British scientists are making final preparations to drill 3km through the Antarctic ice to a lake that has been cut off from the rest of the world for up to half a million years.
The 12-man team hopes to find lifeforms in Lake Ellsworth that have evolved in isolation to withstand the cold, lack of nutrients and total darkness.
Early next week they will begin melting a 36-cm wide borehole through the ice using a unique hot-water drill.
Pumping 90,000 litres of water at high pressure through a continuous 3.5km hose should allow them to break through to the lake in three or four days.
Chris Hill of the British Antarctic Survey said the mood in the camp was good.
"We are just a few days away from starting the drilling. That will be the point of no return," he said.
"We are doing last minute checks, connecting all the pipes and electricity together, checking out all the systems we have been developing over the last three and a half years that have never been put into such extreme conditions before.
"So it's quite a tense time at the moment, but everything seems to be going very well."
Lake Ellsworth is roughly the same size of Lake Windermere in Cumbria. It is buried beneath the remote West Antarctic ice sheet, where daytime temperatures are minus 25 degrees Celsius and winds gust up to 100mph.
The team has hauled almost 100 tonnes of equipment 280km across the ice to reach the drill site.
The precious cargo includes special probes that will be used to collect water samples and punch out a three-metre long sediment core at the bottom of the lake.
The equipment has been designed from scratch and has been cleaned to space-industry standards to avoid contaminating the pristine water of the lake.
Scientists expect to find microbes in the sludge on the lake bed. They could have been cut off from the main line of evolution for millions of years and the researchers want to know how they survive, and whether they produce any unique chemical compounds.
Professor John Parnell, from the School of Geosciences at the University of Aberdeen, said: "Finding evidence of such compounds would show us that if life can withstand even the deepest, darkest and most isolated conditions for more than a million years, then it has the ability to exist anywhere - and by that I mean not just on Earth."
Scientists believe vast seas of liquid water exist below the icy surface of Europa, one of Jupiter's moons.
But the lake could also hold clues to the Earth's past climate.
Chris Hill said the sediment core acts as a time record and may show Antarctica was once far warmer.
"There is a strong body of evidence that the ice sheet has collapsed at some point in our history causing a significant sea level rise across the planet," he said.
"It is known to be unstable now and is likely to collapse at some point in the future. We just don't know when or what could cause it."
Scientists, engineers and other specialists from nine universities, the British Antarctic Survey and the National Oceanography Centre are part of The Lake Ellsworth Consortium.
The £7m mission is funded by the Natural Environment Research Council.
