Despite existing in the extreme cold desert of Antarctica's McMurdo Dry Valleys, there is liquid water beneath the permanently frozen surface of one of the valley's largest lakes.
A new study published in Geophysical Research Letters says that, while this ancient, super salty aquifer doesn't provide anything like the water humans pull out of the ground to drink or irrigate crops, it is a cozy habitat for all sorts of microbes.
Hilary Dugan, a post-doctoral researcher at the University of Wisconsin-Madison's Center for Limnology, was lead author of the paper and says the research yields new information not just on the hydrology of Antarctica's dry valleys, but even points to interesting parallels between life under the ice and life on Mars.
Dugan
"We believe the aquifer beneath Lake Vida is a remnant of a time when the water levels across [the valley] were much higher than present. Upwards of 200 meters higher," she says. "If you stand on the surface of Victoria Valley today, there is no indication of the amount of water stored beneath ground."
The subsurface can hide what Dugan calls the "legacy of past climate states." While current conditions may not indicate much going on beneath the surface, a look down deep can reveal not just an unexpected habitat, but one teeming with microscopic organisms. It's these kinds of conditions, Dugan says, that scientists are hoping for as they search for water (and possibly life) on Mars.
To get a look under Antarctic ice, however, is not an easy task. The first attempt researchers made on Lake Vida in the 1960s involved lots of dynamite and was called off after researchers blasted a hole 11 meters down with no end to the ice in sight.
Dugan's team used tools that were a little more sophisticated — a combination of ground penetrating radar (GPR) and an airborne electromagnetic unit (AES) survey. But it still wasn't easy.
For the GPR readings, Dugan walked 55 kilometers-worth of transects across Lake Vida's surface, pulling her equipment behind her on a sled. For the AES, they had to commission a helicopter to hover over sample sites with a large "transmitter loop" capable of getting readings up to 600 meters below the surface.
The yellow “transmitter loop” creates a magnetic field and offers researchers a profile of what’s beneath the frozen surface of Lake Vida. (Visualization by Hilary Dugan)
"We now know that there are at least 27 meters of surface ice, and there are microbes that live in a dark, salty … downright inhospitable environment," she says. In fact, the habitat these microbes call home exists at -13 degrees Celsius and only stays in liquid form because it is seven times saltier than sea water.
Dugan's study is one of the first projects to even attempt to map groundwater in Antarctica (seeing as 98 percent of the continent is covered by an ice sheet, sub-glacial hydrology has taken the front seat). But, she says her findings suggest that there's a lot more going on beneath the continents slivers of exposed surface than meets the eye.
"Part of what inspired this work was an attempt to understand the extent of this brine habitat," she says. "And, spoiler alert, it was much larger than we thought it was!"
Considering that the extreme ecosystem beneath Lake Vida is likely not an anomaly, that may mean we've still got a lot to learn about life on (or under) Earth before we ever get around to finding it on other planets.