Titan, the largest of SaturnΓÇÖs moons, was discovered in the late 1650s by Christian Huygens. Titan is unusual in that it lacks the craters and canyons typical of other moons in the solar system. TitanΓÇÖs atmosphere, seen here as a faint haze on the surface, is also unique. Composed mainly of methane, nitrogen, and hydrogen, it is denser than our own atmosphere. At one time, Titan was thought to be the largest moon in the solar system, but Voyager observations revealed it to be 5,150 kilometers in diame- ter, putting it in second place behind JupiterΓÇÖs Ganymede. Even so, Titan is larger than the planets Mercury and Pluto.
