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article imageAncient Antarctic microbes suggest life but not as we know it

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By Robert Myles     Dec 5, 2012 in Science
In a study released last week, scientists attached to Nevada’s Desert Research Institute (DRI) revealed the existence of bacteria in one of Earth’s most alien habitats, 20 metres below a frozen lake in Antarctica.
The pioneering study was published in the Proceedings of the National Academy of Science (PNAS) and co-authored by Dr. Alison Murray and Dr. Christian Fritsen of DRI. The habitat examined was dark, salty, well below freezing point and buried beneath Lake Vida, one of the most remote frozen lakes in Antarctica. The research has provided data on biochemical processes not linked to sunlight, carbon dioxide and oxygen or photosynthesis, reports the Scientific American which goes on to say that the conditions at Lake Vida are similar to habitats on Mars and which are believed to be present elsewhere in the solar system. The Lake Vida Antarctic research potentially gives new framework for evaluating the likelihood of extraterrestrial life and how it might be sustained.
Approximate location of Lake Vida
Approximate location of Lake Vida
Wikimedia Commons
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Lake Vida is one of a number of unique lakes found in the McMurdo Dry Valleys region of the Antarctic continent. Features of the lake are:
• It contains no oxygen
• It contains some of the highest levels of nitrous oxide of any body of natural water on Earth
• A briny liquid six times saltier than seawater permeates through the icy environment
• It has an average temperature of minus 13.5°C
Said Dr. Alison Murray, lead author of the report, who has wide experience of Antarctica having previously participated in 14 expeditions to the frozen continent and the surrounding Southern Ocean,
“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. This work expands our understanding of the types of life that can survive in these isolated, cryoecosystems and how different strategies may be used to exist in such challenging environments.”
Scanning electron micrograph of very small and numerous bacterial cells inhabiting icy brine channel...
Scanning electron micrograph of very small and numerous bacterial cells inhabiting icy brine channels in Antarctica’s Lake Vida, which lies in the Victoria Valley, one of the northernmost of the Antarctic dry valleys.
Credit: Christian H. Fritsen, Desert Research Institute
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Notwithstanding the inhospitable environment, the report says the salty brine is home to diverse bacteria with the ability to survive in the absence of sunlight as an energy source. Earlier studies of Lake Vida going back almost 20 years show that the brine and its bacterial denizens have existed for over 3,000 years without external influences.
For the DRI Antarctic field explorations conducted over five years from 2005, Dr. Murray colleagues developed strict criteria when examining the brine in Lake Vida to guard against contaminating this unique ecosystem. Researchers worked in secure, sterile tents pitched on the surface of Lake Vida as ice cores were drilled from below the surface and samples of the brine taken for chemical and organic analysis.
The geochemical analyses pointed to there being chemical reactions between the brine and the iron rich sediments of the lake which produced nitrous oxide and molecular hydrogen. The scientists have theorized that the hydrogen may be the source of energy needed to support the various microbial life-forms in the brine.
“It’s plausible that a life-supporting energy source exists solely from the chemical reaction between anoxic salt water and the rock,” explained Dr. Christian Fritsen, a systems microbial ecologist and Research Professor in DRI’s Division of Earth and Ecosystem Sciences.
“If that’s the case,” echoed Dr. Murray. “This gives us an entirely new framework for thinking of how life can be supported in cryoecosystems on earth and in other icy worlds of the universe."
Stressing the potential of the research to illustrate the possibilities of life existing in alien environments on other worlds beyond Earth, Dr. Murray said additional research is progressing to analyze the abiotic, chemical interactions between the Lake Vida brine and the sediment. The unique microbial community is also being examined by using a variety of genome sequencing approaches.
The Lake Vida research is supported jointly by the National Science Foundation (NSF) and NASA.
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