Meteorite Impacts Could Have Fostered Life on Early Earth
H. M. Sapers; (inset) NASA WorldWind;Wikimedia Commons

ScienceShot: A Tiny Bacterial World, Long Buried in Ice

What life lies in Antarctica's vast Lake Vostok is still a mystery, but a strange, long-isolated bacterial community inhabits the dark depths of another lake on the continent. A diverse group of microorganisms has been living isolated within the frigid brine of an ice-covered Antarctic lake for thousands of years, a new study suggests. Lake Vida, a 6.8-square-kilometer body of water, sits high in snow-free McMurdo Dry Valleys. Researchers drilling into the lake in 2005 and 2010 (field camp from 2010 shown above) discovered that the lake's pale yellow brine, which is a chilly -13°C, contains microbes representing at least eight distinct groups of bacteria, several of which haven't been previously recovered from high-salinity ecosystems. While some of the bacteria make their living by oxidizing sulfur or by consuming organic matter, others gain their energy by consuming dissolved hydrogen, genetic analyses suggest. The lake's 16-meter-thick cap of ice is so thick that light doesn't penetrate it, and carbon-dating of organic matter trapped 12 meters below the surface of the ice suggests that the brine has been isolated for more than 2800 years, the researchers report online today in the Proceedings of the National Academy of Sciences. Because the lake, whose deepest waters are largely unfrozen due to their high salinity, sits atop permafrost hundreds of meters thick, it is almost entirely isolated from its surroundings. However, chemical reactions between the brine and lake-bottom sediments may provide a trickle of nutrients to the lake's microbes, which—thanks to the frigid temperatures and a limited food supply—reproduce, on average, only once every 120 years, the researchers estimate.

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