It's been one of the greatest challenges that ever came along in my life; it was one of the more difficult things to do.

We feel that this stands as a symbol of the insatiable curiosity of all mankind to explore the unknown.

The way I see it, commercial interests should manage a lunar base while NASA gets on with the really important task of flying to Mars.

To send humans back to the moon would not be advancing. It would be more than 50 years after the first moon landing when we got there, and we'd probably be welcomed by the Chinese. But we should return to the moon without astronauts and build, with robots, an international lunar base, so that we know how to build a base on Mars robotically.

Being first outside the spacecraft would bring much more responsibility, and I really wasn't looking for that.

The universe is the way it is. It's not going to be changed by supplications.

It's not easy to get human beings into orbit. So far only three nations have been able to do that, with all the resources that they put together. And I'm just a little skeptical that that's going to be done by the private sector without making use of what has been done by the government.