It is no coincidence that the founding of the Planetology Section of the American Geophysical Union in 1968 came during the decade that the United States and the USSR were launching the first spacecraft to the moon, to Mars, and to Venus. Although astronomers had been studying the planets for centuries, for the first time large numbers of earth scientists, physicists, and chemists were attracted to the study of the solar system. Scientists working in fields such as meteorities, meteorology, and mineralogy, which both hitherto have been quite isolated from one another, gradually realized they had many common scientific interests and problems. These interrelationships have been greatly accentuated following the Apollo lunar landings and the return of samples from the moon. The developments of many years in the fields of geology, petrology, geoehronology, seismology, geomagnetism, and innumerable other fields were quickly brought to bear on the study of a new planetary body.