Planet Facts

The inner four planets closest to the sun — Mercury, Venus, Earth and Mars — are often called the “ terrestial planets" because their surfaces are rocky. Pluto also has a rocky, albeit frozen, surface but has never been grouped with the four terrestrials.
The four large outer worlds — Jupiter, Saturn, Uranus and Neptune — are sometimes called the Jovian or "Jupiter-like" planets because of their enormous size relative to the terrestrial planets. They're also mostly made of gases like hydrogen, helium and ammonia rather than of rocky surfaces, although astronomers believe some or all of them may have solid cores.

The inner four planets closest to the sun — Mercury, Venus, Earth and Mars — are often called the “ terrestial planets" because their surfaces are rocky. Pluto also has a rocky, albeit frozen, surface but has never been grouped with the four terrestrials.