What Does Composition Mean in Planets?

Types

• Planets are divided into two composition categories for classification, according to nineplanets.org. The first category is Terrestrial and the second is Jovian. Planets in the Terrestrial category are Mercury, Mars, Venus and Earth. Jupiter, Saturn, Neptune and Uranus fill in the Jovian category.

Features

• The Terrestrial planets are defined by rock and metal composition. These planets have a solid surface and high density. Typically there are no rings and few satellites, according to nineplanets.org. The rocky planets also have a slow rotation. Jovian planets are made up of gases, with helium and hydrogen being the most common. These planets feature much lower density, faster rotations and many satellites.

Fun Fact

• Pluto is no longer considered a planet, and is not classified as either Terrestrial or Jovian. However, according to Windows to the Universe, Pluto's atmosphere is much like Earth's, but the interior composition is more like the icy moons of Jupiter.