Hidden biosphere discovered beneath world's driest hot desert

In a discovery with potential relevance to the search for extraterrestrial life, scientists have identified microbial life 13 feet beneath Earth's most extreme desert. This research appears in PNAS Nexus.

Northern Chile's Atacama Desert is the world's driest hot desert. While higher life forms are scarce, the hyper-arid, salt- and sulfate-rich soil supports bacterial life.

The upper 80 centimeters of soil might protect against intense UV radiation and retain some moisture. But what about deeper layers? Dirk Wagner and his team aimed to explore the deeper subsurface. They dug over four meters in a playa within Yungay Valley to gather soil samples.

They developed a unique extraction technique to confirm that the DNA came from living organisms.

The team first removed loose DNA, then extracted DNA from intact cells for sequencing. In the top 80 cm, Firmicutes dominated the microbial community, while below 200 cm, Actinobacteria were prevalent.

Some bacteria were genetically similar to Geodermatophilus pulveris and Modestobacter caceresii. The researchers propose that these microbes may have settled in the soil around 19,000 years ago before being buried by playa deposits. They hypothesize that this deep biosphere could extend indefinitely downward, depending on gypsum for water. Notably, Mars also contains gypsum, suggesting it might support microbial life in a similar way.