Named for Leon T. Silver, professor of geology at the California Institute of Technology. Famed for his studies of the regional geology and precise determinations of ages of precambrian and mesozoic crystalline rocks of the southwestern United States, Silver also made important contributions to the study of the moon. He played a major role in the geologic training of astronauts for the Apollo 15, 16 and 17 missions to the moon and in the planning and conduct of these missions. (M 24917) _ _.