1972 – Apollo 17 becomes the sixth and final Apollo mission to land on the Moon. Apollo 17 (December 7–19, 1972) was the eleventh and final mission of NASA's Apollo program, the sixth and most recent time humans have set foot on the Moon. Commander Gene Cernan and Lunar Module Pilot Harrison Schmitt walked on the Moon, while Command Module Pilot Ronald Evans orbited above. Schmitt was the only professional geologist to land on the Moon; he was selected in place of Joe Engle, as NASA had been under pressure to send a scientist to the Moon. The mission's heavy emphasis on science meant the inclusion of a number of new experiments, including a biological experiment containing five mice that was carried in the command module. Mission planners had two primary goals in deciding on the landing site: to sample lunar highland material older than that at Mare Imbrium and to investigate the possibility of relatively recent volcanic activity. They therefore selected Taurus–Littrow, where formations that had been viewed and pictured from orbit were thought to be volcanic in nature. Since all three crew members had backed up previous Apollo lunar missions, they were familiar with the Apollo spacecraft and had more time for geology training. The mission broke several records for crewed spaceflight, including the longest crewed lunar landing mission (12 days, 14 hours), greatest distance from a spacecraft during an extravehicular activity of any type (7.6 kilometers or 4.7 miles), longest time on the lunar surface (75 hours), longest total duration of lunar-surface extravehicular activities (22 hours, 4 minutes), largest lunar-sample return (approximately 115 kg or 254 lb), longest time in lunar orbit (6 days, 4 hours), and greatest number of lunar orbits (75).
