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Salt miners on the Salt Flats of the Atacama Desert in Chile.
Reuters/Ivan Alvarado
No signs of visible life.
TOUGH STUFF

Microscopic life found in the driest desert on Earth are the closest thing to what may live on Mars

By Katherine Ellen Foley

The Atacama desert running along the coast of Chile is the driest place on our planet. Rain happens once every decade or so. It’s so dry that the upper layers of the ground are whitewashed with salt that has had every last drop of moisture sucked out of it.

Just thinking about this desert is enough to make anyone want a glass of water and some chapstick. But scientists have found evidence that some microbes like archaea, bacteria, and fungi are able to make a home of the salt flats. This life is the first of any kind found to be a more or less permanent resident of the desert, and gives hope to the idea that other microbes may be able to survive in other arid areas—like Mars.

The discovery, which was published Feb. 26 in the Proceedings of the National Academies of Sciences, was led by a team of astrobiologists at Technical University Berlin, who worked with scientists in the UK and the US. This group sought out the most remote parts of the desert, which were least likely to be contaminated by larger forms of life like people or animals. We all tend to carry trillions of microbial hitchhikers, after all.

They started collecting samples of soil along the Pacific coast of the desert and farther inland in 2015, just after a “major” El Niño event caused a whopping 8 millimeters of rain. The thinking was that rainfall would spark any dormant life inhabiting the salty soils to ramp up their own activity, and in doing so leave chemical footprints detectable by scientists.

Sure enough, the team found snippets of genomes, traces of cellular energy, and waste products. When they returned the next two years, they found similar forensic evidence of microbes, suggesting that bacteria living in the flats were full-time residents, as opposed to just struggling passersby carried by the wind.

Notably, none of the genetic material in these samples matched up exactly with existing databases. Although they were able to isolate genes from known microbial life, they couldn’t find any whole, living microbes. However, that doesn’t mean that the search was futile.

The Atacama desert “can serve as a working model for Mars,” Dirk Schulze-Makuch, an astrobiologist at the Technical University of Berlin, told Science.

All of the evidence the researchers could find suggested that the microbes they found were dormant. Similar to the state of plant seeds, dormancy occurs for some forms of life when resources are scarce. They carry out the bare minimum of cellular maintenance to stay alive until the right conditions return, which in this case is probably rainfall. If life does exist on Mars or the other similarly promising exoplanets, it would most likely be in a similar slow-living state.