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Doubt over fossil findings could aid future Mars missions

Research that suggests structures found within ancient rocks may be mineral deposits instead of fossils may aid in the search for extra-terrestrial life.

Astrobiologist Sean McMahon, from the University of Edinburgh, has completed a study which he believes will make it easier for researchers to distinguish between fossils and non-biological structures in future Mars missions.

The study has focused on microscopic tubes and filaments that resemble the remains of tiny creatures. Previous research suggested such structures found in Mars-like rocks were among the oldest fossils on Earth.

McMahon, who is developing techniques to seek evidence that life once existed on the red planet, created tiny formations in the lab that mimicked the shape and chemical composition of iron-rich structures commonly found in rocks that are billions of years old.

He 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.

Being able to make a clear distinction between fossils and non-biological structures could save future Mars missions valuable time and resources when searching for extra-terrestrial life, McMahon said.

However, 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.

“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,” he said.

“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.”

The study, published in the journal Proceedings of the Royal Society B, was funded by the European Union’s Horizon 2020 program.

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