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.
A seven-time champion in Basel, Federer had thrown some doubt on how long he would play on after he beat his old nemesis Rafael Nadal of Spain in the Australian Open final. It was his first major title since Wimbledon in 2012.