THE PHYSICS OF PLANETARY INTERIORS

Our knowledge of the planets and the satellites of the Solar System has grown enormously during the last twenty years particularly due to the stimulus from space missions within the System. Studies of the interiors, atmospheres and interplanetary regions have all benefited from these developments. The result has been an increase in our understanding of the general workings of the planets and satellites and relative planetology has become an active area of quantitative study. These aspects are likely to develop significantly in the future and the effects on our appreciation of the Earth itself will be very significant. Conditions within the interiors of the planets and larger satellites are reviewed in the present paper against the more general background of the physics to be expected for a planetary body in general. No other planetary system has yet been discovered for comparative study so our Sun with its group of planets and satellites remains to us unique. This may not be so, in fact, and our subject would be supported considerably if other planetary systems were known.