Jupiter's Great Red Spot in 1890 and 2015. The Great Red Spot (GRS) on Jupiter is a large storm system which has existed for at least a few hundred years. Here, it is shown in 1890 (left) with a length of 36,000 kilometres, and in 2015 (right) with a length of 15,500 kilometres. The GRS consists of cold clouds which rotate anti-clockwise several kilometres above the surrounding cloud deck. Jupiter is a gas giant and the fifth planet from the Sun and the largest. It has a diameter more than ten times that of Earth. It is mostly hydrogen and helium. The outer surface clouds are coloured by trace chemical elements and blown by winds into bands and storm systems.