Carbon-Rich Diamond Planets Possible Gateway to Life

Carbon-rich diamond planets may be more common than astronomers previously thought, according to new research.

These types of planets are located far beyond Earth's solar system, some of which could contain vast deposits of graphite or diamonds. Their apparent abundance prompted astronomers to question whether these carbon-intense environments could sustain life.

"Despite the relatively small amount of carbon on Earth, carbon has been critical for the emergence of life and the regulation of our climate through the carbon-silicate cycle," Yale doctoral candidate John Moriarty, who led the research, said in a statement. "It's an open question as to how carbon-rich chemistry will affect the habitability of exoplanets. We hope our findings will spark interest in research to help answer these questions."

Astronomers generally believe that rocky exoplanets - planets outside our solar system - are composed largely of iron, oxygen, magnesium, and silicon, with only a small fraction of carbon. In contrast, carbon-rich planets could have between a small percentage and three-quarters of their mass in carbon. (Earth has 0.005 percent.)

Moriarty and his colleagues Debra Fischer and Nikku Madhusudhan developed an advanced model for estimating exoplanet composition that involves tracking changes in composition of the gaseous pools, or disks, in which planets form as they age.

They found that in disks with carbon-oxygen ratios greater than 0.8, carbon-rich planets can form farther from the center of the disk than previously understood, and a ratio as low as 0.65 means those planets form close to their host star.

Previous models, based on static snapshots of these disks, did not predict that such diamond planets could form with such low carbon-oxygen ratios.

"Our study shows that extraterrestrial worlds can be extremely diverse in their chemical compositions, including many that are drastically different from our earthly experience," Madhusudhan said.

"This work further expands the range of factors that may bear on the habitability of other worlds," he added.

So far, there are more than 1,000 confirmed exoplanets and more than 3,000 exoplanet "candidates."

The findings were recently published in Astrophysical Journal.