Second largest planet. Saturn is the second-largest planet in the solar system and is made up mostly of hydrogen and helium. The rings are composed of ice and rock particles ranging in size from grains of sand to boxcars. The shepherd moons gravitationally herd in the ring particles that would otherwise spread out into deep space. Lakes of methane.
Scientists believe Titan's surface is coated with the residue of a sticky brown organic rain.
Most complex spacecraft. The Cassini spacecraft is the most complex interplanetary spacecraft ever built. Because of Cassini's challenging mission, the long distance Cassini must travel, and the value of its scientific return, each component and the system as a whole has undergone an unprecedented program of rigorous testing for quality and performance. Because of the very dim sunlight at Saturn's orbit, Cassini could not conduct its mission to Saturn on solar power. RTGs have been used on 23 previous U.S. missions.