Ice giant in mass. In 1952, science fiction writer James Blish coined the term "gas giant" and it was used to refer to the large non-terrestrial planets of the Solar System. However, in the 1990s, the compositions of Uranus and Neptune were discovered to be significantly different from those of Jupiter and Saturn. They are primarily composed of elements heavier than hydrogen and helium, constituting a separate type of giant planet altogether. Because during their formation Uranus and Neptune incorporated their material as either ices or gas trapped in water ice, the term "ice giant" came into use. Modelling the formation of
Formation and evolution of the Solar System planet, with abrasion by meteorites and Saturn's gravity eventually taking the rest, leaving Saturn unadorned. However, data from the "Cassini" mission led scientists to revise that early view. Observations revealed 10 km-wide icy clumps of material that repeatedly break apart and reform, keeping the rings fresh. Saturn's rings are far more massive than the rings of the other giant planets. This large mass is thought to have preserved Saturn's rings since it first formed 4.5 billion years ago, and is likely to preserve them for billions of years to come. In the long term, the greatest changes in the Solar