The Perseverance rover is searching for signs of ancient life on Mars. The image is from NASA/JPL-Caltech.
The search for life on the Red Planet could be hampered by the existence of dozens of nonbiological "false fossils" on Mars.
The Perseverance rover touched down on Mars in February, and the European Space Agency will launch the Rosalind Franklin rover in 2022. biosignatures are traces of past life left behind when the planet may have been a good place to live.
There is a new paper suggesting a possible complicating factor in that search.
Astrobiologists are holding out hope for life on Mars.
"There is a chance that one day, we will observe something on Mars that looks really biological, only to realize several years later, after further research, that this thing was actually formed by nonbiological processes," said co-author Julie Cosmidis.
Sean McMahon, an astronomer at The University of Edinburgh in Scotland, and Cosmidis worked together to identify the potential false biosignatures before the rovers found them.
False positives.
A biosignature can be evidence of an product or an animal. Natural physical or chemical processes can't make biosignatures. Astrobiologists have been looking for signs of primitive life on other worlds for decades.
The hunt for biosignatures is limited. McMahon told Live Science that they are good at spotting life even when it isn't there.
Many things that look like biosignatures can be created without life.
McMahon said that the range of structures, materials and chemical compositions that can be produced nonbiologically overlaps with the range of things that can be produced biologically. We're not sure if some phenomena are biological or not.
Cosmidis said that paleontologists have been confused by these fake fossils. It can be difficult to identify ancientbacteria and other single-celled organisms.
Scientists claimed to have found fossils of organisms in a meteorite in 1996. Their discovery was hailed as the first proof of alien life and even prompted a speech from President Bill Clinton. These fossils were not made by life-forms, according to further tests.
It could take years to vet the Martian samples because scientists won't be able to test them properly until they are returned to Earth.
"False biosignatures are often disproved only after further analysis by different researchers using different techniques," Cosmidis said. We won't have this option for Mars until years after the samples are collected.
There are a lot of false biosignatures on Mars.
One of the best examples is carbon-sulfur biomorphs, tiny spheres that can form spontaneously from reactions between carbon and sulfide. She said that the resulting biomorphs would be very well suited for rock types that are common on Mars.
Under a microscope, carbon-sulfur biomorphs were created. Credit: Julie Cosmidis
It will be tempting to think that the spheres and organic filaments in the rocks are fossils, but they could be carbon-sulfur biomorphs.
stromatolites, which are large structures left behind by photosynthetic algae that grow upward as cones, domes and columns, are examples of pseudo-microbialites. It will be hard to tell if the structures are genuine because they can be similar in appearance but not in substance.
McMahon and Cosmidis recreated false biosignatures in Martian conditions and tried to come up with new examples. There are more than a dozen fake fossils listed in the new paper.
The researchers hope that their work will help to prevent an error from being made, which would undermine decades of work in the search for alien life.
Errors and their corrections are a normal part of science. There is a risk that the public will distrust the scientists if they talk about the search for life on Mars.
The researchers say that they are committed to finding life on Mars.
Cosmidis said that they are not trying to dismiss the efforts that NASA and the European Space Agency are making to find life on Mars. We want to help the researchers involved in these missions make better and more informed interpretations of the objects they observe.
The paper was published in the Journal of the Geological Society.
Live Science published the original article.
