World's driest desert may hold clues to alien life on Mars

For the first time, researchers have observed specialised bacteria in the world's driest desert, that can rebound after lying dormant for decades, a finding that points towards the possibility of alien life lurking in the soils of Mars. Scientists from Washington State University (WSU) in the US studied the driest corner of South America's Atacama Desert, where decades pass without any rain.

Scientists have long wondered whether microbes in the soil of this hyperarid environment, the most similar place on Earth to the Martian surface, are permanent residents or merely dying vestiges of life, blown in by the weather. In a study published in the journal Proceedings of the National Academy of Sciences, researchers showed that even the hyper-arid Atacama Desert can provide a habitable environment for microorganisms.

The researchers found that specialised bacteria are able to live in the soil, going dormant for decades, without water and then reactivating and reproducing when it rains. "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," said Dirk Schulze-Makuch, from WSU, who led the study. "Our research tell 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," said Schulze-Makuch.

Researchers went to the Atacama for the first time in 2015 to study how organisms survive in the soil of Earth's driest environment. After an extremely rare shower, the researchers detected an explosion of biological activity in the Atacama soil. They used sterilised spoons and other delicate instrumentation to scoop soil samples from various depths and then performed genomic analyses to identify the different microbial communities that were reproducing in the samples.

The researchers found several indigenous species of microbial life that had adapted to live in the harsh environment. The researchers returned to the Atacama in 2016 and 2017 to follow up on their initial sampling and found that the same microbial communities in the soil were gradually reverting to a dormant state as the moisture went away.

"In the past researchers have found dying organisms near the surface and remnants of DNA but this is really the first time that anyone has been able to identify a persistent form of life living in the soil of the  Atacama Desert," Schulze-Makuch said.

"We believe these microbial communities can lay dormant for hundreds or even thousands of years in conditions very similar to what you would find on a planet like Mars and then come back to life when it rains," he said. While life in the driest regions of Earth is tough, the Martian surface is an even harsher environment. It is akin to a drier and much colder version of the Atacama Desert. However, billions of years ago, Mars had small oceans and lakes where early lifeforms may have thrived.

As the planet dried up and grew colder, these organisms could have evolved many of the adaptations lifeforms in the Atacama soil use to survive on Earth, Schulze-Makuch said. "We know there is water frozen in the Martian soil and recent research strongly suggests nightly snowfalls and other increased moisture events near the surface," he said. "If life ever evolved on Mars, our research suggests it could have found a subsurface niche beneath today's severely hyper-arid surface," he said.