Diamonds beneath Mercury: Unimaginable quantities hint at planetary secrets

The study published in Nature Communications suggests that a layer of diamonds several miles thick could be beneath Mercury's surface. Although the costs of extracting them would be enormous, confirming this theory would provide valuable information about planet formation processes.

Mercury is a planet that may appear brighter than stars, but this is due to its proximity to the Sun. As noted by IFL Science, the planet reflects only 9% of light, mainly due to the large amount of graphite on its surface. MESSENGER, a space probe, showed that the graphite on Mercury dates from the planet's formation. According to research by Yongjiang Xu from the Chinese Centre for Advanced Science and Technology in High-Pressure Research, the carbon on Mercury could have transformed into diamonds under immense pressure.

Initially, Mercury's surface was an ocean of magma, from which gases such as carbon dioxide and methane were released. Despite Mercury having lower gravity and pressure than Earth, new models suggest conditions may have been conducive to diamond formation. High pressure and temperatures can transform carbon into diamonds, mainly when sulphur in the magma oceans contributes to the process.

Another scenario suggests that diamonds may have formed during the crystallisation of Mercury's core. As the inner core solidified, carbon could have been pushed outward, forming a layer of diamonds between the core and the silicate mantle. This layer might contribute to the planet's magnetic field. Although this layer's exact thickness and size are unknown, research indicates its presence.

As early as 2022, scientists at the Lunar and Planetary Science Conference presented similar conclusions. At that time, Kevin Cannon, a geologist from the Colorado School of Mines, explained that the graphite on Mercury’s surface could have transformed into diamonds due to pressure waves from asteroids or comets hitting the planet’s surface at speeds of tens of kilometres per second. He also added that these are most likely not large gemstones but small, cloudy diamonds used industrially as abrasive materials. According to experts, Mercury may contain up to 18 quintillion tonnes of them.