Studying satellite images of Argentina’s Puna de Atacama desert, CU Boulder geologist Brian Hynek noted something strange. In the monotone grey of salt and sand plains, he noted a number of green and blue spots of unknown origin.
The Puna de Atacama is a high plateau desert more than 3,000 meters above sea level, surrounded by even higher peaks of the Andean Mountain Range. It’s among the driest environments on Earth. Here, rain rarely, if ever, falls, and sunlight beats down unforgivingly, creating an environment few animals or plants can survive. So the spots were unlikely to be some kind of vegetation or human-made.
Together with Maria Farías, a microbiologist and co-founder of PUNA.BIO Environmental Consulting, Hynek decided to visit the area to solve this mystery.
After hours driving on dirt roads and walking in mud, they found that the spots are a network of twelve lagoons, hosting a unique community of microbes that form giant mounds of rock in the shallow water.
Hynek’s preliminary observations suggest that these communities may resemble stromatolites, the earliest signs of life that existed on Earth over 3.5 billion years ago.
“This lagoon could be one of the best modern examples of the earliest signs of life on Earth,” explains Hynek, professor in the Laboratory for Atmospheric and Space Physics (LASP) and Department of Geological Sciences. “It’s unlike anything I’ve ever seen or, really, like anything any scientist has ever seen.”
Stromatolites, in general, refer to a range of microbial communities that are associated with layers of rock. They exist on Earth today, including off the coast of the Bahamas and Australia, but modern stromatolites tend to be relatively small. They also grow passively by trapping grains of sand and other detritus floating in the ocean.
Ancient stromatolites, in contrast, could stretch to 6 meters tall. They actively pulled in calcium and carbon dioxide from the surrounding water, causing minerals to precipitate around them.
The mounds in the Atacama lagoons looked a lot more like some of those ancient communities than anything alive on Earth today. They are large, some 4 meters wide and several meters high, and show a layered structure ranging in color from brown to pink to green. The colors reflect different microbial communities, from brown microbes that live without oxygen, to pink salt-tolerant microorganism to green photoautotrophic cyanobacteria forming the outer layer of the stromatolite.
Why they formed at this one, harsh location isn’t clear. The lagoon environment could resemble the conditions on ancient Earth, Hynek says—the waters are salty and acidic and, because of the high elevation, are exposed to severe levels of solar radiation, allowing only specialized microscopic life to survive.
After presenting their first results at the AGU annual meeting earlier this month, the researchers hope to return to the lagoons as soon as possible.
However, they may be running out of time. A company from outside Argentina has already leased the area to mine for lithium and other rare elements deposited from the evaporating water.
“This entire, unique ecosystem could be gone in a matter of years,” Hynek says. “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.”
Additional material and interviews provided by the University of Colorado Boulder.
