Illustration of Saturn (right) and its largest moon Titan (left). Titans diameter measures 5150 kilometres. The atmosphere is mainly composed of nitrogen, with small traces of methane. The atmospheric pressure of Titan is higher than that of Earth, and the view of its surface is obscured by a layer of clouds. The orange colour of the atmosphere is a result of sunlight reacting with methane, creating a thick smog of hydrocarbons. The surface temperatures of Titan are extremely cold, with an average temperature of around -179 degrees Celsius.