Gas giants, such as Jupiter, Saturn, Uranus, and Neptune, do not have a solid surface like the terrestrial planets (Mercury, Venus, Earth, and Mars). They are primarily composed of gases and lack a well-defined solid surface.

The structure of gas giants is typically divided into three main layers:

1. Atmosphere: The outermost layer is the atmosphere, which consists mainly of hydrogen and helium with trace amounts of other gases such as methane, ammonia, and water vapor. The atmosphere of gas giants can be very thick and can extend for thousands of kilometers.

2. Mantle: Below the atmosphere lies the mantle, which is composed of a mixture of hydrogen and helium in a liquid or supercritical state. The mantle is extremely dense and hot, with temperatures reaching several thousand Kelvin.

3. Core: At the center of the gas giant is the core, which is believed to be composed of heavy elements such as iron and rock. The core is under immense pressure and temperature, but its exact composition is not well understood due to the difficulty of directly observing or sampling it.

Overall, gas giants primarily consist of gases and do not have a solid surface like terrestrial planets. Their structure is dominated by the dense atmosphere, the liquid or supercritical mantle, and the solid or liquid core. However, it's important to note that our understanding of the interiors of gas giants is still evolving, and ongoing research continues to refine our knowledge of their composition and internal dynamics.