Various possible landing sites were discussed in early planning. Among these were Copernicus, Gassendi and Tycho, large impact craters containing central peaks that were thrust upward at the time of impact, bringing material from deep within the lunar crust to the surface. Such craters provide a record of the solar system's early history; a similar record on Earth has long since been obscured by plate tectonics, erosion and other processes. "The moon," Schmitt says, "is where we're going to get the information ultimately on what kind of environment existed on Earth at a time when the precursors to life were actually forming."
For both Apollo 17 and the canceled missions, Schmitt pressed NASA officials to consider a particularly ambitious objective: the Tsiolkovsky crater, located on the moon's far side. "None of the Apollo missions were planned to land on the far side, and that is an awfully large area to leave unexplored," Schmitt says. His proposal, perceived as too costly and risky, made little headway. Among its requirements would have been placing a communication satellite beyond the moon to maintain a radio link with Earth.
Other sites considered included the Marius Hills, Hyginus Rille and Schroter's Valley, the latter noted for its variety of geologic materials. Whereas some areas were more scientifically attractive than others, "anyplace you land on the moon and collect samples intelligently would've been valuable," says Don Wilhelms, a retired U.S. Geological Survey geologist who during Apollo was part of an interagency group vetting possible landing sites. Canceling the missions was "a missed opportunity," Wilhelms says. "You had existing technology at the peak of its effectiveness. So it was a waste."
In Schmitt's view, the greater error was terminating the Apollo program, not just its last three missions. "We never should have stopped building Saturn 5s and Apollo spacecraft," Schmitt says. "Everything that's happened since, including space stations, could have been done with that technology base. In addition, you would have continued to have the ability to reach out into deep space, a capability that included being able to divert asteroids in case one looked like it might be on a collision course with the Earth. For a brief, shining three or four years, we could do that with the Saturn 5."