Alan Stern & David Grinspoon

Our Galaxy and Beyond

Air Date: June 27, 2018

Scientists Alan Stern and David Grinspoon talk about their new book “Chasing New Horizons: Inside the Epic First Mission to Pluto.”


HEFFNER: I’m Alexander Heffner, your host on The Open Mind. Today we invite our viewers into an enthralling space exploration with two leading scientists. Coauthors of “Chasing New Horizons: Inside the Epic First Mission to Pluto,” an intimate guide to what our guests describe as the greatest exploration project of contemporary space travel. Dr. Alan Stern is principal investigator of the New Horizons mission, which leads NASA’s exploration of the Pluto system. A planetary scientist, space program executive, and aerospace consultant and author, Stern has participated in over two dozen scientific space missions. Dr. David Grinspoon is an astrobiologist, award-winning science communicator, and prize-winning author. In 2013, he was appointed the inaugural Chair of Astrobiology at the Library of Congress. He is a frequent adviser to NASA on space exploration strategy. And he’s on the science teams for several interplanetary spacecraft missions. Welcome to you both, gentlemen. Congratulations on this book.

STERN: Thanks.

GRINSPOON: Thanks very much.

HEFFNER: And on the successful mission. It’s really astounding how this machine that you designed has as you just said, explained to me, traveled the depths of the solar system unlike most any other objects. Tell us about the origin of this exploration.

STERN: Well it started back in the 1980s when we started to learn enough about the Pluto system that it started to merit actually sending a spacecraft there to study it up close. And then in the 1990s, we discovered this massive region in the outer solar system that had previously been unknown called the Kuiper belt, which is the third zone of our solar system and which is populated by a whole zoo of small planets like Pluto. So the National Academy of Sciences ranked the priority for this mission to be very high to go study that new class of planets in that new region of the solar system. Our team won a competitive effort and built New Horizons and launched it in 2006, and it’s been flying across the solar system to the very frontier ever since.

HEFFNER: With photographic evidence on Twitter disseminated to all of us here on planet Earth, right?

GRINSPOON: Yeah, that’s one of the wonderful things about 21st century planetary exploration. And in particular, this mission unlike no other, the encounter with Pluto happened at a time when everybody’s connected in this new way. So previous first planetary encounters which really goes back to the Voyagers in the 1980s which was the last time we visited a planet in our solar system for the first time, happened in a different era where you had to like pick up the morning paper to see the new picture. This time, for Pluto, they were instantly on the internet and people were sharing and it was a sort of worldwide wave of the pictures and the excitement spreading in this connected way that was completely new and that was one of the sort of surprising and fun things was this instantaneous global reaction when we got to Pluto.

HEFFNER: And we won’t have our foot, or our feet on the ground and I don’t know if that would even be biologically possible at some juncture in the future, maybe…

STERN: We could send people in the future.


GRINSPOON: Absolutely.

HEFFNER: What were the implications in terms of, I like that idea of astrobiology, right? What is relevant to the human experience about Pluto? And what can it tell us in the long run?

STERN: Well there are a couple of things that we learned that I think are directly relevant. One is that this little planet has, it’s so far away, and so cold, and so so incredibly old, it actually has many parallels to the Earth. Glaciers that have avalanches that flow just like in Greenland, clouds on the, in the sky, hazes in the sky, mountain ranges as big as the Rockies, and we believe we have pretty good evidence that down under the surface there’s a global ocean. And it could harbor life. And in the future we could send missions there to actually look for that. Pretty amazing.

HEFFNER: On the ground level though the conditions would not permit life, right? On the ground level. But beneath?

STERN: Not as we know it. But we don’t know the limits of biology.

GRINSPOON: I mean we were very surprised by the way in which Pluto turns out to be “alive” in air quotes, in a geological sense. You know it’s moving and flowing and complex in ways we didn’t understand. So it, this speaks to our inability to really project the diversity of processes happening elsewhere in the universe until we actually go there and explore. That’s true about geology, it’s probably also true about biology as well. So we can say life is impossible on the surface of Pluto, and you know it seems to us like it would be certainly. As Alan says, life as we know it. But I think we gotta be careful when we use the word impossible when we’re talking about other planets ‘cause we keep getting surprised. And certainly now we have discovered, we think hints that Pluto on the inside has conditions that actually might be able to support life.

HEFFNER: What did you make of the earlier reclassification of Pluto as the dwarf planet, and what do your findings, again, correct me if I’m wrong but you’re largely relying upon photographic evidence that is very textual, granular, did that, I believe the reclassification predated the more intimate pieces of evidence…

STEN: Absolutely, that was a decade ago and you know really the pendulum is swinging back in the other direction. As planetary scientists, we recognize that the small planets have all the attributes of planets that are larger than them. The same way that you know a Chihuahua’s still a dog, even though it’s very small. Pluto’s about the size of the continental United States. So it’s not a small object at all. And with all the types of geological features and atmospheric features and five moons, I think most planetary scientists, the real experts in this area, consider the small planets including Pluto to be full-fledged planets just smaller.

HEFFNER: What manually and in terms of of its own makeup, you know the chemicals and the properties, had to be constructed in order to withstand all the challenges that were some unknown variables.

STERN: Well you know the spacecraft had to be designed to withstand the rigors of launch, the very high acceleration. And then exposure to the space vacuum to pretty warm temperatures when it was leaving the vicinity of the Earth, close to the sun, and then extremely cold temperatures all the way out at Pluto, three plus billion miles away. Inside the spacecraft are all the systems that it requires to go on that journey, so guidance systems, computer systems, thermal control systems, communication back and forth to the Earth. And then on the outside of the spacecraft are thrusters, both to change the course and to change the way that it’s pointed, and seven scientific instruments with telescopes, cameras, spectrometers, and so forth that are used to study the fly-by targets, like Pluto.

HEFFNER: And when you think about the table of elements and what had to be contained within the craft to not dissolve or explode, what was it, what is it made of?

GRINSPOON: Well you know, it’s made out of a lot of the same components that that machines on Earth are made of, you know computers and so forth, you know silicon, and aluminum and but they’re just a lot of it had to be sort of hardened and built in a just incredibly reliable way. But there are some unusual components too that, for one thing there’s a, there’s a plutonium power source because when you’re operating that far from the sun you can’t use solar power. And the plutonium itself introduced huge challenges for the project because when you read the book you realize that there was a ticking clock. This thing had to be launched in a hurry because there was a window, or Jupiter was in the right place to, you know to sling it on to Pluto and they couldn’t do it at all if they didn’t launch by this certain window. But the regulatory challenges alone to get the permission to launch plutonium, and as it should be, are very stringent. And there was a real question whether that would happen on time. And then the lab making the plutonium, Los Alamos shut down for a security breach, had nothing to do with the spacecraft. It was just bad timing. And there was a real question of whether that plutonium would be ready on time. So there’s some unusual components. There’s also kevlar blankets, the stuff they make bulletproof vests out of, surrounding the spacecraft to protect it in case it hits even a tiny bit of interplanetary space you know if a tiny micro-meteorite at that speed when you’re moving thirty-thousand miles per hour, the smallest thing, something the size of a grain of rice can explode with you know it’s like heavy ordinance at that speed. So it’s got these protective blankets surrounding it to to protect from that…

HEFFNER: You, and you identify the human and chemical challenges to achieving this which you chronicle in this book. And it was quite an impressive and mammoth undertaking. For our viewers who are interested in space exploration, and see it both for its scientific good and as a source of human and intellectual creativity, and lifeblood, who were your allies in this process?

STERN: People rarely see that inside story, and the book does tell that. But it also tells the very human story of young scientists with a dream to go and explore the next planet that’s never been explored, and how they marshalled the scientific community and ultimately the National Academy of Sciences to back that and provide the input to the political system. And then how we competed with other teams that also wanted to fly the mission. Our team won, that battle was described. And so it’s kind of an adventure story. And then we were against this ticking clock that David described to get the spacecraft built very quickly for our very special launch window to use Jupiter to accelerate the spacecraft to high speed. And then we tell the story of the flight mission which included a near-death experience for the spacecraft, barely ten days before reaching Pluto. So all of that is woven together.

HEFFNER: Tell us about that. The nearly fatal event.

STERN: Yeah and that’s actually that’s the way the book opens. With this event. And it took place on exactly ten days before the fly-by that had been planned for fifteen years. We’d had a successful flight all the way across the solar system. Really very few problems and no really big ones. And then suddenly on a day unfortunately meant for fireworks, July the Fourth 2015, my cellphone rang and I found out we had lost contact with the spacecraft. That’s something that should never happen. And, in the history of spaceflight usually when it does happen it means something catastrophic like an explosion has taken place. Or we might’ve hit something. As it turned out, our computer, our main computer had been overloaded by some of the instruction that had been given. And had to reboot. And so the spacecraft recognized that there was a problem and thought that the main computer might be defective, switched to the backup system, and then after a couple hours the backup system called back to Earth for help and said here I am, what do you want me to do? And we were in the position of having to recreate all of the fly-by plans that had been put in the spacecraft but which were erased in that reboot. And doing that under a ticking clock and we only had three days to do it. And our mission operations and engineering teams swung into action. And I’ll tell you, Alexander, it was just like in the movie Apollo 13. You know 24/7, running the procedures on the simulators, people sleeping on desks and on hall room floors. Living out of vending machines. To get this done, because that’s basically our , was going to fly by Pluto in ten days whether we had it ready to make the observations or not.

GRINSPOON: And one factor that made this episode particularly harrowing was at that point, when you’re almost at Pluto, you’re three-billion miles from Earth. So at the speed of light, it takes four and a half hours to get a signal to the spacecraft. So that’s nine hours round trip. Just to say hey are you okay? And then you wait nine hours and the spacecraft goes yeah, I’m alive, what should I do? And then it takes another nine hours to send the next command. You don’t have very many of these nine hour blocks left before you’re gonna get to Pluto. And it’s either gonna be fixed or not. So the, it was very tense, and it really was like a scene out of a movie that the team did what they needed to do and got it on track with hours to spare.

HEFFNER: Amazing. Well a lot of troubleshooting went a long way in protecting your mission. The spacecraft is in hibernation mode at the moment. What does that mean…

STERN: We’re on a one way exit of the solar system, making studies of other objects in the Kuiper belt, much smaller objects, the kind that Pluto was made from. And we’re on our way now to intercept one of those with a very close fly-by on New Year’s Eve and New Year’s Day at the end of this year. We are flying towards it in hibernation, so the spacecraft is taking care of itself. We’re not operating it day-to-day from mission control. But we’ll wake it up on June the Fourth, and take it out of hibernation, start preparing the spacecraft for that next fly-by. And that next set of exploration.

HEFFNER: So did we glean anything, before I ask you more specifically about what we’ve learned as it relates to Pluto, did we learn anything about the preceding planets?

GRINSPOON: So, so the big encounter before Pluto was Jupiter. Because the challenge of getting to Pluto you know it’s a long way to go and nine years is actually a pretty fast trip there and the way it got there so fast was first of all it was the fastest launch ever off of Earth of any spacecraft. But you don’t launch at Pluto. You make a beeline to Jupiter. And the reason why is because Jupiter’s huge gravity, then if you hit it just right, slingshots it out to Pluto. But that Jupiter encounter was very valuable. It was about a year after launch. So a relatively quick trip to Jupiter and then a long trip out to Pluto. But the Jupiter encounter allowed the team to first of all practice a fly-by before they got to Pluto so they could make sure that the spacecraft was working and make sure their team had the procedures down and the instruments were working. They knew how to do everything, but it also was a very scientifically interesting opportunity to visit Jupiter quite some time after we had had a spacecraft there. And they made some really cool discoveries. They actually one of the moons of Jupiter is very volcanically active, a moon called Io. And they actually sort of fortunately were able to make a movie of a volcano blasting off on the surface of Io just as New Horizons was whipping through the Jupiter system. And so there were some really cool discoveries at Jupiter. And then there was this long trip to Pluto where they didn’t really go near anything, and it was mostly

STERN: Although we crossed the orbits of Saturn and Uranus and Neptune in turn, the planets weren’t anywhere near. They were in other portions of their orbit. So we had this long eight year journey from Jupiter in 2007 to Pluto in 2015 across this gulf of space, two and a half billion miles. It’s almost impossible to imagine how far that is. Traveling almost a million miles per day in which we didn’t pass anything. We’re just out in the wilderness of the solar system.

HEFFNER: And you say ultimately this spacecraft will descend into beneath, sort of an inaccessible…

GRINSPOON: It’s moving fast enough so that it will escape the sun’s gravity entirely. And that’s very rare, most of the spacecraft we send around the solar system end up in orbit around the sun or crashed into the planet that they’re investigating. Only four previous spacecraft have been on trajectories where they actually escape the solar system and wander the galaxy. The two Pioneers Ten and Eleven, and the Voyager spacecraft which in a way were sort of the predecessor for New Horizons, they made it as far as Neptune but didn’t- didn’t explore planets beyond that. Now New Horizons, after Pluto and after this encounter with Ultima Thule on New Year’s Eve, it is going fast enough that it’s going to keep going. And it will be the fifth human-made craft that will actually leave the solar system and just wander forever the galaxy. It’s going to outlive not just the human race, not just it’s gonna outlive the planet Earth. Because nothing happens to you when you’re out there, there’s no, you don’t intersect anything, there’s no weather, there’s nothing. So we have these few relics of our civilization that will literally last forever and this is now one of them.

HEFFNER: And at a certain point, it will not be trackable. I mean, you will not get back-

STERN: Right so the spacecraft is very healthy now, and it has plenty more exploring to do. But it’s only got a certain amount of fuel and a certain amount of power in the nuclear battery. And we use those up, they’re consumables. And sometime in the late 2030s, we’ll get to a point where there’s not enough power to run the radios to communicate back to the Earth in the main computer. And at that point, the mission will have to end.

HEFFNER: So you’re making the argument to the new NASA administrator about the next phase of this project. I know it’s not complete yet, but I want to give you a chance to reflect on answers to questions that you ask in “Chasing Horizons.” The you know there were questions that were just for your learning about Pluto that were not accessible and you had hoped, we touched on whether Pluto is internally active. You’ve explored the surface composition. You’ve assessed a comparison against or contrast against Neptune and its moons. The ultimate human benefit here back on planet Earth, when you think of the nature of Pluto and its relevance in the solar system, and the next voyage, whether that’s back to Pluto, whether that’s an unmanned craft or a manned craft, what are you hoping will lead you to the next mission that will sort of be the impetus to continue these journeys.

STERN: Let me first say I think that there are two major contributions that New Horizons has made. And one is on this new knowledge. This first mission, not only through the Pluto system, but to the Kuiper Belt and to this whole new class of planet that’s so populous in the outer solar system. And you know one of the great things about NASA and the US Space Program is that that knowledge is made available to people everywhere on the Earth, for all mankind so to speak. But secondly, and this mission more than any modern space mission, engaged the public in ways that had never been seen before. I think it shows that the public really loves going new places and seeing new things, and loves the sheer joy of exploration. And we know that we hear from school children all the time that they want to go into science and engineering careers. Kids write that they saw the exploration of Pluto and now they want to do something like that in their lifetime. And we need scientists and engineers to power this economy. So I think that’s a very powerful outcome from a scientific space mission. Now, NASA’s currently conducting 90 different space missions, most of them robotic, some of them to the planets, some of them to study the Earth, some of them to study the universe around us. And even the sun. And about half of those are already in flight, and about half are being built to be launched in the next several years. New missions are coming up all the time as old missions finished. And so there are new missions for example that are being built now to study the ocean inside of Jupiter’s moon Europa, which may also harbor life. There are new missions like the Parker Solar Probe just about to be launched this summer that will skim the surface of the sun for the first time and really touch the solar atmosphere. The James Webb Space Telescope, which will be much more powerful than the Hubble, will be launching in a couple of years to study the universe and the origin of stars in galaxies. These are just three of the many missions that NASA is now building, but one of the things that we’d like to see is a return to Pluto with an orbiter to study it in much more detail. To bring much more advanced scientific instruments, and to stay, not just to fly by and glimpse it, but to stay and map it and study its satellites, and its interior, and look for that ocean. And really rewrite the textbooks that New Horizons first wrote.

GRINSPOON: ‘Cause you know one thing that’s tantalizing about knowing Pluto the way we do now, we had this close fly-by of one side of Pluto. And it turns out to be incredibly interesting, there’s this heart-shaped, huge geographic feature that’s made of fresh-flowing nitrogen ice, you know basically glaciers on the surface of Pluto surrounding by these towering icy mountains and you know just a lot of like scientifically and aesthetically really astounding terrain. And then there’s the other side of Pluto, which we only photographed from a great distance ‘cause Pluto’s turning on its axis. And you had to fly close by one side. So we have vague pictures of the other side that we got from a telescope from the spacecraft when it was much farther out, before the close encounter. So we need an orbiter ‘cause now we wanna see the rest of it in that kind of detail. Now we, now that we know how interesting it is. And these results are fascinating enough to make us realize we need a more in depth and longer-lived stay at Pluto to really answer the questions raised by New Horizons.

HEFFNER: Of those projects that you described that NASA’s working on, which you described roughly half of them are in flight. You said ballpark ninety or so. Which are the most attended to at the moment? I mean if we think of NASA’s budget and its operation as something that is limited by whatever human capital is pushing forward new projects, NASA’s priorities right now are what?

STERN: Well NASA has a whole series of priorities to study the Earth and the universe…

HEFFNER: But principally as it pertains to planetary exploration, I’m just wondering where the next trip to Pluto configures in relation to some of the other planets we’ve talked about.

GRINSPOON: That’s a hot topic right now because there’s this process called the, you know these decadal surveys where the National Academy of Sciences ranks missions. And when you read “Chasing New Horizons”, you realize that was an important part of the story of how New Horizons got selected in the first place. It has to rise to the top of this ranking, where there’s a lot of people competing for their priority. You know there’s the Mars people, and the, you know they have people everybody wants their mission. So Pluto had to rise to the top of that set of priorities and it did. There’s another one of those processes just beginning now, and so there are some of us and Alan just described why he really believed that you know a Pluto orbiter ought to be high on that list. There are people pushing for other missions. And they, you know there are a lot of good ideas.

HEFFNER: In terms of the humanitarian impact that a mission could potentially bring back home…

GRINSPOON: We need to know how planets work. We have an ethical obligation to know how planets work ‘cause we find ourselves as stewards of a planet here. And not currently doing a really great job of it, but we have ideas of how to do a much better job of it. Without having Earth observations from space, you know which is one thing that NASA does so we can monitor the changing climate and the changing human impact on the planet and just get smarter about the carbon cycle and all these functions that we are finding ourselves affecting. But also without the insights of comparative planetology where we go to other planets and gain new, surprising insights into how planets work in general, including the Earth. We’d be in trouble. We actually I think owe it to future generations to do everything we can to understand in as deep a way as we can how planets work. And so when even when we go to a place like Pluto, which you might not think is very Earth-like. As Alan said, you know there are a lot of analogous features there. And you know it always causes us to rethink how the heat flow works inside of a planet, how mountains form, how atmospheres interact with surfaces. We’re learning about all these things and ultimately it broadens our knowledge of how all planets work including- including this one.

HEFFNER: Alan, final word on this question of prioritization of the planetary missions and which might be in addition to a second Pluto journey most fruitful.

STERN: Yeah. Well I think that to answer your question that one of the most fruitful things that NASA is doing and should be doing is to go back to exploring the planets with humans. We’re so much more capable as explorers than the robots are. Field geology and things like that. And of course NASA is now embarking on a program to send humans back to the moon and on to Mars and possibly other destinations as well and…

HEFFNER: What might be those other destinations?

STERN: Well the … Asteroids for example, in orbit between the Earth and Mars.

HEFFNER: And any other planets besides Mars that could be feasible [PH]?

STERN: In the more distant future I think that it’s possible that we’ll be exploring all the planets with human beings. And you know this is something that’s hugely inspiring, and it’s a great push for the, a technological society like our own. NASA’s the best in the world at it, and it’s NASA’s number one priority.

HEFFNER: Thank you, both. I appreciate your time.

GRINSPOON: Thank you.

STERN: Thanks a lot.

HEFFNER: And thanks to you in the audience. I hope you join us again for a thoughtful excursion into the world of ideas. Until then, keep an open mind. Please visit The Open Mind website at to view this program online or to access over 1,500 other interviews. And do check us out on Twitter and Facebook @ OpenMindTV for updates on future programming.