Dr Edgar Mitchell said he was aware of several UFO visits during his career, but each one had been covered up. The 77-year-old, who was a crew member of the Apollo 14 mission, said sources at the space agency had described aliens as resembling little people who look strange to us". Dr Mitchell told Kerrang! Radio that human technology was "not nearly as sophisticated" as theirs and had they been hostile, he warned: "We would be been gone by now". He said: "There's not much question at all that there's life throughout the universe, we are not alone at all. I'm most assured about that. 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. It's been well covered up by all our governments for the last 60 years or so, but slowly it's leaked out and some of us have been privileged to have been briefed on some of it. I've been in military and intelligence circles, who know that beneath the surface of what has been public knowledge, yes - we have been visited. Dr Mitchell, along with Apollo 14 Commander Alan Shepard, still holds the record for the longest ever moonwalking session at nine hours and 17 minutes following their 1971 mission. Officials from NASA, were quick to play the comments down. In a statement, a spokesman said: "NASA does not track UFOs. NASA is not involved in any sort of cover up about alien life on this planet or anywhere in the universe.