On February 5th, 2012, the Russian team has finally managed to penetrate through almost 4000 m (3,768 m) of Antarctica’s ice and reached the surface of Lake Vostok.
The Russian science team, despite cold and limited money for scientific research, has been drilling down toward Lake Vostok for ~ 20 years now.
What is in the water there?
The lake is believed to be the largest of ~ 140 sub-glacial Antarctica’s lakes (250 km long and 50 km wide). Its overlying ice sheet provides a continuous climate record of the past 400,000 years, while its under-ice water might have been isolated from outside world for 15-25 million years.
The idea of sub-glacial lakes was first proposed by Russian scientist (however largely known as anarchist and revolutionary) Pyotr Kropotkin. He proposed that the pressure exerted by the huge mass of Antarctic ice could be enough to raise the temperature at the bottom of the ice sheet to the melting point. This theory was later developed by another Russian scientist I. A. Zotikov. It was later confirmed that is also warmed by geothermal energy.
In 1964, Andrey Kapitsa after several years of seismic soundings research, suggested the existence of a sub-glacial lake in the region where soviet Antarctic station Vostok were located. That is how it gets its name.
In 1996, two teams of Russian and British scientists performed a combined research to define the lake shape and surface by combining a variety of data, including airborne ice-penetrating radar imaging observations and space-based radar altimetry.
Why this lake is so interesting?
There are several reasons why scientists are so much interested in probing the lake Vostok.
- It is one of rare places which are still unexplored on Earth.
- The lake Vostok presents the most extreme environment, as well as is the scientific work which is done there.
- The 4km thick ice sheet that covers the lake has been accumulated and lay undisturbed for at least 420, 000 years. By examining this ice, we can reach for a unique and incessant climate record ever existed on Earth.
- Scientists hope that studies of Lake Vostok and other sub-glacial lakes will advance knowledge of Earth’s own climate and help predict its changes.
- Its under-ice water might have been isolated from outside world for 15-25 million years. After discovery of extremophily in 1980-1990, there is a possibility that a unique microbial life may be possible in the lake despite its harsh conditions (e.g. high pressure, cold, low nutrient input, high oxygen concentration and an absence of sunlight).
- Microbiologists believe that the lake could offer a hint for unique life forms.
- If life in Lake Vostok would be found and confirmed, we could hope for finding life on icy moons of Jupiter and Saturn (Europa and Enceladus).
- The drilling technology developed and mastered on Lake Vostok can be later used for drilling on icy moons Europa and Enceladus.
- It is believed that the search for evidence of life in samples from Lake Vostok has similar technical challenges and similar analytical procedures to those involved in the exploration of a sub-glacial ocean on Jupiter’s moon Europa.
Vostok Station is one of the coldest place on Earth (the temperature of -89 C was recorded in 1983). The current temperature, is about 40 C below zero; it is a late summer there and the Antarctic season is about to close. The drilling is slow, an average 50 m per season. In 2010, the expedition stopped somewhere 10- 50 meters short of the lake surface due to inclement weather and the scientists were forced to abandon the expedition. The contamination of the lake water due to drilling is another big problem.
Deep ice core drilling at Lake Vostok (where the Vostok station located) began in 1970s, when a set of open holes were drilled using a thermal drill system suspended on cable. The deepest one reached 952.4 m in May 1972. Because temperatures on the Vostok Station are the coldest ever recorded on Earth (reaching -89C), the major problem was that the hole made by thermal drill get frozen very fast and then closed by new formed ice. Therefore, a new technique was introduces for drilling at greater depths. To prevent freezing and closing the hole, the borehole was filled with a eco-neutral fluid to prevent bacterial and other contamination.
The possibility of contamination of the lake is the major problem. Besides obvious ecological damage (if microbial life exists in Lake Vostok after such a long isolation it requires strict protection), contamination, if happens, will also bias scientific results. Sediments on the lake’s floor could provide clues to its long-term climate change, while isotopes in its water could help in determining how sub-glacial lakes form.
The drilling technique used by the Russian team include 3 stages
1. An ecologically inert liquid (e.g., polydimethylsiloxane) was injected to the Hole #5G-2 bottom using a special tanker.
2. The hole is deepened down to the ice-water boundary. The access to the lake was completed using the coreless thermal drill system. The drill was cleaned by the produced melt water. This water created a second clean layer separating the bottom of the hole from the drilling fluid. There is 3-4 bars pressure difference between lake water and the hole. Therefore once the tip of the thin pilot drill made contact with the lake surface at 3.769 m it was turned down and pulled up. This will allowed lake water to enter into the hole and to fill up its lower 30–40 meters, pushing drilling fluid up and away from the untouched lake water and thus preventing possible contamination.
3. The third stage could be conducted the next Antarctic season, after checking the frozen sample in the hole.
Possibilities of life
Lake Vostok environment comprises high pressure, low carbon and chemical content, at least 15 million of years isolation, complete darkness and the probable excess of oxygen in water. This doesn’t look like a habitable environment at all. However, after discovering of extremophillies with their ability to live under almost any conditions, there is an optimistic hope that microbial life in the lake may be possible no matter what.
According to Bulat et al (2010) accretion ice was found free of microbial DNA. The only positive results, which passed both the artifacts and contaminant controls criteria checks, include thermophile Hydrogenophilus thermoluteolus. This was first found in accretion ice from 3607 m depth and was confirmed later by examining another ice sample from 3561 m depth.
Because lake water temperature is below freezing point (-2 C, due to pressure), the only niche for thermophiles should be within the deep faults of the bedrock encircling the lake. Combined with geochemical and geophysical considerations, these results nevertheless suggest the presence of a deep biosphere, possibly flourishing nearby active faults of the bedrock, where the temperature could reach up to 50C and in situ hydrogen is probably present.
However, these results highlight another (no less important) problem of searching for life samples with very low levels of microbial biomass. Such samples often show high probability of forward-contamination which results in false positives. Therefore, a special set of indexing contaminant criteria were developed by Bulat et al., (2004) for DNA studies allowing recognition of majority of the findings as possible contaminants. The framework is shown below:
I think that developing of these techniques is as important as finding life in water of Lake Vostok. This is especially important for future search for life in sub-glacial oceans of Europa and Titan.
In the 2012–13 season, the Russian team plans 1) to gather water sample from the drill and 2) to send an underwater robot into the lake to collect more water samples and sediments from the bottom. If this happens, that robot would be a predecessor for more ambitions cryorobot proposed for exploration of Jupiter’s moon Europa. The cryorobot for Europa suppose to melt through the ice until it reached the moon’s ocean. Once it reached the water (or if it reaches the water), it would deploy an autonomous underwater hydrorobot which would gather information and send it back to Earth.
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