What are the primary characteristics of the inner planets?

Three Major Characteristics of the Inner Planets. The four inner planets - - Mercury, Venus, Earth and Mars - - share several features in common. Astronomers call them the "terrestrial planets" because they have solid, rocky surfaces roughly similar to desert and mountainous areas on the earth.

The four inner planets share several features in common.

(Mercury, Venus, Earth and Mars)

They are called terrestrial planets because they have solid, rocky surfaces roughly similar to desert and mountainous areas on the earth.