People communicate in Twittering ways. I've learned how to do that.

Kids, help your parents if they don't know how to use a smartphone.

When we get there, if we don't find any life on Mars, from that point on there will be life on Mars because we'll bring it there, whether it's germs and leftover urine bags, whatever it is.

Everyone who's been in space would, I'm sure, welcome the opportunity for a return to the exhilarating experiences there. For me, a flight in a shuttle, though most satisfying, would be anticlimactic after my flight to the moon. Plus, if I pursued a flight myself, people would think that was the reason I am trying to generate interest in public spaceflight. And that's not the purpose - I want to generate interest in long-range space exploration.

There's no guarantee that the United States will be around 200 years from now.

The society of life on Mars, or the challenge of making Mars more livable, will have significant benefits on our attempts to modify and change in some ways the environment here on Earth.

When the time comes to start building deep space transports and refueling rocket tankers, it will be the commercial industry that steps up, not another government-owned, government-managed enterprise.