Rocks from the Australian Outback dating all the way back to 3.5 billion years may help scientists determine whether life ever existed on Mars. Only ancient microbes, according to researchers studying the Australian rocks, could have shaped them the way they are.

They recommend that NASA’s Perseverance rover look for resemblances when uncovering rocks of similar age on Mars. The wheeled robot is searching for proof that biology established itself on Mars early in its history.

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Scientists from the Natural History Museum (NHM) in London, in collaboration with NASA, have described a variety of large and small features in a sequence of domes in Western Australia that seem to have been created by ancient microbes. They don’t have any microbe fossils or organic (carbon-rich) compounds that could be evidence of past life. The NHM-led team, on the other hand, believes it has identified signatures denoting the rocks’ biological origin.

Perseverance is examining a large crater called Jezero and is expected to come across locations next year that may exhibit phenomena similar to those seen in Earth rocks.

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The researchers used a wide range of high-resolution analytical and graphic methods to characterize frameworks whose presence, they argue, can only be revealed by life’s activity rather than something that might naturally occur in the environment.

The rippling upper portion of stromatolites, which forms as photosynthesizing microbes grow towards the light, is one large-scale feature. The undulations appear because biology does not grow at a uniform rate in three dimensions. 

Microscopically, tiny columns or pillars within the rock hint at the links between the specific “mats” of microbes that create the stromatolites.

“The biological structures found in the Dresser Formation are known as stromatolites, which are the preserved remains of ‘microbial mats’ stacked on top of one another. These mats form when communities of bacteria and other microbes secrete sticky substances that bind them together,” the Natural History Museum in the UK said in a press release. Dr. Keyron Hickman-Lewis of the museum was part of the study, which has been published in the journal Geology

Hickman-Lewis, a paleontologist, said, “If an archaeologist discovered the foundations of a ruined city, they would nonetheless know it was built by people because it would bear all the hallmarks of being built by people – doorways and roads and bricks.”