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AGAINST all odds, living organisms should be able to survive deep beneath the Antarctic ice, a physicist in California has predicted. He thinks that bacteria can survive in thin veins of water that form between ice crystals, despite the darkness, crushing pressure and temperatures well below freezing.

Traces of bacteria have been found in ice cores from above Lake Vostok, a glacier-covered crescent of water near the South Pole-but these were assumed to be dead organisms that had been trapped in the ice. Then researchers from the University of Hawaii managed to revive some bacteria after thawing the cores, suggesting that the microbes may merely have been dormant, according to John Priscu of Montana State University in Bozeman, who helped find the bugs (New Scientist, 4 December 1999, p 34). 鈥淥ur thought was that these microbes were in a state of suspended animation,鈥� he says.

Now Buford Price, a physicist at the University of California at Berkeley, has calculated that Vostok may contain small amounts of liquid in which bacteria can live, rather than having to exist in a dormant state. Dissolved ions such as sulphate, sodium and chloride concentrate between ice crystals and lower the local freezing point, just as salt does on an icy road, he says.

Based on measurements of ions in the Vostok ice cores, Price calculates that a network of veins roughly the diameter of a human hair permeates the ice 3500 metres down or more (see Diagram).

Price says water veins deep down should contain enough nutrients in the form of dissolved organic molecules for dozens of bacteria to live in each millilitre of liquid. In the colder ice nearer the surface, roughly one microorganism per millilitre could survive. 鈥淭here are barely enough nutrients,鈥� he says, 鈥渂ut not zero nutrients, and that鈥檚 the exciting thing.鈥�

To test whether Vostok bacteria can function in the ice, Price proposes scanning frozen ice core samples for the energy-carrying molecule NADH, which fluoresces in light of certain wavelengths. NADH breaks down fast in dead cells, so its presence would indicate that metabolism is taking place. 鈥淚鈥檇 like to be the first one to get a core sample from very deep in Vostok,鈥� Price says.