Concluding remarks

A predominant aim of planetary exploration is to discover as much as possible about the origin of the Solar System. The conference papers and discussion are considered with this in mind. Comparative studies of surface features show that the 'geologies' of the terrestrial planets and the Moon and other large satellites are quite different. This is due in part to the presence or absence of water in various states. Other differences mentioned are the manifestations of tectonism and the chemical composition of these bodies. One paper suggests that interstellar molecules must have entered directly into the formation of the earth. Models for the major planets are proposed and satellites considered. The trend is to show that the formation of a satellite system must be a different process from the formation of a planetary system. Finally the formation of planets in pairs is noted. (U.K.)