Kepler-22b
It is thought that the object has a mass similar to that of Neptune (~35 Earth masses). Another possibility is that Kepler-22b is an "ocean-like" world. It might also be comparable to the water-rich planet GJ 1214 b although Kepler-22b, unlike GJ 1214 b, is in the habitable zone. If it has an Earth-like composition, the compression of material in the interior of the planet would give an overall mass greater than 40 Earth masses. Such a planet would also produce surface gravity greater than 7 times that on Earth. This is ruled out to at least 1-sigma uncertainty by radial velocity measurements of the system, suggesting Kepler-22b does not have Earth-like composition. It is likely to have a more volatile-rich composition with a liquid or gaseous outer shell; this would make it similar to Kepler-11f, the smallest known gas planet.