On March 4th, 2018 we learned about

Resilient bacteria in Chilean desert raise hopes of finding microbes on Mars

Life as we know it needs water. Aside from the larger-scale functions we need water for, even bacteria struggle if their proteins unravel when no water is available. So when researchers in the found traces of bacteria and algae in the hyperarid Atacama Desert, it was assumed that these organisms were essentially unlucky. A place that can go years between rainfalls just can’t support life, and so these microbes and accompanying bits of DNA that turned up in soil samples were thought to have been blown in by the wind, and left to decompose among the rocks.

Dormant, but not dead

As it turned out, many of these parched organisms were just waiting for the rain. Soil samples were collected shortly after a rainfall in 2015, and found to be much more biologically active than anyone expected. Researchers were able to see that the microbes were healthy and reproducing, and had apparently only been dormant in the previous dry spell. It’s not an unprecedented survival strategy, as other organisms, such as tardigrades, are also known to become dormant in response to dehydration. However, the idea that these desert microbes essentially spend most of their existence waiting for the next drop of moisture shows that life is worth looking for in even the most extreme environments.

Red Planet proxy

The reason anyone was looking in Atacama in the first place is thanks to its resemblance to another extreme environment that may also be home to dormant organisms. The minimal rainfall and rocky terrain has made the Chilean desert a proxy for the surface of Mars here on Earth. Sure, there’s a lot more oxygen, not as much radiation from the Sun, etc. in Chile, but it’s the closest approximation of our neighboring planet available. As such, it’s been used to test equipment bound for Mars, and in this case, see if there was any hope of finding living things in hyperarid conditions. After all, if nothing could survive in Atacama, the colder and even drier Martian landscape would be an impossible place for any organism to survive.

Instead, it looks like there’s a definite chance that the harsh conditions of Mars could be home to at least dormant microbes. The Red Planet was once wetter and warmer than it is today, and thus more likely to be home to at least microbial organisms like bacteria. As the planet lost much of its atmosphere and grew colder and drier, some of those microbes could have adopted a similar strategy to what was found in Atacama— going dormant until the next round of moisture arrives. Instead of rain, that would most likely be some kind of frost or snow, or possibly just some sub-surface run-off soaking through the Martian soil. It’s no guarantee that we’ll find any native Martian species, but it supports the idea that it’s still worth looking.

Temporarily full of flowers

Funnily enough, the rains can sometimes bring even more than microbes in Atacama. Unusual rainfall in the fall of 2017 actually spurred the growth of flowers and various plants. While it was a lovely sight for tourists, it wasn’t exactly what Mars researchers would want for their investigations.

Source: Life in world's driest desert seen as sign of potential life on Mars by Washington State University, Phys.org

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