Imagine climbing diamond mountains, or hiking around the graphite shores of a lake of tar. Sound a little sci-fi? Well a new discovery suggests planets like that might be out there—planets littered with carbon minerals, instead of the oxygen-rich silicates, like quartz, that cover the Earth. Because astronomers have found the first carbon-rich exoplanet, with more carbon than oxygen in its atmosphere—instead of the 1 to 2 carbon to oxygen ratio found in our solar system.

The exoplanet, called WASP 12 b, is a gas giant, like Jupiter. By taking the spectrum of heat radiating from the planet, the researchers found that the planet's atmosphere was loaded with carbon, in the form of carbon monoxide and methane. The study appears in the journal Nature. [Nikku Madhusudhan et al., "A high C/O ratio and weak thermal inversion in the atmosphere of exoplanet WASP-12b"]

The finding suggests one commonly accepted model of planetary formation, where icy chunks glom into a core, wouldn't work here. Instead the core may have formed from carbon-rich fragments, like tar. But more than that, this unusual planet is more proof of the diversity of the universe—and it makes those dreams of diamond planets a tiny bit more plausible.

—Christopher Intagliata

[The above text is an exact transcript of this podcast.]

[Scientific American is part of Nature Publishing Group.]