Solar system planets. Artwork of the nine planets of the solar system arrayed from left to right 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 small planet of rock and ice. Planetary rings and moons and a background of historical charts of the solar system are shown. The Milky Way galaxy runs down right in the background.