The one thing we can't really train for is weightlessness, real weightlessness. It's a ton of fun. It's pure Newtonian physics. You push in one direction, you go in the opposite direction with an equal force.

You're less apprehensive when you know what to expect. Also, the first flight is very important in this performance-driven culture I work in; it establishes your reputation. If you don't do well, it's probably your last flight.

Will we go explore? Absolutely. That's what humans have been doing since we left the caves in Ethiopia. Why? Because this is part of our nature. We're curious. We want to push the envelope. That will never stop. We will see people on Mars, hopefully in our lifetime. My hope is that the endeavour is so large, so complex, so technically challenging, so demanding and so uplifting, that it will be done with a consortium of nations. I hope the people who do set foot on Mars will do so for all mankind, and not just one nation in particular.

My husband and I don't worry about each other the way we might if we didn't have similar jobs. I sometimes get an email where he tells me he's heading off on a mission to do terrain avoidance 50 feet above the ground at 500 knots. And I just say, "Okay, have a good flight."

Most astronauts are very down-to-earth people. Many of us, three-quarters, have an engineering degree, and we have a very Cartesian, rational approach to things. You don't go and get swept off your feet. That's not your job and that's not why you're hired. So if you get so mesmerized that you forget to do what you're supposed to do, whether it's to open the cargo door of the space shuttle or configure something inside, then you should not be there as a professional operator.

Some people will always be volunteers to explore, and it is, in my mind, a privilege.

You're always under the microscope, you don't know which mission you're going to get. It's a surprise.