One can read about the scientific results of the Pioneer Venus exploration program in a highly valued special issue of the Journal of Geophysical Research, 85(A13), December 30, 1980, but these results are only a part of the impact of what has been one of the most sophisticated scientific endeavors in history. In this program numerous spacecraft—the U.S. Mariner 2, 5, 10, Pioneer 1, 2, and the Soviet Venera 4-10, 11, 12 missions—were launched to study Venus. There were six probes to Venus's surface, one to its upper atmosphere, and three to observe its environment. Pioneer 1 is still in operation, in Venus orbit with a periapsis less than 200 km and an apoapsis of 66,000 km. As a result of the probes there are now diamonds and sapphires on Venus, the windows provided for spacecraft instruments to take measurements of the atmosphere, surface, and solar flux.