What’s the cost of humans going to Mars? What’s the cost of not going? Why go at all? These are all good questions, but they don’t come close to being answered by James Cameron in this month’s Wired.

The Martian rovers have been exploring Mars quite capably, and are far beyond their engineering limits. The findings from the rover explorations are being tallied now. Just a few months ago, I sat in the office of Steve Squyres, the principal investigator for the Mars rovers, and he showed me a long list of papers that the various teams would be writing about their scientific findings. The Martian robotic rovers have been an outstanding success.

But Cameron, advocating human exploration, has no better answers. He believes, seemingly based only on his exploration of the Titanic, that exploration is romantic, worthy for its own sake. He believes the lack of enthusiasm is because people want to solve problems here on Earth first. He wants us to go to Mars just because–just because it’s out there, presumably waiting. But he makes no argument why humans should go to the moon and Mars. And this is the bottom line. What can people do that robots cannot? What can they discover that planetary astronomers cannot? Would people trundling across the surface of Mars have been any more likely to find methane in the planet’s atmosphere, a discovery that might hint at the possibility of life there? Cameron has no answers, and it’s the lack of a real answer that the U.S. public senses–and why it is not more enthusiastic about sending humans to Mars.

If even our most vaunted explorers–or movie directors!–can’t make their case, why should the U.S. public back their cause?