"I felt that the world was just too beautiful to have happened by accident. There has to be something bigger than you and bigger than me," Cernan said "In the Shadow of the Moon." "And I mean this in a spiritual sense, not a religious sense. There has to be a creator of the universe who stands above the religions that we ourselves create to govern our lives."
He moved to an administrative position with NASA after his return and then retired in 1976, after about 20 years with the Navy and 13 years with NASA.
After leaving NASA, he joined Coral Petroleum, Inc. of Houston and later started his own company, a space-related technology and marketing firm. He also has been a special consultant to ABC News, covering space programming.
He currently lives in Houston and is on the Board of Directors of the Young Astronaut Council and the US Space Foundation.
After 10 years with NASA, Harrison Schmitt left science for politics.
The Apollo 17 astronaut was one of the last to walk on the moon. Three years after his 1972 lunar mission, he left NASA to run for the U.S. Senate in his home state of New Mexico.
He spent one six-year term as a Republican, serving on the Commerce, Science and Transportation Committee, the Science, Technology and Space Subcommittee of Commerce and others.
He later worked as consultant, freelance writer and speaker on space, technology and public policy issues. In a 2006 interview with Astrobiology Magazine, he said that his experience on the moon was almost indescribable.
"Being there is an essential ingredient. It's the same as trying to describe to someone what it's like to stand on the rim of the Grand Canyon. Or to have your first child. Any meaningful event that you've had in your life is probably that kind of experience. It has a personal meaning, and it will be different for every individual," he said.
"But sometimes people just want a description of what it was like," he continued, "The black sky, the brilliantly illuminated slopes of the mountains, the bright sun, and then our Earth as a big blue marble hanging over one of the mountains. The physical feeling of walking on the moon is like walking on a giant trampoline, to some degree."