False fossil could mislead the search for life on Mars

At some stage a Mars rover will almost certainly find something that looks a lot like a fossil.


It is often acknowledged that the search for life on Mars might produce false-positive results. Martian rocks containing different types of non-biological deposits resemble life products if the planet ever supported life.

According to a new study, such fossil-like specimens could mislead Mars explorers searching for signs of ancient life. Distinguishing these false fossils from what could be proof of old life on the surface of Mars is key to the success of current and future missions.

In this new study, scientists from Universities of Edinburgh and Oxford reviewed known processes that could have generated false biosignatures on early Mars. These processes often generated deposits that look like bacterial cells and carbon-based molecules that closely resemble the building blocks of all known life.

Scientists noted, “Because signs of life can be so closely mimicked by non-living processes, the origins of any fossil-like specimens found on Mars are likely to be very ambiguous.”

However, further study is required to know more about how lifelike deposits could form on Mars, aiding the search for evidence of ancient life there and elsewhere in the solar system.

Dr. Sean McMahon, Chancellor’s Fellow in Astrobiology at the University of Edinburgh’s School of Physic and Astronomy, said: “At some stage, a Mars rover will almost certainly find something that looks a lot like a fossil, so being able to confidently distinguish these from structures and substances made by chemical reactions is vital. For every type of fossil out there, 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 these form.”

Julie Cosmidis, Associate Professor of Geobiology at the University of Oxford, said: “Life-mimicking processes have fooled us in the past. On many occasions, objects that looked like fossil microbes were described in ancient rocks on Earth and even in meteorites from Mars. Still, after deeper examination, they turned out to have non-biological origins. This article is a cautionary tale in which we call for further research on life-mimicking processes in the context of Mars so that we avoid falling into the same traps over and over again.”

Journal Reference:

  1. Sean McMahon, Julie Cosmidis. False biosignatures on Mars: anticipating ambiguity. DOI: 10.1144/jgs2021-050


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