Exploration is wired into our brains. If we can see the horizon, we want to know what's beyond.

My favourite thing to do on this planet is to scuba dive.

I'm in favor of changing the destination of humans. There are a lot of manned missions that can be done, but not in the direction of the moon.

Is the destiny of the human species to sit back and play with our mouse and computer and imagine, fantasize?

Does it make sense for the U.S. to expend hundreds of billions of dollars to mount a new Apollo-style program to return to the moon? Or have we blazed that trail? Shouldn't we help other nations achieve this goal with their own resources but with our help?

In my mind, public space travel will precede efforts toward exploration -- be it returning to the moon, going to Mars, visiting asteroids, or whatever seems appropriate. We've got millions and millions of people who want to go into space, who are willing to pay. When you figure in the payload potential of customers, everything changes.

Mars has been flown by, orbited, smacked into, radar examined, and rocketed onto, as well as bounced upon, rolled over, shoveled, drilled into, baked and even blasted. Still to come: Mars being stepped on.