As programs like NASA's Hubble Space Telescope, Kepler, and TESS continue to provide observations into the properties of exoplanets, scientists are gradually able to put together what certain planets look like, what they are made of, and whether they can be habitable or even populated.
A team of researchers from Arizona State University and the University of Chicago have determined, in a recent report published in The Planetary Science Journal, that, given the right conditions, certain carbon-rich exoplanets could be formed from diamonds and silica.
"These exoplanets are unlike anything in our solar system," said the report's lead author Harrison Allen-Sutter.
As stars and planets are made, they do this from the same gas cloud, so their compositions in bulk are identical. A star with a lower carbon-to-oxygen ratio would have planets like Earth, composed of silicates and oxides with a very low amount of diamond.
Yet exoplanets orbiting stars with a higher ratio of carbon-to-oxygen than our sun are more likely to be rich in carbon. The research team proposed that these carbon-rich exoplanets could turn to diamond and silicate, if water were present, producing a composition rich in diamond.
To validate this theory, the team wanted to use high heat and high pressure to simulate the interior of carbide exoplanets. To do just that, they used diamond-anvil high-pressure cells. Next, they dipped silicon carbide in water and squeezed the sample to very high pressure between diamonds. They then performed laser heating to monitor the reaction between silicon carbide and water, taking X-ray measurements as the laser-heated the sample at high pressures.
As they expected, the silicon carbide reacted with water and formed into diamonds and silica, through high heat and pressure.
So far, on other planets, we have not discovered life, but the search continues. In space and on Earth, planetary scientists and astrobiologists are using advanced tools to identify planets with the right properties and the right place around their stars where life could occur.
However, for carbon-rich planets, which are the subject of this research, they possibly don't have the properties required for life.
Though Earth is geologically active (an indication of habitability), the findings of this study suggest that carbon-rich planets are too hard to be geologically active, and this lack of geological action will render the uninhabitable atmospheric composition. Atmospheres are vital to life as it provides us with clean oxygen, protection from the harsh space atmosphere, and even pressure to create liquid water.
Regardless of habitability, this is yet another step to help us understand and classify our ever-increasing and growing exoplanet observations.