The countdown reached ten seconds and I could almost hear an invisible crescendo of stirring background music. 'Anchors aweigh!' Five, four, three, two, one... and we had ignition!

Chemical propulsion is obsolete to go anywhere other than the moon. Three days - that's acceptable. But for Mars, we need propulsion technologies to get us there in, say, 60 days - then spend whatever length of time we want to spend and return when we want to come home.

After Apollo 17, America stopped looking towards the next horizon. The United States had become a space-faring nation, but threw it away. We have sacrificed space exploration for space exploitation, which is interesting but scarcely visionary.

I'm quite disappointed that I'm still the last man on the moon.

Curiosity is the essence of human existence.

Another hundred years may pass before we understand the true significance of Apollo. Lunar exploration was not the equivalent of an American pyramid, some idle monument to technology, but more of a Rosetta stone, a key to unlocking dreams as yet undreamed.

When you head on out to the Moon, in very short order, and you get a chance to look back at the Earth, that horizon slowly curves around in upon himself, and all of sudden you're looking at something that is very strange, but yet is very, very familiar, because you're beginning to see the Earth evolve.