For the generations of Americans who grew up watching "Star Trek" and "Star Wars," it's almost impossible to react to the loss of the space shuttle Columbia as some of our parents and grandparents might have, shaking their heads in sorrowful exasperation: those brave young men and women had no business up there in the first place. Homer Hickam's sweet memoir, Rocket Boys, captures the transition vividly. If you grew up watching satellites in the night sky and humans rocketing into space, doubts don't register. Space is the final frontier.

For the Columbia astronauts, that turned out to be grimly true. But in their lives, and less impressively in our own, Captain Kirk's mantra expresses a heartfelt assumption. Of course space is the final frontier, which mankind, perhaps alongside Vulcans, Wookies, and other rational species, will explore and occupy. A future, however distant, without the Galactic Republic or the United Federation of Planets would be not only a disappointment but a surprise.

But why, exactly? The urge to explore space ("conquer" has fallen out of favor) is usually justified as a scientific imperative. In its cruder version, the argument is that the space program creates "spinoffs." There are many of these—not including, by the way, the products most associated with astronauts, Tang, Velcro, and Teflon, which the Los Angeles Times notes were all developed independently of the space effort. Although NASA's list of spinoffs is long, it's a little deflating to find on it, alongside CAT scans, such breakthroughs as smoke detectors and cordless drills.

So its advocates typically offer a second scientific argument for America's space program. This might be called the "pure theory of space exploration": forget utility, it's all for the sake of knowledge. We have to explore the universe in order to satisfy our desire, as a species, to know. There is a certain nobility to this argument, but it shoots too high and begs too many questions. As a species, after all, we're ignorant of many things. Why is it more important to probe the vastness of space rather than the ocean depths? For that matter, why astrophysics and not metaphysics? Thus the idealism of this appeal often collapses back into the materialist logic of spinoffs: the knowledge that comes from exploring space will relieve man's estate more reliably than oceanography, let alone fruitless metaphysics.

Modern science's idealism is elusive; in its own way, utopian. It can't help trying to turn the earth into a paradise…unless instead it tries to lift man off the earth and into paradise. The latter is a revealing variation on the pure theory of space exploration. If human imperfections (e.g., greed, wars, budget cuts) frustrate science in its desire to transform the earth, then the alternative is to transform man by taking him away from the earth.

Here one encounters the romanticism of manned space-flight at its most extravagant: we as a species must soar into the heavens because we expect to discover heaven, a pure, beautiful, undefiled realm in which man himself can be regenerated. Space represents a second chance for mankind, a new world where we may start over and avoid our earthly mistakes. Though itself a product of mundane political bargaining, the international space station is a symbol of this aspiration, that through scientific cooperation men may overcome all their political and cultural divisions.

The same impulse sparks the resistance to the "militarization" of space. This pristine realm should not be forced to give up its innocence, to spoil its promise by taking sides, as it were, in the human fray. Yet man can't avoid taking the earth with him into space, because he takes his nature with him, with all the moral virtues and vices that entails. 

In the happy faces of the Columbia crew before liftoff and while in orbit, we saw something that had nothing to do with spinoffs or the accumulation of knowledge: the sheer fun of the adventure. Their joy was connected, of course, to the mission's riskiness, for both as participants and observers we recognize that great and noble deeds, including deeds of exploration, make a kind of claim on the human soul. It was not the crew's racial, ethnic, and international diversity that made the ship's loss so poignant. It was the fact that this multifarious equality culminated in so many expressions of human excellence. Theirs was, in that sense, a very American story. 

We need to remind ourselves that most exploring has been tied, one way or another, to empire; to the military, diplomatic, and commercial dictates of politics. This consideration, so clear in the space program's formative anxieties about Sputnik and Yuri Gagarin, has faded from mind, leaving the space program adrift. We honor the Columbia Seven best by thinking boldly about space exploration and exploitation, commercial and governmental. When he stepped off the ladder and onto the surface of the moon, Neil Armstrong declared that he had taken a giant step "for mankind," and he had. But he planted on the lunar surface an American flag.