The first footfalls on Mars will mark a historic milestone, an enterprise that requires human tenacity matched with technology to anchor ourselves on another world.

American greatness was elevated significantly after Sputnik.

There are always door openings. And gradually, it accumulates. The opportunities open up in front of you.

By venturing into space, we improve life for everyone here on Earth - scientific advances and innovations that come from this kind of research create products we use in our daily lives.

Do we really need these big, gigantic, heavy rockets? What if we launch a rocket that's empty, and its sole purpose is to act as a source of fuel on the Moon? Who should build that? Well, I think the U.S. should build that.

We can continue to try and clean up the gutters all over the world and spend all of our resources looking at just the dirty spots and trying to make them clean. Or we can lift our eyes up and look into the skies and move forward in an evolutionary way.

Astronauts working for the government will always need to be either pilots or mission specialists. Those who want to be pilots should have military experience - ideally, a test pilot background.