Neil Armstrong

Neil Armstrong stepped into history on July 20, 1969, leaving the first human footprint on the surface of the moon. "That's one small step for man, one giant leap for mankind," Armstrong is famously quoted as saying after walking on the moon, but in interviews he claimed that he meant to say "one small step for a man."

Armstrong died in 2012 at age 82 following complications resulting from cardiovascular procedures.

At left: Armstrong sits inside the lunar module after his historic walk on the surface of the moon.

Alan Bean and Charles Conrad

Apollo 12 Astronaut Alan L. Bean holds a container filled with lunar soil during a moonwalk with Charles Conrad, Jr., in November 1969. Conrad, who took this picture, is reflected in Bean's helmet visor.

Charles "Pete" Conrad, the third man to walk on the moon, poses at left in 1965 before his first space flight aboard Gemini 5. Conrad died after a motorcycle accident in Ojai, California, in 1999. He was 69. Apollo 12 lunar module pilot Alan Bean poses in 1969 at right.

Bean resigned from NASA in June 1981 to devote his time to painting. He died on May 26, 2018, at the age of 86, after suddenly falling ill while travelling.

Edgar Mitchell and Alan Shepard

Edgar Mitchell, left, conducts a seismic experiment during the first Apollo 14 moonwalk with Alan Shepard on Feb. 5, 1971.

The photograph was captured by an automatic camera mounted on a vehicle the mission used to haul equipment. The crew of the Apollo 14 lunar landing mission, from left, Stuart Roosa, commander Alan Shepard and lunar module pilot Edgar Mitchell. Roosa remained in orbit while the other two landed on the moon.

Mitchell died at 85, in Florida, in early 2016. After NASA, Mitchell devoted his life to exploring the mind, physics and unexplained phenomena such as psychics and aliens. Shepard died in 1988. Before walking on the moon, Shepard became the first American in space with a suborbital flight in 1961.