The intriguing thing about life on Earth is that it’s been found nearly any place on the surface—or even near-surface—where scientists have looked. Now a research team led by Jacqueline Goordial from McGill University in Canada reports on one location, in the McMurdo Dry Valleys of Antarctica, where no microbial activity could be observed.
University Valley is an especially harsh place, a valley 1.5 kilometers long and 500 meters wide, located at about 1,700 meters above sea level. Here the permafrost originates from vapor deposition rather than liquid water. Temperatures average -23 C, with less than 80 hours per year (!) above freezing, compared to the lower coastal zones in Antarctica, which typically have more than 50 days above freezing.
The researchers drilled two cores into the permafrost at University Valley, took multiple samples from the surface and at depth (down to 55 centimeters), and analyzed them using a variety of biological and molecular (genetic) tools. In the extremely organic-poor soils no metabolic activity was detected under ambient conditions, no biofilms could be identified, and no RNA could be extracted. This suggests an extremely low biomass and negligible microbial activity. The DNA that could be extracted from the soil samples likely derived from dead or dormant organisms blown into that location.
The main problem for life at University Valley seems to be the near-complete lack of liquid water. At lower elevations in the Dry Antarctic Valleys, where conditions are still quite harsh, salt-rich liquid water veins exist in the permafrost, providing a habitat where cold-loving microbes can metabolize and grow. At University Valley, however, it seems that the rare combination of near-permanent subfreezing temperatures and lack of nutrients make this one of the few uninhabited places on Earth. University Valley may in fact be the harshest environment in the McMurdo Dry Valleys. It also is very similar to the northern subpolar regions on Mars, where the Phoenix spacecraft landed.
If the research by Goordial’s team can be confirmed by others, it would mean that we may have found the dry and cold limit of life on Earth. We could then extrapolate to Mars, and predict where Martian microorganisms might survive, and where they might not—assuming, of course, that any indigenous Martian organisms don’t have any tricks in their evolutionary toolbox (unknown to us) that have adapted them to extreme cold and dryness.