US astronaut Edgar Mitchell
Edgar Mitchell was part of the crew of Apollo 14 and walked on surface of the MoonReuters

US astronaut Edgar Mitchell – the sixth man to walk on the moon and only one of 12 who ever achieved the feat – has died aged 85. He led a colourful life on his return from the planet founding the Institute of Noetic Sciences, which aimed to support "individual and collective transformation through consciousness research" and also revealing a belief in aliens.

His death in a hospice in West Palm Beach Florida was just one day before the 45th anniversary of his moon landing. As part of Nasa's Apollo 14 mission in 1971, the fourth in the US Apollo series, Mitchell spent more than nine hours on the Moon conducting experiments. His mission followed the ill-fated Apollo 13 journey that was aborted due to an explosion in an oxygen tank.

Mitchell and Captain Alan B Shepard Jr., made it to the lunar surface , landing on the Moon's Fra Mauro Highlands – the proposed landing site of the Apollo 13 mission. The pair spent a total of 33 hours at the site and collected 45kg (94lb) of moonrock as well as completing the longest moonwalk in history.

It was revealed that Mitchell had gone through a spiritual conversion during his time in space that led to his belief that aliens had previously visited Earth. He later wrote in his biography that it had dawned on him 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".

In a radio interview in 2008, Mitchell accused the US government of covering up the existence of alien life forms. He said: "I happen to have been privileged enough to be in on the fact that we've been visited on this planet and the UFO phenomena is real. Some of us have been privileged to have been briefed on some of it."

Astronomer Jonathan McDowell took to Twitter and said: "Another of the Twelve has left us – Ed Mitchell. Of those who trod alien soil, only Buzz, Al, Dave, John, Charlie, Gene and Jack remain."

A former Navy test pilot, Mitchell joined the astronaut service in April 1966, five years prior to his trip to the Moon. Apollo 14 was his only spaceflight. Mitchell was married and divorced twice. He is survived by four daughters and a son.