July 28, 2008 -- Of the more than 6 billion people in the world, only 12 have ever set foot on the moon, providing them the unique opportunity to peer at the Earth from hundreds of thousands of miles away.
For many, the experience appears to have changed them. The select group has returned to regular life and dispersed into a wide array of careers, spiritual and philosophical leanings, and apparent perceptions of the world they temporarily gazed at from space.
Most recently, NASA astronaut Edgar Mitchell, a member of the Apollo 14 mission that landed on the moon in 1971, elaborated on his own fluid thoughts on the universe, 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 last week.
"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 in which some believe the U.S. military covered up the crash scene of an alien spacecraft.
Other moon-walkers have admitted to changing after being launched into outer space -- some becoming more open-minded about the possibility of extraterrestrial life, others more spiritual, and some choosing to change career paths all together.
Alan Bean, who flew the second moon landing on Apollo 12 in 1967, became a painter after returning to Earth.
Speaking in British filmmaker David Signton's 2007 documentary "In the Shadow of the Moon," astronaut Gene Cernan, who made the last moon-landing in 1972, said he became a believer in the idea of a greater power after traveling to outer space.
"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."
Perhaps the saddest transformation was that of Buzz Aldrin, who made the first moon landing with Neil Armstrong in 1969, and later suffered from severe depression and alcoholism, both of which he wrote about extensively in his memoir "Return to Earth."
Space historians and other former astronauts told ABCNews.com that while Mitchell's case may be extreme, those who travel into the galaxy sometimes return with an altered view of the universe -- and perhaps even about its inhabitants.
Do Space Travels Change Astronauts?
"There is some evidence that astronauts are changed by going into space," said Mike Neufeld, the chair of the space history division at the National Air and Space Museum in Washington, D.C.
Neufeld noted that while Mitchell's beliefs in extra-terrestrial life have certainly come to light over the years, the former moon-walker 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.
Calls and e-mails sent to Mitchell by ABCNews.com were not immediately returned.
"There's nothing negative you can say about Mitchell or his Apollo 14 mission," said Neufeld. "But his involvement with ESP and his work since has always made him some sort of an outsider."
NASA's response to Mitchell's claims have been limited.
"NASA is not involved in any sort of cover-up about alien life on this planet or anywhere else in the universe," NASA Headquarters spokesman David Steitz said today. "Dr. Mitchell is a great American, but we do not share his opinions on this issue."
'Things Pale in Comparison'
Former astronaut John Herrington, who made three space walks in 2002 on the last space shuttle mission before the Columbia accident, told ABCNews.com that his experience as an astronaut definitely affected his perspective on the universe.
"You see the world from a different perspective -- you have a much grander view," said Herrington. "It does fundamentally change the way you look at the world."
Herrington said that he can also understand the depression that some encounter upon arriving back on earth.
"In anything that you put an incredible amount of effort into, a lot of times you come back from it and things pale in comparison," said Herrington. "There's a little depression, a little let-down."
"You worked hard and now the experience is over," added Herrington.
For Mitchell, the four decades back on Earth have done nothing to sway his belief in extraterrestrial life among the stars.
"There's not much question at all that there's life throughout the universe -- we're not alone in the universe at all," he said last week. "It is a real phenomenon."