I think it's inevitable that there will be Earthlings establishing a presence on Mars. And I would say that it would certainly take place by 2050 or shortly thereafter.

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.

Globalisation means many other countries are asserting themselves and trying to take over leadership. Please don't ask Americans to let others assume the leadership of human exploration. We can do wonderful science on the Moon, and wonderful commercial things. Then we can pack up and move on to Mars.

In space, you don't get that much noise. Noise doesn't propagate in a vacuum.

A hybrid human-robot mission to investigate an asteroid affords a realistic opportunity to demonstrate new technological capabilities for future deep-space travel and to test spacecraft for long-duration spaceflight.

My first inclination is to be a bit skeptical about the claims that human-produced carbon dioxide is the direct contributor to global warming.

NASA needs to focus on the things that are really important and that we do not know how to do. The agency is a pioneering force, and that is where its competitive advantage lies.