Alan Stern

“The solar system is completely wide open. Almost anywhere we go, I'm sure we would learn a lot.”

“To say that what a planet is doesn't matter would be to imply that a planetary scientist couldn't explain to someone what the field is about.”

“I think when people see Pluto revealed by New Horizons, its satellite system, its complex surface, its atmosphere, I think they'll have a hard time saying 'That's not a planet' because it obviously will be, and I think most people are already coming to that opinion anyway, but I think that's really going to drive it home viscerally.”

“Science is really about individual experts reaching a consensus.”

“Absence of evidence is not evidence of absence.”

“No one working as an astronomer is shackled in chains. This is a tremendous profession. There are lots of neat people, and you get to do cool things. If I had to say something negative, it's that there's often a whole lot of travel that takes me away from my children. That can be a bummer a lot of times.”

“People know a planet when they see one, and I think that's a pretty darn good test, in fact, for planethood.”

“Liquids may have existed on the surface of Pluto in the past.”

“Of course Pluto is a planet: It's massive enough to have its shape controlled by gravity rather than material strength, which is the hallmark of planethood.”

“I'm hopeful that commercial space exploration will takeoff. To really fuel the spaceflight revolution will require an investment of hundreds of billions of dollars a year, and I think that's only going to happen in the commercial sector - if there are large profits to be made.”

“We were very surprised to find out that Pluto is still geologically alive. It has upended our ideas of how planetary geophysics works.”

“Typically in science, individual scientists make up their minds about scientific fact or theory one at a time. We don't take votes. We just don't vote on quantum mechanics, the theory of relativity, why the sky is blue, or anything else.”

“Pluto is the new Mars.”

“The costs of badly-run NASA projects are paid for with cutbacks or delays in NASA projects that didn't go over budget. Hence the guilty are rewarded and the innocent are punished.”

“If you put Earth out beyond Neptune, you wouldn't be able to call it a planet because it couldn't clear its zone.”

“You could not have predicted the amazing discoveries at Pluto, even though we have been to a couple of objects in the solar system that were at least a little analogous to Pluto.”

“America's space program has been the envy and inspiration of the world. It has made landmark scientific discoveries that are a lasting legacy of this nation's greatness. It has studied Earth in ways no other nation can match.”

“Are governments the only entities that can build human spacecraft? No - actually, every human spacecraft ever built for NASA was built by private industry.”

“The Kuiper belt region, which I call the third zone because it lies beyond the rocky terrestrial planets and beyond the giant planets, is a bizarre frontier.”

“The first mission to Mars did not expect to find craters and river valleys, and yet they did. The first mission to Jupiter didn't expect to find ocean worlds and volcano worlds, but they did.”