We don't know how many planets we're going to have to examine before we find life, and not finding it on 10 or 100 doesn't mean it's not there. This may be very tricky.

The most striking thing to me about human space flight and my own personal experience is that I've seen dramatic changes on Earth. We humans are rapidly changing the planet. I've watched Amazonia as the rainforest has been cut down. That's something I've seen out the window. I'm very worried about that.

Our country... invests a tiny fraction of 1 percent in NASA, and this is what's so amazing to me, is with that small investment, we do so much for the country.

I look forward to working with the NASA team to help enable new discoveries in our quest to understand our home planet and unravel the mysteries of the universe.

To help enable the kind of science Hubble is performing makes my life worthwhile.

Absolutely the most fun thing to do in space and rewarding thing, in many ways, is to look back at planet Earth.

Once in a while, the universe lets you be free alone and in peace.

I have had the privilege to be a member of many high-performance teams at NASA, both on and off the planet.

Small bodies in our solar system, like comets and asteroids, help us understand how the solar system formed and provide opportunities to advance exploration.

The strangest thing I've found is that when I got to space, I felt more comfortable in space that I've ever been on Earth before. I just felt this is my home.

I got lucky and got assigned to Hubble.

The best would be to fly in space with family and friends.

There are some things worthy of risking your life for.

The surface of Mars is bathed in ultraviolet light, bathed in radiation. Mars's magnetic field is essentially gone, so the surface of Mars is essentially sterilized.

Hubble uniquely has been able to look in the atmosphere of a planet orbiting a nearby star and figure out what's in that atmosphere.

Getting a team of scientists on Mars could be transformative.

I think it's really a sign of great American strength that we do invest the money we do in technology, in these hard projects, in NASA.

Life outside of Earth is probably going to be really hard to find.

One of the things that happens in space is that there is a fluid shift. You get a lot of extra pressure, and it fills your sinuses, and the horseradish is a miracle worker for cleaning that out.

What we do at NASA is inspiring. It's reaching, it's visionary, and it inspires people on Earth to try hard things.

I don't particularly want to jump out of an airplane with a parachute if I don't have to. I don't want to go bungee jumping. I like adventure with a real purpose that I can buy into.

The first thing to know about space food - it is the ambiance; it is the environment. It is not the food.

Being an astronaut, there are not a lot of things that have really shocked me in my life.

We're being very careful that we don't send a spacecraft to Mars with the intention of detecting Martian life - and find out that we detected the Earth life that we took with us.

At the age of six, I declared that I wanted to be an astronaut. My mother thought that was just fine, as it would encourage me to learn science, and besides, there really was no chance I would ever actually become an astronaut.

The Martian atmosphere is very thin. It's like our atmosphere at 100,000 feet.

The things I like to do involve a lot of mental focus, a combination of physical and mental challenge. That is what mountain climbing is.

Sometimes astronauts feel a little ill or get minor scrapes. I trained as a crew medical officer to do basic treatment.

We need to move off the planet. And Mars is the next best place.

I'm an incurable romantic. But I'm not an adrenaline junkie.

I thrive with high-performance challenges in front of me.

I'm absolutely compelled for NASA to send international astronauts to Mars to find out if Mars ever harbored life.

If I could live in space, I would definitely do that.

Hubble has really opened our eyes to what the universe is made of, its structure, and has helped us learn how little we know about the universe.