Triumph of the Martian Triangle: A Nasa spaceprobe goes missing and conspiracy theories abound and multiply, but why are we so fascinated by the Red Planet?

IT ALL began a century ago with a wealthy American astronomer, Percival Lowell, who thought he had seen evidence of intelligent life on Mars. Peering through his telescope, he observed what he took to be artificial canals forming the vast irrigation system of a Martian civilisation.

The canals turned out to be a trick of the eye. Lowell and other astronomers who thought they could see the dark straight lines were subconsciously connecting up dark blotches on the planet's surface. It would not be the first time imagination has triumphed over the reality of the Red Planet.

After last week's failure to regain radio contact with the Mars Observer, a spaceprobe sent by the space agency Nasa to explore the planet, conspiracy theorists were quick to rekindle the notion that the US space administration was trying to suppress evidence that we are not alone.

But the conspiracy theorists have always had rich pickings with missions to Mars. Of 20 or more attempts since 1962, the large majority have failed, many because of mysterious black-outs with communications. The last Russian mission - the two Phobos probes sent in 1989 - failed when mission controllers lost contact with the first probe after sending incorrect signals. Radio contact was lost with the second and never regained. It is still not clear why. Is there a Martian Triangle to rival the Bermuda Triangle? Are the little green men shooting them down, as one correspondent to a newspaper suggested last week?

Richard Hoagland, of the Californian Independent Mars Investigation Team, believes intelligent life did once exist on Mars. He contends that an extra-terrestrial civilisation has left behind huge monuments, notably pyramids and immense sculptures of a human-like face that an earlier Nasa probe had photographed.

It is probably a trick of the light. But Mars has been a source of fictional inspiration, from the canals to H G Wells's War of the Worlds, where men from Mars came to requisition water on the nearest planet that had it, Earth. This is understandable, given the real possibility of finding life there - albeit of a primitive variety.

It was the Romans who gave the planet its name. The flaming red colour of the small point of light in the sky clearly invoked the right image for their God of War. Galileo was first to see the planet through a telescope, in 1610. The planet is about half the size of Earth and, at a distance of between 50 million and 100 million miles depending on its orbital position from us, would have appeared not much bigger than a crater on the Moon.

Some of the earliest observers of the planet noticed how 'waves of darkening' periodically appeared as the polar ice caps melted during the Martian summers. They assumed the release of water was causing a blooming of vegetation. More recent observations showed it was more likely to be dust storms created by ferocious winds. However, the broadcaster and popular astronomer Patrick Moore says: 'If we are going to find life anywhere in the solar system, it will be on Mars.'

Mars certainly has many of the ingredients necessary. It may possess water, probably in large amounts frozen in an underground permafrost; its thin atmosphere has carbon dioxide, and small amounts of nitrogen and oxygen. Although the planet is currently experiencing an ice age, past temperatures could have been within a range - greater than 0C and less than 100C - where life is feasible.

Peter Cottermore, author of a scholarly book on Mars and a former lecturer at Sheffield University, said that even if life did exist there it was difficult to imagine that it could survive the extreme cold that envelops the planet now.

No serious scientist suggests that Martian life - if it did ever get going - managed to develop much beyond the microbe stage. Nothing that has been gleaned from the space probes that managed to get there - notably the two Viking missions of 1975 - has shown evidence of life itself.

The geological features have been more revealing. Viking and earlier Mariner probes mapped huge Martian volcanoes, three times the size of Everest, and a canyon called Valles Marineris several times the size of the Grand Canyon. Most intriguingly, Mars appears to have remnants of dried-up riverbeds and a shallow ocean. It is this that led scientists to speculate that the planet must have huge reserves of hidden water. And where there is water, there could be life.

One of the more futuristic ideas being knocked about by Nasa eggheads is to 'terraform' Mars - changing it to make it look like Earth by melting the permafrost and causing water vapour to be released. This would make it possible to introduce vegetation which would produce oxygen and create a breathable atmosphere for a human colony.

'It's probably a long shot, and a very expensive exercise,' Dr Cottermore said. Meantime, scientists planning the next mission to Mars - a Russian-led venture due for launch in October 1994 - face dwindling space budgets and the possibility of technical failure.

Mars Observer's fate is a setback for the Russian Mars '94 mission, which intended to use the radio communications of the US probe, said Alan Johnstone of the Mullard Space Science Laboratory at University College London.

But scientists such as Dr Johnstone remain enthusiastic about landing people on the most hospitable planet in our solar system. 'It's the closest world, one that looks nearest to us,' he said. 'Mars is still a place you can go to.'

(Photograph omitted)