The giant planets are made up primarily of gases and liquids. The characteristic structure is that of a relatively shallow atmosphere merging seamlessly into a deep liquid “ocean,” which in turn merges smoothly into a denser liquid or solid core. There is no abrupt transition from atmosphere to solid ground, as is found on the terrestrial planets. Although shallow compared with the depth of the liquid layers below, the atmospheres of the giant planets are still much thicker than those of the terrestrial planets—thousands of kilometers rather than hundreds. As with Venus, only the very highest levels of the gas giants’ atmospheres can be seen. In the case of Jupiter or Saturn, the uppermost layer of thick clouds obscures deeper layers. There are only a few thin clouds on Uranus. Atmospheric models indicate that thick cloud layers must lie below, but strong scattering of sunlight by molecules in the cloudless part of the atmosphere obscures these lower cloud layers. Neptune displays a few high clouds with a deep, clear atmosphere showing between them.