Laurie Taylor has a close encounter of the bizarre kind at the fourth European Mars Conference, held at the Open University last week.

"What you need to understand," said the delegate at the coffee machine outside the Open University's Berrill Lecture Theatre, "is that most of these people want to go to Mars themselves."

It wasn't that easy a notion to entertain. This might have been the first evening of the fourth European Mars Conference, but already more than two thirds of the delegates had arrived in Milton Keynes and not many looked either young or lithe enough to fit into an average space shuttle.

I muttered something to this effect to my companion, a fiftyish man with a bulging Tesco bag and a tie with a crescent moon motif. "Well, that's the problem with Mars. It's overdue. Everyone expected that we'd be there already. But the politicians didn't find anything on the Moon, so there's no enthusiasm for spending billions more to find nothing on Mars." I was rather pleased to find so many mature Mars lovers. When I decided to gate-crash this particular conference, I'd expected that, as a greying emeritus professor of sociology, I'd stand out among a crowd of enthusiastic, young space scientists. But, as I was beginning to realise, the Mars Society was not so much involved in the circulation of high-powered interplanetary scientific research as in persuading politicians to part with the necessary cash for a manned flight.

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This populist side of the society was evident on the literature stands, which were stacked with videos about the Red Planet; glossy postcards showing a spaceman driving over a red desert beneath the legend "Greetings from Mars"; and a conference pack containing a Beagle 2 Mars pen that glowed red (what else?).

At least this conference had been spared one of the highlights of the recent meeting of the Mars Society in Chicago, where the delegates had participated in a "space song contest". (The winning entry, Thank God Dreams Survive , was sung to great applause at the Saturday-night banquet.) I had plenty of time to check the literature because the first session, cryptically called "Why Mars?", was running late. It seemed the sound system was not working. When it eventually started, the first speaker was a man who I soon learnt was the star turn: a former engineer at Lockheed Martin Astronautics, creator of the Mars Society, formulator of the Mars Direct Mission Plan and author of The Case for Mars . "Will you please welcome, all the way from America, Robert Zubrin," intoned the chairman.

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"Robert, is there a compelling reason for manned flight to Mars?"

Talk about a leading question. Zubrin was off and running. Of course there must be a manned flight to Mars. We must find out if there is life there and if it has a separate evolutionary origin to life on Earth. This can't be done with robots. "Human explorers are essential." After all, what else is the American Government going to spend its money on? "Propping up another South American dictator?" Pretty soon he moved on to his own proposals for how to get to Mars. He fervently opposes using the Moon as a way station to Mars. It's much cheaper, he insists, to go straight there.

And then he's racing on to the rocket science needed for such a trip.

I got temporarily lost in the science, but he never lost my attention. He's smart and funny. "People ask about the effects of large doses of radiation on the crew from such a mission. Forget it. If we sent a crew of smokers to Mars without any tobacco, a trip this length (about eight months) would substantially reduce their likelihood of contracting cancer." The other speakers on the panel did their best to keep up.

Andrew Ball, a postdoctoral research fellow at the Open University's Planetary and Space Sciences Research Institute (PSSRI), told us proudly about the interest generated by Beagle 2 's ill-fated trip to Mars. The probe, we learnt, had been assembled less than 100m from where we were sitting, and "more people had followed its progress than watched Only Fools and Horses ".

But Ball wondered gently whether we had the right to land humans on Mars in the knowledge that they might contaminate any existing life. (Zubrin snorted: "Look, Earth once existed without life. Life is an intrusion on Earth. Do we want dead planets?") Ball's doubts about humans on Mars were further drowned out by American film-maker Sam Burbank, who proceeded to tell us that he was "the liberal artist here" and that his reasons for wanting to make the trip were "emotional". "We need the inspiration that we'd get from going."

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We filed out of the lecture theatre to our quarters for the weekend, the Accenture Building. This monument to uninspired branding is surrounded by satellite buildings, all in similar mid-Tesco style and named after well-known British birds.

I was directed to Lapwing and a compact, clean and wholly efficient Space Shuttle of a bedroom, where the only hint of previous human habitation was provided by a small cigarette burn immediately beneath a sign thanking me for "not smoking". By Saturday morning, our number had swelled to about 60 as a small crowd of younger people had signed up for the day. First up was a worthy introduction to the PSSRI by its deputy head, Ian Wright. "We have the fourth largest collection of meteorites in the world," he told us proudly, before talking about the lessons learnt by the instrument-building team in which he served from the relative failure of Beagle 2 .

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And then, fresh from one of his many book signings, it was time for Zubrin again. Even though other leading and articulate experts on space travel, such as John Zarnecki and Alex Ellery, contributed to the conference, it was almost impossible to imagine the Mars Society surviving if Zubrin ever decided to stay at home. He already admits to a certain weariness. "I've been doing it a long time. It's incredibly slow. But look how far we've come in the five years since we started the Mars Society. Europe is now doing planetary missions. Only recently I spoke to the US Senate. Sam Burbank is going to make a movie about going to Mars. We have allies: scientists, artists. We're gonna win."

I began to wonder how other space scientists rated Zubrin. There was something slightly megalomaniac about his extreme intolerance of other space projects. At his best he sounded and looked like Henry Fonda about to conquer the West (he was told off on one occasion for using the imperialist language of frontiers. "It upsets the Europeans," said one speaker), but there were also moments when his eye-level, straight-talking, slightly folksy insistence on being the sole possessor of the truth uneasily recalled the flawed rectitude of a Richard Nixon.

Before packing, I thought I should check my view with the conference's public relations officer, the flamboyant Artemis Westenberg. Was Artemis her real name? "It is. I'm the Greek goddess of the moon. I'm a Jew and my parents in the Netherlands didn't want to use any of the usual names because that would have reminded them of their persecuted relatives. So they went backwards to Greece and found Artemis."

And how did she enjoy being a PR officer for Mars? "It's very important.

I'm regularly on the television and radio. I'm also the PR for Nasa in Europe. I take all the news about space and give it a human-interest twist." She looked me full in the face and gave a broad grin: "I'm a famous Dutch person."

A strange conference. I met and talked to several scientists who were all commendably loyal to the Mars Society, but also vaguely ill at ease with its readiness to employ populist sentiment and imagery to advance its cause of a manned flight to Mars. There were also doubts about an all-comers policy that allowed the likes of me such ready admittance. "You do inevitably get sci-fi nutters," grumbled one young delegate. As I left for the station, bellowing out across the atrium were the crashing opening chords of Also Sprach Zarathrustra . What else?

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