Aspects of the physics of planetary interiors

Data from space missions of various kinds coupled with those from Earth-based observatories allow the Solar System to be studied as a composite physical system rather than individual planets. Those physical principles which are characteristic of planetary bodies over the full range of possible sizes can be identified. This article offers a broad general survey of the physics of planetary interiors in these terms, without concentrating in detail on any particular planetary body. The aim is to highlight significant areas which could repay future study, as well as to explain what is already understood. (author)