Animation of the interior of the planet Jupiter. Jupiter is the largest planet in the solar system, more than eleven times the diameter of Earth, with some 318 times Earth s mass. It is a gas giant, whose visible surface is actually the tops of clouds. The uppermost clouds are ammonia and ammonia compounds, overlying a hydrogen layer. Convection and circulation constantly bring trace chemicals such as sulphur, phosphorus and hydrocarbons to the surface, where they acquire an orange/brown colour on exposure to sunlight. The atmosphere extends down around 5000 kilometres, although there is no real boundary, as the gas pressure increases with depth until liquid and gas phases are essentially indistinguishable, in a supercritical fluid state light blue. Below this layer is a layer where the pressure and temperature on the supercritical fluid hydrogen causes it to form metallic hydrogen dark blue, essentially a sea of protons and unbound electrons. This layer occupies more than 75 of the planet s radius. At the very centre of the planet there is thought to be a rocky core grey, several times the mass of Earth but as little as 3 of the mass of Jupiter.