If two billion people wanted to watch a robot fly by Pluto, imagine what it will be like when the first humans step on Mars. It'll be the most unifying event anybody could ever put on.

If the Pluto mission was a cat, then it would've been dead long ago because they only get nine lives, and we've had significantly more than nine stoppages and odd twists and turns.

The Kuiper belt region, which I call the third zone because it lies beyond the rocky terrestrial planets and beyond the giant planets, is a bizarre frontier.

Just speaking for myself, I think the return of people to the Moon has a lot to offer for understanding the formation and evolution of terrestrial worlds; so would the exploration of near-Earth asteroids by people.

Having a diverse suite of U.S.-manned spaceflight systems to access space is inherently robust.