Scientists are still unsure.
(PHYSORG)-In December 2009, astronomers announced the discovery of a super-Earth known as GJ 1214b. At the time, they reported signs that the newfound world likely had a thick, gaseous atmosphere. Now, a team led by Jacob Bean (Harvard-Smithsonian Center for Astrophysics) has made the first measurements of GJ 1214b's atmosphere. However, the measurements raise as many questions about the planet's atmospheric composition as they answer...
Researchers suggested three atmospheric possibilities for GJ 1214b. The most intriguing was a thick blanket of steam vaporized by the nearby star. (This option led to the nickname "waterworld," although it's too hot for an ocean.) The second option was a mini-Neptune with a rocky core surrounded by ices and a hydrogen/helium atmosphere. The third model has no equivalent in our solar system - a big, rocky world with a soupy mix of gases (mainly hydrogen) recently emitted by volcanoes.