John Young: NASA's most prolific astronaut, Young was the first person to fly into space from Earth seven times counting his lunar liftoff as Commander of Apollo 16 in 1972. He also served as Command Module pilot on Apollo 10.

Prior to Apollo, he flew two Gemini missions. He was the pilot on Gemini 3 with Gus Grissom as Commander. Young scored a space "first" by smuggling a corned beef sandwich onto the spacecraft - a feat for which he was reprimanded. He became Commander of Gemini 10 in 1966 even though NASA had some reservations about his suitability give the sandwich incident. Young was also the Commander of the first space shuttle flight, aboard Columbia in 1981. His final space flight was in 1983 aboard Columbia. He retired from NASA in 2004. Age: 81.

Charlie Duke: Lunar Module pilot for Apollo 16 in 1972. He served as CAPCOM for Apollo 11 where his distinctive southern drawl became familiar to audiences around the world. As CAPCOM, he became the voice of a Mission Control made nervous by a long landing that almost expended all of the lunar module Eagle's fuel. Duke's famous first words to the Apollo 11 crew on the surface of the Moon were flustered, "Roger, Twank... Tranquility, we copy you on the ground. You got a bunch of guys about to turn blue. We're breathing again. Thanks a lot!"

Apollo 16 was the first scientific expedition to inspect, survey, and sample materials and surface features in the Descartes region of the rugged lunar highlands. Duke commenced the then-record setting lunar surface stay of 71 hours and 14 minutes by maneuvering the lunar module Orion to a landing on the rough Cayley Plains. In three subsequent excursions onto the lunar surface, he logged 20 hours and 15 minutes in extravehicular activities involving the emplacement and activation of scientific equipment and experiments, the collection of nearly 213 lb (96 kg) of rock and soil samples, and the evaluation and use of Lunar Rover-2 over the roughest surface yet encountered on the moon.

Duke is one of the astronauts featured in the book and documentary In the Shadow of the Moon. At the end of the documentary, in response to Moon landing hoax theories, he says "We've been to the Moon nine times. Why would we fake it nine times, if we faked it?" Duke became a Christian after his Apollo 16 flight, and is active in prison ministry. In 1990, he wrote the highly regarded MoonWalker. Age: 77.

Ken Mattingly: Possibly made more famous by being the guy who helps save the crew in the Apollo 13 movie, Mattingly was originally slated to be the Command Module Pilot on Apollo 13, but was removed from the mission due to exposure to German measles (which he never contracted) and was replaced by the backup Command Module pilot, Jack Swigert.

He eventually got into space, serving as Command Module pilot on Apollo 16. Following his return to Earth, Mattingly served in astronaut managerial positions in the Space Shuttle development program. He commanded STS-4, the fourth and final orbital test flight of the Space Shuttle Columbia and STS-51-C, the first Space Shuttle Department of Defense mission.

In 1989, Mattingly retired from NASA and the Navy with the two-star rank of Rear Admiral (upper half), and entered the private sector. He worked as a director in Grumman's Space Station Support Division. He then headed the Atlas booster program for General Dynamics in San Diego, California. At Lockheed Martin he was vice president in charge of the X-33 development program. He is currently working at Systems Planning and Analysis in Virginia. Age: 76.