Saturn is about 120 000 km across, and is flattened at the poles because of its very rapid rotation. A day is only 10 hours long on Saturn. Strong winds account for the horizontal bands in the atmosphere of this giant gas planet.
The delicate colour variations in the clouds are due to smog in the upper atmosphere, produced when ultraviolet radiation from the Sun shines on methane gas. Deeper in the atmosphere, the visible clouds and gases merge gradually into hotter and denser gases, with no solid surface for visiting spacecraft to land on.