Gas giant planets. Artwork showing the four gas giant planets: Jupiter (bottom left),Saturn (lower right),Neptune (upper centre) and Uranus (upper left). These four are the largest planets,and are composed largely of gases,having no true surface. By contrast,the four inner planets,Earth,Mars,Mercury and Venus,are made up mainly of rock. Jupiter is the largest of all the planets,and is famous for its "red spot" (bottom left corner),a storm system many times larger than Earth. Saturn has large rings,possibly the remnants of a moon struck by a comet. Uranus and Neptune both have smaller,fainter ring systems. The planets are not shown to scale |