"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," said Cernan in the documentary.
"And I mean this in a spiritual sense, not a religious sense," said Cernan. "There has to be a creator of the universe who stands above the religions that we ourselves create to govern our lives."
Charles Duke, the youngest man to walk on the moon, found religious affirmation after flying on Apollo 16 in 1972. He left NASA in 1975 to enter private business and formed the Duke Ministry for Christ.
But though moon travel appears to have changed these astronauts, space experts say they were already interested in the pursuits they chose after their moon missions.
"There is some evidence that astronauts are changed by going into space," said Mike Neufeld, the chairman of the space history division at the National Air and Space Museum in Washington, D.C.
But while Neufeld noted that Mitchell's thoughts in extraterrestrial life have certainly come to light over the years, the former moonwalker had always been interested in the paranormal.
"He was interested in ESP before he was ever launched -- he conducted an ESP experiment on Apollo 14," said Neufeld.
Alan Bean, the Apollo 12 moonwalker who later became a full-time painter, said the moon missions gave the astronauts the courage to live their lives the way they'd always wanted to live them.
"I remember thinking in lunar orbit, that if I got back from this, I was going to live my life differently, in that I was going to try to live it … like I want to live it," he said in an interview with Chaikin. "Mostly it made me have a lot of courage to do what I wanted to do and be happy about it. … That's one thing that really allowed me to be an artist. I probably wouldn't have had the courage to be an artist."
"It doesn't change you, it reveals who you are," he said.
ABC News' Emily Friedman contributed to this report.