By Dr David Whitehouse
Science editor, BBC News website
Russian scientists have said they will resume drilling into Lake Vostok in the Antarctic, to within 100m of the waters that sit below its ice-cap.
Vostok base was the site for the coldest recorded temperature on Earth (-89C)
Lake Vostok's waters may hold many new species as it is an ecosystem that has been sealed-off from the outside world for millions of years.
Scientists had previously drilled into the ice above the lake but had stopped well short of the water-ice interface.
Some have expressed concern that the new drilling may contaminate the lake.
According to Valeri Lukin, chief of the forthcoming Russian Antarctic Expedition, Russia is going to continue deep drilling to sub-glacial Lake Vostok.
"We got the permit only in the middle of last January, when the season was drawing to the end. This year, we've overhauled the drilling equipment and inspected the well. Now, it is fully ready for drilling operations to go on.
LAKE VOSTOK - ANTARCTICA
There are more than 70 sub-glacial lakes in Antarctica; Vostok is the biggest
At 10,000 sq km, it's about the extent of Lake Ontario, but twice as deep (500m in places).
Its waters have been hermetically sealed from air and light for perhaps 35 million years
Overlying ice layers reveal a 400,000-year environmental record with microbes present throughout the core
Many scientists consider Vostok to be a good model for the ecosystems that might exist on Jupiter's frozen moons
"We'll resume them during the 2005-2006 season under the programme of our expedition, and plan to work another 50m," Lukin said.
This will take the base of the well to within 100m of the water interface.
He added that current efforts to investigate the lake had revealed an island located in the central part of the lake.
Lukin said that the ultimate goal was to reach the water under the ice, which he believes will be done during the 2007-8 season.
"We hope it will happen in 2007," he remarked. "The lake's main mystery is that we'll for the first time extract what existed according to the entirely different laws of evolution several million years ago without contact with the present-day atmosphere," he added.
Deep ice drilling above the relic lake was suspended in the late 1990s when the well leading towards the unique sub-glacial water body reached 3,623m. Only 130m remains to go.
Lukin said that Russian specialists had created equipment capable of penetrating the lake without infecting it with modern microbes.
Many scientists believe that deepening the Russian drill hole by 50m will pose little risk of contaminating the lake as there will be a 100m buffer zone above the water.
But some researchers have expressed concern to the BBC News website about the cleanliness of using a hole that was drilled for purposes other than entering the lake.
Other scientists have told us that the Russian plans, although true to the letter of the Antarctic Treaty, demonstrate its weakness.
The Russians require no ratification of their plans to drill into Lake Vostok and are only obliged to file an Initial Environmental Evaluation (which they have done) followed by a Comprehensive Environmental Evaluation, which is pending.
When this is delivered, international scientists say they will express their reservations to their Russian colleagues.