Scientists have discovered a vast network of salty aquifers beneath the surface of Antarctica, thanks to an airborne imaging system used there for the first time. The finding may have interesting implications for the search for life elsewhere, such as Mars, since it is known that, at least on Earth, a large variety of microscopic life forms can thrive in those kinds of environments.
Researchers from the University of Tennessee, Knoxville, and Dartmouth College made the discovery using SkyTEM, an airborne electromagnetic sensor. The system can detect and map otherwise unseen features below the icy surface, using an antennae suspended beneath a helicopter to create a magnetic field which can probe the subsurface to a depth of about 1,000 feet. Large areas of rugged terrain were able to be studied, thanks to the use of the helicopter.
The research is being funded by the National Science Foundation.
“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,” said 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 Ross Virginia, a Dartmouth Professor, SkyTem’s co-principal investigator and director of Dartmouth’s Institute of Arctic Studies, added: “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. 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 work is especially interesting to planetary scientists, since liquid water brines are thought to be possible for short times on the surface of Mars, and there may also be aquifers of water deeper down where there is more warmth. This would increase the chances that microscopic life could have existed, or may still exist, on Mars.
Underneath Antarctica it was found that the brines form extensive, interconnected aquifers below the surface, beneath glaciers and lakes with permafrost. The brines extend from the coast to at least 7.5 miles inland in the McMurdo Dry Valleys, which are the largest ice-free regions in Antarctica. They may be the result of freezing and/or evaporation of a large ancient lake or older ocean deposits. The fact that the lakes in the McMurdo Dry Valleys are now known to be interconnected rather than isolated is significant, since being connected helps to sustain ecosystems through times of climate change, such as lake dry-down events. The finding also shows that there is indeed liquid water, albeit salty, beneath the ice sheets where the pressure is below the melting point.
The same may be true for Mars, which in many ways resembles the Antarctic environment, in particular the McMurdo Dry Valleys, with freezing cold temperatures, permafrost, dry soil, and lack of vegetation. This location is considered to be one of the most Mars-like on Earth.
Specifically, SkyTEM took images of Taylor Valley along the Ross Sea which indicate that brines may exist there at temperatures as low as -68˚ F, including beneath lower Taylor Glacier. Blood Falls, an iron-rich brine that seeps out of the glacier, is already known to host an active microbial ecosystem. Extremophile organisms have no problem living in these conditions.
Since there are also known to be ancient glaciers on Mars, similar conditions may exist below them as well, which could be capable of still supporting microscopic life. The Mars Phoenix Lander landed on permafrost terrain near Mars’ north pole, with similar conditions to Antarctica. The lander scooped up water ice deposits; might there be brines deeper down? Odd “droplets” seen on one of the lander’s legs after landing are thought to have possibly been brine which splashed onto the leg after landing engines heated the soil. The Curiosity rover also recently found evidence that brines may be common on Mars. Liquid water, even salty water in very limited amounts, could theoretically help microbes to survive in Mars’ hostile environment. The Recurring Slope Lineae (RSL) dark streaks on many equator-facing slopes may be brines briefly flowing on the surface. Common in the summer, they may originate from either melting ice or subsurface aquifers. If they are brines, it would be the first time liquid water has been seen on the surface of another planet.
Besides Mars, there are other places where these findings might be pertinent, such as small icy moons like Europa and Enceladus. They also resemble Antarctica in that they are ice-covered worlds with liquid water beneath the surface. That water, an entire ocean of it on both moons, is salty and similar to sea water on Earth. On Enceladus, the water makes its way to the surface through huge cracks, spewing into space as geysers of water vapor. The Cassini spacecraft has directly sampled some of those plumes, finding water vapor, ice particles, salts, and organic material. Both moons are now considered to be prime candidates in the search for evidence of life elsewhere in the Solar System. There may also be subsurface water on other moons as well, including Titan and Ganymede, among others.
The SkyTEM discovery in Antarctica not only provides new insight into how life can exist in extreme conditions here on Earth, it also helps to show how life might be possible in similar kinds of environments elsewhere in the Solar System or even beyond. As the saying goes, “follow the water,” even if it is a bit more salty than desired.
The study was published in the journal Nature Communications.