Note: Discovered in 1655 by the Dutch astronomer Christiaan Huygens, Titan is the largest of Saturn's moons, bigger than the planets Mercury and Pluto. It is the only moon in the Solar System that possesses a dense atmosphere (10 times denser than Earth's), and although hazy, it is relatively cloudless. Although this atmosphere is rich in organic material, this does not necessarily imply any proof of the existence of living organisms. Its lack of craters on the surface implies that Titan is relatively young.