We've explored every type of environment in the solar system at least once.
The space station is the most unique laboratory we've ever built. The reason we have it is to do research on materials, people, medical matters, pharmaceuticals - the possibilities are nearly endless.
Yes, the money could be better spent on Earth. But would it? Since when has money saved by government redlining been spent on education and cancer research? It is always squandered. Let's squander some on Mars. Let's go out and play.
Together, NASA and Hubble are opening new vistas on the universe.
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.
Exploration, of course, is going to new places, but I don't think we go to new places just solely to say: "Well, we've been there," and come back, interesting though it may be. To me, each time we go farther into space we should use that to do basic research - basic research that can't be done before you go there.
NASA is an engine of innovation and inspiration as well as the world's premier space exploration agency, and we are well served by politicians working to keep it that way, instead of turning it into a mere jobs program, or worse, cutting its budget.
The more we know about life out there the easier it will be to improve life down here.
We need to be very thoughtful about how we propose to spend the money that NASA does have for space exploration. And we need to be clear that there's the human spaceflight part of NASA, and there's the science space part of NASA, and there's also aeronautics. Those are all very different things that NASA does.
Having walked on the Moon, I know something about what we need to explore, really explore, in space.
There's no denying the public's appetite for cosmic discovery.
Would offering the Mars Prize damage NASA? I don't think so.
I am very excited to be supporting one of the world's most visionary efforts to seek basic answers to some of the fundamental question about our universe and what other civilisations may exist elsewhere.
The best way to study Mars is with two hands, eyes and ears of a geologist, first at a moon orbiting Mars... and then on the surface.
I would say keep supporting space flight, keep telling the public and the politicians why it's important to advance science and explore the galaxy. I encourage the Japanese to keep doing what they're doing.
The space station here is a magical place and an incredible science facility.
The head of NASA ought to be a space professional, not a politician.
As a researcher, I look forward to being able to do space science in a space environment.
Some things are only capable of being done in space. Examples of that are looking at our Earth from that far away, and understanding the entire processes of storms and weather patterns, and oceans, and coastlines.
We'll continue our quest in space. There will be more shuttle flights and more shuttle crews and, yes, more volunteers, more civilians, more teachers in space. Nothing ends here – our hopes and our journeys continue.
Televised speech following the loss of the space shuttle Challenger.
Space, the whole universe - I know no better place to find new physics.
Why should man's first flight to the moon be a matter of national competition? Why should the United States and the Soviet Union, in preparing for such expeditions, become involved in immense duplications of research, construction and expenditure?
Exploring and colonizing Mars can bring us new scientific understanding of climate change, of how planet-wide processes can make a warm and wet world into a barren landscape. By exploring and understanding Mars, we may gain key insights into the past and future of our own world.
The Moon may not be quite as appealing as Mars, but it's still a complex and poorly understood world, with many questions still unanswered.
It's just this beautiful laboratory in space, and it's doing a lot of really cool things. So being up there and just being able to fly through that big station one more time and do some experiments while you're up there and get that view out of the cupola... priceless.