Studying whether there's life on Mars or studying how the universe began, there's something magical about pushing back the frontiers of knowledge. That's something that is almost part of being human, and I'm certain that will continue.

If they asked me if I wanted to go into space tomorrow, I'd do it in a heartbeat. On the other hand, if they asked me if I wanted to go into training for three years and then go into space again, I'd probably say no.

I slept just floating in the middle of the flight deck, the upper deck of the space shuttle.

All adventures, especially into new territory, are scary.

The view of earth is absolutely spectacular, and the feeling of looking back and seeing your planet as a planet is just an amazing feeling. It's a totally different perspective, and it makes you appreciate, actually, how fragile our existence is.

When you can feel that close to something you're used to seeing from this great distance, well, it changes a person.

It takes a couple of years just to get the background and knowledge that you need before you can go into detailed training for your mission.