One of the ironies to emerge from the midair disintegration of the Columbia on 1 February is that CNN's breaking news of the tragedy was, for many people, their first clue that a shuttle mission was under way. For two weeks, the shuttle had been looping the globe to the complete obliviousness of the vast majority of the world's population, which was preoccupied for the most part with the fate of Iraq.
This everyday neglect is worth remarking on, not least because, set against its backdrop, the flood of hyperbolic tributes that followed Columbia's loss strikes an odd chord. Suddenly a space programme that had been thoroughly routinised was reimbued with transcendental import, while astronauts we had grown accustomed to seeing as high-priced mechanics were made over as heroes ("noble" and "decent", in the words of President Bush). In the face of disaster, it seems, we were being invited collectively to indulge a nostalgia for a space age that, in truth, died long ago.
That said, it is hard to say exactly when the space age died, because over the years Nasa - chief purveyor of the world's space aspirations - has been dealt so many potentially fatal blows. For more than three decades, budgets have been slashed and visionary programmes terminated in favour of more pragmatic goals. The result is that earth-orbit has prevailed over missions to Mars, the International Space Station has triumphed over lunar bases, and robotic probes have replaced human voyages of exploration and discovery. Most spectacularly, Columbia's demise was eerily foreshadowed by the explosion of Challenger in 1986, when another seven-person crew, which included the first "teacher in space", met its sorry end above American skies.
Yet of all the landmarks that line the route of the space age's death march like so many stations of the cross perhaps the most disturbing is the first, which came in 1969, minutes after Neil Armstrong and Buzz Aldrin touched down on the moon's surface for the very first time. Norman Mailer, in Houston to witness the Eagle's landing, recorded the switch- blade moment when he voiced his own incredulity at seeing reporters file out of the live telecasts in droves. Already bored with foot-printing and flag-planting, they weren't going to hang around to see Neil and Buzz scamper around collecting rocks. That's how early ennui set in.
We still do things in space. We launch satellites and scientific probes, build space stations and space telescopes, and in the days of Mir at least, embark on missions of guile and endurance. But Mailer's point nevertheless holds: that the failure of the space age is first and foremost a failure of imagination.
Like millions of people born in the 1960s, I was entranced by the moon landings and thoroughly convinced that floating space colonies, missions to Mars and intergalactic joyrides were par for the course. What I was no doubt picking up on was the conviction that technology would somehow transform the human condition - a conviction that permeated culture at large, thanks to space science seeming, for a while, at least, to keep pace with the science-fiction futures predicted by writers such as Isaac Asimov and Arthur C Clarke. The message they conveyed was that space exploration was as natural to us as, in the words of one space pundit, "a child running around on its own legs".
By the time Stanley Kubrick's 2001: a space odyssey hit cinema screens in 1968, few people thought to question the scene where, via a deft match cut, a bone club hurled into the air by primitive man morphs poetically into the arm of a rotating space station. Mankind's future in space, Kubrick seemed to be implying, was not just an evolutionary adaptation. It was prefigured in the very birth of technology.
The trouble is that, poetics aside, technology could not ultimately fulfil the space age's air-whipped fantasies of cosmic conquest. Indeed, we never even made it past first base on the moon, which is a feeble effort by cosmic standards - like chucking tin cans across the backyard. Part of the difficulty is that the distances involved in space travel are simply too great for the old imperialist metaphors to work. It's the problem of seeing the moon as a kind of Ascension Island, midway between human colonies that might some day trade with one another.
In addition, it quickly became clear that human bodies are not well suited to long-haul space travel. Even relatively short stays in space can produce profound changes in the body, consistent with what Nasa euphemistically terms "space adaptation syndrome": a loss of red blood cells, a reduced ability to exercise, a diminution of bone density, weight loss, cardiac arrhythmia, even a lengthening of the body. It is almost as if experience's answer to the space pundit's urging that we venture boldly into the cosmic unknown is to suggest that going into space entails some kind of trespass, or evolutionary crime. At the very least, there are real, physical punishments involved in space travel.
Even before the Apollo programme fell to earth, we had managed to internalise much of the space age's outward-bound rhetoric. When, a short while ago, I asked the Apollo 12 astronaut Dick Gordon what we achieved by going to the moon, he told me: "We discovered the earth." Virtually all the Apollo astronauts were overcome by extraordinary homesickness as they circled Luna's alien sphere. "It makes you realise just what you have back there on earth," said Apollo 8's Jim Lovell. Frank Borman was moved to read from Genesis, Bill Anders took hundreds of photographs of our blue-green globe, while Russell Schweickart marvelled at how the lonesome marble he surveyed through the window of Apollo 9 could contain "all of history and music and poetry and art and death and life and love, tears, joy, games".
Over and above the historic first of "getting there", Apollo's lasting legacy is that it redefined going to the moon for future generations as the gestalt-shifting moment that gave us singular insight into the fragility and preciousness of our home planet. It is no accident that the first Earth Day coincided with Apollo's demise; that Anders's photographs became icons of the Earth First! and Whole Earth environmental movements; or that space-age mystics everywhere began waxing eloquent about the existence of one global soul. Bit by bit, our outbound surge into space was redirected inwards, and from here everything else flowed: Gaia, designer Buddhism, transcendental meditation, anti-nuclear protests, tree-hugging and rebirthing. The space age, in other words, came home to roost on earth.
What all this portends in the wake of Columbia's loss is still up for grabs. Already Nasa's friends in big aerospace and Congress are beating the drum for more federal funding. Budget cuts, they argue, were responsible for unforgivable corner-cutting. Only by pumping more money into the remaining three shuttles can we preserve the manned space programme. Meanwhile, champions of increased automation, notably the former shuttle engineer Don Nelson and the New York Times columnist Paul Krugman, say that Columbia's destruction should encourage Nasa to retire its aging shuttle fleet once and for all. Their mantra is that there's nothing astronauts do in space that machines cannot do better.
Whichever camp wins the day will have to contend with an imaginative universe that is very different from the one we inhabited in the space age. Our technology-fuelled dreams, of artificial intelligence, cloning, nanotechnology and so on, have more to do with biology than cosmology. At the same time, science fiction itself has changed. In contrast to the realistic science fiction about rockets and space travel that dominated the 1950s and 1960s, such as George Pal's film Destination Moon and Robert Heinlein's The Moon is a Harsh Mistress, the genre came to be dominated in the 1980s by epic tales of galaxies far distant, both in time and in kind, from our own - think Star Wars, for a start. Later, sword and sorcery - wizards in alternative universes - have grabbed our attention, and hyperrealist tales of cybernetic intrigue; space operas are almost nowhere to be found.
Perhaps what is needed is a new mythos for space, one that leaves behind the imagery of colonialism and pioneering, of empire-building and alien contact. I don't claim to know what it might look like. But I know that if it's going to hold us in its grip it needs to allow us to continue to reach for the stars - if not literally, then at least metaphorically.
Marina Benjamin's new book, Rocket Dreams: how the space age shaped our vision of a world beyond, is published by Chatto & Windus (£12.99)