As we look for signs of life on Mars, we need to look for “false fossils” that may be abundant on the Red Planet, according to new research.
The Marsman Perseverance lists his mission among the first to explore the red planet. The robot scientist has been tasked with looking for signs of ancient microbial life on a dusty, dry planet – small microfossils that would be evidence that Mars was once habitable.
It would indeed be an amazing, incredible discovery – but the new paper urges caution in interpreting what we find, both from this and future sources.
Astrobiologist Sean McMahon of the University of Edinburgh and geobiologist Julie Cosmidis of the University of Oxford in the UK say researchers need to keep an eye on non-biological mineral deposits that look a lot more fossilized.
In a new article, the couple has outlined dozens of non-biological or abiotic processes that can produce pseudophossils — structures that look like fossils of microscopic organisms, such as may have ever appeared on Mars.
“At some point, a Mars walker will almost certainly find something that looks a lot like fossil, so it’s vital to reliably separate them from the structures and substances caused by chemical reactions,” McMahon said.
“There is at least one non-biological process for each type of fossil that creates very similar things, so there is a real need to improve our understanding of how these are formed.”
This perception is not really surprising. Mars is an absolute feast for pareidolia and conspiracies. All you need is one fun-looking stone and rumors are raging.
Nor is it just afternoon newspapers and conspiracy theorists – scientists have also surrendered to Mars fantasies. You may remember a time when mycologists thought they had found mushrooms on Mars, or an entomologist who thought they had found bugs.
Microfossils can therefore be quite problematic. Even here on earth we have difficulty distinguishing between really old rocks and fossils of ancient microbes.
But if we begin the analysis of potential microfossils on Mars knowing the processes that can produce pseudophossils, we have a better chance of interpreting what we see accurately.
Many of the physical processes involved in weathering and the deposition of sediment layers can produce rocks that look frightening fossils.
Another mechanism is a chemical garden, where the mixing of chemicals can produce structures that look biological. Many different types of minerals can also combine pseudophossils, known as biomorphs, that look amazingly biological.
Below is an example of chemical garden pseudophossils.
Even the textures of a stone can look biological because organisms can carve patterns or holes in the stone. And the isotope ratios of different elements may look similar to the isotope ratios in biological contexts.
Because we don’t know what life on Mars could have been like – it might be quite different from life here on earth – and because, as McMahon and Cosmidis pointed out, there are likely to be many unknown processes that can produce pseudophossils, biologists looking for life on Mars really need to be well careful.
Researchers also point out that further work on the chemistry and physics of Mars, perhaps even experimentation, could reveal some of these unknown processes and shed more light on the emergence of such formations. This work could even help us better understand the Earth’s rock and fossil records.
“We have been tricked into life-mimicking processes in the past,” Cosmidis said.
“Objects that often looked like fossil microbes were photographed in the earth’s ancient rocks and even in Martian meteorites, but after deeper examination, their origins turned out to be non-biological. This article is a warning report “
The study has been published in a journal Journal of the Geological Society.