Mitchell alleged there was a conspiracy of silence, saying he'd been privy to the intelligence ''that we have been visited on this planet and the UFO phenomenon is real, though it's been covered up by governments for the last 60 years or so''.

In a statement, his former employee dismissed the claims: ''NASA does not track UFOs. Dr Mitchell is a great American, but we do not share his opinion on this issue.''

But ufologist Doug Moffett says Mitchell's validation is important, given his interplanetary expertise, and it lends more weight to sightings reported in Australia.

''I've been doing this for 15 years, talking to hundreds and hundreds of people and you obviously get a sense that these people are very genuine, they're not crazy, they're not pulling your leg,'' says Moffett, who investigates cases. ''Some of the things that have been reported to me, to explain them away as Venus or a weather balloon is very frustrating.''

Although he has never seen a UFO, Moffett believes that discounting the possibility of aliens is illogical when many revelations, such as astronomer Galileo's claims in the 17th century that the Earth travels around the Sun, were once considered heretical but are now accepted fact.

''There are people out there who believe [extraterrestrial visitation] is impossible. And I can't get my head around how anyone could come to the conclusion it's impossible when we don't know how many technologically advanced civilisations there are in the universe. The answer is a pineapple, we do not know.''

Australian UFO Research Network national director Diane Frola says Mitchell is one of a number of astronauts who have publicly supported the idea of alternate civilisations. According to the thriving pro-UFO community on the internet, in 1965 the first American to walk in space, Ed White, and fellow astronaut James McDivitt saw a metallic object with long arm-like structures from their Gemini spacecraft.

McDivitt apparently took pictures that have never been released.

Orbiting the world in a Mercury capsule in 1963, Gordon Cooper told the Australian tracking station that he could see a glowing, greenish object ahead of him. Speaking to a United Nations panel in 1985, he said, ''I believe that these extraterrestrial vehicles and their crews are visiting this planet from other planets ... Most astronauts were reluctant to discuss UFOs.''

In 1979 Maurice Chatelain, the former chief of NASA Communications Systems, commented that ''all Apollo and Gemini flights were followed, both at a distance and sometimes also quite closely, by space vehicles of extraterrestrial origin flying saucers, or UFOs, if you want to call them by that name. Every time it occurred, the astronauts informed Mission Control, who then ordered absolute silence.''

To Frola these testimonies, together with Mitchell's, lend weight to the idea that ET may be out there.

''So are they sending loopy astronauts up there or what? I don't think they are. I think they're quite qualified and they're trained to be observant and they know exactly what they're looking at. So my feelings are if Edgar says they're out there, I believe him.''

Frola says credible people report seeing UFOs, from police officers to pilots, but many prefer to keep any sightings to themselves, fearing damage to their reputations. For researchers such as herself, the stereotype is unfair and has been caused by a small category of people who tell of cosmic confrontations. ''The UFO field has had this stigma for so long about the people involved in it. Are they all nuts? They must be crazy cos they're seeing little green men.''

Some people, however, do see little green men, or grey ones, as it turns out. Sheryl Gottschall, of UFO Research Queensland Inc, has held three support groups for about 12 to 15 Earthlings who have had otherworldly interactions, she has also spoken to 300-500 who have told her of their close encounters.

''We've received reports about alien abduction experiences which have left many people traumatised. These are unwilling contacts with small aliens often referred to as the greys. But we've also received reports that have been of friendly contact too, some with human looking ETs,'' says Gottschall, who believes that support groups provide an acknowledgement of their feelings and experiences.

''These people live with the theme of 'life interrupted', hijacked, if you will, by their close encounters and it's often quite difficult for them to reintegrate after their experience into society.''

Meanwhile astronomy buff Ross describes himself as simply open-minded. He says most sightings can be explained away while others remain frustratingly unidentified, such as his second sighting in about 1970.

''I was riding my motorbike this particular day just cruising around Wagga going around one of the hills there. It was a bright sunny day, broken cloud, and even though I was sort of looking straight ahead I was aware of a blue flash above. I looked up while I was riding and there was this brilliant blue ball of light,'' he says. ''It went for maybe a couple of seconds, two to three seconds and then it was gone, one side of the sky to the other.''

In the following days, others reported seeing strange sights. ''One lady reckons she saw this football-shaped thing take off from her back paddock,'' Ross says.

His third sighting, in 1986, was of a bright red/orange light which was slowly travelling from the Belconnen area, west of Chisholm, over Fisher then Isabella Plains.

Even though he has spent decades investigating UFOs and is ''discouraged'' by the lack of evidence, he remains convinced there is life in outer space. ''Oh, yeah, how could there not be?''

He says the sheer size of the cosmos means other beings could feasibly co-exist.

''There are so many life forms here, just on this planet alone, and to think that this one little speck of dust in an immense universe could be the only one harbouring some sort of life form, to think that nothing else could be anywhere else, is ludicrous.''