Chile's Atacama Desert competes with parts of Antarctica for the title of the driest place on Earth. This makes it a great analog for Mars, so the discovery of life rebounding after a rare rainfall has excited scientists who witnessed it. If nothing else, it proves just how resilient life can be.
The entire Atacama is very dry, but some parts experience rain often enough that, when it comes, flowers spring to life in awe-inspiring displays of beauty. The heart of the Atacama, however, is drier still, caught in the world's greatest rain-shadow, where the Andes soak up any water the prevailing winds may hold. Here some weather stations have never received rain, and so much salt is deposited between times that when rain falls it instantly becomes very saline.
However, Professor Dirk Schulze-Makuch of Washington State University had the extraordinary luck to happen to be studying lifeforms in the Atacama in 2015 when some locations got their first rain in years.
Microbes have been found even in the driest Atacama, but these could have blown in on the wind (something that certainly would not occur on Mars). Some biologists have argued these unfortunate microbes are slowly dying, unable to survive the long periods between drinks.
In Proceedings of the National Academy of Sciences, Schulze-Makuch reports that even in this most hostile environment, life has adapted. Although some of the microorganisms found there may indeed be lost wanderers unable to survive, his team witnessed the way the first touch of water brought many bacteria back from dormancy.
On return trips, Schulze-Makuch observed microbial communities reverting to dormancy as water dried up. He also found supporting evidence the microbes he studied were part of an active community, including biomolecules associated with viable cells, and differences in the make-up of microbial communities based on soil types and depths, with more salt-loving species buried where salinity is even greater, while UV-resistant bacteria dominate the surface.
"It has always fascinated me to go to the places where people don't think anything could possibly survive and discover that life has somehow found a way to make it work," Schulze-Makuch said in a statement. "Jurassic Park references aside, our research tells us that if life can persist in Earth's driest environment there is a good chance it could be hanging in there on Mars in a similar fashion."
If life flourished during the era when Mars was wet, Schulze-Makuch argues, it would get opportunities to revive when ice frozen in the soil melts. Nevertheless, the combination of UV radiation, much greater cold, and even longer gaps between wet periods, certainly means any Martian life would face a much tougher environment even than the Atacama.