A remote desert ecosystem may hold clues to Earth’s earliest days

Researchers have discovered a unique lagoon ecosystem in Argentina’s high Puna de Atacama Desert, they announced at a meeting of the American Geophysical Union last week. The ecosystem, which features bizarre rocky formations that teem with microbial life, is thought to resemble the kinds of conditions prevalent on Earth in its earliest days.

The discovery, made by geologist Brian Hynek of the University of Colorado at Boulder and Argentine microbiologist Maria Farías, occurred after the scientists saw something unexpected on satellite images of a region they’d been surveying in April 2022: a remote network of lagoons surrounded by salt plains in a notoriously inhospitable desert. When the pair hiked to the high-altitude site to investigate, they discovered 12 lagoons filled with clear waters and greenish, rocky mounds.

Those large mounds, some several feet high, are stromatolites, the researchers say — and they hark back to what Earth may have looked like billions of years ago. Neither plant nor animal, a stromatolite is a structure that forms when microbial communities interact with sedimentary rocks to form layered microbial mats in which biofilm produced by the tiny microbes traps minerals and sediments, building upward over time.

The strange structures are thought to have been the earliest life forms on Earth, and the oldest examples formed about 3.5 billion years ago.

Modern-day examples are rare and are mostly found in salt-rich environments like Australia’s Shark Bay, and some fossilized stromatolites still exist in places like the Capitol Reef National Park in Utah.

In an abstract, the scientists write that they have “results from this unique ecosystem and can detail how the very local geochemistry and microbial communities lead to stromatolite growth in these hypersaline closed basin environments …. These types of settings were likely very prevalent on early Earth and also possibly Mars.”

The newly discovered stromatolites are very much alive, the researchers say, and more closely resemble ancient stromatolites than smaller modern ones. Preliminary results show the mounds consist mostly of gypsum with an outer layer of cyanobacteria and a pinkish core that contains single-celled microorganisms called archaea.

“We think these mounds are actually growing from the microbes, which is what was happening in the oldest ones,” Hynek said in a news release .

The researchers will soon return to the lagoons to confirm their initial results, they say. But time is of the essence: The area is slated for lithium mining that could endanger the lagoons and the newly discovered formations. “This entire, unique ecosystem could be gone in a matter of years,” Hynek said in the news release. “We’re hoping that we can protect some of these sites, or at least detail what’s there before it’s gone or disturbed forever.”