In 1984, he joined other astronauts in founding the Mercury Seven Foundation to raise money for scholarships for science and engineering college students. In 1995, it was renamed the Astronaut Scholarship Foundation and he was president and chairman until 1997.
After a long illness, said to be leukemia, he died in July 1998.
In the 1979 book "The Right Stuff," author Tom Wolfe said he had two sides, "the Icy Commander and Smilin' Al,'' but also that he but he ''set a standard of coolness and competence that would be hard to top.''
One of the more controversial moonwalkers, in the years after his 1971 journey to the moon, Edgar Mitchell has made headlines for arguing that alien visits to Earth have been covered up by governments for more than 60 years.
"I happen to be privileged enough to be in on the fact that we have been visited on this planet and the UFO phenomenon is real," Mitchell said on Britain's Kerrang Radio in July 2008.
"It has been covered up by governments for quite some time now," added Mitchell, who grew up in Roswell, N.M., the location of the controversial 1947 incident (or perhaps non-incident) in which some believe the U.S. military covered up the crash scene of an alien spacecraft.
The Apollo 14 astronaut was the sixth man to walk on the moon but retired from NASA the following year.
In 1973, he founded the Institute of Noetic Sciences to sponsor research into the nature of consciousness. He published "Psychic Exploration" in 1974.
He traces his interest in consciousness back to his moments on the moon.
"There was a vague feeling that something was different. That my life had gotten very disturbing, very distressing at a subconscious level," he said in an interview with Chaikin. "What I do remember is the awesome experience [on the trip back from the moon] of recognizing the universe was not simply random happenstance … That there was something more operating than just chance… I've assiduously spent the last fifteen years figuring out what was true."
In April, the 78-year-old spoke at the National Press Club in Washington after the X-Conference, a convention of UFO researchers and activists.
"We are being visited," he said, according to the U.K.'s Guardian. "It is now time to put away this embargo of truth about the alien presence. I call upon our government to open up ... and become a part of this planetary community that is now trying to take our proper role as a spacefaring civilization."
Reaching the moon was a spiritual experience for astronaut James Irwin.
"I felt the power of God as I'd never felt it before," he said about the July 1971 Apollo 15 mission. He was the lunar module pilot for the flight and explored the moon's surface for three days.
One year after the mission, Irwin resigned from NASA and the Air Force to form the religious organization High Flight Foundation in Colorado Springs, Colo.
According to High Flight's Web site, the astronaut started the organization to encourage others to experience "the Highest Flight possible with God."
"Jesus walking on the earth is more important than man walking on the moon," it quotes Irwin as saying.
The group organizes religious retreats and trips to the Holy Land. Irwin even led expeditions to Turkey's Mount Ararat in search of evidence of Noah's Ark.
In 1991, at age 61, he died of a heart attack.