AIDED by radio and seismic waves, scientists have discovered more than 70 lakes that lie buried under thousands of feet of ice in this glacial continent. Of these, the largest lake is a body of seemingly fresh water 140 miles long and 30 miles wide, located next to Russia's Vostok research base in East Antarctica. Though the existence of the subglacial Lake Vostok has been known for two decades, scientists gauged its large dimensions and its potential importance to science has come to light only recently. Scientists hope to find 'fossil' microbes, bacteria and viruses which have remained the same over as much as a million years. But they have yet to figure out how to study these organisms without polluting the lake. Last year, an international group of scientists meeting in London had stressed on the need to prepare an environmental impact assessment of the project. One of the ways could be to conduct experiments in a smaller lake.