Mitchell died Thursday night at a West Palm Beach hospice after a short illness, his daughter, Kimberly Mitchell, said. Mitchell's passing coincides with the 45th anniversary of the Apollo 14 mission, which ran from Jan. 31-Feb. 9, 1971.
Mitchell, one of only 12 humans to set foot on the moon, was not a typical strait-laced astronaut: In later years, he said aliens visited Earth and faith healers were legit. He attempted to communicate telepathically with friends at home during his Apollo mission. He had an "epiphany" in space that focused him on studying consciousness, physics and other mysteries.
"What I experienced during that three-day trip home was nothing short of an overwhelming sense of universal connectedness," Mitchell wrote in his 1996 autobiography. "It occurred to me that the molecules of my body and the molecules of the spacecraft itself were manufactured long ago in the furnace of one of the ancient stars that burned in the heavens about me."
His passion for exploration led him to become an astronaut, and he joined NASA in 1966. He helped design and test the lunar modules that first reached the moon in 1969 with Neil Armstrong and Buzz Aldrin.
Shepard, the first American in space in 1961, picked Mitchell to be on Apollo 13's three-person crew. But they were bumped to the next mission so Shepard would have more time to train — he had been grounded for years because of an inner ear disorder.
The delay was an unexpected benefit: Apollo 13's astronauts were nearly killed when an oxygen tank exploded as they neared the moon in 1970. They made it home safely, but never set foot on the moon. A year later, Shepard, Mitchell and Stu Roosa were the first crew to try again amid falling support for the moon missions from President Nixon, Congress and the public.
"Had we blown it, had it failed for whatever reason, that would probably have been the end of the Apollo program right there," Mitchell said in 1997. But they didn't let that get to them: "When you're carrying that personal load, you just don't have room to carry a national load as well."
Fortunately, their mission, the third lunar landing and Mitchell's only trip in space, was a success.
Unlike the two moon missions before them that went to smoother areas, Shepard and Mitchell landed in a hilly region while Roosa orbited overhead.
They collected about 95 pounds of samples in more than nine hours walking the lunar surface. They showed for the first time that astronauts could walk long distances on the moon, covering nearly two miles on their second expedition on the surface. That proved the crews of later missions could walk back to their spacecraft if the buggy-like Lunar Rover broke down.
Their mission was best known to the public because Shepard became the first and only golfer on the moon. Mitchell joked when Shepard duffed his first shot: "You got more dirt than ball that time." Less well known was that Mitchell made the only "javelin" throw on the moon when he tossed an unneeded metal rod.
Apollo 14 did have its share of glitches. Shepard and Mitchell almost didn't make it to the surface because of problems in the lunar module.
First, a loose piece of metal in a switch made an abort signal go off as they prepared to travel down to the moon. If the descent engine had been on at the time, the module would have automatically aborted the landing. They traced the problem's cause by tapping on the switch with a flashlight and a pen.
Computer programmers back home wrote instructions to get around the abort problem and Mitchell entered them with just minutes to spare. Shepard later wrote that Mitchell remained "Mr. Unflappable" during the scare.
Once they started for the surface, though, the landing radar wasn't working correctly. Shepard and Mitchell agreed to take the dangerous and rule-breaking step of landing without radar, but didn't have to when the device started working just in time.
They had to give up searching on foot for Cone Crater's rim, one of their mission's top geological sites. They stopped because they spent too much time looking for it and had to stick to tight schedules. When Mission Control told them they should consider giving up, he used colorful language for an astronaut: "Think you're finks!"
But it was the telepathy experiment on the ride home that would give Mitchell more notoriety. Even before he left, he told The Associated Press about his fascination with psychic phenomena and extrasensory perception and that he thought humans weren't the only intelligent life in the universe.
Those interests almost got him removed from the mission, said Gene Cernan, the last man to walk on the moon and backup commander for Apollo 14. Cernan wrote in his autobiography that despite Mitchell's impeccable skills and vast intelligence, flight crew director Deke Slayton and Shepard were bothered with the fascination.
"Ed just wouldn't let it go, and Deke said he was uncomfortable with the possibility that Mitchell's full attention would not be on the mission," Cernan wrote.
Mitchell claimed the experiment was a success. He thought of certain symbols on a list and the friends on Earth tried to determine which ones. They were supposed to attempt the experiment at certain times, but a launch delay caused them to try at different times.
He said the results were wrong about 90 percent of the time, much more than the half that chance would suggest. He and his friends said that meant that subconsciously they knew something was wrong because of the delay, so they communicated incorrect symbols.
But most press reports dismissed him and some colleagues shunned him.
Edgar Dean Mitchell was born Sept. 17, 1930, in Hereford, Texas, and grew up working on his father's cattle ranch in New Mexico. He joined the Navy and got a doctorate from the Massachusetts Institute of Technology before joining NASA.
He left NASA in 1972 and founded the Institute of Noetic Sciences, which is dedicated to exploring the mysteries of the human mind and the universe. He also searched for ways to link the spirituality of religion with the hard facts of science.
In later years, he claimed the U.S. government covered up evidence that aliens had landed here. He also tried to prove that the supposed psychic spoon bender Uri Geller and faith healers were legit.
In 2011, he became embroiled in a legal fight with NASA over his plans to auction a 16mm camera he had brought home from the moon mission. The camera had been bolted to the l lunar module and would have been left on the moon if Mitchell hadn't removed it.
Although Mitchell contended it was a gift, NASA sued to stop the auction and eventually Mitchell agreed to donate it to the National Air and Space Museum in Washington.