Using an airborne imaging system for the first time in Antarctica, scientists have discovered a vast network of unfrozen salty groundwater that may support previously unknown microbial life deep under the coldest, driest desert on our planet. The findings shed new light on ancient climate change on Earth and provide strong evidence that a similar briny aquifer could support microscopic life on Mars.

The scientists used SkyTEM , an airborne electromagnetic sensor, to detect and map otherwise inaccessible subterranean features. The system uses an antennae suspended beneath a helicopter to create a magnetic field that reveals the subsurface to a depth of about 1,000 feet. Because a helicopter was used, large areas of rugged terrain could be surveyed.

The SkyTEM team was funded by the National Science Foundation and led by researchers from the University of Tennessee, Knoxville, and Dartmouth College, which oversees the NSF's SkyTEM project.

"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," says lead author Jill Mikucki, an assistant professor at UTK. "These new below-ground visualization technologies can also provide insight on glacial dynamics and how Antarctica responds to climate change."

Co-author Dartmouth Professor Ross Virginia is SkyTem's co-principal investigator and director of Dartmouth's Institute of Arctic Studies. "This project is studying the past and present climate to, in part, understand how climate change in the future will affect biodiversity and ecosystem processes," Virginia says.

"This fantastic new view beneath the surface will help us sort out competing ideas about how the McMurdo Dry Valleys have changed with time and how this history influences what we see today."

The researchers found that the unfrozen brines form extensive, interconnected aquifers deep beneath glaciers and lakes and within permanently frozen soils. The brines extend from the coast to at least 7.5 miles inland in the McMurdo Dry Valleys, the largest ice-free region in Antarctica. The brines could be due to freezing and/or evaporation of a large ancient lake or much older ocean deposits.

The findings show for the first time that the Dry Valleys' lakes are interconnected rather than isolated; connectivity between lakes and aquifers is important in sustaining ecosystems through drastic climate change, such as lake dry-down events. The findings also challenge the assumption that parts of the ice sheets below the pressure melting point are devoid of liquid water.

In addition to providing answers about the biological adaptations of previously unknown ecosystems that persist in the extreme cold and dark of the Antarctic winter, the new study could help to scientists to understand whether similar conditions might exist elsewhere in the solar system, specifically beneath the surface of Mars, which has many similarities to the Dry Valleys. Overall, the Dry Valleys ecosystem - cold, vegetation-free and home only to microscopic animal and plant life - resembles, during the Antarctic summer, conditions on the surface on Mars.

SkyTEM produced images of Taylor Valley along the Ross Sea that suggest briny sediments exist at subsurface temperatures down to perhaps -68F, which is considered suitable for microbial life. One of the studied areas was lower Taylor Glacier, where the data suggest ancient brine still exists beneath the glacier. That conclusion is supported by the presence of Blood Falls, an iron-rich brine that seeps out of the glacier and hosts an active microbial ecosystem.

Scientists' understanding of Antarctica's underground environment is changing dramatically as research reveals that subglacial lakes are widespread and that at least half of the areas covered by the ice sheet are akin to wetlands on other continents. But groundwater in the ice-free regions and along the coastal margins remains poorly understood.

Co-authors on the paper include researchers from the University of Tennessee-Knoxville, Dartmouth College, University of California-Santa Cruz, University of Illinois at Chicago, Louisiana State University, University of Wisconsin, Aarhus University in Denmark and Sorbonne Universites, UPMC University in France.