Apollo Lunar Landing Sites
The specific locations of the first two Apollo landing sites were selected mainly for reasons related to safety and orbital timing and partly for political reasons. In later missions, scientific objectives became an increasingly important factor. Harrison Schmitt had input into the later landing sites as he was the leading geologist at NASA. The Apollo landing sites were located relatively near the equator within what was known as the "Apollo Zone." This area had been studied extensively with telescopic images, and a near-equatorial landing would be most favorable for return-to-Earth trajectories. Landings had to be made during the lunar day on the near side in a way that would be favorable for the particular launch and orbital configuration and that would allow alternate site selection in the event of a launch delay. This combination of factors restricted the possible landing sites.
Both the Apollo 11 and Apollo 12 missions were targeted to land on smooth, flat mare surfaces deemed to have low numbers of impact craters. An eastern site was preferred for Apollo 11, which would leave a western site for backup, but too far east would require a night splashdown on the return to Earth. Mare Tranquillitatis was the only suitable landing site. The Apollo 12 site was selected to investigate a western mare region and, specifically, to land at a previous Surveyor site to demonstrate pinpoint landing accuracy. Apollo 12 landed within 160 meters (525 feet) of the Surveyor 3 spacecraft, within walking distance, and provided a clear demonstration of U.S. superiority in the space race with the Soviet Union.
Apollo 11: First Manned Landing
The landing sites, once selected, were studied carefully beforehand using the results of Ranger, Surveyor, Lunar Orbiter, and previous Apollo missions, and each had specific scientific goals. The Apollo 11 landing site would answer questions about the origin and composition of an old mare surface. Apollo 12: Another Mare Site
The Apollo 12 (Surveyor 3) site was selected because it appeared to contain basalts of a different type and age. The site lay on one of the bright rays from the crater Copernicus, offering the chance to sample some of the ray material
Apollo 14: the Fra Mauro Highlands
An area on the rough highlands north of Fra Mauro Crater was chosen as the Apollo 14 site. The intent was to investigate the Fra Mauro Formation, thought to be material ejected by the Imbrium Basin impact. This material would potentially provide a date for the Imbrium event and a sample of rocks from deep within the Moon's crust
The Apollo 15 site was located at the edge of Mare Imbrium at the foot of the mountains forming its main topographic ring. This geologically complex site provided for investigation of Mare Imbrium, the Apennine Mountains, and a long channel-like feature called Hadley Rille. This site was the farthest north of the six landed missions, and it provided the third leg of a triangle for the seismic and laser-ranging arrays.
Apollo 16 targeted the lunar highlands, away from the basalt-filled basins. The main objectives were to determine the age of the highlands and whether they were volcanic. A site was selected along the edge of the smooth Cayley Plains adjacent the Descartes Mountains so as to explore and sample both features. The site contained two small, fresh craters that penetrated the surface formations and that provided natural drill samples of the underlying materials.
Apollo 17: the Taurus Littrow Valley
The Apollo 17 landing site, like the Apollo 15 site, was chosen to be at the interface between a mare and a highland region. The Taurus Littrow Valley, along the southeastern edge of Mare Serenitatis, was selected to investigate the age of the basin, the different kinds of highland landforms surrounding the basin, the basalts that filled the basin, and the dark mantling materials thought potentially to be young volcanic ash deposits. Also, craters in the Taurus-Littrow Valley floor were thought to be secondary craters from the Tycho event, providing the possibility of sampling Tycho ejecta and dating the impact.