Apollo 16's lunar module Orion touched down in the Descartes highlands, a mountainous region chosen specifically because scientists expected to find volcanic rock there. John Young and Charles Duke instead discovered the area was built from ancient impact breccia, an unexpected result that reshaped understanding of the Moon's geologic history, while Ken Mattingly orbited above in the command module Casper.
Mission planners picked the Descartes highlands precisely because its rugged terrain looked, from orbital photos, like it might be volcanic in origin, a chance to sample different lunar material than earlier missions had collected from flatter mare regions. When Young and Duke actually got their hands on the rocks, the story changed entirely: the highlands turned out to be composed of breccia, rock fused together by ancient asteroid impacts, not lava.
Young and Duke spent just over 20 hours across three moonwalks, driving the Lunar Roving Vehicle across the pale, cratered terrain and collecting 95 kilograms of samples, including a rock nicknamed Big Muley, the largest lunar sample ever returned, weighing almost 12 kilograms. Young famously drove the rover in a deliberate skid at one point, delighting in the low-gravity handling in what NASA later called the 'Lunar Grand Prix.'
The mission also carried the first ultraviolet camera and telescope used on the Moon's surface, capturing images of Earth's atmosphere and deep-sky objects impossible to see through Earth's own hazy air. Command module pilot Ken Mattingly, who had been pulled from Apollo 13 just days before launch over measles exposure, finally got his flight, orbiting alone above the lunar surface for three days.
Key people: John Young, Charles Duke, Ken Mattingly