It sometimes seems as if our planet has no secrets left - but deep beneath the great Antarctic ice sheet scientists have made an astonishing discovery. They've found one of the largest lakes in the world. It's very existence defies belief. Scientists are desperate to get into the lake because its extreme environment may be home to unique flora and fauna, never seen before, and NASA are excited by what it could teach us about extraterrestrial life. But 4 kilometers of ice stand between the lake and the surface, and breaking this seal without contaminating the most pristine body of water on the planet is possibly one of the greatest challenges science faces in the 21st century.
In 1957 the Russians established a remote base in Antarctica - the Vostok station. It soon became a byword for hardship - dependent on an epic annual 1000 km tractor journey from the coast for its supplies. The coldest temperature ever found on Earth (-89°C) was recorded here on the 21st July 1983. It's an unlikely setting for a lake of liquid water. But in the 1970’s a British team used airborne radar to see beneath the ice, mapping the mountainous land buried by the Antarctic ice sheet. Flying near the Vostok base their radar trace suddenly went flat. They guessed that the flat trace could only be from water. It was the first evidence that the ice could be hiding a great secret.
But 20 years passed before their suspicions were confirmed, when satellites finally revealed that there was an enormous lake under the Vostok base. It is one of the largest lakes in the world - at 10,000 square km it's about the extent of Lake Ontario, but about twice as deep (500m in places). The theory was that it could only exist because the ice acts like a giant insulating blanket, trapping enough of the Earth’s heat to melt the very bottom of the ice sheet.
Biologists believe that because the lake has been cut off from the rest of the planet for 15 million years or more - well before the human race evolved - microbial life in the lake could have quietly been evolving into strange and unique forms. It's a uniquely hostile environment for life - permanently low temperatures, hundreds of atmospheres of pressure, and no light for photosynthesis. In fact, as NASA have realized, the conditions directly replicate those found on Europa - the icy moon of Jupiter. So finding microbial life in Lake Vostok has a greater significance, but what are the odds of finding life in a cold, dark world?
A discovery in Romania sheds new light on how life might survive in Lake Vostok. Shafts sunk into limestone by the Black Sea resort of Moville penetrated a previously unknown cave. Until that point it had been completely cut off from the surface - so just like Lake Vostok its an isolated world, with no light for photosynthesis. Scientists were surprised to find life not only existing, but thriving and found 33 species entirely new to science in the Romanian cave. The secret of the cave's ecosystem was microbes that had adapted to live on chemicals found in the cave's pools. Instead of using light to photosynthesize, these microbes used hydrogen sulphide in the water as their energy source - a process known as chemosynthesis. Now new research by geologists suggests that hot springs could be present in Lake Vostok, dramatically increasing the chances that it could be home to exciting new forms of bacterial life. But how to get into the lake?
At the Vostok base itself scientists have been drilling down into the ice beneath the base for more than 10 years. The ice core they've extracted contains information on the Earth's climate over the last half million years. When the lake was discovered they realized they were close to penetrating the ice above it, and gaining the first access ever to its pristine waters. But there was a problem… The drilling operation involved 50 tonnes of kerosene, used to keep the drill hole open. If the drill went into the lake, the purest body of water on the planet would have had its first oil slick. So the drilling was stopped 120m from the surface of the lake.
However, there is another type of contamination, in a way more threatening than kerosene pollution, and that is the introduction of bacteria from the surface. At the moment, science is struggling to devise a high-tech robot probe that will be sent down 4 km of ice, into the lake to search for signs of life. The challenge is to create a probe that will produce zero contamination.
But now scientists have realized that they already have what they want, right in their very hands. The last few metres of the ice core drilled out on the the way down to lake Vostok, is actually lake water that has frozen onto the bottom of the ice sheet. The question is does this frozen chunk of Lake Vostok's water contain life, and if so, how can it be proved that this is life from the lake, and not contamination from the world above.
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