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.
Sunday's men's final sees world No. 2 Roger Federer, aged 33 like Williams, battle top-ranked Novak Djokovic in a repeat of the 2014 finale the Serb won in five sets. But the final Saturday at Wimbledon, just like the final weekends in New York, Melbourne and Paris in the last 11 months, belonged to Williams.