A team of researchers co-led by Dr Slawek Tulaczyk of the University of California, Santa Cruz, and Dr Jill Mikucki of the University of Tennessee, Knoxville, has found compelling evidence that under the ice-free McMurdo Dry Valleys lay brines that may support microbial ecosystems and retain evidence of ancient climate change.
The McMurdo Dry Valleys are a row of valleys west of McMurdo Sound, Antarctica, so named because of their extremely low humidity and lack of snow and ice cover. Photosynthetic bacteria have been found living in the relatively moist interior of rocks. Scientists consider the Dry Valleys to be the closest of any terrestrial environment to Mars. Image credit: NASA / GSFC / METI / ERSDAC / JAROS / ASTER Science Team.
Dr Tulaczyk, Dr Mikucki and their colleagues believe the brines may provide insight on how microbes survive extreme conditions, and also provide the basis for future exploration of a subsurface habitat on Mars.
“The findings allow scientists to better learn how Antarctica has responded to climate change over time, and also help them understand glacial dynamics,” said Dr Mikucki, who is the first author on the paper published in the journal Nature Communications.
“It may change the way people think about the coastal margins of Antarctica. We know there is significant saturated sediment below the surface that is likely seeping into the ocean and affecting the productivity of things that feed ocean food webs. It lends to the understanding of the flow of nutrients and how that might affect ecosystem health.”
Using a novel airborne electromagnetic mapping sensor system called SkyTEM, the scientists discovered that brines form extensive aquifers below glaciers, lakes and within permanently frozen soils.
“These unfrozen materials appear to be relics of past surface ecosystems and our findings provide compelling evidence that they now provide deep subsurface habitats for microbial life despite extreme environmental conditions,” Dr Mikucki said.
“We believe the application of novel below-ground visualization technologies can not only reveal hidden microbial habitats, but can also provide insight on glacial dynamics and how Antarctica responds to climate change.”
The researchers also found evidence that brines flow towards the Antarctic coast from roughly 11 miles (18 km) inland, eventually discharging into the Southern Ocean.
It is possible that nutrients from microbial weathering in these deep brines influence near-shore biological productivity in that ocean.
“Over billions of years of evolution, microbes seem to have adapted to conditions in almost all surface and near-surface environments on Earth. Tiny pore spaces filled with hyper-saline brine staying liquid down to 5 degrees Fahrenheit (minus 15 Celsius) may pose one of the greatest challenges to microbes,” Dr Tulaczyk said.
“Our electromagnetic data indicate that margins of Antarctica may shelter a vast microbial habitat, in which limits of life are tested by difficult physical and chemical conditions.”
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J. A. Mikucki et al. 2015. Deep groundwater and potential subsurface habitats beneath an Antarctic dry valley. Nature Communications 6, article number: 6831; doi: 10.1038/ncomms7831
