The purpose of going to Mars is for humans to first begin to occupy, permanently, another planet in the solar system. The astronauts or pilgrims, whatever you might call them, are going to be very historically unique human beings.

When I am getting ready to cross a street, I look both ways before crossing. My bones, my muscles, are not what they used to be, so I am careful when I go up and down stairs, because I've heard stories of older people falling and having very disabling injuries. I have enough things that begin to go a little bit wrong as I get a little bit older.

We could have human intelligence in orbit around Mars, building things there.

There's a historical milestone in the fact that our Apollo 11 landing on the moon took place a mere 66 years after the Wright Brothers' first flight.

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.

America can take man to the moon, and America can take men to Mars - and beyond.

What comes after the moon? I think you can guess: Mars.