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The Pyrenean ibex, an impressive mountain goat that lived in the central Pyrenees in Spain, went extinct in 2000. But a...
Tight budgets are forcing NASA to consider turning off one or more planetary science projects that have completed their...
Ebola is not a stranger to West Africa—an outbreak in the 1990s killed chimpanzees and sickened one researcher. But the...
In an as-yet-unpublished report, an international panel of geoscientists has concluded that a pair of deadly...
Tropical disease experts tried and failed before to eradicate yaws, a rare disfiguring disease of poor countries. Now,...
Since 2002, researchers have reported that agricultural communities in the hot and humid Pacific Coast of Central...
Balkan endemic kidney disease surfaced in the 1950s and for decades defied attempts to finger the cause. It occurred...
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Ancient Ecosystem Discovered Beneath Antarctic Glacier
16 April 2009 (All day)
Scientists have found life in an ecosystem trapped underneath a glacier in Antarctica for nearly 2 million years. The microbes, they suggest, are surviving the dark, oxygen-free waters by drawing energy from sulfur and iron. The findings provide insight into how life may have survived "Snowball Earth"--periods when some scientists speculate that the planet was entombed in ice--and hint at the possibility of life in other inhospitable environments, such as Mars and Jupiter's icy moon Europa.
Researchers have found microbial life surviving in the most unusual places: the depths of cold and dark oceans, seething geothermal vents, and the deepest layers of permafrost. And ever since scientists discovered Antarctica's dark and mysterious subglacial lakes in the late 1960s and early 1970s, they've wondered if microbes could make a life for themselves there too. But the challenges of drilling through kilometers of ice and concerns about contaminating these pristine lakes have curtailed previous efforts to find out.
Blood Falls, a small, saltwater outflow from Taylor Glacier's subglacial lake in Antarctica's Dry Valleys, offers an alternative. The lake sits beneath 400 meters of ice and trickles out at the glacier's end, painting an orange stain across the ice as its iron-rich waters rust upon contact with air. The subglacial lake was originally part of a marine fjord system that became trapped as Taylor Glacier enclosed it between 1.5 million and 2 million years ago. Its sporadic outflow allows researchers to explore the lake without drilling or risking contamination of the isolated environment.
Geomicrobiologist Jill Mikucki, now at Dartmouth College, collected water samples from Blood Falls over 6 years. A battery of tests revealed that its waters contained almost no oxygen and hosted a community of at least 17 different types of microorganisms. But how could they have survived for so long, with no light or oxygen? Mikucki and her team uncovered three main clues. First, a genetic analysis of the microbes showed that they were closely related to other microorganisms that use sulfate instead of oxygen for respiration. Second, isotopic analysis of sulfate's oxygen molecules revealed that the microbes were modifying sulfate in some form but not using it directly for respiration. Third, the water was enriched with soluble ferrous iron, which would happen only if the organisms had converted ferric iron, which is insoluble, to the soluble ferrous form. The best explanation, the team reports in tomorrow's issue of Science, is that the organisms use sulfate as a catalyst to "breathe" with ferric iron and metabolize the limited amounts of organic matter trapped with them years ago. Lab experiments have suggested this might be possible, but it has never been observed in a natural environment.
"I think this is a fantastic study," says Alan Kaufman, a biogeochemist at the University of Maryland, College Park. It presents "a spectacular new environment that we can explore to understand life on the edge," he says. "A place like this ... would be probably as close of an analog as we can find on this planet for subpermafrost life habitats on Mars," says glaciologist Slawek Tulaczyk of the University of California, Santa Cruz. Ultraviolet radiation and other hazards would most likely lock life away beneath the surface of the Red Planet, he notes.