The clayey subsoil in the driest place on Earth could signal life on Mars

The driest desert on Earth could be a key to finding life on Mars.

Several microbes discovered in the clay-rich, shallow layers of soil in Chile’s Atacama Desert suggest that similar deposits beneath the Martian surface could contain microorganisms, which could easily be found by future rover missions or landing craft.

Led by Cornell University and Spain’s Centro de Astrobiología, the scientists now offer a planetary primer for identifying microbial markers in the rover’s surface excavations in Martian clay, in their work published Nov.5 in Nature Scientific Reports.

In that dry environment in Atacama, scientists found layers of wet clay about a foot below the surface.

“The clays are inhabited by microorganisms,” said corresponding author Alberto G. Fairén, a visiting scientist in Cornell University’s Department of Astronomy. “Our discovery suggests that something similar could have happened billions of years ago – or could still happen – on Mars.”

If microbes existed on Mars in the past, their biomarkers would likely be stored there, Fairén said. “If microbes still exist today,” he said, “the last possible Martian life may still rest there.”

The red planet will see rovers cross the surface in the next few years. NASA’s Perseverance rover will land on Mars in February 2021; The European rover Rosalind Franklin will arrive in 2023. Both missions will look for microbial biomarkers in the clay beneath the planet’s surface.

“This document helps guide research,” Fairén said, “to indicate where we should look and what tools to use in the search for life.”

In the Yungay region of the Atacama Desert, scientists found that the clay layer, a previously unreported habitat for microbial life, is inhabited by at least 30 salt-loving microbial species of metabolically active bacteria and archaea (single-celled organisms).

The researchers’ Atacama discovery strengthens the idea that early Mars may have had a similar subsoil with protected habitable niches, particularly during the first billion years of its history.

“That’s why clays are important,” he said. “They store organic compounds and biomarkers extremely well and are abundant on Mars.”