A 5-km-long ice-sealed super-concentrated saltwater lake found under 19 m of ice in the region of Antarctica known as McMurdo Dry Valleys. Discovery of the all-year-round liquid nature of the lake was announced in December 2002 together with that of 2,800-year-old microbes, which had been revitalized after extraction from ice core samples above the lake. The water remains liquid because it is seven times saltier than seawater and so will not freeze even at -10°C – the temperature below the ice cover. Because the body of water has been isolated for thousands of years, it may represent a previously unknown type of ecosystem and serve as an important natural laboratory for researchers interested in looking for evidence of microbial life on other worlds, including Mars. Conceivably, a Lake Vida-type ecosystem served as the final niche for life on Mars before the surface water froze solid. If so, given that the organisms in the Vida samples managed to survive the low temperatures, lack of light, and hypersalinity (see halophiles) for millennia and to begin photosynthesising again when unfrozen, it is possible that the same revitalization could occur with microbes on Mars. Research at Lake Vida could help scientists find out more about possible life in Lake Vostok, the largest of over 70 sub-glacial lakes in Antarctica, which lies more than 4 km beneath the East Antarctic Ice Sheet.
