Correct identification, honed on Earth, could help avoid false Eureka! moments during fossil hunts on Mars:
Astrobiologist Sean McMahon created tiny formations in the lab that closely mimic the shape and chemical composition of iron-rich structures commonly found in Mars-like rocks on Earth, where some examples are thought to be around four billion years old.
Dr McMahon created the complex structures by mixing iron-rich particles with alkaline liquids containing the chemicals silicate or carbonate.
This process — known as chemical gardening — is thought to occur naturally where these chemicals abound. It can occur in hydrothermal vents on the seabed and when deep groundwater circulates through pores and fractures in rocks.
His findings suggest that structure alone is not sufficient to confirm whether or not microscopic life-like formations are fossils. More research will be needed to say exactly how they were formed…
Dr Sean McMahon said: “Chemical reactions like these have been studied for hundreds of years but they had not previously been shown to mimic these tiny iron-rich structures inside rocks. These results call for a re-examination of many ancient real-world examples to see if they are more likely to be fossils or non-biological mineral deposits.” – Sean McMahon. Earth’s earliest and deepest purported fossils may be iron-mineralized chemical gardens. Proceedings of the Royal Society B: Biological Sciences, 2019; 286 (1916): 20192410 DOI: 10.1098/rspb.2019.2410
Paper. (open access)
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