Some carbon-rich exoplanets could be made of diamonds and silica

A study was recently published from researchers at Arizona State University and the University of Chicago that determined some carbon-rich exoplanets could, under the right circumstances, be made of diamonds and silica. The researchers say that these exoplanets are unlike anything in our solar system.When stars and planets form, they form from the same gas cloud, meaning the bulk compositions are similar. Stars With lower carbon to oxygen ratio will form planets like the Earth comprised of silicates and oxides with a minimal diamond content. Scientists point out that the diamond content of Earth is about 0.001 percent.

However, exoplanets that form around stars with a higher carbon-oxygen ratio than our sun are more likely to be carbon-rich. The researchers hypothesized that these carbon-rich exoplanets could convert the carbon to diamond and silicate if water is present, creating a diamond-rich composition. To test the hypothesis, researchers mimicked the interior of carbide exoplanets using high heat and high-pressure.

First, they immersed silicon carbide in water and compressed the sample between diamonds to a very high pressure to monitor the reaction between the silicon carbide and water. They conducted laser heating and took x-ray measurements while they laser-heated the sample at high pressures. As predicted, the silicon carbide reacted with water and turned into diamonds and silica at high heat and pressure.

Researchers say that carbon-rich planets aren't likely to have the properties needed to support life. Despite that carbon-rich planets are not expected to support life, the new study is an additional step in helping scientists understand and characterize exoplanets searching for extraterrestrial life. Researchers also note that the more we learn about exoplanets, the better they'll be able to interpret new data from future missions such as the James Webb Space Telescope.