Dr. Henry Throop is a scientist at the Planetary Science Institute, who served as a Science Team Collaborator and worked as Program Officer in the NASA’s New Horizons mission. The asteroid 193736 Henrythroop is named after him.
CosmosNow – Hello Dr. Throop! Welcome! We are really honored to have you on the fourth Confab with CosmosNow. We are really excited to get some amazing and inspiring answers from you.
Dr. Henry Throop – Sure, that sounds fun. Thank you CosmosNow for letting me indulge! I’m more than happy to answer your questions.
CosmosNow – How’s your experience in India, teaching here and working with space communities.
Dr. Henry Throop – I lived in India for three amazing years, from 2015 through 2018. While in the country, I was working on my own NASA research and working with the New Horizons mission to Pluto and the Kuiper Belt. I was teaching university in Bombay, and I was giving many lectures. Really, more than anything I loved getting the chance to work with scientists, students, and the public across the country. I gave over 100 talks, at places from ISRO sites, to universities, to planetariums, to primary schools. And across India, people were united in loving astronomy, and being so curious about exploring the world around us.
Whatever country you’re from, people want to go out and explore and see why we are here and find out what is beyond. And the people across India do that more than anyone else. So much of that energy is present just in the city of Bombay as well. It’s the greatest city in the world — so much happening, and so dense, but full of such a diversity of people. Everyone has their life, and their story and I loved talking with every single person I got the chance to.
CosmosNow – Whom do you look up for inspiration? What inspired you to be an astronomer?
Dr. Henry Throop – I spent a summer as a college student where I got the chance to do astronomy research, an internship. That was really the first time that I had the chance to see what research was about, and I loved it! I was accepted into an MSc / Ph.D. program after that, and I have been so lucky to be able to participate in the great NASA missions that we have now exploring the solar system.
Dr. Henry Throop – As a member of the New Horizons science team, one of my roles was to plan observations of Pluto. Our spacecraft was already headed for Pluto — it was solidly on its 9-year trajectory after a launch in 2006 — but we hadn’t planned out the step-by-step instructions for taking images: for instance, how many images of this side, what exposure time, and so forth. I worked with the other members of the science team on planning observations and ended up developing the GeoViz program, which we used to plan all of the observations. It’s essentially a ‘solar system simulator,’ that will tell you what is visible from the spacecraft, depending on where you are. You can read more about it here.
CosmosNow – What’s your stand on Pluto’s reclassification as a planet?
Dr. Henry Throop – It will change again. The IAU’s definition of a planet is not a good one — by a literal reading of it, it excludes exoplanets, and it implies that Saturn, Jupiter, and the Earth are not planets either. The fact of the matter is that the word ‘planet’ is a very old Greek word which means ‘wandering star’, and it has never really been defined properly since then. So it’s definitely a good idea that the word ‘planet’ should have a modern definition. The IAU one is just not very good. It doesn’t really matter though: most astronomers call Pluto a planet, and you can too.
CosmosNow – Speaking about Pluto, you are co-discoverer of its smallest moon Styx. How exactly the team came across Styx and what was your role in its discovery?
Dr. Henry Throop – We discovered Styx while using the Hubble Space Telescope in 2012. We were actually not looking for new moons — we were mostly looking for rings and dust that could have been around Pluto and would have been a hazard to the New Horizons spacecraft. I was involved in estimating how much dust there might be in the Pluto system, and we used these calculations to show that we really had to have time on Hubble to make this search. After we got the time on Hubble and took the observations, one of our team members, Mark Showalter, was looking at the images very carefully. And he noticed that there was a very very faint moon seen in several of the images. It was clearly moving not like a star, but like a moon. The New Horizons team had already discovered Pluto’s moons Nix, Hydra, and Kerberos in earlier Hubble searches, so we had an idea there might be more moons still undiscovered.
CosmosNow – You have extensive knowledge about Pluto and outer solar system, what’s the one thing that fascinates you about Pluto? What’s the one thing that makes it different from other planets?
Dr. Henry Throop – I fully expected Pluto to be geologically ‘dead’ — that is, covered with craters and nothing else, kind of like the Moon. It is so cold, and because it formed so long ago, we would not expect its core to remain warm, or for it to sustain any geology such as volcanism or plate tectonics. But what we found at Pluto was that the surface was shockingly young. Many parts of it looked like they were far less than a million years old — which compared with the age of Pluto and the Solar System, is extraordinarily fresh and young. We could tell this because over large parts of it there were almost no impact craters at all. We have concluded that Pluto is geologically active, and there is a lot of change going on with the surface. It is still cold, but not quite as cold as we expected it to be, and the core much be slightly warmer than we predicted. So, we were wrong in our predictions. That’s great! It’s much more interesting to be wrong than to be right.
CosmosNow – Traces of Ammonia were found on Pluto’s surface and images from New horizons hinted towards cryovolcanism as recent activity going on. What could be concluded from this?
Dr. Henry Throop – Members of the science team are still looking at the images and what they imply. But cryovolcanism is a real possibility on Pluto. This is like regular volcanism on Earth — except that instead of with lava (melted rock), it is with melted ice. At Pluto’s temperatures, liquid water freezes almost as hard as a rock. We’re in a different realm of physics, at these super-cold temperatures, and so a lot of our physical intuition about how ices work on Earth is very different at the cold temperatures of Pluto, and the high pressures these ices have in Pluto’s interior.
CosmosNow – If we had some way to meet physicist/astrophysicist from the past, whom would you like to meet? What would you ask them?
Dr. Henry Throop – We are living in a great time now! We have built on the shoulders of great people in the past, and we really are in a truly golden age of exploration of the solar system. I think it would be crazy to have the Italian astronomer Galileo Galilei visit us now, and see the progress that we have made in 400 years. He was the first to see the craters on the moon, and the moons of Jupiter, and the stars in the Milky Way. And now we have visited every planet close up, and mapped them out, and sent spacecraft all over the solar system, and found exoplanets orbiting thousands of distant stars. My mind is blown by it every day. But maybe Galileo would just say, ‘well, of course!’
CosmosNow – Your vision for humanity’s future beyond Earth in the field of space exploration.
Dr. Henry Throop – People are curious about exploring the world around us. We have been for thousands of years — from walking long distances across the plains to taking boats across the ocean to now taking spacecraft to the outer regions of the solar system. We will continue to explore and be curious. But as for moving humanity out to other planets — that’s not easy. The Earth is a wonderful place to live, and even the worst places on Earth are so much more habitable than anywhere else we know of. Mt. Everest or Antarctica look warm and homey compared to anywhere else in the solar system. So for now, Earth is our home base, and we can use it to explore the Solar System and beyond.