A chemical process that produces methane without living organisms could have warmed up the young Earth – and may complicate the search for life elsewhere
By Michael Marshall
1 August 2023
In Earth’s early history, the sun was dimmer than it is now
Shutterstock/Chocolatealogy
A recently-discovered chemical process could have led to widespread formation of the greenhouse gas methane when Earth was young. The reaction doesn’t involve living organisms, so could have occurred early in our planet’s history.
“We identify a potential new source of methane prior to the origin of life,” says Johannes Rebelein at the Max Planck Institute for Terrestrial Microbiology in Marburg, Germany.
If enough methane was formed, it could help explain why Earth stayed warm at a time when the sun was dimmer than today.
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The discovery could also further complicate the search for life on other planets. Methane in the air of a planet is thought to be a signature of life, but astronomers will need to rule out the new process as an explanation for any detection of this gas.
Methane is a common chemical compound: each molecule consists of a single carbon atom surrounded by four hydrogen atoms. It is a greenhouse gas that traps the sun’s heat, warming the planet.
Today, most methane is made by living organisms, which use complex molecules called enzymes to do so. However, in 2022, Rebelein and his colleagues identified a process by which methane can form in living organisms without enzymes. Chemicals containing carbon, sulphur and nitrogen were transformed into methane, driven by highly reactive substances, including electrically-charged iron and reactive oxygen species.