There are plenty of rocks in the sky. Forget the eight other planets in our own solar system (we will get to those in a moment); there are, if Sir Patrick Moore's abacus is not playing tricks on him, 100,000 million stars in the universe, many of them with orbiting planets of their own.
Yet the only one we ordinary folk - those of us without telescopes and with social lives - get truly excited about is a little one, half the size of our own planet, 35 million miles away: Mars. It has been the subject of hundreds of movies, books and television shows, and is simply better box-office than anything else in space. Mars sells - and not just in the sweet shops.
But our obsession with the place says more about our fears and aspirations here on Earth than anything about life (or the lack of it) amid the violent sandstorms and temperatures of minus 90C on Mars.
Look at the evidence. There are only two real rivals for our attention in space: the Sun and the Moon. The Sun gets newspapers named after it (and not just in Britain) and a song about having its hat on.
And the Moon? More than 30 years after its brief "giant leap for mankind" moment in the sun - if you'll excuse the expression - it now seems, well... so last century. And what else are you left with? Pluto must make do with a canine Disney character. Venus gets a name-check in the title of a self-help book - and shares it with, guess who, Mars. If David Bowie had written a song about "Life on Neptune", you'd assume that it was a reference to some kind of drug.
The truth is that none of these planetary bodies comes close to achieving Mars's grip on the public imagination. The lure of the planet goes back at least two centuries, perhaps further. In 1726, Jonathan Swift wrote of two Martian moons in Gulliver's Travels: "...two lesser Stars, or Satellites, which revolve around Mars, wherof the innermost is distant from the Centre of the Primary planet exactly three of his diameters, and the outermost five; the former revolves in the Space of Ten Hours and the latter in Twenty-one and a Half." Not the author at his most poetic, but perhaps at his most prophetic. Swift's science was, as things turned out, amazingly good - it was another 100 years before astronomers discovered that the moons he described did, in fact, exist.
There are dozens of Hollywood movies about Mars and Martians. Few of them have troubled Oscar juries. When TS Eliot gave his opinion that science fiction was "the product of the pre-adolescent mind", did he know that grown men would make a lot of money producing movies with titles such as Santa Claus Conquers the Martians, Robinson Crusoe on Mars and Flash Gordon's Trip to Mars?
The most recent Martian movie came out three years ago: Antony Hoffman's Red Planet (not to be confused with 1952's Red Planet Mars or 1959's The Angry Red Planet) starred Val Kilmer and declared on the poster: "Not A Sound. Not A Warning. Not A Chance. Not Alone." And not a hope of impressing the critics.
More people will remember Arnold Schwarzenegger and Sharon Stone's Martian adventures in Total Recall, loosely based on a Philip K Dick story. It is the tale of an earthbound construction worker who can't stop dreaming about Mars - and ends up in his fantasy world, embroiled in a civil war on the planet. More incredible than the plot is that Arnie's acting is pretty good.
Television, too. If you never glimpsed Biker Mice from Mars, maybe you recall Captain Scarlet's battles with the Mars-born Mysterons, or My Favorite Martian, a sitcom from the early Sixties about a newspaper reporter who rescues a visitor from space and passes him off as his uncle.
So why the obsession with the planet? Mars is more than just a giant rock in the sky. It is a blank canvas on which we can project ourselves: its similarities and proximity to Earth make it accessible to our imaginations, its otherworldliness and wildness a channel for our anxieties and hopes. The similarities are impressive. A day on Mars - that is, one full spin on its axis - takes 24 hours and 37 minutes. The planet has seasons, just as we do: it gets sunnier in spring and its ice caps grow bigger in winter. It may well have - or have had - life. So we can identify with it.
But it also has fierce differences: temperatures that cannot be countenanced on Earth, and no oxygen to breathe. And any astronaut who made his way to the planet and was foolish enough to lose his glove would see his blood literally boil, on account of the planet's low pressure.
As Loyd Grossman might say in another context: who would live in a place like this? In our imagination, only the most wicked and ruthless beings would survive such appalling hardships. If they are tough enough to survive all that, what would they do if they got hold of us? This might explain the power of the Orson Welles radio adaptation of The War of the Worlds, which famously spread terror throughout the United States when it was broadcast in 1938.
It is not just right-wing politicians who can capitalise on the fact that we humans are worried about foreigners: authors and movie-makers know this truth, too. And who could be more foreign than a life form hailing from somewhere with a volcano that covers an area the size of Spain?
Heather Couper, The Independent's astronomer, is well placed to comment on the planet's appeal, having laid claim to her portion of Mars mania with her book Mars: The Inside Story of the Red Planet and a three-part series on the subject startingnext week on Radio 4 (Wednesday, 9pm).
"Mars is the closest you get in our solar system to an earthlike environment. You've got polar caps made of ice and snow, canyons, you've got bloody great volcanoes. It is not like the Moon, all arid and barren. But Mars is also a metaphor for us, mapping our ideas about life on to another world. Each generation and each culture maps their thoughts out on Mars because it is so similar to Earth. There is also a possibility that there could be life there." In fact, more than a possibility, Couper says; she is convinced that Beagle 2, the British probe that will arrive on Mars on Christmas Day, will detect signs of life on the planet.
"Mars is less unlike the Earth than any other world we know," agrees Sir Patrick Moore. "It is smaller than us and further from the Sun, but nevertheless there may be a certain amount of life there." Given that there are those 100,000 million stars, and their associated planets, life on Mars means that there is probably life all over the place, he says.
And if there are other creatures out there, and any of them are as high up the food chain as we are, they too will be fascinated by their neighbouring planets - particularly those that mirror their physical attributes and reflect their deepest fears.Reuse content