Neptune and Uranus, two gas giants in our solar system, do not have a solid surface like Earth or Mars. Instead, they are composed primarily of hydrogen, helium, and trace amounts of other elements, with no well-defined solid surface.
Our understanding of the internal structure of gas giants like Neptune and Uranus comes from a combination of observational data, theoretical models, and spacecraft missions. Here are a few key points:
Density Measurements: Scientists can estimate the overall density of a planet by studying its gravitational effects on nearby objects or spacecraft. From these measurements, it is evident that the average densities of Neptune and Uranus are much lower than those of rocky or terrestrial planets like Earth or Mars. This suggests that their interiors are primarily composed of gases rather than solids.
Interior Models: Based on theoretical models and calculations, scientists believe that the cores of Neptune and Uranus consist of relatively small, dense rocky or icy material surrounded by thick layers of hydrogen and helium. However, the precise composition and structure of these cores are still not fully understood.
Spacecraft Data: While we haven't directly landed a spacecraft on Neptune or Uranus, the Voyager 2 spacecraft provided valuable information during its flybys of both planets in 1989. Voyager 2 revealed details about their atmospheres, magnetic fields, and general structure. However, it did not reach the core or directly observe a solid surface.
Regarding an object falling from space into Neptune or Uranus, it would not simply pass through the gas giants' cores unharmed. As the object descends through the atmosphere, it would encounter increasing pressure and temperature. At some point, the object would be crushed and vaporized due to the extreme conditions within the planet. However, the exact depth at which this would occur is uncertain due to the complexity of the planets' interiors.