news feature Life in the deep freeze Unknown ecosystems and untapped records of the Earth’s past may lie hidden in the lonely waters of Antarctica’s Lake Vostok. But the lake’s millions of years of isolation may be about to end, as Helen Hidden depths: Lake Vostok (ringed) has Gavaghan reveals. lain undisturbed below the ice sheets of Antarctica for millions of years. ad the biologists not intervened, a Curiosity about the lake and others in the as a test run,but it is Vostok that is getting the unique source of data might have area has grown since then, and ambitious lion’s share of the attention. The lake has NASA Hbeen damaged for ever. Drilling plans to explore the area will soon be finalized. been mapped in far more detail than the innocently through the ice sheets that cover But although the case for halting the drilling others, and no larger body of subglacial Antarctica, a team of climate researchers at was clear,deciding what to do next has proved water has yet been found in the region. first had no idea that they were also heading to be far more complex.Antarctic exploration Formed in a geographical basin similar to towards a valuable biological resource: a is expensive,and for a project on this scale,the a rift valley, Lake Vostok is at least 240 km huge subglacial lake languishing in near- needs of researchers from the different disci- long by 50 km wide.The latest depth analysis isolation some 4,000 metres below the ice. plines and countries involved have to be by Russian scientists,carried out by studying The drilling started in 1989, when scien- balanced. Even if funds can be raised and how the ice, water and lake floor reflect tists based at the Russian Antarctic research a consensus reached, the technological chal- sound and radio waves, reveals a body of station of Vostok launched a project to lenges of entering an almost pristine eco- water that is up to 1,200 metres deep, and a obtain information on the Earth’s climate system without polluting it are considerable. lake bottom that is covered by sediments history from Antarctic ice crystals. But as which can reach hundreds of metres in thick- evidence for the existence of the lake, now Breaking the ice ness3.Although the temperature of the lake is dubbed Lake Vostok, accumulated in the The job of overcoming these obstacles rests early 1990s, serious questions were raised with an international, multidisciplinary team Vostok Station about how deep the borehole should be. that is designing a strategy for exploring To biologists, Lake Vostok offered poten- Vostok and other subglacial lakes in the east tially rich pickings.If it has remained isolated Antarctic. The group met for the first time in since the Antarctic ice sheet formed,perhaps Bologna, Italy, last November, where it out- as much as 20 million years ago, novel eco- lined a plan to access Lake Vostok at two Ice sheet 1 systems may have developed in its waters. places in three to six years’ time . Sediment Borehole Sediment on the lake’s floor could tell the would be recovered around three years later. history of that life, and of the ice sheet above Refined plans will be released at a meeting in Frozen it. But much of the biological value would Shanghai in July, and about 10 nations are lake have been lost if unsterilized drilling equip- expected to participate in the project. Lake water ment had contaminated the lake’s waters. Drilling through to Vostok remains “the Vostok In 1995, biologists Cynan Ellis-Evans and jewel in the crown”,says John Priscu,an ecol- David Wynn-Williams of the British Antarc- ogist at Montana State University in Boze- tic Survey in Cambridge attended a meeting man, who chairs the exploration group. But at the nearby Scott Polar Research Institute, the group’s remit extends to all the subglacial where researchers were discussing the lakes in the region, 86 of which have now Bedrock drilling project. “We spent two days edu- been identified2, although other large lakes cating them about the potential biology of may still await discovery. At the Bologna the lake,”recalls Ellis-Evans.At the end of the meeting, Ignazio Tabacco, a geophysicist Sediments meeting, the group reached a consensus that from the University of Milan, presented FROM:ADAPTED M. STUDINGER/R. E. OBSERVATORY EARTH BELL/LAMONT-DOHERTY the drilling should stop before it reached the evidence which suggested that some of the The borehole beneath Vostok station extends lake.It was duly halted in 1998,with the bore- other known lakes may be linked together. into areas of frozen lake water. hole some 120 metres from the lake’s surface. The group might decide to enter one of these 828 © 2002 Macmillan Magazines Ltd | wwwNATURE | VOL 415 | 21 FEBRUARY 2002 | www.nature.com news feature about 13 7C, it is prevented from freezing because of the extreme pressure generated by the weight of the ice sheet. J. C. PRISCU For Priscu and his fellow biologists, the lake’s allure is its environment: total darkness, low nutrient levels, a pressure of 380 atmos- pheres and almost complete isolation from the atmosphere for millions of years. Life has been found in other harsh habitats, such as under Alpine glaciers and in geothermal springs. Biologists studying such areas always find something new, says Ellis-Evans. He cites the example of the enzyme Taq DNA poly- merase, which was discovered in microbes living in the hot springs of Yellowstone Signs of life: ice cores from deep within a National Park. Unlike most other enzymes, borehole in Antarctica have yielded bacteria Taq DNA polymerase is stable at temperatures (right) which may have come from Lake Vostok. of around 70 7C. It now forms an important part of the polymerase chain reaction used to ed Alpine lake,by comparison,might contain amplify DNA sequences in the laboratory. tens of millions of microbes per millilitre. Priscu cautions against relying too heavi- Life under a glacier ly on the ice samples, pointing out that Already, there are hints that life may exist in microbes in the ice from the surface of the erals and oxygen that have sunk through this Lake Vostok. The borehole that nearly lake may not be typical of life elsewhere in the glacier could be entering at the north of the reached the lake in 1998 was drilled to lake,or in the sediment.It is also possible that lake. At the same time, friction between the extract ice that originally fell as snow microbes may have been transferred to the water and sediment on the lake floor could hundreds of thousands of years ago. But as ice from the drilling equipment, an effect release further nutrients into the water. the hole passed around 3,500 metres in that researchers try to minimize by working But any life that is present will still need depth, researchers noticed changes, such as with samples from the centre of the ice core. an energy source to make use of these nutri- the appearance of large ice crystals, in the But Bulat has studied the microbes found in ents.With no light reaching the lake,the only ice they were recovering. Analysis of these the kerosene fluid used by the drill to deliver source would appear to be the energy samples suggested that they were frozen hydraulic power, and says that this fluid released by reactions involving the sulphides lake water. appears to be the source of at least some of and the organic matter that are entering the The samples contained no climate the life found in the core. lake. If so, the distribution of this matter by information, but they did provide biologists the circulation of water will have a big effect with the first extracts from the lake itself.Two Cold comfort on the lake’s ecosystem. Geothermal heating studies, published in 1999, revealed the The small amount of ice that biologists cur- is likely to play a role in the circulation, presence of life, including organisms related rently have to work with also hampers the although studies of the chemical composi- to modern-day Actinomycetes and a- and analysis. So a Russian proposal, made at the tion of the lake ice have ruled out the possi- b-proteobacteria4,5. Microbiologists have Bologna meeting, to drill another 50 metres bility of major hydrothermal activity on the already been surprised by the unusual into the existing bore is likely to find favour. lake’s floor7. Several models of the circula- metabolic quirks shown by some a-proteo- But other issues remain unresolved. The tion, based on the likely heating and the bacteria6 from other environments, which microbes may, for instance, be entering the density difference caused by the melting makes it likely that life in Lake Vostok will lake by sinking slowly through the ice sheet. glacier, have been proposed, but only entry offer some interesting twists. Starved of data from the water itself, into the lake will determine which is correct. Based on the sample analysis, researchers researchers are currently trying to work out How to reach the lake without contami- estimated that the lake would contain a how life may have survived in the lake. Nutri- nating it is another open question. Adapting hundred thousand to a million microbes per ents, for example, could be supplied by melt- technology used by the oil and gas industry in millilitre4. But Priscu and, independently, ing at the base of the glacier.Geologists believe the Arctic seems the most likely alternative.At Sergey Bulat of the Petersburg Nuclear that the bottom of the ice sheet is melting at the Bologna meeting, Erik Blake of Icefields Physics Institute,now say that levels may be as the north end of the lake and freezing at the Instruments in Yukon, Canada, described L low as a few hundred per millilitre.An isolat- south.If this is correct,organic material,min- how the drilling fluid is delivered through a J.