A frigid brine, isolated from the outside world for about three millennia underneath a thick layer of ice in an Antarctic lake, harbors life, according to a research team that includes scientists from the University of Colorado Boulder.
The finding, published in the Proceedings of the National Academy of Sciences, offers a hint to how life might be able to thrive in extreme, icy conditions elsewhere in our solar system, such as those found on Saturn’s moon Enceladus, Jupiter’s moon Europa or on Mars.
The science team, led by Peter Doran at the University of Illinois at Chicago and funded by the National Science Foundation, drilled into Lake Vida’s 60-foot-thick cap of ice during expeditions to East Antarctica in 2005 and 2010. Scientists at CU-Boulder’s Institute of Arctic and Alpine Research were tapped to measure the amount of organic matter — a byproduct of life — dissolved in the salty solution that seeped into the drilled bore holes. INSTAAR researchers have honed their expertise in measuring dissolved organic matter in lakes and streams by working for decades at long-term ecological research sites in the alpine regions above Boulder and in the Dry Valleys of Antarctica.
The new study provides a window into one of the most unusual ecosystems on Earth, said Alison Murray, lead author of the study and a scientist at Nevada’s Desert Research Institute. "Our knowledge of geochemical and microbial processes in lightless icy environments, especially at subzero temperatures, has been very limited up until now. This work expands our understanding of the types of life that can survive in these isolated, cryo-ecosystems and how different strategies may be used to exist in such challenging environments."
INSTAAR fellow Diane McKnight and Kaelin Cawley, a doctoral student at CU-Boulder during the study, found that the concentration of dissolved organic matter in the brine, which has an average temperature of just 8 degrees Fahrenheit, was orders of magnitude greater than the concentration typically found in surface waters open to the environment. Carbon dating of the dissolved material also revealed that much of it is younger than the cap of ice covering the lake, eliminating the possibility that the material entered the water solely from the outside and, instead, suggesting that it was created by the bacteria living in the sunless and oxygen-free depths of the lake.
“The largest fraction of that dissolved organic material has chemical characteristics consistent with it having been produced in the system after it was ice-sealed,” said McKnight, who is also a professor of civil, environmental and architectural engineering. “I look at these as products of potential microbial material; it’s hard to explain it any other way.”
Because sunlight does not reach to the bottom of Lake Vida, another energy source is needed to establish an environment where the bacteria can flourish. The researchers believe that the alternative energy source may be the product of abiotic chemical reactions: When the salty water reacts with the lake’s iron-rich sediments, the result is energy-rich hydrogen as well as nitrous oxides.
Researchers from NASA, Michigan State University, Montana State University, the University of Georgia and Indiana University — as well as Australian scientists from the University of Tasmania and Curtin University of Technology — worked on the Lake Vida project.