Just before the modules were due to separate, Mattingly detected oscillations in the backup steering of the CSM’s main engine. Under mission rules, Orion had to re-dock with Casper in case flight control decided to scrub the mission — but after several hours of analysis, Mission Control judged the fault workable and cleared the landing. Because of the six-hour delay, Young and Duke began their descent to the surface from a higher altitude than any previous mission.
The Orion module landed on 21 April 1972 in the Descartes highlands — the first landing in a mountainous region of the Moon, chosen in hope that it was volcanic terrain. After stepping onto the surface, Young said: “There you are: mysterious and unknown Descartes, highland plains. Apollo 16 is gonna change your image.” He became the ninth person on the Moon; minutes later he was followed by 36-year-old Duke — still the youngest person ever to stand on its surface.
While trying to connect a thermometer into a drilled hole, Young caught his foot on a cable and accidentally unplugged the instrument — the bulky suit meant he could not see his own feet, and a repair would have taken too long. At a giant boulder nicknamed “House Rock,” the pair collected samples that conclusively disproved the expectation that the Descartes highlands were volcanic — an important, if “negative,” scientific result. The crew drove the rover 26.7 km and gathered 95.8 kg of samples, including the largest rock of the entire Apollo program, nicknamed “Big Muley.”
NASA Apollo 16 Mission Report · Apollo Lunar Surface Journal — Apollo 16 · NASA Image and Video Library — full list on Apollo 16