Published online by Cambridge University Press: 12 April 2016
The planetary program has always been conducted with the hope that the results would reveal great insight into the early period of solar system history and perhaps into the actual formation processes themselves. However, little knowledge has been gained of this very early stage for several reasons: The intense surface bombardment of all larger bodies, particularly in the inner solar system during that period; the subsequent differentiation of large bodies; and atmospheric effects and continued bombardment of the surface. The most promising approach to acquisition of knowledge pertaining to the early state of the solar system, its origin and evolution, therefore seems to be in the study of small bodies, e. g., comets and asteroids.