Jupiter's interior. Cutaway computer artwork showing the interior structure of the planet Jupiter. Jupiter is the fifth planet from the Sun and the largest in the solar system, with a mass two and a half times that of all the other planets put together. A rocky core (small sphere, centre) about the size of Earth lies at its centre, where the temperature is 20,000-30,000 degrees Celsius. Around the core is a vast layer of liquid hydrogen (blue), which accounts for most of the planet's mass. The inner part of the hydrogen layer (light blue) is under such high pressure that it acts like molten metal. Uppermost is a thin atmosphere of hydrogen (dark blue), water and ice (yellow), ammonium hydrosulphide (brown) and ammonia crystals (red).