The McMurdo Dry Valleys of Antarctica are considered the driest, coldest places on the planet, and form one of the world’s most extreme deserts. The landscape is so inhospitable that it is often considered the "closest of any terrestrial environment to Mars.” And yet deep below the surface, scientists may have discovered something extraordinary: underground lakes swimming with life. Descriptions of the remarkable find have been published in Nature Communications.
The valleys make up the largest area of ice-free ground on the southern continent, with the snow and ice scoured away by the katabatic winds that blast the region at speeds of up to 200 kilometers per hour (124 mph). All the winds leave behind are a few small scattered lakes, one or two glaciers, and the remains of mummified seals, some of which are thousands of years old. Beneath the frozen soil, however, things appear a little different.
There have been hints before that life might be a little more active under all the ice and rock than most people expect. Seeping out of the snout of the Taylor glacier is what looks like blood, but is actually iron concentrated in the ice. The bacteria causing the “Blood Falls,” as it’s affectionately known, were found in 2009 and originate four kilometers (2.5 miles) further up in the glacier. Now, it seems that it may be part of a much larger underground system of hyper-salty lakes and aquifers.
Microbiologist Jill Mikucki from the University of Tennessee was part of a team of international researchers that detected the extensive briny water underlying much of the valley. They found liquid water 300 meters (980 feet) below the frozen surface—stretching from the coast to at least 12 kilometers (7.5 miles) inland. The water is thought to be around twice as salty as seawater, and the scientist fully expect the deep brine ecosystem to harbor similar microbial communities to those seen in groundwater.
To make this discovery, the team used a novel airborne electromagnetic sensor system. This involved flying a six-sided sensor beneath a helicopter over the valleys and recording the electromagnetic responses from the ground. The scientists were then able to distinguish between electrically conductive brine-saturated sediment and resistive ice-bearing formations. From this data, they were then able to infer the existence of the extensive aquifers.
Image: The Helicopter carrying the electromagnetic sensor. Credit: J.Mikucki
Based on the chemical composition of the material trapped in the ice, it appears that the water beneath the ground and ice is most likely the remnants of an arm from the ocean that once extended into the area around 1.5 million years ago. This theory is consistent with DNA analysis of the outpourings from Blood Falls, which show that at least some of the microorganisms appear to come from relatives of marine bacteria.
Mikucki thinks that the continuous flow from this subsurface network might serve a critical role in the local ecosystem, and could be recycling nutrients back into the Southern Ocean: "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.”
The implications of this study are not limited to our own planet. As many consider the Dry Valleys the closest environment we can get to Mars on Earth, some think that this discovery in Antarctica could mean that similar briny liquid water could have formed deep within the Red Planet itself.