Apollo 16, NASA's fifth crewed lunar landing and the first to explore the Moon's central highlands, ended with a Pacific splashdown near Christmas Island, where the USS Ticonderoga recovered the crew. John Young and Charlie Duke spent about 71 hours on the surface at the Descartes region and drove their rover roughly 27 kilometers. They brought home about 95 kilograms of rock and soil, samples that overturned scientists' belief that the highlands were volcanic.
Apollo 16 launched from Cape Kennedy in mid-April 1972 with a scientific goal. Geologists had chosen the rolling terrain near the crater Descartes because they expected it to preserve ancient volcanic rock, a type of lunar crust no earlier crew had sampled. The mission nearly ended before the landing. While Young and Duke waited in lunar orbit in the lander Orion, Ken Mattingly found an oscillation in a backup steering system for the main engine of the command module Casper. Mission controllers spent about six hours studying the problem before clearing the landing, and they later shortened the flight by a day.
Once on the surface, Young and Duke made three moonwalks totaling more than 20 hours. They drove the Lunar Roving Vehicle to the rims of North Ray and South Ray craters and up the slopes of Stone Mountain. The rocks they collected were almost entirely breccias, fragments fused together by ancient impacts, and showed little trace of volcanism. "Well, back to the drawing board," one geologist remarked as the samples came in. Duke, at 36 the youngest person to walk on the Moon, left behind a photograph of his wife and two sons with a note on the back. Young leapt off the ground to salute the flag, and the jump was caught on camera in the Moon's low gravity.
The journey home produced another first. During the coast back to Earth, Mattingly climbed out of Casper on a spacewalk to retrieve film cassettes from the spacecraft's scientific instrument bay, with Duke assisting from the hatch. The mission lasted just over 11 days. Its capsule came down under three parachutes in the central Pacific, and the crew was flown to the Ticonderoga. Apollo 16's findings changed how scientists understood the lunar highlands and showed how much violent bombardment had shaped the early Moon.