Jupiter, Saturn, Uranus, and Neptune are the Jovian (the adjectival form for the word “Jupiter”), or Jupiter-like, planets. They are giant planets, composed primarily of light elements such as hydrogen and helium.

Mercury, Venus, Earth, and Mars are the terrestrial (derived from “terra,” the Latin word for “earth”), or Earth-like, planets. They are small in size, have solid surfaces, and are composed of rocks and iron.