Titan. Image of Titan, the largest moon of Saturn, made by the Voyager 1 spacecraft. This image has been processed to show true colours. Titan is the only satellite in the solar system to have an appreciable atmosphere. The surface is hidden by a shroud of aerosol-like clouds. Titan has a radius of 2575 km, and orbits Saturn at a mean distance of 1,221,850 km. It was discovered by Huygens in 1655.