Most of Earth’s diamonds formed billions of years ago, during the supercontinent cycle, as carbon fragments around 100 miles deep were crystallized by unimaginable forces of heat and pressure. But diamonds can also flash-form due to meteorite impact.
According to Science News, Surveys of Mercury’s surface and experiments with molten rock suggest the swift planet’s crust retains fragments of an old shell of graphite, which is a form of carbon. It’s theorized that Mercury first formed with an ocean of magma, from which this graphite crust crystalized.
Time, Heat and Pressure
Planetary scientist Kevin Cannon, of the Department of Geology and Geological Engineering at Colorado School of Mines, believes billions of years of violent urelite/meteorite impacts, may have flash-baked much of Mercury’s graphite crust into diamond. According to Cannon:
The planet Mercury may be unique in the solar system in having formed a graphite floatation crust during magma ocean cooling, and this initial graphite layer has been linked to the Low Reflectance Material (LRM) identified by the MESSENGER mission… If urelites started with just 8.5 wt.% C and ended up with significant coarse-grained diamond, it seems unavoidable that a graphite crust would not have experienced at least partial transformation to diamond through the late heavy bombardment (full transcript).
16 Quadrillion Tons?
Curious how pervasive this diamond forging could have been, Cannon used computers to simulate 4.5 billion years of violent meteorite impacts on a graphite crust. His findings show that if Mercury possessed a skin of graphite just 300 meters thick, the impacts would have generated 16 quadrillion tons of diamonds, which is around 16 times Earth’s estimated reserves.
An opportunity to scout for diamonds on Mercury may come in 2025, when the European Space Agency’s BepiColombo mission reaches the planet. Diamonds reflect a distinct signature of infrared light. According to Cannon, “Potentially, this could be detected.”