I tell public audiences, don't go to a podiatrist for brain surgery; don't go to an astronomer for planetary science.
— Alan Stern
Why would you listen to an astronomer about a planet?
We're in the space exploration business, and the outer solar system is a wild, wooly place. We haven't explored it very well.
I tend to think of Pluto and its moons as presents sitting under a Christmas tree. They're wrapped, and from Earth all we can do is look at the boxes to see whether they're light or heavy, to see if something maybe jiggles a bit inside. We're seeing intriguing things, but we really don't know what's in there.
Most of the oceans in the Solar System are deep beneath ice shelves.
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.
At the time of Apollo 11, I was a grade-schooler, and I remember every time an Apollo mission would take place that, like a lot of little boys, I'd gather in front of the TV for hours and hours and hours with my little brother.
During one of the Apollo missions, I saw Walter Cronkite showing off the flight plan. It just mesmerized me. All this detail! That's what I wanted.
The New Horizons Pluto mission will be the first mission to a binary object and will help us understand everything from the origin of Earth's moon to the physics of mass transfer between binary stars.
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.
In science, we take large numbers of disparate facts and reduce them to see patterns. We use the patterns to reduce the amount of information. It's the reason we name species and genera and families in biology. It's also the reason we have names for certain types of geological features and so on in other fields.
No one predicted Mercury would be a planetary core with the mantle stripped off. No one predicted volcanoes on the Jovian moons, or oceans on the inside of them. I can tell you, for every single planet, huge 'we never guessed that' things.
It says something very deep about humans and our society, something very good about us, that we've invested our time and treasure in building a machine that can fly across three billion miles of space to explore the Pluto system.
How can an adjective in front of a noun not describe the noun? There are dwarf stars, but they're still considered stars.
As a planetary scientist, I don't know what else to call Pluto: It's big and round and thousands of miles wide.
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.
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.
I actually started my career in planetary science with a master's thesis on Pluto.
There are lots of really interesting little planets out there in the Kuiper Belt, but Pluto's the only one that's got all the cool attributes.
Pluto is still active four and a half billion years into its history. It was expected that small planets like Pluto would cool off long ago and not still be showing geological activity. Pluto is, in fact, showing numerous examples of geological activity on a massive scale across the planet.
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.
As a researcher, I look forward to being able to do space science in a space environment.
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.
Just because Pluto or comets aren't as big as Jupiter doesn't mean they are not scientifically important - indeed, just the reverse is often true. Sometimes, great things come in small packages.
Just speaking for myself, I think the return of people to the Moon has a lot to offer for understanding the formation and evolution of terrestrial worlds; so would the exploration of near-Earth asteroids by people.
A river is a river, independent of whether there are other rivers nearby. In science, we call things what they are based on their attributes, not what they're next to.
I've been on 26 space missions; they range from suborbital to orbital to shuttle experiments to planetary missions.
The big lesson of planetary science is when you do a first reconnaissance of a new kind of object, you should expect the unexpected.
If you put Earth out beyond Neptune, you wouldn't be able to call it a planet because it couldn't clear its zone.
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.
Human beings have long wondered whether they are alone in the universe.
People dig exploration.
I like the planets because they are real places that you can go to and send machines to. Faraway astronomy - galactic astronomy and extra-galactic astronomy - is really cool stuff, but to me, it's about destinations.
New Horizons isn't just visiting Pluto; it's visiting this entire region. Whatever it finds, this will be a signal moment for planetary exploration - the capstone to our first reconnaissance of the planets of our solar system.
One of the implications of the discovery of the Kuiper Belt and its many small planets is that many scientists now think of the solar system as having not two but three zones.
Science is really about individual experts reaching a consensus.
I think if you were between maybe 6 and 16, there was nothing like Apollo, and I wonder if there can be something like that again. We'll just have to see.
Absence of evidence is not evidence of absence.
By going to Pluto, we have a chance to anchor, with real data, models of the early evolution of Earth's atmosphere.
Discovering that our solar system has many more planets than we ever expected, and that most of them are ice dwarfs rather than like Earth and the other rocky terrestrials, is just another step in the revolution in viewpoint that removed the Earth from the center of the physical universe and makes Earth all the more special.
My field is called planetary science.
It shouldn't be so difficult to determine what a planet is. When you're watching a science fiction show like 'Star Trek' and they show up at some object in space and turn on the viewfinder, the audience and the people in the show know immediately whether it's a planet or a star or a comet or an asteroid.
Every mission has life-or-death moments.
Going to the Kuiper Belt is like an archaeological dig into the history of the solar system.
A miniature poodle is not not a dog just because it's miniature.
I just think it's patently absurd for scientists to categorize objects on the basis of the numbers of objects that they can remember.
There was a time when Pluto - which NASA's New Horizons spacecraft at last explored in 2015, a mission I led - was considered the last planet. We now know there are thousands of other - possibly inhabited - planets.
