Final answer:
The particles forming Saturn's rings are primarily composed of water ice. Enceladus, one of Saturn's moons, contributes ice crystals to the E Ring, highlighting the abundance of icy objects in the outer solar system.
Step-by-step explanation:
The composition of the particles forming Saturn's rings is best described as water ice. Saturn's ring system is made up of icy particles that typically have dimensions of a few centimeters. One of Saturn's moons, Enceladus, contributes to maintaining the tenuous E Ring by erupting geysers of water ice. The presence of these ice particles in Saturn's rings illustrates the chemical composition differences prevalent in various regions of the solar system. As we move farther from the Sun, the formation of water ice becomes more common due to the cooler temperatures that allow oxygen to combine with hydrogen and condense.