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Jupiter s moon Europa has an ocean under its icy surface. Credit: NASA/JPL/Ted Stryk Jupiter's moon Europa has an ocean under its icy surface. Credit: NASA/JPL/Ted Stryk

Ancient microbes discovered in one of Earth's darkest habitats

Sen—Scientists have discovered ancient microbes in one of the most remote lakes of Antarctica, nearly 65 feet beneath the icy surface. The findings help to increase knowledge of how life can sustain itself in extreme environments beyond our own planets. 

"This system is probably the best analog 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 NASA's Ames Research Centre, Moffett Field. 

McCay was part of the team of scientists from NASA, the Desert Research Institute (DRI), the University of Illinois and nine other institutes who uncovered the community of bacteria in Lake Vida. The lake is the largest of several found in the McMurdo Dry Valleys. It contains no oxygen, is mostly frozen and possesses the highest nitrous oxide levels of any natural water body. It is one of Earths darkest, saltiest and coldest habitats. 

According to the paper's lead author Alison Murray, a molecular microbial ecologist and polar researcher at the DRI, "this study provides a window into one of the most unique ecosystems on Earth. Our knowledge of geochemical and microbial processes in lightless icy environments, especially at subzero temperatures, has been mostly unknown up until now."

The work carried out by the team expands on the current understanding of the types of life that can survive in these isolated environments, as well as how different strategies may be used to exist in such challenging environments.

The icy environment consists of a briny liquid, around six times saltier than seawater with average temperatures of minus 8 degrees Fahrenheit. Despite these conditions and the isolated nature of the habitat, the team found that the brine harbours a surprisingly diverse and abundant variety of bacteria that survive without a current source of energy from the Sun. This follows past studies of Lake Vida dating back to 1996 which indicated that the brine and its inhabitants have been isolated from outside influences for more than 3,000 years. 

The study is significant because the microbial ecosystem discovered expands our current understanding of environmental limits for life and helps define new niches of habitability. Geochemical analyses on samples suggests chemical reactions between the brine and the underlying iron-rich sediments generate nitrous oxide and molecular hydrogen. It is possible that the latter may play a part in providing the energy needed to support microbial life in the brine. 

Research is now being carried out to analyse the abiotic, chemical interactions between the Lake Vida brine and its sediment. Scientists are also investigating the microbial community by using different genome sequencing approaches. Its possible that the results could help explain the potential for life in other salty, cryogenic environments beyond Earth, such as possible subsurface aquifers on Mars. 

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