"Going back to the moon is not visionary in restoring space leadership for America. Like its Apollo predecessor, it will prove to be a dead end littered with broken spacecraft, broken dreams and broken policies."

"Mars is far more attractive as an outpost colony for earthlings than the moon is."

"Armstrong described the lunar surface as 'beautiful.' I thought to myself, 'It's not really beautiful. It's magnificent that we're here, but what a desolate place we are visiting.'"

"It's real easy to manufacture what you think the people want to hear. But that's not very honest."

"Nobody ever asks who was the seventh person on the Moon. The only thing they know is who's number one and who's number two. Does anybody know who the last man was?"

"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 beauty of Hawaii probably surpasses other places. I like the Big Island and the two mountains, Mauna Loa and Mauna Kea, where you can look out at the stars."

"Going to Mars would evolve humankind into a two-planet species."

"The life expectancy of people going to Mars may be decreased by the higher level of radiation that they receive."

"For the future, primarily, we must educate people in science, engineering, technology and math."

"It was interesting to think that the very first liquid ever poured on the Moon, and the first food eaten there, were communion elements."

"Retain the vision for space exploration. If we turn our backs on the vision again, we're going to have to live in a secondary position in human space flight for the rest of the century."

"Because of his military service, Dad was buried in Arlington National Cemetery."

"America's can-do spirit cast a warm glow across nations and cultures, generating more goodwill and support for our country's ideals and causes than had otherwise been possible."

"I've been to the Titanic in a yellow submarine and the North Pole in a Russian nuclear ice breaker."

"My favourite thing to do on this planet is to scuba dive."

"I know: If you're looking down at Earth, you're looking through an atmosphere that has a bit of haze in many places and not just occasional clouds."

"Nobody cares about the bronze or silver medals."

"Walking around on the moon was significantly easier than we'd thought it would be. There weren't any balance problems, so you weren't tumbling over."

"The biggest benefit of Apollo was the inspiration it gave to a growing generation to get into science and aerospace."

"It's time to open the space frontier to citizen explorers."

"I wrote 'Reaching for the Moon' because I wanted to tell kids that all of us have a moon, a dream, that we can strive for. Even if you don't attain it, you can at least reach for it."

"Every couple of years, we could dispatch people from Earth to Mars."

"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."

"Space travel for everyone is the next frontier in the human experience."

"Instead of planning the retirement of the Space Shuttle program, America should be preparing the shuttles for their next step in space: evolving, not shutting them down and laying off thousands of people."

"The guys who walk on Mars are going to be historic."

"A family needs to work as a team, supporting each other's individual aims and aspirations."

"Some things just can't be described. And stepping onto the moon was one of them."

"I think there would be no shortage of applicants to the government astronaut corps to be settlers on the planet Mars. And I think this would be very inspiring."

"Before deciding what to do about national space policy, Obama set up an outside review panel of space experts, headed up by my friend Norm Augustine, former head of Lockheed Martin and a former government official."

"I want to reach a new generation. That's why I am Twittering now. I have a BlackBerry, an iPhone and a Mac."

"Being first outside the spacecraft would bring much more responsibility, and I really wasn't looking for that."

"The much-hyped Ares 1-X was much ado about nothing."

"We must still think of ourselves as pioneers to understand the importance of space."

"I was motivated to improve the U.S. strategy of going back to the moon in 1985. That's a long time ago. Going back to the moon would be a great achievement for tourism adventure flights."

"There's a need for accepting responsibility - for a person's life and making choices that are not just ones for immediate short-term comfort. You need to make an investment, and the investment is in health and education."

"To move forward, what's required is a unified space agenda based on exploration, science, development, commerce, and security."

"When I was a little kid, we only knew about our nine planets. Since then, we've downgraded Pluto but have discovered that other solar systems and stars are common. So life is probably quite prevalent."

"I didn't start skiing until I was 50. My wife Lois taught me how to ski. I'm proficiently conservative."

"There's a historical milestone in the fact that our Apollo 11 landing on the moon took place a mere 66 years after the Wright Brothers' first flight."

"I think humans will reach Mars, and I would like to see it happen in my lifetime."

"I think both the space shuttle program and the International Space Station program have not really lived up to their expectations."

"There are always door openings. And gradually, it accumulates. The opportunities open up in front of you."

"If we can conquer space, we can conquer childhood hunger."

"I still say, 'Shoot for the moon; you might get there.'"

"There may be aliens in our Milky Way galaxy, and there are billions of other galaxies. The probability is almost certain that there is life somewhere in space."

"Globalisation means many other countries are asserting themselves and trying to take over leadership. Please don't ask Americans to let others assume the leadership of human exploration. We can do wonderful science on the Moon, and wonderful commercial things. Then we can pack up and move on to Mars."

"I was the first Navy, Marine or Air Force person who had been an astronaut to return back to the Air Force. I had certain expectations about what would be a reasonable and desirable position to be assigned to after my years of service."

"Computers allow us to squeeze the most out of everything, whether it's Google looking up things, so I guess that tends to make us a little lazy about reading books and doing things the hard way to understand how those things work."