Apollo 16 was NASA's fifth crewed Moon landing and the first mission to explore the lunar highlands. Launched on April 16, 1972, it carried Commander John Young (on his fourth spaceflight and second trip to the Moon), Command Module Pilot Ken Mattingly, and Lunar Module Pilot Charlie Duke.

The crew landed in the Descartes Highlands, a region scientists believed was formed by volcanic activity. Over three days and three EVAs totaling 20 hours and 14 minutes, Young and Duke drove the Lunar Rover 16.6 miles across the highland terrain, collecting 211 pounds of samples including “Big Muley” — the largest rock returned by any Apollo mission (26 lbs).

The geological findings surprised scientists: rather than volcanic rocks, the samples were primarily impact breccias, reshaping understanding of the Moon's highland formation. Mattingly conducted groundbreaking orbital science from the Command Module Casper, and during the return trip performed a deep-space EVA at 173,000 miles from Earth to retrieve film canisters from the service module.

Apollo 16 splashed down on April 27, 1972, in the South Pacific and was recovered by the USS Ticonderoga. The mission demonstrated that the lunar highlands held crucial clues to the Moon's ancient history and proved that crews could safely operate the Lunar Rover in rugged highland terrain.