By Dr David Whitehouse BBC News Online science editor

Scientists from the US, France and Russia have finally agreed to share equally samples of an ice core drilled from the ice sheet covering Lake Vostok, which is sited deep in the Antarctic interior.

There is huge excitement about the sub-glacial lake because it may have been isolated from the outside world for 2-10 million years and could contain lifeforms never before documented by researchers.

Glaciologists, geochemists and biologists will now be able to scrutinise an 11.7-metre (38.5-foot) segment from the bottom of the core - the part of the ice sample believed to be frozen water from the lake itself and not from the overlying ice sheet.

If scientists do eventually find activity in the lake it will help them better understand where to look for extreme lifeforms elsewhere in our Solar System.

Valuable insights

The ice core was drilled in 1998, to learn more about the subglacial lake known to exist under the ice at Russia's Vostok Station, high on the polar plateau.

A Russian station sits high above the subglacial lake

Researchers believe the lake has been cut off from the biosphere for many millions of years. And because of this, they are keen to see in which direction evolution has taken any life there might be in the cold, dark water.

The ice samples were drilled at Vostok Station under the terms of a US, French and Russian scientific collaboration. The drill stopped about 100 metres (330 feet) above the water to avoid contamination of the lake.

The ice core has already revealed fascinating information about the past 420,000 years of the Earth's climate.

But there was disagreement about who would analyse the so-called basal ice - the ice at the lower end of the core that is probably frozen lake water.

Future discussions

The samples governed by the agreement were left at Vostok Station until the 2001-2002 austral summer, when arrangements were made to bring out some of the remaining ice from a storage trench.

Now that researchers have agreed on the way the ice samples should be studied, they will be able to address major questions such as:

• How is the ice formed and what is its age?
• What does the geochemistry of the ice reveal about the lake and its origin?
• What kinds of organisms are present in the lake and how did they get there?

Scientists from the US, France, and Russia will continue to examine the ice after a review of research proposals submitted to the nations' Antarctic programmes.

Plans for a future subglacial lake exploration and research are scheduled for discussion at an upcoming meeting in Shanghai, China in July.

Eventually, scientists may go into the lake with a probe, but they need to find the technology that will allow them to do this without contaminating any unique ecosystem that may exist there.

The American space agency (Nasa) is known to be very interested in the Vostok project because it could say something about how extreme lifeforms might exist on other planets or moons in our Solar System.