Size and density of the planets

The planets appear to be divided according to size and density.

The inner planets are small and rocky (the terrestrial planets):

• Mercury
• Venus
• Earth
• Mars

The outer planets are 'gas giants':

• Jupiter
• Saturn
• Uranus
• Neptune

Nearly every planet has an atmosphere.

Note: Pluto (formerly regarded as a planet) has been re-classified as a dwarf planet in the Kuiper meteorite belt. It may be further declassified to a binary dwarf planet, as it is only slightly larger than its moon. (International Astronomical Union