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. Alan Stern More Quotes by Alan Stern More Quotes From Alan Stern This is in a real sense the capstone of the initial missions to explore the planets. Pluto, its moons and this part of the solar system are such mysteries that New Horizons will rewrite all of the textbooks. Alan Stern new-horizonsmoonreal It used to be said that Pluto is a misfit. But now we know Earth is the misfit. This is the most populous class of planet in our solar system and we have never sent a mission to this class. Alan Stern plutoearthclass We're just learning that a lot of planets are small planets, and we didn't know that before, fact is, in planetary science, objects such as Pluto and the other dwarf planets in the Kuiper Belt are considered planets and called planets in everyday discourse in scientific meetings. Alan Stern dwarveseverydayscience Naming celestial objects is usually done by astronomers and professionals. Other people who are interested in space never get the opportunity to do that kind of thing. Alan Stern spaceopportunitypeople It's strictly coincidental that Pluto of course was named for the god of the underworld and we're describing these Halloween moons Alan Stern plutohalloweenmoon It'll be the fastest spacecraft ever to Jupiter...13 months after launch. We pass the Moon in just nine hours. Alan Stern jupitermoonnine To keep everyone invested in your vision, you have to back up a little bit and really analyze who the different stakeholders are and what they individually respond to. Alan Stern yourbackyouvision 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. Alan Stern outonlycoolinteresting Pluto is showing us a diversity of landforms and complexity of processes that rival anything we've seen in the solar system. Alan Stern usseenanythingdiversity 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. Alan Stern smallgreatimportantsometimes We really just didn't realize the diversity of planetary types in our solar system. Pluto looked like a misfit because it was the only one we saw. And just as a Chihuahua is still a dog, these ice dwarfs are still planetary bodies. They're large enough to make themselves round by self gravity, and they surely pass the test of planethood. Alan Stern realizediversityselfdog Just because Pluto orbits with many other dwarf planets doesn't change what it is, just as whether an object is a mountain or not doesn't depend on whether it's in a group or in isolation. Alan Stern dependgroupmountainchange 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. Alan Stern planetgravitystrengthenough Pluto is as far across as Manhattan to Miami, but its atmosphere is bigger than the Earth's. Alan Stern farthanmiamiearth As a planetary scientist, I don't know what else to call Pluto: It's big and round and thousands of miles wide. Alan Stern callbigknowmiles The big lesson of planetary science is when you do a first reconnaissance of a new kind of object, you should expect the unexpected. Alan Stern newyouunexpectedscience 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. Alan Stern smallcoollonghistory Human beings have long wondered whether they are alone in the universe. Alan Stern humanaloneuniverselong Going to the Kuiper Belt is like an archaeological dig into the history of the solar system. Alan Stern solargoinglikehistory 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. Alan Stern neveryousinglei-can
