Figure 4-5 RIVUXG A Jovian Planet and a Terrestrial Planet (a) This Hubble Space Telescope image gives a detailed view of Jupiter’s cloudtops. Jupiter is composed mostly of the lightest elements, hydrogen and helium, which are colorless; the colors in the atmosphere are caused by trace amounts of other substances. The giant storm at lower right, called the Great Red Spot, has been observed raging for more than 300 years. (b) Mars, a terrestrial planet, is composed mostly of heavy elements similar to Earth, including iron, oxygen, silicon, magnesium, nickel, and sulfur. The planet’s red surface can be seen clearly in this Hubble Space Telescope image because the Martian atmosphere is thin and nearly cloudless. Olympus Mons, the extinct volcano surrounded by clouds on the right-hand side, is nearly 3 times the height of Mount Everest.