It was challenging to understand what was necessary to successfully carry out all the training simulations that we, as crewmen, would experience, and make a very successful use of that training and education.

The g-forces increased and I wasn't able to continue to hold the camera against the window, so I had to lay it back against my chest, but still continued to photograph the re-entry until there was no more unusual visual effects of the energy in the atmosphere. And it was very comforting to understand that the people in Houston, the controllers, had very high confidence that we were on the right path.

The moon I see now is the same moon I saw before. Except that before, when I looked at it, it was in anticipation of what it would be like when I got there. That's behind me now.

Fighter pilots have ice in their veins. They don't have emotions. They think, anticipate. They know that fear and other concerns cloud your mind from what's going on and what you should be involved in.

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.

I think I need to continue to think and plan and marry all of the different things that we could do that make transportation in space from the earth to the space station, from the earth to the moon to space stations around the moon to visiting an asteroid.

There's a tremendously satisfying freedom associated with weightlessness. It's challenging in the absence of traction or leverage, and it requires thoughtful readjustment. I found the experience of weightlessness to be one of the most fun and enjoyable, challenging and rewarding, experiences of spaceflight. Returning to Earth brings with it a great sense of heaviness, and a need for careful movement. In some ways it's not too different from returning from a rocking ocean ship.