Voyager image showing cloud and storm systems in the planet's atmosphere. Alternating bands of ascending (lighter-coloured) and descending clouds (darker-coloured) are seen. These clouds travel in eastwards and westward belts at speeds up to 540 kilometres per hour. At lower left is the Great Red Spot (GRS), a large storm system that has existed for at least a few hundred years. It consists of cold clouds that rotate anticlockwise several kilometres above the surrounding cloud deck. Jupiter is the largest planet in the solar system. It has a diameter of around 140,000 kilometres, more than ten times that of Earth. It is a gas giant and is mostly hydrogen and helium. Processed colour image by the U.S. Geological Survey, originally taken by Voyager 2 in 1979.