ASTROGEOLOGY

scientific discipline concerned with the geological aspects of all solid bodies in the solar system, including the major planets and their satellites, asteroids, comets, and meteorites. Astrogeological research extends to those terrestrial features produced by the latternamely, meteorite craters and tektites (small glassy objects resulting from meteorite impacts). As the name implies, astrogeology constitutes a bridge between the fields of astronomy and geology. Since the late 1960s, spacecraft have enabled researchers to collect much valuable geophysical and geochemical data not only about the Moon and inner planets but also about the principal satellites of such outer planets as Jupiter, Saturn, and Uranus. In addition, high-resolution photographs from space probes have made it possible to determine the surface features of these objects and construct their geologic histories. Much also has been learned about the early history of the solar system from detailed analyses of the chemical composition, physical properties, and isotopic age of meteorites recovered from the Earth's surface.