Saturn's moon Titan. Artwork of the largest of Saturn's moons, Titan, with Saturn in the background. Titan is formed of ice and rock, but has a thick atmosphere of nitrogen and organic compounds, mainly methane and ethane. This gives the moon its characteristic orange colour. The atmosphere may resemble that of a primitive Earth, containing the organic compounds from which life originated. Saturn is the second largest of the planets in the solar system, having a diameter in excess of 120,000 kilometres. It is the sixth most distant planet from the Sun.