I don't think we're going to build a 50-person spacecraft or a 100-person spacecraft.

Returning to the Moon with NASA astronauts is not the best usage of our resources. Because OUR resources should be directed to outward, beyond-the-moon, to establishing habitation and laboratories on the surface of Mars that can be built, assembled, from the close-by moons of 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.

Over the years, I think I've matured in my spiritual evolution and development to understand a bit more than the narrow religious thinking - to move beyond that through a sort of perfection of the grandiose nature of the universe, and how perfect it is it in its sense and how satisfied we should all be in our place in that.

As time goes by, I'm increasingly impressed by how very special and timely it was that we got the degree of national commitment needed to put people on the Moon. For the first time, this nation was united in trying to develop an interplanetary capability. We've been trying to repeat that situation ever since.

This has been far more than three men on a mission to the Moon; more still than the efforts of a government and industry team; more, even, than the efforts of one nation. We feel this stands as a symbol of the insatiable curiosity of all mankind to explore the unknown.

I'm sure that there are places in the deserts in Australia that could be similar to where we might want to go on Mars.