After 20 years of drilling, a team of Russian researchers is close to breaching the prehistoric Lake Vostok, which has been trapped deep beneath Antarctica for the last 14 million years. Vostok is the largest in a sub-glacial web of more than 200 lakes that are hidden 4 km beneath the ice. Some of the lakes formed when the continent was much warmer and still connected to Australia. The lakes are rich in oxygen (making them oligotrophic), with levels of the element some 50 times higher than what would be found in your typical freshwater lake. The high gas concentration is thought to be because of the enormous weight and pressure of the continental ice cap.

If life exists in Vostok, it will have to be an extremophile — a life form that has adapted to survive in extreme environments. The organism would have to withstand high pressure, constant cold, low nutrient input, high oxygen concentration and an absence of sunlight. The conditions in Lake Vostok are thought to be similar to the conditions on Jupiter’s moon Europa and Saturn’s tiny moon Enceladus. In June, NASA probe Cassini found the best evidence yet for a massive saltwater reservoir beneath the icy surface of Enceladus. This all means that finding life in the inhospitable depths of Vostok would strengthen the case for life in the outer solar system.