Mercury has a layer of diamonds 11-miles thick under the surface

In an intriguing development that enhances our understanding of Mercury, researchers from China and Belgium have unveiled a remarkable secret residing deep within the planet. Their study indicates that Mercury’s core-mantle boundary (CMB) may possess a diamond layer that extends up to 18 kilometers (11 miles) thick.

What might the existence of this diamond layer reveal about Mercury’s geological history and the processes that shape our solar system?

Mercury: The enigmatic inner planet

This mind-boggling research was spearheaded by Dr. Yanhao Lin from the Center for High Pressure Science and Technology Advanced Research (HPSTAR) in Beijing.

Mercury, the smallest and innermost planet in our solar system, continues to intrigue scientists with its distinct characteristics and extreme conditions.

Its dark, cratered surface and dense metallic core have been the focus of extensive research, particularly through NASA’s MESSENGER spacecraft, which orbited Mercury from 2011 to 2015.

This mission uncovered remarkable insights into the planet’s composition and history. Among the most thought-provoking discoveries was the presence of significant amounts of graphite, a form of carbon, on Mercury’s surface.

This finding hints at a carbon-rich past that may provide valuable clues about the planet’s formation and evolution.

Carbon-rich past

Previous missions had suggested that Mercury’s surface graphite came from an ancient layer that floated up from a molten surface layer or magma ocean.

As Mercury cooled, this carbon formed a graphite crust. However, Dr. Lin and his team challenged the assumption that graphite was the only carbon-bearing phase during Mercury’s magma ocean crystallization.

Dr. Lin explained, “Many years ago, I noticed that Mercury’s extremely high carbon content might have significant implications. It made me realize that something special probably happened within its interior.”

Mercury’s diamond interior

To investigate, the researchers recreated the conditions of Mercury’s interior using high-pressure and temperature experiments combined with thermodynamic modeling.

They used synthetic silicate to mimic Mercury’s mantle composition, achieving pressure levels up to 7 Giga Pascals (GPa), about seven times the pressure found at the deepest parts of the Mariana Trench.

“We use the large-volume press to mimic the high-temperature and high-pressure conditions of Mercury’s core-mantle boundary and combine it with the geophysical models and thermodynamic calculations,” said Dr. Lin.

Diamonds under Mercury’s interior pressure

Under these extreme conditions, the team studied how minerals in Mercury’s interior melt and reach equilibrium phases, focusing on graphite and diamond.

They also analyzed the chemical composition of their experimental samples. The results were surprising.

By integrating experimental data with geophysical simulations, the researchers estimated Mercury’s CMB pressure at around 5.575 GPa. At roughly 11% sulfur content, they observed a significant 358 Kelvin temperature change in Mercury’s magma ocean.

This led them to propose that while graphite was the dominant carbon phase during the magma ocean crystallization, the crystallization of the core might have led to the formation of a diamond layer at the CMB.

Sulfur and Mercury’s magnetic field

“Sulfur lowers the liquidus of Mercury’s magma ocean. If the diamond forms in the magma ocean, it can sink to the bottom and be deposited at the CMB. On the other hand, sulfur also helps the formation of an iron sulfide layer at the CMB, which is related to carbon content during planetary differentiation,” explained Dr. Lin.

Planetary differentiation refers to how a planet’s interior becomes structured, with heavier minerals sinking to the core and lighter minerals rising to the crust.

One of the most intriguing implications of these findings is for Mercury’s magnetic field, which is surprisingly strong for such a small planet.

“Carbon from the molten core becomes oversaturated as it cools, forming diamond and floating to the CMB. Diamond’s high thermal conductivity helps transfer heat effectively from the core to the mantle, causing temperature stratification and convection change in Mercury’s liquid outer core, and thus affecting the generation of its magnetic field,” said Dr. Lin.

In simpler terms, the heat transfer from the core to the mantle influences temperature gradients and convection in Mercury’s liquid outer core, impacting its magnetic field generation.

Mercury, diamonds, and future exploration

Dr. Lin also pointed out the broader implications of this study for our understanding of other terrestrial planets.

“It 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,” he concluded.

This discovery about Mercury’s diamond layer enriches our knowledge and ignites curiosity about the hidden wonders of our solar system.

So, what does this mean for us? Mercury, often overshadowed by larger planets, holds secrets that challenge our understanding of planetary formation and behavior.

The full study was published in the journal Nature Communications.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates.

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–