Ice Giant (planet)

An ice giant is a giant planet composed mainly of elements heavier than hydrogen and helium, such as oxygen, carbon, nitrogen, and sulfur.

Ice giants consist of only about 20% hydrogen and helium in mass, as opposed to the Solar System's gas giants (Jupiter and Saturn), which are both more than 90% hydrogen and helium in mass. In the 1990s, it was realized that Uranus and Neptune are a distinct class of giant planet, separate from the other giant planets. They have become known as ice giants because their constituent compounds were ices when they were primarily incorporated into the planets during their formation, either directly in the form of ices or trapped in water ice. The amount of solid volatiles within the ice giants today is, however, very small.