ercury, Venus, Earth, and Mars. These four planets are the closest to the Sun. They are called the inner planets. The inner planets are made up mostly of rock. The outer planets are Jupiter, Saturn, Uranus, Neptune, and Pluto. Jupiter, Saturn, Uranus, and Neptune are large balls of gases with rings around them. They are all impossible to stand on. All nine planets travel around the Sun in a different orbit.
             Mercury is the closest planet to the sun. Not only is it closes to the sun, its also the 2nd smallest in the solar system. Mercury spins around very slowly; one day equals two earth years. It has a cratered surface, much like Earth's moon. It is 0.4 A.U. from the Sun on the average and its surface temperature is 800 to -275 F (427 to -170 C).
             The second planet in the solar system is Venus. Venus is 0.7 A.U.
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