If one is interested in very detailed modeling, though, one can define and utilize a scale height for different chemical components of an atmosphere. The release of gravitational energy and the birth of a star means it is hotter in the center of the S.S. than in the outer regions. This is why there is a gradient in density within the solar system. This is also why most of the Jovian planets are mostly H and He because these materials be accreted and retained by big bodies in the outer solar system and they are the most abundant things in the Universe.
Planets form hot internal heat from gravitational contraction, collisions, and radioactive decay.
Throughout their lives, solid S.S. body s surfaces are shaped by cratering . Evolution of planetary surfaces mainly comes from geological processes requiring an internal energy supply. Once interiors cool, then geologic activity stops and surfaces become fossils. Thus, the evolution of planetary surfaces depend heavily on the planet s mass because this is a measure of internal thermal energy. Outgassing baking rocks and releasing gases.