Kamis, 20 Oktober 2011

Unknown Life in Antarctic Lake

As biting winds cut through the below-freezing air around them, a team of researchers will next year seek to discover previously-unknown life by exploring an Antarctic lake that redefines the notion of "remote."

Lake Ellsworth is roughly 10 km (6.2 miles) long and is estimated to be several tens of meters deep. The reason Its depth can only be estimated is that, although it has been mapped by radar, Lake Ellsworth has never been seen by human eyes.

It lies beneath 3 km (1.86 miles) of ice, one of 387 so-called subglacial lakes in the Antarctic continent, its liquid state maintained by geothermal heat from below Earth's crust. It has been isolated from the rest of the world for perhaps a half million years, but now a British expedition is on its way to Antarctica to bring a temporary halt to the lake's isolation and, in the process, yield information about past life on Earth, possible life on future planets, and our own planet's climate, past and present.

The expedition, a collaboration between the British Antarctic Survey (BAS), the United Kingdom's National Oceanography Center and a number of British universities, will use a hot water drill to break down through the ice to the lake. A titanium probe will be lowered to take samples of water, and a corer will extract up to three metres of sediment.

Time will be of the essence: the borehole will begin to freeze almost as soon as it is opened, and within 24 hours will have frozen completely shut.

The researchers hope that, inside the sediment, they will find previously undiscovered microbial life, nurtured by the geothermal warmth and possibly quite unlike any species presently known.

"Finding life in a lake that could have been isolated from the rest of the biosphere for up to half a million years will tell us so much about the potential origin of and constraints for life on Earth and may provide clues to the evolution of life on other extra-terrestrial environments," said David Pearce, science coordinator at BAS, at a press conference to announce the expedition.

"If we find nothing (it) will be even more significant because it will define limits at which life can no longer exist on the planet," he continued.

The researchers are also hoping to find clues about the planet's climatic past, and consequently its climatic future.

"There is some evidence from outside Antarctica that sea levels were higher at various times in the last million years -- 125,000 years ago, 380,000 years ago -- but we have no evidence that the water came from the West Antarctic Ice Sheet," Professor Mike Bentley of Durham University told the BBC.

"So one of the things we're looking for in our sediment core is... marine sediments that would look very different from lake sediments."

The age of those sediments will help cast light on how long the West Antarctic Ice Sheet was able to remain stable during warmer times in the past, a matter of import as scientists seek to predict the likelihood of its collapsing, and once again causing sea levels to rise, as a result of global warming.

"If we can find out if or when the ice sheet retreated or collapsed, it could tell us what kind of conditions would lead to a West Antarctic retreat in the future," said Bentley.
by "environment clean generations"

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