But when the question of how to explore the lake came up, not long after its discovery, the Vostok scientists faced a serious dilemma. The lake is under immense pressure, and to breach the ice would have devastating consequences.
Roger Federer: Swiss star will play on until at least 2019. Updated 1815 GMT (0215 HKT) February 21, 2017. Chat with us in Facebook Messenger. Find out what's happening in the world as it unfolds.
Roger Federer and Novak Djokovic are still on course for an epic meeting in the men's final at Wimbledon. Both pulled off straight-sets quarterfinal victories on Wednesday, and if the two men can survive the semifinal round, they will meet on Centre Court for the championship on Sunday.