A glittering trove of ‘9 miles thick’ space diamonds found near Earth – gems worth billions if you can solve two problems

MERCURY could be hiding a treasure trove of solid diamonds miles thick beneath its surface.

The innermost planet in our solar system has intrigued scientists for decades.

It has a weak magnetic field, just 1% of Earth’s strength. It has a huge core in relation to its insignificant size. And despite being the smallest planet in the solar system, it is the second densest.

Those characteristics have made it a topic of fascination for years – and now, it seems that researchers have discovered yet another curious detail.

A study published on June 14 in Nature Communications suggests that Mercury’s core-mantle boundary includes a diamond layer.

The diamond layer is between 15 and 18 kilometers thick and is located deep within the planet’s interior.

NASA’s MESSENGER probe, the first to visit Mercury in thirty years, mapped the entire planet and revealed that its surface is rich in carbon.

The researchers proposed that they were looking at the remains of an ancient layer of graphite that was pushed to the surface.

This theory suggests that Mercury once had a molten surface layer or ocean of magma containing a large amount of carbon. As the planet cooled, this carbon formed a graphite crust.

But scientists now believe there’s more to it — and that’s where the mantle, or middle layer, comes in.

Researchers had long suspected that the mantle’s temperature and pressure were the right conditions for carbon to form graphite.

Because it was lighter than the mantle, the graphite floated to the surface.

But more recent evidence has indicated that Mercury’s mantle may be 80 miles, or 50 kilometers, deeper than previously thought.

This means that the pressure and temperature at the boundary between the core and mantle are significantly higher – and these extreme conditions can cause carbon to crystallize, forming diamonds.

To study Mercury’s interior, researchers used a combination of high-pressure and temperature experiments and thermodynamic modeling.

They managed to reach pressure levels seven times greater than those found in the deepest parts of the Mariana Trench.

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Under these conditions, scientists examined how minerals in the planet’s interior melt and reach equilibrium phases.

The diamond layer is believed to be between 15 and 18 kilometers, or 9 and 11 miles, thick.

But it is inaccessible for now. The minerals are buried about 300 miles, or 485 kilometers, below the surface – and space explorers would first have to contend with the planet’s extreme heat.

The paper proposes that core crystallization led to the formation of a diamond layer at the core-mantle boundary.

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They also suggest that the current temperature at the boundary is close to the point at which graphite can turn into diamond, stabilizing the temperature as a result.

The experiments demonstrated that minerals like olivine likely formed in the mantle, in line with previous studies.

The team took the experiment a step further by adding sulfur, another common mineral on the planet’s surface.

This adjustment produced a temperature change of 358 Kelvin in Mercury’s magma ocean.

Under these conditions, diamonds may have crystallized when Mercury’s inner core solidified, the team deduced.

Co-author Yanhao Lin said the results have implications for understanding the formation of carbon-rich exoplanets.

“It may also be relevant to understanding other terrestrial planets, especially those with similar sizes and compositions,” Lin explained.

“The processes that led to the formation of a diamond layer on Mercury may also have occurred on other planets, potentially leaving similar signatures.”