Scientists Discover Potential 10-Mile-Thick Diamond Mantle Beneath Mercury's Surface Using NASA's MESSENGER Data

Scientists Discover Potential 10-Mile-Thick Diamond Mantle Beneath Mercury's Surface Using NASA's MESSENGER Data
Image credit: Space.com

The solar system's smallest planet, Mercury, may be hiding a significant secret beneath its crust. Using data from NASA's MESSENGER spacecraft, scientists have determined that a 10-mile-thick diamond mantle could lie beneath Mercury's surface. This discovery sheds light on Mercury's unique characteristics, including its dark surface, dense core, and abrupt end to its volcanic era.

NASA MESSENGER Spacecraft 
Image credit: NASA

Mercury has long puzzled scientists with its unusual properties. Among these mysteries are patches of graphite, a type of carbon found on the planet's surface. Researchers suggest that Mercury once had a carbon-rich magma ocean, which floated to the surface, forming graphite patches and giving the planet its dark hue. This process likely also led to the creation of a carbon-rich mantle beneath the surface, which the team now believes is composed of diamond rather than graphene.

The team's findings, led by Olivier Namur, an associate professor at KU Leuven, are based on geophysical data collected by the MESSENGER mission. Launched in 2004, MESSENGER became the first spacecraft to orbit Mercury, mapping the planet and gathering crucial data about its geology and magnetic field before concluding its mission in 2015.

Everything you need to know about MESSENGER Spacecraft 
Image credit: NASA

To understand how Mercury's diamond mantle could have formed, the team replicated the planet's interior conditions using a large-volume press. They applied over seven gigapascals of pressure and temperatures up to 3,950 degrees Fahrenheit to a synthetic silicate representing Mercury's mantle material. This experiment, combined with computer modeling, revealed how minerals in Mercury's mantle could have transformed under such conditions, leading to diamond formation.

Namur explains that diamond on Mercury could have formed through two processes: the crystallization of the magma ocean and the crystallization of Mercury's metal core. As Mercury's core crystallized over time, carbon in the residual melt reached a solubility threshold, causing diamond to form. These diamonds, less dense than metal, floated to the core-mantle boundary, creating a diamond layer.

MESSENGER Spacecraft on Planet Mercury 
Image credit: Wikipedia

The discovery of this diamond mantle highlights the differences in the formation of Mercury compared to other rocky planets like Venus, Earth, and Mars. Mercury, forming closer to the sun from a carbon-rich dust cloud, contains less oxygen and more carbon, leading to the diamond layer. Similar diamond formation in Earth's core has also been suggested by researchers.

The researchers hope this discovery will help explain other mysteries about Mercury, such as the early end of its volcanic phase around 3.5 billion years ago. The team plans to investigate the thermal effects of the diamond layer at the mantle-core boundary, which may have contributed to Mercury's rapid cooling and the termination of major volcanism.

Full image of Planet Mercury 
Image credit: NASA

The next steps include awaiting data from the BepiColombo mission, set to arrive at Mercury in 2026, to further refine their understanding of Mercury's internal structure and evolution. This research has been published in the journal Nature Communications.