America must dream again, and have the faith to achieve the dream.

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.

We can't start over and develop a Saturn 5-type vehicle from scratch.

The honor you have given us goes not to us as a crew, but to ... all Americans, who believed, who persevered with us. What Apollo has begun we hope will spread out in many directions, not just in space, but underneath the seas, and in the cities to tell us unforgettably what we will and must do. There are footprints on the moon. Those footprints belong to each and every one of you, to all mankind. They are there because of the blood, sweat, and tears of millions of people. Those footprints are the symbol of true human spirit.

Any observations from the Moon or a sense of realising this or that about the greater meaning of things wasn't as influential for me as the experience of coming back and dealing with being a person who's been to the Moon.

I have no doubt that humans will go to Mars. And I feel that America has led so many things in space - we have invested so much, and we have a lot to gain - that America could and should be the nation that should lead the settlement of Mars.

I'm convinced that sending people to Mars is so expensive that if you go once and bring the people back and then go again and bring the people back, we're eventually going to run out of money. But what if we send people the first time and they don't come back? What if they stay there?