Apollo 16 was the fifth crewed mission to the lunar surface.
At 36 years of age, Charles Duke was the youngest person to walk on the moon.
Ken Mattingly was to have piloted the command module on the ill-fated Apollo 13 mission, but the flight surgeon grounded him 72 hours before the scheduled launch. Charles Duke had exposed the crew to German measles, to which Mattingly had no immunity.
The command module (see right) was named after Casper the Friendly Ghost, allegedly after some children remarked that the spacesuited astronauts looked like the cartoon character.
The lunar module was named "Orion" for the constellation because the crew would depend on star sightings to navigate.