A rare ecosystem containing examples of the world’s oldest fossils provides a window into early life on Earth

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Scientists have discovered a previously hidden ecosystem with an expanded system of lakes in the salt plains Puna de Atacama – an arid plateau in Argentina – contains giant stromatolites that could offer a glimpse of early life on Earth and perhaps even on Mars, according to new research.

Stromatolites are Layered rocks Resulting from the growth of blue-green algae, or cyanobacteria, through the process of photosynthesis. These structures are considered one of the oldest ecosystems on Earth. According to NASA, It represents at least the oldest fossil evidence of life on our planet 3.5 billion years ago.

“It certainly resembles some of the oldest macrofossils on our planet, and is actually a rare type of environment on modern Earth,” he said. Brian Hyneka professor at the University of Colorado Boulder’s Department of Geological Sciences, who helped document the ecosystem. “It’s a window into the distant past to see what life was like 3.5 billion years ago on our planet.”

Ancient giant stromatolites were widespread in Earth’s Precambrian Era, which includes an early time period of ca. 4.6 billion to 541 million years agoBut it is now sparsely spread throughout the world. The most developed areas are in the Bahamas and the Shark Bay region of Western Australia, according to the non-profit conservation organization. Bush Heritage Australia.

Hynek said modern stromatolites are relatively small, while ancient stromatolites would have grown to be up to 20 feet (6 meters) long and 16 to 22 feet (5 to 7 meters) wide. Beneath the waters of the Puna de Atacama lakes, recently discovered stromatolites are up to 15 feet (4.5 meters) wide and several feet high. According to a press release From the University of Colorado Boulder.

Stromatolites also tend to grow in alkaline conditions, but the lagoon system at Puna de Atacama is acidic. Stromatolites found today are almost entirely carbonate rocks (made of limestone), but these structures are mostly composed of minerals Gypsum and halite (Saltpeter), Hynek said.

Hynek said it was unclear why the stromatolites were so large, but he speculated that the internal ecosystem remained undisturbed for a long period of time, allowing them to grow unimpeded.

Unlike modern stromatolites, ancient stromatolites grew during a period when the atmosphere lacked oxygen. In these conditions, stromatolite microbes are used Anoxygenic photosynthesiswhich do not require oxygen, to convert light energy into compounds that support living cells.

“It is amazing to find structures that could be biological in origin (produced by living organisms) at this unusual altitude,” he said. Peter Fisher, a professor of marine sciences at the University of Connecticut who has studied stromatolites extensively, said in an email. “The main problem with this discovery, whether biological or not, is that these form in the presence of oxygen (in the current atmosphere). Until 2.3 billion years ago, there was no oxygen.

Hynek said that while the stromatolites were in an oxygen-containing environment The distant layers in the rock are thought to have little oxygen and are actively formed by microbes using anoxygenic photosynthesis. This would make the structures similar to those found on ancient Earth.

Hynek discovered the lake system through satellite images in April 2022 when he was studying another lake in northwestern Argentina that contained smaller stromatolites with microbes that use anoxygenic photosynthesis.

“We are not sure if microbes are actively involved in their growth (in the newly discovered stromatolites). We think they are. We are facing a big problem,” said Hynek, who documented the initial observations with microbiologist Maria Farias, co-founder of environmental consultancy Punabio SA. . But we haven’t done the experiments yet to try to figure that part out. “There’s a lot of work to be done. We’ve only just discovered them and have barely scratched the surface.

Hynek and Farias were scheduled to present their findings on December 11 at the 2023 meeting of the American Geophysical Union in San Francisco, according to a press release.

If stromatolites are produced by microbes using anoxygenic photosynthesis, the discovery could provide insight into the possibility of life on ancient Mars, Hynek said.

“We have identified more than 600 Ancient lakes on Mars; Maybe there was an ocean. “It was like Earth early on,” he said. Hynek also said Gypsum and halite mineralsfound in stromatolites in Argentina, are also found in salt deposits throughout Mars.

“If Mars developed life through photosynthesis, this is the kind of thing we would be looking for (stromatolites) – which The kind of thing we’re looking forsaid Hynek, who is also a research associate at the University of Colorado Boulder Laboratory for Atmospheric and Space Physics.

“If we want to find any kind of fossils on Mars, this is our best guess as to what they are, because they are the oldest in the terrestrial rock record.”

Hynek said he hopes to return to the lake soon to conduct more research on stromatolites.

“Stromatolites on Mars? A long shot, but who knows. “So far there are no carbonates on Mars, but the research is continuing,” Fisher said.