* Russian expedition says broke through to lake on Feb. 5
* Scientists suspect lake hides unknown life forms
* Say harsh environment holds clues to life on other planets
* Drilling into subglacial lakes raises contamination fears
By Alissa de Carbonnel
MOSCOW, Feb 13 (Reuters) - The race is on to discover life in the most remote and extreme environment known on Earth.
Russia has set the pace, piercing through Antarctica's icy crust to reach a freshwater lake to try to find ancient or new kinds of life that have adapted to the extremely cold, sunless climate and may shed light on the origins of evolution.
Scientists from the United States and Britain are close on Moscow's heels, sure that their technology will speed analysis of the depths, hidden away for tens of millions of years.
If life is found in the icy darkness, it will provide the best answer yet to whether life can exist on other planets like Mars, Jupiter's moon Europa or Saturn's satellite Enceladus.
"It's like the first flight to the Moon," said Valery Lukin, head of the Russian Antarctic mission, comparing the achievement to the U.S. space race victory over the Soviet Union in 1969.
After 20 years of stop-go drilling, Russia was the first to pierce through 3,769 metres (12,365 ft) of solid ice to Lake Vostok - the largest and most isolated of over 350 known subglacial lakes, untouched for some 15-25 million years.
But the drilling technology it used means Russian scientists will have to go back to collect frozen samples of the lake water for analysis in 2013.
That leaves the door open for U.S. or British scientists to steal the lead. Both teams will be equipped with microscopes, enabling them to analyse the freshwater samples each expedition will bring up from two other shallower subglacial lakes.
Both will also head to the bottom of the world in the next Antarctic summer from mid-October this year until February; the British team to lake Ellsworth, the Americans to lake Whillans.
"They have broken through the ice, opened a window to that world, so we can all more or less follow suit and now do some real science," said John Priscu, a scientist with the U.S. Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) mission.
"Most of the drill is on a vessel right now, so it's on its way," he said.
"The United States programme will have microscopes in the field ... We should know what is there as we sample it," said Priscu, who suspects an oasis of life may lurk under the featureless white, possibly teeming around thermal vents.
Unlike the U.S. and British programmes, Russia will have to take a sample of frozen water from the lake home for analysis.
A century after the first expeditions to the South Pole, the discovery of Antarctica's hidden network of subglacial lakes via satellite imagery in the late 1990s set off a new exploratory fervour among scientists the world over, who say the ice cap acts like a blanket trapping the Earth's geothermal heat.
Priscu and British mission scientists denied it was a race, saying they were exploring different Antarctic lakes.
But scientists say there is an undeniable draw to be at the cusp of such a discovery.
"We are scientific explorers," said Martin Siegert, head of the University of Edinburgh's School of Geosciences who is leading the British expedition. "Science is driven by competition, people want to be the first to do things."
Russia has dreamed of dipping a toe into the mysterious Lake Vostok - the world's third largest body of water - since discovering its Soviet-era Antarctic station sat above it.
"This is a great event," Russian Prime Minister Vladimir Putin said on Friday, congratulating the Lake Vostok expedition.
Presented with a cup of water from the melted borehole ice, Putin joked it was a drink fit for dinosaurs.
Despite the success, a bitterness lingers among Russian scientists that they were forced to suspend drilling for years over international criticism of their environmental standards.
To answer concerns that drilling fluid could pollute the pristine lake, the Russian team engineered new technology.
The Russian borehole, pumped full of kerosene and anti-freeze, hangs like a needle over the lake. But Russia says it used a smaller drill to punch through the last metres, then immediately withdrew it to allow the lake water to percolate up the borehole and freeze there, creating a frozen plug.
"I can say that absolutely nothing fell into the lake," said Nikolai Vasilyev, who led a team from the St Petersburg Mining University to operate the drilling.
Speaking by satellite phone from aboard the Russian icebreaker, the Akademik Fyodorov, Vasilyev said the last hours of drilling were particularly tense.
When the breakthrough came after years of work in one of the coldest spots on Earth, it was just hours before the last Feb. 6 flight out before the onset of Antarctica's winter - where the coldest temperature on Earth was recorded of minus 89.2 Celsius (minus 128.6 Fahrenheit).
"We finished at night and the plane was to fly the next day so it was very tense," Vasilyev said. "It is very, very difficult work. Every centimetre is a step towards something new and unknown."
By contrast, the U.S. and British missions will drill with hot water from melted glacier ice that is filtered and UV radiated, which they say is environmental safer.
"The other reason we use it is it's quick," Siegert said.
Where as Russia spent years mechanically chewing through thick ice crystals to reach Lake Vostok, Siegert says it will take his team three days to melt down to lake Ellsworth.
The British expedition will then immediately deploy a probe into the lake to collect samples of the water columns and of the bottom sediment. It will have only 24-36 hours to run research before the drill hole freezes up again.
Lukin, however, said he has his doubts over the technology - concerns Russia may put to the U.S. and British missions at the next international panel of the Scientific Committee on Antarctic Research (SCAR) in June.
"Imagine the ancient water of Lake Ellsworth: It is absolutely untouched. Maybe there is life there and a pot of boiling water is poured in," Lukin said.
"Do we want to study micro-biodiversity or microbe soup?"
In the future, Russian researchers also plan to explore Lake Vostok with a submersible, he said.
The space exploration metaphors are not incidental. Studies of Antarctica's subglacial lakes also offer insights into the search for life beyond Earth, both in terms of technology, such as drilling and contamination controls, as well as how life evolves and what makes for habitable environments.
"Space is very much an integral part of the subglacial lake programme as a next step," said microbiologist David Pearce with the British Antarctic Survey.
Scientists say they suspect the Antarctic waters are supersaturated with oxygen and other gases and may be home to bacteria and single-celled microorganisms called archea.
They say that even if the dark waters under Antarctic prove barren, it will be a cutting-edge discovery: The only known sterile place on the planet.
"It is learning about the limits of the terrestrial biosphere," said astrobiologist Charles Cockell of the Open University.
"Ultimately who gets the samples really doesn't matter." (Additional reporting by Irene Klotz; Editing by Elizabeth Piper)