Bands of clouds form beautiful swirls and loops around Jupiter's Great Red Spot in this image from a spacecraft. Clouds in some of the bands extend much higher than those in adjoining bands. Jupiter's cloud layer is hundreds of miles thick. Because the giant planet has no solid surface, scientists define its "surface" as the depth in the atmosphere where the pressure equals the surface pressure on Earth. This depth is well below the tops of the clouds in some of these colorful bands. [NASA/JPL/SSI]