Carbon-rich alien planets could be made of diamonds

This visualization shows a carbon-rich planet with a high concentration of diamond and silica. (Image credit: Shim/ASU/Vecteezy)

Some far-off alien planets could be made of diamonds, scientists say.

With the right conditions like the presence of water heat and pressure, exoplanets with high concentrations of carbon could turn into diamonds, scientists found in a new study. These exoplanets could also form silica, an oxide of silicon that is found as quartz in nature, the researchers added

"These exoplanets are unlike anything in our solar system," lead author Harrison Allen-Sutter, a graduate associate at Arizona State University's School of Earth and Space Exploration, said in a statement

Related: Super-Earth planet likely made of diamond

Stars and planets in the same solar system form from the same cloud of gas and dust, so they usually have some similarities in composition. While planets like Earth often orbit stars with lower carbon-to-oxygen ratios, exoplanets that orbit around stars with a higher carbon-to-oxygen ratio are more likely going to be carbon-rich. 

So, while Earth has a low diamond content (about 0.001%), carbon-rich exoplanets could be diamond-heavy, researchers said in the same statement.

To test how and if such planets could form diamonds (and silica), scientists mimicked the interiors of carbon-rich exoplanets in the lab. They did this using high heat and high-pressure diamond-anvil cells (high-pressure devices used to compress small pieces of material to extreme pressures.) The researchers then submerged silicon carbide, which is made up of silicon and carbon, in water and compressed it to high pressures between two diamonds. As this went on, they also used lasers to heat the sample. 

In monitoring this process with X-ray measurements, researchers found that the silicon carbide turned into diamonds and silica. 

However, the science team does not think these diamond planets would likely not be capable of hosting life. The researchers estimate that most carbon-rich planets like this would not be especially geologically active, which could make their atmospheres inhospitable to life, according to the statement. 

"Regardless of habitability, this is one additional step in helping us understand and characterize our ever-increasing and improving observations of exoplanets," Allen-Sutter said in the statement. "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."

This work was published Aug. 26 in The Planetary Science Journal. 

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Chelsea Gohd
Senior Writer

Chelsea “Foxanne” Gohd joined in 2018 and is now a Senior Writer, writing about everything from climate change to planetary science and human spaceflight in both articles and on-camera in videos. With a degree in Public Health and biological sciences, Chelsea has written and worked for institutions including the American Museum of Natural History, Scientific American, Discover Magazine Blog, Astronomy Magazine and Live Science. When not writing, editing or filming something space-y, Chelsea "Foxanne" Gohd is writing music and performing as Foxanne, even launching a song to space in 2021 with Inspiration4. You can follow her on Twitter @chelsea_gohd and @foxannemusic.

  • rod
    A very interesting report and intense pressures used and reported, 50 Gpa, more than 493,000 earth standard atmospheres for the pressue. The exoplanet 55 Cnc e is cited as a possible diamond exoplanet in the report,
    With more than 4300 exoplanets now, I do not know if any are known for sure to be diamond exoplanets. The paper cited concludes.

    It will be interesting to see if exoplanets like this study models are confirmed.