Nearly 20 metres beneath the icy surface of a remote Antarctic lake, an international team of scientists has uncovered a community of bacteria existing in one of Earth’s darkest, saltiest and coldest habitats.
Lake Vida, the largest of several unique lakes found in the McMurdo Dry Valleys, contains no oxygen, is mostly frozen and possesses the highest nitrous oxide levels of any natural water body on Earth. A briny liquid, which is approximately six times saltier than seawater, percolates throughout the icy environment where the average temperature is minus 22 degrees Celsius.
Despite the very cold, dark and isolated nature of the habitat, the report – published online in the Proceedings of the National Academy of Sciences Early Edition – finds the brine harbours a surprisingly diverse and abundant variety of bacteria that survive without a current source of energy from the Sun. Previous studies of Lake Vida dating back to 1996 indicate the brine and its inhabitants have been isolated from outside influences for more than 3 000 years.
“This system is probably the best analogue we have for possible ecosystems in the subsurface waters of Saturn’s moon Enceladus and Jupiter’s moon Europa,” said Chris McKay, a senior scientist and co-author of the paper at Nasas Ames Research Centre.
To sample unique environments such as this, researchers must work under secure, sterile tents on the lake’s surface. The tents kept the site and equipment clean as researchers drilled ice cores, collected samples of the salty brine residing in the lake ice and assessed the chemical qualities of the water and its potential for harbouring and sustaining life.
Geochemical analyses suggest chemical reactions between the brine and the underlying iron-rich sediments generate nitrous oxide and molecular hydrogen. The latter, in part, may provide the energy needed to support the brine’s diverse microbial life.
Additional research is under way to analyse the abiotic, chemical interactions between the Lake Vida brine and its sediment, in addition to investigating the microbial community by using different genome sequencing approaches. The results could help explain the potential for life in other salty, cryogenic environments beyond Earth, such as purported subsurface aquifers on Mars.