Russian researchers are drilling down through the ice towards Lake Vostok as they seek to unlock the secrets of what some say is the last great unexplored frontier on earth.
The lake under the Antarctic ice is important because it is so pristine, but all that could be lost forever if the tiniest particle of outside matter is allowed in when the Russian drill pokes through into the water.
Many experts say ultra-clean technology to pierce through to the lake without contamination is not ready.
Russian scientists have drilled down to within about 130 metres of the lake and - defying misgivings from their peers in other countries - say they will break through by 2008.
Valery Lukin, head of the Russian Antarctic Expedition, said: "The drilling will continue.
"We are not violating any rules. If our activities don't suit people, what can I say?
"It's like this: Who was the first to fly to the moon? The Soviet Union or the United States? That time the Americans won and we halted our lunar programme," he said.
"This time we are going to be first"
Russian Antarctic Expedition
"Now this time we are going to be first. So what? We just got luckier, that's all ... It's all been turned into politics. Some people don't like (what we are doing) because it is not them doing it."
Russian scientists finished their latest stint of drilling this year, rushing to beat the onset of the Antarctic winter in a spot where the coldest temperature ever - minus 89.2 Celsius - was recorded.
They bored 27 metres deeper towards the lake and plan to start again in December.
Oldest frozen lake
Antarctica has more than 70 sub-glacial lakes.
They exist because the pressure of the ice above keeps the water from freezing. Lake Vostok, at 15 million to 20 million years old, is thought to be the oldest.
Exploring the lake will be like taking a journey back through time to discover what life looked like before man appeared on Earth, say scientists.
Antarctica has more than 70
Cynan Ellis-Evans of the British Antarctic Survey said, "Things like antibiotics that we have come up with, all the pollutants ... that are man-made, none of those have ever been seen by this lake."
With so much at stake, the Russians are moving too fast, said Ellis-Evans.
"We are desperately worried ... that they are planning to go at (this lake) with a system which they haven't satisfied everybody is appropriate," he said.
"If something goes wrong .... we could be left with a situation which may not be easily retrievable."
Vostok has an added fascination for scientists because conditions there - cold, with no light or air - mirror those on Europa, one of Jupiter's moons where space probes have found evidence of an ocean below the frozen surface.
If living organisms are found in the lake, it could strengthen the argument for the presence of life beyond our planet.
The lake conditions could mirror
those on one of Jupiter's moons
Lake Vostok is a prestige project for Russia.
Russia's Antarctic research station is a few hundred metres from the bore hole and gave its name to the lake when its existence was established in 1996.
Russia, in agreement with other countries involved in Antarctic research, suspended drilling in 1998 while a safe technique for breaching the ice was sought.
Since then, Russia has restarted drilling, saying it believed it had come up with the right technique.
"There can be no negative effect (or) contamination of the lake," said Lukin. "I base this certainty on the laws of physics and practical experience (of the use of similar techniques elsewhere)."
Under the 1961 Antarctic Treaty, all nations are free to carry out civilian, non-nuclear research on the continent as long as they share their plans and their findings with other countries - something Russia has done throughout.
Ellis-Evans said he would be delighted if the Russians became the first to reach Lake Vostok.
His main concern, he said, is that it is done without damaging the thing that makes the lake so fascinating for scientists.
"(This is) arguably one of the most pristine environments on Earth, so how can we possibly think of just clumsily going in there and potentially contaminating it?" he said.
"We are ... worried that everybody is going to lose out."