Argentina’s Atacama desert, considered the driest place on Earth, hides a rich ecosystem of lagoons teeming with life, researchers have discovered.
Geologist Brian Hynes and micobiologist Maria Farias discovered the lagoons last year. They were studying a different lagoon with stromatolites and looking at aerial images of the region. To their amazement, they spotted a completely different system of lagoons.
The pair immediately went to see if they were correct. After a long hike, they found themselves knee-deep in salt slush. The lagoons existed. In fact, 12 lagoons stretched across 10 hectares. All had many stromatolites beneath the water.
Living fossils
Stromatolites are microbial communities that fossilize into giant rocks through the photosynthesis of cyanobacteria. Scientists think the underwater structures are one of the oldest ecosystems on the planet. Ancient stromatolites existed up to 4.6 billion years ago, but very few of them still exist.
The biggest difference between ancient stromatolites and modern ones is their size. The older ones were far larger. The large green mounds in the lagoons are 4.5 meters wide, which is closer to the size of ancient stromatolites than modern ones.
Hynes and Farias think these could closely mirror the stromatolites that existed 3.5 billion years ago. During the Achaean period, there would have been much less oxygen in our atmosphere. The cyanobacteria would have had to carry out anoxygenic photosynthesis.
Ancient stromatolites in northern Canada. Photo: Jerry Kobalenko
Earliest life on Earth
Though the layers at the top of the newly found stromatolites do have access to oxygen, Hynek thinks the lower layers are using anoxygenic photosynthesis. This would make them incredibly similar to those from early in Earth’s history.
“This lagoon could be one of the best modern examples of the earliest signs of life on Earth,” said Hynek. “It’s unlike anything I’ve ever seen or, really, like anything any scientist has ever seen.”
Another big difference is what these stromatolites are made of. The outer layers contain cyanobacteria, while the inner layers contain a lot of archaea, single-celled organisms found in extreme environments.
Gypsum and halite make up most of the rock layers. Again, these minerals often occur in stromatolite fossils, but not in modern stromatolites, which are usually made up of carbonate rock.
Hynek cracked open a stromatolite revealing its pink center. Photo: Brian Hynek
Connection to Mars
These valuable ecosystems could provide information into potential life on Mars. The anoxic conditions of the lower layers resemble those of both early Earth and of Mars. So if there had ever been life on Mars, then the macrofossils could look similar to the stromatolites.
“We’ve identified more than 600 ancient lakes on Mars,” Hynes said in a statement. “There may have even been an ocean. So it was a lot more Earth-like early on. If we’re going to find any fossils on Mars, this is our best guess as to what they would be, because these are the oldest ones from Earth’s rock record.”
Why the stromatolites formed here is still a complete mystery. The researchers are now working against the clock to learn more about the ecosystem. The area is earmarked for a lithium mine. Once the work begins, the lagoons could undergo irreversible changes.
