Each of Saturn's moons is unique and different from the others. One result of their differences would be their size, shape, color and atmosphere. The first of Saturn's moons to be discovered was Titan. Titan was discovered by Christiaan Huygens in 1655 (Saturn: Lune). Titan is the second largest moon in our solar system, being slightly larger than Mercury and, because of this, has an effect on the orbits of nearby moons around Saturn. Its atmosphere consists of thick clouds of nitrogen and a small amount of methane (Saturn: Moons and Charles Choi). Many moons possess an amazing feature, separating themselves from the rest of the moons. Lapeto, for example, is as bright as snow, and the opposite side is as dark as a pitch-black sky at night (Saturn: Moons). Pan, along with another planet orbiting within the rings, helps shed materials in a thin gap in the rings known as the Encke Gap. The most interesting fact about Saturn's moons is that sixteen of its moons keep the same side toward the planet as they rotate, a phenomenon known as tidal locking (Saturn: