Atacama Desert offers clues about life on Mars

In order to search for life on other planets, scientists are studying extreme environments on Earth to understand what that life might look like if they find it. Future Mars rovers like NASA’s 2020 rover and the European Space Agency’s ExoMars missions will search the red planet in the coming years for signs of past life.

So where’s the best mock Mars on Earth? These researchers think the closest analog is Chile’s Atacama Desert.

The Martian surface is harsh, a dry, cold, irradiated environment. But ancient Mars may have been habitable for microbial life because it supported water. The rovers going to Mars in the coming years will be searching for biosignatures in Martian soil, drilling and sampling below the surface to find evidence of this potential ancient life.

Researchers investigated how microbial life can be transported in the Atacama Desert and found that it could be easily carried on dust particles by wind. Their study published Thursday in the journal Scientific Reports.

Samples were taken from three sites across two regions of the desert, which is incredibly arid, receives large amounts of UV radiation from the sun and has salty soil. They found 23 bacterial species and eight fungal species.

Only three of the species were shared across regions. But two of the species had intriguing origins. A bacteria called Oceanobacillus oncorhynchi comes from aquatic environments, while Bacillus simplex is found in plants. So how did they end up in the arid core of the desert?

The researchers believe that they came from the Pacific Ocean and the desert’s coastal range.

Time of day also mattered. Samples collected in the morning hours were traced to nearby points of origin. In the afternoon, microbes and marine-based samples came from remote locations — carried on dust particles.

So even across one of the driest and irradiated places on Earth, life can still be found. The researchers believe the same could be true of Mars.

Mars has a constant wind cycle and even endures dust storms that can cover the entire surface of the planet. And, as the study authors point out, their findings also have implications for efforts to protect planets we land on from contamination. Microorganisms on rovers or landers could eventually be dispersed across the planet by dust storms.

In a study released earlier this year, researchers used a rover to drill for samples of bacteria below the surface in the Atacama Desert.

The rover found patches of unusual microbes that were highly specialized. The researchers believe that the patchy distribution is because of the soil’s chemistry and the lack of nutrients and water. They compared the rover’s samples with those that they took from the desert manually. The microbial life was similar in both types of samples.

“We found microbes adapted to high salt levels, similar to what may be expected in the Martian subsurface,” said Stephen Pointing, study author and director of the science division at Yale-NUS College in Singapore. “These microbes are very different from those previously known to occur on the surface of deserts.”