Imagine visiting a planet where the aliens wear incredibly expensive glass jewelry but they bulldoze tons of diamonds into giant mounds.
We haven't found such a place. But for the first time an extrasolar planet rich in carbon has been detected that may be chock full of crystallized carbon - diamonds.
The carbon-rich Jupiter-sized planet was first detected last year by the Wide-Angle Search for Planets (WASP) that looks for the shadows of planets passing in front of their stars. The planet, called WASP-12b, is so hot that NASA's Spitzer Space Telescope and the Canada-France-Hawaii Telescope at Mauna Kea, Hawaii were able to spectroscopically detect the signature of carbon in its atmosphere.
The observations reveal that the planet has more carbon than oxygen and silicates, unlike the chemical abundances on Earth. It's not impossible the interiors of Jupiter, Saturn, Uranus, and Neptune could have similar carbon/oxygen ratios to WASP-12b, but they are much harder to observe and measure.
Incredible pressures in the interior of gas giant planets could convert carbon into diamonds. A novel twist on this idea appeared in Arthur C. Clarke's 1997 science fiction sequel "3001: The Final Odyssey." A gigantic diamond mountain ejected from the core of Jupiter is found on the icy moon Europa.