Layered rocks from Western Australia are among the earliest known life forms on Earth, according to a new study. The fossils in question are stromatolites, layered rocks formed by the feces of photosynthetic microbes. The oldest stromatolites, which scientists believe were made by living organisms, date back to 3.43 billion years ago, but there are older examples as well. Stromatolites dating back 3.48 billion years have been found in the Dresser Formation of Western Australia.

However, billions of years have erased any traces of organic matter in these ancient stromatolites, raising the question whether they were indeed created by microbes or by other geological processes.

“We were able to find specific microstructures that indicate biological processes in certain layers of these rocks,” he said. Keiron Hickman-LewisA paleontologist from the Natural History Museum in London, who conducted the research.

Microbial mats

These findings may have implications for life-seeking. Marcy, Hickman-Lewis told Live Science. The stromatolites in the Dresser Formation are covered with iron oxide as a result of the reaction of iron with oxygen in the atmosphere. The surface of Mars is similarly oxidized—hence its rusty orange color—but its rocks may contain similar structures left over from ancient Martian life, Hickman-Lewis said.

Hickman-Lewis and team studied Western Australian stromatolites, first discovered by the co-author in 2000. Francis Westall at the National Center for Scientific Research (CNRS) in France. They used a variety of high-resolution 2D and 3D imaging techniques to look at the stromatolite layers at a fine scale.

What they saw pointed to biological growth in all its scattered glory. The researchers observed irregular layers, including small dome-like shapes. photosynthesisbecause the microbes with the most access Sunwill grow stronger than microbes that are not very high in the structure. They also saw the columnar structures typical of modern stromatolites still found in various parts of the world.

“Microbial mantles form layers that are uneven in thickness and tend to wrinkle or shrivel, or move up and down at very small spatial scales,” said Linda Kah, a sedimentologist and geochemist at the University of Tennessee who was not involved in the new study. . . By putting all the structural clues together, “you get something that looks like a microbial mat,” he told Live Science.

Martian microbes?

Evidence that Dresser Formation stromatolites are signs of ancient life does not make them real. oldest life on the planet. This (possible) honor can go to the stromatolites found in it. 3.7 billion year old Greenland rocks. or maybe microfossils from Canada It could be 4.29 billion years. However, it is very difficult to distinguish biological life from inorganic processes in these very ancient rocks, so this and other finds from a similar time period are controversial.

Based on the minerals in the stromatolites, the researchers reported November 4 in the journal Geology., Western Australia’s microbial blankets probably formed in a shallow lagoon fed by hydrothermal vents, also connected to the ocean.(opens in new tab). According to Hickman-Lewis, methods used to study Western Australian stromatolites could be useful in the search for life on Mars, especially if Martian samples can be returned to Earth. Scientists should “see some of the analysis here as a trial run of the analyzes we’ll have to do in about a decade when we get materials from Mars.”