Saturn's moon Titan, Cassini image. Titan's atmosphere (orange) is at left, and a blue-green haze is seen on the moon's limb. Beyond that is the thin crescent-shaped sunlit southern polar region of Saturn (centre right), with the rest of Saturn unlit (upper right). Titan, the largest moon of Saturn, has a diameter of 5150 kilometres. Its thick atmosphere reaches 880 kilometres above its surface, and is mostly nitrogen with traces of methane. This image was obtained by the Cassini spacecraft at a distance of 26,000 kilometres, and was taken on 26 December 2005.