Mercury, the smallest planet in our solar system, has bewildered scientists with its remarkably dark surface and high core density.
In 2009, NASA's MESSENGER spacecraft revealed graphite on Mercury's surface, leading researchers to speculate that the planet may have once had a carbon-rich magma ocean.
A new study published in Nature Communications proposes that the boundary between Mercury's core and mantle could feature a layer of diamond up to 18 kilometres thick.
Dr Yanhao Lin, a co-author of the study, said that the research challenges the assumption that graphite was the only stable carbon-bearing phase during Mercury's magma ocean crystallisation.
"Many years ago, I noticed that Mercury's extremely high carbon content might have significant implications,” he told PHYS.ORG.
“It made me realise that something special probably happened within its interior.”
To test the theory, the scientists recreated Mercury's extreme interior conditions using high-pressure and high-temperature experiments.
These experiments provided insights into how minerals in the interior melt and reach equilibrium, focusing on the phases of graphite and diamond.
He added: "[This research] also could be relevant to the understanding of other terrestrial planets, especially those with similar sizes and compositions.”
“The processes that led to the formation of a diamond layer on Mercury might also have occurred on other planets, potentially leaving similar signatures."
Researchers in 2022 suggested that Mercury's surface was also littered with diamonds.
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