes, known as extremophiles has shown us that the boundaries of where life can exist, and even thrive are far wider than previously imagined. The image above shows a ‘black smoker’ hydrothermal vent – deep in the ocean spewing out water anywhere from 60 – 400 degrees Celsius. Typically these objects are surrounded by life forms, including Thermophiles, microbes that thrive in extremely hot temperatures. Until these deep sea hydrothermal vents were discovered in the early 1980’s we had no idea that life could survive, let alone thrive in such an inhospitable environment without sunlight and under such enormous pressure. The Grand Prismatic Spring in Yellowstone National Park in the U.S. is also home to various types of thermophiles, which thrive in the Grand Prismatic hot spring, despite it’s average 70 degree Celsius temperature.

Grand Prismatic Spring – Yellowstone National Park (Image courtesy of Wikimedia)

By looking at sites such as Lake Vostok we hope that we will discover something that will confirm our understanding of the boundaries for life or perhaps give us new information! We hope to find a new type of bacteria, similar perhaps to the psychrophile, or cryophile, extremophiles that can grow and reproduce in temperatures as low as -15 degrees Celsius. These organisms are currently found on Earth in small pockets of briny water surrounded by sea ice, alpine and arctic soils, deep ocean waters, glaciers and snowfields.

Although the Russians have been working on Lake Vostok for some time, they aren’t the only ones taking a good look at sub glacial lakes. Researchers from Britain and the U.S. are also working on Antarctic sites. The Americans have drilled more than 800m to reach Lake Whillans, whilst British researchers have stalled testing on Lake Ellsworth while they test new hot-water drilling methods.

If we find microbes surviving in the waters of Lake Vostok, or another subglacial lake that has been subject to enormous pressure, freezing conditions, lack of sunlight – that suggests that life could exist on one of the icy moons of the solar system. With the knowledge gained from sites like Lake Vostok we can plan missions to the icy moons in search of life. Research has shown that subsurface oceans may exist on a number of solar system moons including Enceladus (Saturn), Titan (Saturn), Europa (Jupiter), and Triton (Neptune). Each of these moons may have an environment capable of harbouring life.

It just may not be life as we know it.

Enceladus and it’s ‘tiger stripes’ – an area near the south pole of the moon that may cover a sub surface ocean (Image courtesy of NASA)

test

The post Lake Vostok and the search for extraterrestrial life appeared first on Australian Science.