 aNDREI KaPITSa, who died on august 2 aged 80, was a Russian geographer who discovered Lake Vostok, one of the world's largest fresh water lakes.  Five hundred metres deep, with a surface area of 14,000 square kilometres (the size of Lake Ontario), the lake had gone undiscovered for so long because it lies some 4,000 metres below the ice cap of antarctica.  The largest of more than 140 subglacial lakes found under the surface of the continent, Lake Vostok is thought to have lain isolated and undisturbed for between 15 and 25 million years, raising the possibility that it may contain undreamed-of life forms that have evolved in a unique environment.  at the end of the 19th century the Russian scientist Peter Kropotkin had theorised that the tremendous pressure exerted by thousands of metres of antarctic ice could increase the temperature at the lowest levels of the ice sheet to the point where the ice would melt; and on the first of four visits to antarctica, in 1956, Kapitsa noticed that the area around the Soviet Vostok research base, high above the polar ice cap, was unnaturally flat.  He wondered, based on Kropotkin's theory, whether there might be a lake under the ice. He called the putative reservoir Lake Vostok and mentioned the possibility of its existence in his PhD thesis on the morphology of the Eastern antarctic ice cap, in 1957.  In 1964, and again in 1966, Kapitsa and his colleagues worked in teams taking seismic measurements to calculate the thickness of the ice. The first time he got a blur of "noise" which obscured waves reflected from the base of the ice. The second time, using seismometers buried in the ice, he got much better results, which led him to conclude that the ice was up to four kilometres deep.  None the less, some of the readings remained baffling, and when most of the data were destroyed in a fire in Moscow, Kapitsa forgot all about them.  It was only in the mid-1990s, when Kapitsa was invited by the Scott Polar Research Institute in Cambridge to join a symposium on antarctica that the significance of his readings became clear. British scientists had been studying airborne echosoundings of the Vostok area and were getting mystifying results. Kapitsa remembered his own bafflement and, on his return to Moscow, found that the seismometer readings that had caused him such problems had survived the fire.  "I looked at them and saw the mistake," he recalled. "When seismic waves go through water, longitudinal waves return and latitudinal waves do not. There were no latitudinal waves." Kapitsa's data proved the presence of water in the ice.  Together, the Scott Polar team and Kapitsa wrote a paper about Lake Vostok, published in Nature in 1996. The paper suggested the possibility that the lake might harbour life, and subsequently an international team of scientists from america, Russia, Britain and France began boring down through the layers of ice towards the lake.  So far, ice samples taken from above the lake have been found to contain bacteria and other microbes such as algae, diatoms and other micro-fungi, raising hopes that the lake itself could yield a biological treasure trove. But drilling for sample cores was halted in 1998, at roughly 100 metres above the suspected waters, due to the lack of a secure means of taking samples without risking contamination to the waters of the lake. a further consideration was that, if Lake Vostok harbours toxic bacterial life, humans would in all likelihood have no defences against it.  Last year, however, the scientists claimed to have come up with methods of probing the lake without the risk of contamination, and drilling has resumed.  andrei Petrovich Kapitsa was born on July 9 1931 in Cambridge, where his father, the Soviet Nobel Prizewinning physicist Pyotr Kapitsa, was working with Sir Ernest (later Lord) Rutherford at the Cavendish Laboratory. His mother, anna, the daughter of admiral aN Krylov, a celebrated Soviet mathematician and naval architect, had trained as an archaeologist.  Pyotr Kapitsa had been allowed to travel abroad relatively freely by the Soviet authorities; but in 1934, on one of his regular visits to Moscow, he was told that his permission to leave the country had been revoked. The rest of the family returned to Moscow the following year, and Pyotr Kapitsa was subsequ 