NASA made four more manned trips to the Moon after Apollo 13, all of which successfully landed crews on the surface. Collectively, the astronauts on the Apollo missions returned almost 842 pounds of lunar soil and rock, samples that continue to form the bedrock upon which our understanding of the solar system’s origins is based. In all, twelve Americans walked on the Moon between 1969 and 1972. And that was it. Since Apollo 17, humankind has never returned.
