Don’t be fooled by fake fossils on Mars, warn biologists • The Register

Scientists should remain skeptical if they study rock samples drilled by NASA’s Perseverance rover for evidence of alien life, lest they be fooled by fake fossils, UK academics have warned.

Definitive signs of ancient microbial life are difficult to find in geological materials, argued Sean McMahon, an astrobiologist at the University of Edinburgh, and Julie Cosmidis, a geobiologist at the University of Oxford. Chemical processes on the surface of Mars could produce substances very similar to those created by living organisms.

Interesting patterns in clay sediments or rock layers can give the impression that they have been deposited by cell life, like stromatolites, for example. Scientists may be excited to find these structures, but before taking the plunge, they should also determine if these marks may have been carved out by geological or chemical processes on Mars.

For every type of fossil, there is at least one non-biological process that creates very similar things, so there is a real need to improve our understanding of how they are formed.

“At some point, a Martian rover will almost certainly find something that looks a lot like a fossil, so it is vital to be able to confidently distinguish them from structures and substances created by chemical reactions,” said McMahon, also a fellow of the chancellery at the school of physics. and astronomy in Edinburgh, said Wednesday.

“For every type of fossil, there is at least one non-biological process that creates very similar things, so there is a real need to improve our understanding of their formation.”

The problem is, scientists don’t know enough about these processes to rule them out. “These phenomena tend to be driven by kinetic processes far from thermodynamic equilibrium, often in the presence of liquid water and organic matter, conditions similar to those which can actually give rise to and sustain life,” wrote the couple in a published article. in the Journal of the Geological Society.

The Boffins have been duped by false fossils in the past. In the 19th century, paleontologists believed they had discovered the oldest fossil in the world. The specimen, known as Eozoon canadense, or “Canada’s dawn animal,” consisted of crystalline calcite and serpentine organized in a wavy pattern like ripples in a pond. At the time, the egg heads were believed to have fallen on a massive imprint of a single-celled organism known as foraminifera.

But decades later, the sample was labeled as a pseudo-fossil after scientists discovered non-biological explanations for the patterned rock. Similar scenarios of weird marks that look like worm tracks or arthropods have already fooled people.

An example of a meteorite from Mars, named ALH84001, made headlines after being studied in 1996 because it contained what appeared to be a morphological fossil. Clusters of nodules made of carbonate and magnetite excited experts, who thought they were made of bacteria. While it’s still not clear how these structures formed, scientists no longer consider ALH84001 a serious candidate to prove alien life on Mars.

“We have been deceived by life-mimicking processes in the past,” said Cosmidis, associate professor in the Oxford Department of Earth Sciences.

“On numerous occasions, objects that resembled fossil microbes have been described in ancient rocks on Earth and even in meteorites from Mars, but upon closer examination they were found to have non-biological origins. This article is an uplifting account in which we call for further research on life imitation processes in the context of Mars, in order to avoid falling into the same traps over and over again.

Instead, Cosmidis and McMahon believe astrobiologists should systematically research more possible non-biological pathways that create false biosignatures in the lab to prepare for Perseverance’s future return mission.

“If we are lucky, simple and unambiguous biosignatures will be discovered on Mars in the coming decades. But in light of the many edifying accounts in the history of paleontology and astrobiology, it seems prudent to anticipate. more ambiguous results, ”they concluded.

“Further work on the physics and chemistry of systems far from equilibrium will ultimately reveal the limits of abiotic self-organization and may even lead to new discoveries on the organizational principles underlying life. on earth. Such efforts have an important part in the interpretation of the Earth’s rock record as well as in the search for life on Mars and elsewhere in the solar system. “®


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