The scientists had been battling conditions of extreme cold at Lake Vostok, as they raced to drill into a lake buried two miles beneath the ice before the weather closed in - which they hoped would reveal more about life on our planet 20 million years ago.

The lake is kept liquid by geothermal heat under the ice. It's thought to be similar to subterranean lakes on Jupiter's moon Europa. Their radio silence has conjured chilling echoes of classic horror film The Thing, where scientists dig up a buried spacecraft in the Antarctic ice, only to unleash an extraterrestrial horror within.

Valery Lukin, chief of the Russian Antactic Expedition, said last month: 'We do not know what is waiting for us down there.'

The lake is thought to be similar to subterranean lakes on Jupiter's moon Europa and Saturn's moon Enceladus. It's unlike any other place on Earth - kept liquid by geothermal heat inside a mile-thick cocoon of ice.

The water inside will have had no contact with man-made pollutants or Earthly life forms for millions of years. Twenty million years ago, the dinosaurs had already been wiped out, but life on Earth looked very different to what it does now - human beings and chimpanzees still shared a common ancestor when the water was sealed inside the lake.