In the 19th Century people were looking for the Northwest Passage. Ships were lost and brave people were killed, but that doesn't mean we never went back to that part of the world again, and I consider it the same in space exploration.

Every day, we get a little bit closer to the kind of expertise and the kind of experience we're going to need to go there. I'd love to be the guy walking on Mars.

I think it's going to be a very important, unique data set in terms of measuring the behavior of your lower body in space and trying to figure out what we can do to preserve bone and muscle density.

I never made a career decision based solely on my desire to be an astronaut. I attended the Naval Academy because I wanted to be a Navy pilot. I majored in math because math had always come pretty easily to me and I liked it.

After assembly complete, when we have a larger crew on orbit, a more complex vehicle, more laboratories and more robot arms, maybe we'll have room for specialists. But right now we don't.

Researchers can measure what kind of angles your legs take up during the day when they're just trailing around behind you in weightless conditions, and what kind of impacts you feel during your exercise. They're going to compare that with what we do on the ground.

It took me a long time to get selected as an astronaut. In fact, I applied for 20 years before I was selected.