Sterile Antarctic valleys knock hopes for Martian life...

....but not conclusively, so don't start with the wailing and gnashing of teeth just yet space fans: In a spot called University valley a team from the McGill University has been hunting for microbes. The reason why they chose University valley is because of it's extremely Mars-like conditions. The valley has been incredibly dry and stayed below freezing for roughly 150,000 years. As analogues for Mars go, it's as good as you'll get on Earth.

Above: University Valley, Antarctica. Courtesy of Jackie Goordial

And they found... nothing. No active microbes anywhere. A few traces that might have been dormant or slowly dying organisms.

“If conditions are too cold and dry to support active microbial life on an analogous climate on Earth, then the colder dryer conditions in the near surface permafrost on Mars are unlikely to contain life.” Says Lyle Whyte,  supervisor on the project. “Additionally, if we cannot detect activity on Earth, in an environment which is teeming with microorganisms, it will be extremely unlikely and difficult to detect such activity on Mars.”

So is that case closed, give up looking for traces of life on Mars? Well....I've kind of given away my thoughts on that at the beginning.

The teams' results are not unexpected, because the University valley site is devoid of liquid water - a combination of being very dry and very cold, so the ice never melts, keeps it that way. The ice that is there is due to water vapour, not any kind of liquid, and the whole summer season the team were there it never got above freezing. And we're fairly sure that life, of the kind we know how to recognise at least, has an absolute requirement for liquid water.
In fact the University valley spot was picked because it resembles the Martian Arctic, a very forbidding place indeed, where the temperatures seldom get even as warm as University valley, and no water has flowed for billions of years. The McGill team went looking for a spot on Earth, that resembles a place on Mars that is harsh even for Mars! And, in the bigger picture, their results may actually be very good for Mars exploration.

Above, the plains of the Martian Arctic, courtesy of JPL/ NASA

Mars is a big place, and we've already seen from Curiosity rover and MRO spacecraft that some more temperate areas may still see small amounts of liquid water today. 

Above: Recurring Slope Linea (RSL) seen from orbit by the MRO spacecraft. These are thought to be formed by present day liquid water - maybe 95% conclusively. Curiosity rover has measured conditions on Mars that would allow small amounts of water to form where perchlorate salts are present in the soil. Courtesy of NASA.

Still, even then, the odds are not great for finding present day Martian life, as the water is infrequent and incredibly salty. But feeling down about that is missing the point: The big aim on Mars has always been to find some traces of ancient life, preserved from a time when Mars was more habitable (and Mars may have had habitable episodes quite late into its history). So the McGill teams findings are actually good for this, even if they do apply to the whole planet - they tell us the chances of getting a false positive from a hitchhiking Earth microbe are low, because Earth microbes won't survive long in those conditions.

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