Mercury’s Cratered Crust May Hold Glittering Gemstones

Fragments of a graphite shell from the planet’s past and a series of violent meteorite impacts may have combined to form sparkling diamonds

An image of planet Mercury showing its cratered surface and sublte color
Researchers turned to Mercury for the possibility of impact-born diamonds because previous surveys of the planet and molten rock found that the surface may have fragments of graphite, a carbon-rich mineral. NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie

Mercury’s cratered surface may hold precious shards of diamonds. The glittering world may have formed from the billions of years of meteorite impacts that flash-baked Mercury’s crust, reports Nikk Ogasa for Science News.

The new research was presented by Kevin Cannon, a planetary scientist at the Colorado School of Mines, during the Lunar and Planetary Science Conference earlier this month.

Mercury is the smallest planet in the solar system and the closest to the sun. Much like Earth’s moon, deep craters riddle Mercury’s surface. In its tumultuous early years, Mercury underwent a violent period called the Late Heavy Bombardment, where the terrestrial planet and the rest of the solar system faced an intense spike in asteroid strikes four billion years ago.

“The pressure wave from asteroids or comets striking the surface at tens of kilometers per second could transform that graphite into diamonds,” said Cannon to Wired’s Ramin Skibba. “You could have a significant amount of diamonds near the surface.”

On Earth, diamonds form 100 miles or so deep below the surface of the upper mantle. Under intense pressure and high temperatures, carbon atoms bond together. The gemstones then rise to the surface during volcanic eruptions, Science News reports. However, meteorite studies suggest that radiant gems can also form upon asteroid impacts.

Researchers turned to Mercury to study the possibility of impact-born diamonds because previous surveys of the planet and molten rock found that the surface may have fragments of graphite, a carbon-rich mineral.

“What we think happened is that when [Mercury] first formed, it had a magma ocean and that graphite crystallized out of that magma,” Cannon tells Science News.

A close up image of planet Mercury's cratered surface
A view of Mercury's cratered southern hemisphere. NASA

Much like the other worlds in the solar system, Mercury, at one point, was covered in magma, which later cooled and hardened. As Mercury’s surface cooled, a layer of graphite floated toward the top of all the molten rock, Wired reports.

Scientists modeled the effects of frequent impacts on the first 12 miles of the planet’s crust over billions of years using computer simulations. The team found the graphite may have been more than 300 feet thick and the impact of a meteorite was strong enough to turn 30 to 60 percent of the carbonaceous mineral into diamonds, per Wired. Under those conditions, 16 quadrillion space gems are estimated to riddle Mercury, but they are most likely tiny, scattered and buried underground.

“There’s no reason to doubt that diamonds could be produced in this way,” says Simone Marchi, a planetary scientist at the Southwest Research Institute who was not involved with the research, to Science News.

Other studies on meteorites that crashed on Earth support that diamonds can form this way. In 2008, researchers analyzed meteorites that fell on the Nubian desert in Northern Sudan. Known as Almahata Sitta, the meteorites contained tiny diamonds, Wired reports.

The research team is planning further simulations to see the remelting of diamonds upon meteorite impacts. Further, researchers may get the chance to analyze Mercury for diamonds when the European Space Agency and Japan Aerospace Exploration Agency’s BepiColombo reaches the planet in 2025. The space mission was designed to study Mercury exclusively.