Exploring Mars is a far different venture from Apollo expeditions to the moon; it necessitates leaving our home planet on lengthy missions with a constrained return capability.

As we reflect back upon the tragic loss of Challenger and her brave crew of heroes who were aboard that fateful day, I am reminded that they truly represented the best of us, as they climbed aloft on a plume of propellant gasses, reaching for the stars, to inspire us who were Earthbound.

The first footfalls on Mars will mark a historic milestone, an enterprise that requires human tenacity matched with technology to anchor ourselves on another world.

We have the ability, at such high fidelity, to simulate the physical world through computers. But when the spiritual world or human behavior comes into play, we don't have a very good model for that at all.

To me, money is a commodity that a person must have to function, not a goal in itself.

I expected the unexpected and went [on the Moon] with an open mind. I think the visual scene was described by my words on first landing - "magnificent desolation." Magnificent for the achievement of being there, and desolate for the eons of lifelessness.

Did the Pilgrims on the Mayflower sit around Plymouth Rock waiting for a return trip? They came here to settle. And that's what we should be doing on Mars. When you go to Mars, you need to have made the decision that you're there permanently. The more people we have there, the more it can become a sustaining environment. Except for very rare exceptions, the people who go to Mars shouldn't be coming back. Once you get on the surface, you're there.