As lunar module pilot of Apollo 16 in 1972, he became the tenth and youngest person to walk on the Moon. Apollo 16 was the tenth crewed mission in the United States Apollo space program, the fifth and penultimate to land on the Moon, and the second to land in the lunar highlands. The second of Apollo's missions," it was  crewed by Commander John Young, Lunar Module Pilot Charles Duke and Command Module Pilot Ken Mattingly. Launched from the Kennedy Space Center in Florida at 12:54 PM EST on April 16, 1972, the mission lasted 11 days, 1 hour, and 51 minutes, and concluded at 2:45 p.m. EST on April 27. Young and Duke spent 71 hours—just under three days—on the lunar surface, during which they conducted three extra-vehicular activities or moonwalks, totaling 20 hours and 14 minutes. The pair drove the Lunar Roving Vehicle (LRV), the second produced and used on the Moon, for 26.7 kilometers (16.6 mi). On the surface, Young and Duke collected 95.8 kilograms (211 lb) of lunar samples for return to Earth. After Young and Duke rejoined Mattingly in lunar orbit, the crew released a subsatellite from the service module (SM). Apollo 16's landing spot in the highlands was chosen to allow the astronauts to gather geologically older lunar material than the samples obtained in three of the first four Moon landings, which were in or near lunar maria (Apollo 14 landed in the Fra Mauro Highlands). Samples from the Descartes Formation and the Cayley Formation disproved a hypothesis that the formations were volcanic in origin.