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A Planet Made of Diamonds?

Illustration of planet cutaway showing diamond interior
Shim/ASU/Vecteezy

It might sound like something straight out of sci-fi. Still, researchers at Arizona State University (ASU) and the University of Chicago say that some planets beyond our solar system may well be made of diamonds and silica. Space prospecting, anyone?

Diamonds, Diamonds Everywhere

The diamond content of planet Earth is about .001%, which is precisely what makes the glittery chunks of carbon valuable to us. But on some other planets out there, diamonds might be as common as the 75% of sedimentary rocks that cover our planet’s surface. In reaching this conclusion, the researchers turned to chemistry.

When it comes to the formation of solar systems, the same chemicals are used to create suns as well as the planets around them. In the case of Earth, our sun has a low carbon-to-oxygen ratio, so our planet is made up of silicates and oxides—both oxygen-rich compounds—with just a scattering of diamonds.

However, it’s entirely feasible that another solar system would have a sun that has more carbon than oxygen, which could form planets by converting that carbon to diamonds in the presence of water.

Using Diamonds to Make Diamonds

To test out the theory, the researchers put some silicon carbide in water. They squeezed it inside of a diamond anvil cell, a tool consisting of two flat diamond surfaces that press together to create the kind of pressure that would be involved in planet formation (see image below). To monitor the reaction of the carbon and water, the researchers beamed the sample with the heat from a laster and monitored the system with X-rays.

Two flat-headed diamonds close to each other illustrating a diamond-anvil cell
Dan Shim

Sure enough, the silicon carbide and water turned to diamonds and silica.

Can’t Move There Just Yet

Unfortunately, even if diamond planets exist, the researchers believe they won’t be habitable by humans do the fact that they won’t have a breathable atmosphere nor Earth’s geological activity, which is an indicator of a planet’s habitability. Still, the discovery, which has been reported in The Planetary Science Journal, is valuable.

“Regardless of habitability, this is one additional step in helping us understand and characterize our ever-increasing and improving observations of exoplanets,” said lead author Harrison Allen-Sutter of ASU’s School of Earth and Space Exploration. “The more we learn, the better we’ll be able to interpret new data from upcoming future missions like the James Webb Space Telescope and the Nancy Grace Roman Space Telescope to understand the worlds beyond on our own solar system.”