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Solar system planets. Artwork of the nine planets of the solar system arrayed from right to left in order of their distance from the Sun. The size of each planet is to scale. The four small, rocky planets of the inner solar system are Mercury, Venus, Earth and Mars. The four large, gas giant planets of the outer solar system are Jupiter, Saturn, Uranus and Neptune. Finally, Pluto is a Dwarf planet of rock and ice. Planetary rings and moons are shown. The planet Uranus is seen tipped on its side due to an impact event in its early history. (KEYSTONE/SCIENCE PHOTO LIBRARY/DETLEV VAN RAVENSWAAY)