Planet Guide and Information - Neptune
Neptune is, in many ways, very similar to Uranus, especially in terms of mass and composition. Internally it is quite different, however, with an internal source of energy causing great perturbations in the gas atmosphere. Put simply, Neptune is very windy causing many surface features which have really only been seen by the Voyager space probe, although the Hubble Space Telescope is also capable of seeing these storms. Again, the atmosphere is made up mainly of hydrogen with a small amount of methane causing the blue/green colouration.