My rather imprecise discussion earlier of space science left some people with the impression that I was speaking in support of President Bush's Moon-Mars initiative. Nothing could be further from my feelings on this issue.

First, there is, in fact, no Bush initiative. This is words, not deeds, and the deeds will be interesting and worthy of debate at some future point, but the words are just hot nothings. Doing something of this sort takes money and a plan, and the Bush Adminstration has offered neither. So perhaps this is best ignored. But the idea, as vaporous as it is, is at least in play, and therefore is worth addressing.

For a number of decades we have been flying astronauts round and round in low earth orbit. There has been a scientific fig leaf of microgravity experiments and the like, but the only real justifiable research one could argue that we have been conducting was self-referential - sending humans into space to learn about sending humans into space. And what is it that we have learned? That it is expensive, dangerous, and not terribly useful. In short, if we have learned anything, we have learned that sending humans into space is, at least as we understand today how we might do it, a bad idea.

During that same time, we have launched unmanned probes to Venus, Mars and the gas giants that have returned a trove of amazing and useful scientific data. Compare and contrast.

The program's defenders point to the unique skills a human in space offers that a robotic probe lacks. Look, they say, at the remarkable Hubble servicing missions, which could not have been done by a robotic satellite. I grant that this is true, but ask at what cost? For the money we've spent on shuttle flights, we could have lobbed up a new Hubble once a year. So what if one of them, or two or five breaks. We'd have a whole bunch more!

There's a great story often retold here in the high desert country of the U.S. southwest about Garcia Lopez de Cardenas, the first European to see the Grand Canyon. It was 1540, and he and his party were hunting for the fabled lost cities of gold. We see the great canyon for its majesty and intrinsic beauty. For Cardenas, it was in the way. His reaction, in essence, was, "Crap, guess we can't go that way." The retelling of the Cardenas story is usually accompanied by a sort of mockery. "What a fool, could he not see?" But I think that misses the point. There was a time three centuries later when technology and the need of this continent's European immigrants had reached the point where the canyon made a different sort of sense. And today, with tough rubber-skinned inflatable boats, radios and the prospect of helicopter rescue, and our post-20th century aesthetic, it makes perfect sense. But I await the making of that case with respect to Mars.