How many astronauts have walked on the moon?

Every Apollo landing crew had three members, but only two descended in the Lunar Module; the Command Module Pilot stayed in orbit. Six successful landings therefore produced twelve moonwalkers: Neil Armstrong and Buzz Aldrin on Apollo 11, Charles Conrad and Alan Bean on Apollo 12, Alan Shepard and Edgar Mitchell on Apollo 14, David Scott and James Irwin on Apollo 15, John Young and Charles Duke on Apollo 16, and Eugene Cernan and Harrison Schmitt on Apollo 17. None of them made a second landing.

The character of the visits changed quickly. Apollo 11 stayed close to its lander and made a single moonwalk of about two and a half hours, mostly collecting samples and setting up instruments within a few dozen metres of the hatch. From Apollo 15 onwards the crews drove a Lunar Roving Vehicle, worked kilometres away from the Lunar Module and spent about three days on the surface. Schmitt, a professional geologist, was the only scientist among the twelve; Cernan, who climbed the ladder last in December 1972, is still the most recent human being to stand on another world.

Twenty-four people have travelled to the Moon, so exactly half of them never touched it. That group includes the crews of Apollo 8, 10 and 13, which orbited or looped around the Moon without landing, and the Command Module Pilots who circled alone overhead while their colleagues worked below, Michael Collins among them. Three men made the journey twice: James Lovell, John Young and Cernan. All twelve moonwalkers were American men, and the whole sequence of landings fitted into three and a half years.