Bacteria found in Antarctic ice core

By BBC News Online Science Editor Dr David Whitehouse

Bacteria have been found deep beneath the Antarctic ice sheet, just above the sub-glacial Lake Vostok.

The lake, which is buried nearly four kilometres under the ice, is one of the deepest-known bodies of fresh water on the planet and has excited researchers ever since its discovery using airborne radio-echo soundings and other techniques in 1974.

The lake's isolation from the rest of the biosphere has led many to speculate that it may contain lifeforms unknown to science. International research institutes, including the US space agency Nasa, are now considering the merits of drilling into the lake.

They will be encouraged by the discovery of bacteria in a core drilled 3,600 meters (11,700 feet) into the ice immediately above the lake. It will also strengthen the view of those who believe that any mission to the buried waters of Vostok would act as a first step to finding extreme lifeforms elsewhere in our Solar System.

Jupiter's moon Europa

"The subglacial lakes of East Antarctica may be among the most isolated ecosystems on Earth and could serve as terrestrial analogues to guide the design of samplers and experiments for life probe missions to the ice-covered ocean of the Jupiter's moon Europa," says Dr David Karl of the University of Hawaii.

Examining the ice core

Roughly the size of Lake Ontario, Lake Vostok is the largest and deepest of the 70 or so under-ice lakes in Antarctica. Its fresh water is kept liquid by the pressure of the overlying ice and, perhaps, by geothermal heating from below.

The core being studied by US, French and Russian scientists was drilled to within 120 meters (393 feet) of the point where the ice and liquid water meet and then halted to prevent any contamination of the lake.

The bacteria found in the core are commonly associated with soils and are related to microbes called proteobacteria and actinomycetes. They could have reached Antarctica on bits of soil that were blown by winds from the Patagonian desert in Argentina and then buried. If so, the microbes could be more than half a million years old.

Climate record

"This lake, and others like it, may contain previously undescribed relic populations of microorganisms that are adapted for life in these presumably oligotrophic (low-nutrient, low-biomass and low-energy flux) habitats," says Karl.

Scientists at Montana State University have found bacteria within "accreted" ice, which is believed to have refrozen from the lake's waters, suggesting that Vostok can support life. Although the bacteria are similar to other known bacteria, the scientists wonder whether the lake may contain larger, more diverse populations.

In addition, the Antarctic ice cores provide a continuous climate record stretching back more than 400,000 years. Obtaining sediment samples from the bottom of Lake Vostok could extend the climate record to cover millions of years.

"From a biologist's perspective, this is the Holy Grail of lake biology," Dr John Priscu of Montana State University said before leaving for another field season on the frozen continent. "Our findings indicate that the microbial world has few limits on our planet."

Dr David Mogk added "I think the message is really, 'Life is where you find it'. If you find it under nearly 4,000 meters of ice, I mean, that's pretty staggering."