A planet is a large space body which reflects the light of a star around which it revolves. The planets in our solar system are classified as inner planets and outer planets. The inner planets, the closest to the Sun, are solid spheres of rock and include Mercury, Venus, Earth, and Mars. The inner planets were constantly bombarded by asteroids and meteorites during their first 600 million years in existence. Consequently, you will find craters of varying sizes on the inner planets and their satellites. The outer planets, with the exception of Pluto, are large gaseous spheres with rings and include Jupiter, Saturn, Uranus, and Neptune. Between the inner and outer planets is an asteroid belt. Every planet, except for Earth, was named for an ancient Roman god or goddess. Some of the planets have naturally occurring satellites, or moons, while others do not. All nine planets orbit the Sun in their own unique way. Scientists have long been searching for additional planets in our solar system. None have been found.
| The Inner Planets | The Outer Planets |
|---|---|
| Mercury | Jupiter |
| Venus | Saturn |
| Earth | Uranus |
| Mars | Neptune |
| Pluto |
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