IRA FLATOW: And now a look to the skies and some of the objects in our solar system. A paper published last week in the journal of Geophysical Research Letters outlines why cold distant Pluto is still very likely to have a liquid ocean buried deep beneath its icy surface. Well, how can this be? It turns out that the planet shows signs of recent expansion, expansion as seen in images from New Horizon, the spacecraft that flew by. And this research calculates that the most likely explanation is the slow conversion of liquid water to ice, which takes up more space. You know, ice– actually, water expands when it freezes. So the make that happen, of course, you need that liquid water, possibly as deep as 50 kilometers.

Here to tell the story are the two co-authors on that research paper, Noah Hammond, a graduate student in the Department of Earth, Environmental, and Planetary Science at Brown University. Amy Barr Mlinar is a senior scientist at Planetary Science Institute. Welcome to Science Friday.

NOAH HAMMOND: Great to be here. Thank you

IRA FLATOW: Let’s talk about– Noah, walk us through your findings. How do we know there’s an ocean on Pluto?

NOAH HAMMOND: Well, it’s really extraordinary. New Horizons flew past Pluto last year and saw images on the surface of these cracks– long tectonic cracks, which were interpreted as extensional tectonic features. And as you said, when an ocean is slowly freezing, that can cause Pluto to get bigger. Pluto expands. So what we did was we ran some calculations called, you know, thermal evolution models. Basically we started with Pluto soon after it formed, and we determined how quickly is it going to lose its heat over geologic time. And we determined that Pluto probably still has an ocean today, if those extensional features on the surface are present.

IRA FLATOW: Wow, wow.

NOAH HAMMOND: Mm-hm.

IRA FLATOW: Pluto is far from the sun, doesn’t seem to have any major tidal forces acting on it. So what kind of energy is keeping that water, liquid, underneath there?

NOAH HAMMOND: Well, what it has is these– we think Pluto is made up of an ice shell on the surface– probably about 150 kilometers thick– and then an ocean. Then it has this rocky core.

IRA FLATOW: All right.

NOAH HAMMOND: And in that core are these heat producing elements. We actually have the same heat producing elements in the earth’s crust, like uranium, potassium. These just give off heat as they decay over time. And that little bit amount of energy is enough to keep an ocean sustained on Pluto.

IRA FLATOW: Hm. Dr. Mlinar, one of the factors that the model relies on is a substance called ice 2. Sounds like a movie. What’s going on with that?

AMY BARR MLINAR: Well, there are actually several different phases of water ice. The phase of ice that we are familiar with in our everyday life is called ice 1. And that’s the phase of ice that floats on water. But then, as ice is compressed, like at high pressures inside Pluto’s interior, it actually– the crystal structure actually changes. And it becomes denser. So if you compress ice under very cold conditions, you get this phase of ice called ice 2. And so, when you compress the ice like this, Pluto can undergo net contraction. And when that ice melts, then Pluto undergoes net expansion.

IRA FLATOW: Hm. And, Noah Hammond, what has New Horizons contributed to our understanding of Pluto and Pluto’s composition? It has really sent back a lot of data, hasn’t it?

NOAH HAMMOND: Oh, it sure has. It’s seen a number of really extraordinary things on the surface. There are these nitrogen ices, which appear to be convecting and refreshing the surface, making it look very geologically young. And I think what we really focused on was the extensional tectonic features because it’s really great that we can look at what’s on the surface to infer what’s on the inside. And that Pluto has an ocean, that has really profound implications for astrobiology and the rest of the or system if liquid water can exist in such a cold dark place.

IRA FLATOW: Yeah. I hear you hinting about life here, when you say astrobiology–

NOAH HAMMOND: Well, I don’t want to get carried away

IRA FLATOW: –want to make sure we’re on the record about what you’re talking about. So you’re not– when you say astrobiology, what do you mean by that?

NOAH HAMMOND: Well, We know that liquid water on Earth is essential for life. So any time you discover liquid water as a possibility on another planet or dwarf planet or moon, it gets astrobiologists excited.

IRA FLATOW: So take us beyond Pluto because Pluto has now been classified as a dwarf planet by some. And there are other, as you say, other dwarf planets out there. Take us beyond Pluto. Do they have findings that have indications or implications for the rest of our solar system?

NOAH HAMMOND: Uh, Amy, do you want to take that?

AMY BARR MLINAR: Yeah. I mean, I think one of the things that’s really amazing about this result is that it looks like Pluto, like a lot of other icy bodies in our solar system, has an ocean. And it certainly wasn’t expected when we went out to Jupiter’s moons with the Galileo mission or to the moons of Saturn with Cassini or Pluto with New Horizons. We didn’t expect to find oceans in any of these icy bodies. And now it looks like that’s a really common feature for icy bodies, both moons of the outer planets and Kuiper belt objects, as well. And so what’s really interesting to me is the possibility that perhaps maybe other Kuiper belt objects might have moons– maybe, you know– excuse me– oceans. You know, oceans appear to be common features in the outer solar system. And that’s really surprising. That’s definitely not something that we expected.

IRA FLATOW: I’m Ira Flatow. This is Science Friday from PRI, Public Radio International. I spoke to Alan Stern, one of your compatriots on the New Horizons project early this week. And he said it seems like we are– Earth is the outlier. We have the external ocean, everybody else has an internal ocean.

AMY BARR MLINAR: [LAUGHING] That’s true.

IRA FLATOW: That one, that is absolutely amazing, don’t you think? Well, let’s talk about what the next questions to tackle about Pluto and the body is like? What else do you want to know, Noah? What’s there to learn?

NOAH HAMMOND: Well, I think it would be really great if we could understand how thick the ocean is and what its chemical composition is. Obviously, that’s going to be really hard to do, since it’s underneath, you know, 150 miles of ice. But you know, it’s not too early to start thinking about the next mission to Pluto, even though it takes a long time to get there. One thing we learned is that it was definitely worth it to go and that Pluto has so many mysteries that are yet to be solved that were revealed by this mission.

IRA FLATOW: Amy, what would you like to learn?

AMY BARR MLINAR: Well, I’m really interested in how Pluto formed. I’m interested in its very earliest history. And you know, how Charon formed. You know, what did that impact look like? How did Pluto, you know, if all the– immediately following the impact. How did Charon evolve after the impact? And I’m also interested in what that can tell us about how the other Kuiper belt objects may have formed.

IRA FLATOW: And so, we’re not quite– should we hit the inner moons, like Europa and Enceladus, before we hit Pluto because they both have oceans also?

NOAH HAMMOND: Well maybe we can hit them on the way.

AMY BARR MLINAR: Yeah. Well, we already are planning on going back to Europa. And the European Space Agency’s planning a mission to Ganymede. So I think we’re going to get really good data for those. I would love to have it return to Enceladus, but I agree with Noah. A return mission to Pluto would be really phenomenal, as well.

IRA FLATOW: But there’s nothing in the works at the moment. And you have to have a lot of money for that, right?

NOAH HAMMOND: Yeah.

AMY BARR MLINAR: Yeah.

NOAH HAMMOND: We live far away.

IRA FLATOW: And– but you have a spacecraft that can travel pretty fast now, don’t you?

AMY BARR MLINAR: Yeah, yeah.

[INAUDIBLE]

NOAH HAMMOND: Yeah. Hopefully with that development of a space launch system, you should be able to get to the outer solar system a lot faster. So that’s something we’re really excited about.

IRA FLATOW: All right. Well, we’ll be following the excitement along with you. Noah Hammond, graduate student at the Department of Earth, Environmental, and Planetary Sciences at Brown University. Amy Barr Mlinar is a senior scientist at the planetary Science Institute. Thank you both for– Mlinar. I’m sorry. I’ve mispronounced your name.

AMY BARR MLINAR: It’s OK.

IRA FLATOW: Mlinar, I’m sure, like I am, everybody mispronounces your name.

AMY BARR MLINAR: No, it’s all right.

IRA FLATOW: Thank you. Have a great weekend. Thanks for joining us.

NOAH HAMMOND: Bye bye.

AMY BARR MLINAR: Thanks so much, Ira.

IRA FLATOW: After the break, a different story from another dwarf planet. What has NASA’s Dawn mission found out about Ceres? Yeah they’re all out there, those dwarf planets. Maybe we’ll get to a few of them. Stay with us. We’ll be right back after this break.

You’re listening to Science Friday. I’m Ira Flatow. We’re talking about the planets, dwarf planets, in our solar system. We just were talking. We were talking about Pluto. And so we’re going to go from the smallest planet in our solar system now to the largest.

SPEAKER 1: It’s a monster. It’s unforgiving. It’s relentless.

IRA FLATOW: No, that it is not a clip from Shark Week special. They’re talking about Jupiter, the giant planet that had all the ingredients to be a star if only it had been a little bigger. Well, what you just heard is a sample of NASA’s trailer for the Juno mission. That’s the orbiter that will soon begin to explore Jupiter, our closest look yet.

The Juno mission asks, where in the solar system did Jupiter actually form? Why is the Great Red Spot shrinking? Does this gaseous giant have a solid core? But first, the Juno craft has to successfully insert into Jupiter’s orbit, braving fast moving debris, powerful radiation in the process. And that event is slated for late Monday night, Independence Day. Forget the movie. This is Juno, Independence Day. And here to tell us more about Juno and what we may learn is my guest, Michelle Thaller. She’s an astrophysicist and Deputy Director of Science Communication for NASA. Welcome to Science Friday.

MICHELLE THALLER: Hey, it’s great to be here, Ira. Thank you very much.

IRA FLATOW: Juno was your idea of a 4th of July party at NASA, right?

MICHELLE THALLER: No kidding. Yes, and that actually was a complete coincidence. We didn’t mean for it to get there on that day. But it’s a wonderful time to celebrate for all of us. So I’m not complaining.

IRA FLATOW: No , no one is. We’ve been looking at Jupiter for a long time now, since Galileo and on. What can Juno tell us about Jupiter that the spacecraft Galileo and Cassini and all those others did not?

MICHELLE THALLER: Well, there’s so many things. The really dramatic thing about this mission is how close we’re getting. We’re in this amazing orbit that takes us just almost kind of skimming over the cloud tops of Jupiter at an altitude of about 3,000 miles. And that puts us well within the very intense, very dangerous radiation belts of Jupiter. So we’ve never really gotten so close to the planet. Now, as you said, that the Galileo spacecraft did actually drop a probe into the atmosphere of Jupiter. But it was only able to really get an up close sample of Jupiter in that one location. And it turns out that we might have had a bit of bad luck. We might have actually landed in a kind of anomalous place in Jupiter. There are fundamental questions like, what is the core like? What is the magnetic field like? What are the clouds made of?– that we can really only answer very up close and personal.

IRA FLATOW: Interesting, because I thought we knew so much. You know, you see pictures of Jupiter graphics all the time. And you know they peel it back. They show you the inside, whatever. But those are just graphics, is what you’re saying.

MICHELLE THALLER: Well, that’s right. I mean, we actually don’t know the size of Jupiter’s core, you know, the density of the core. One of the big questions is, is there some large rocky body underneath all of that thousands and thousands of miles of gas and also liquid hydrogen? And in this case, we’re going to be getting so close to Jupiter that the gravity, the way the spacecraft responds to the gravity of Jupiter alone, should tell us what the core is like. So that’s never been done before. And the radiation belts are so intense that they block out a lot of the very detailed measurements you could make of the content of oxygen, of water, of methane. A lot of this information just doesn’t get through those intense radiation belts.

[SOUND EFFECT]

IRA FLATOW: That was a cool sound, was it not? Can you tell us what that was or should I fill them in? Why don’t you do it?

MICHELLE THALLER: Oh, sure. That was actually from an instrument called Waves on board the Juno spacecraft. And what you were listening to there was the radio waves that we recorded when we basically hit the sonic boom. We hit the shockwave that Jupiter makes with respect to the solar wind. The sun has this wonderful, very diffused wind of high energy particles that travels at about a million miles an hour. And Jupiter’s magnetic field is so strong that these wind particles sort of shock around it, actually sort of create a bow shock that we call it. And so that was the sound that Juno made on June 24th as it actually passed into the magnetic realm of Jupiter.

IRA FLATOW: So this is pretty harsh environment that it’s going to be passing through?

MICHELLE THALLER: Oh, it’s incredible. I mean, there’s never been a spacecraft that’s had to withstand this much radiation. Here on Earth, going around, the unit of radiation intensity is called a rad. And here on Earth, we experience about a third of a rad. That’s about the radiation level you and I are at right now. Over the course of its lifetime, Juno is going to experience tens of millions of rads. So yeah, I mean we had to make this thing really, really solid and built to last.

IRA FLATOW: Does it have like protection on it, like armor, things like that protect it from this?

MICHELLE THALLER: Oh, absolutely. So all of the instruments– and this is a new idea. This is the first time we’re trying it this way. All of the science instruments on Juno are actually in vaults. They’re in this 400 pound titanium box. And it’s in there to survive the radiation of Jupiter. Now the Juno spacecraft is only going to be orbiting Jupiter a little bit more than two years. I mean, we think eventually the radiation will just fry us. I mean, we know that’s going to happen. But we have some cameras and very sensitive instrumentation in there that should survive the whole mission lifetime in that vault.

IRA FLATOW: Wow. And so Juno will have the death of other–the kind of death of other spacecrafts that have entered into its realm and go plunging into the planet.

MICHELLE THALLER: Yes, we call that the Viking funeral. Yeah, absolutely. So after its science mission– and February 2018 is the planned date that we will deliberately plunge Juno down into Jupiter, where it will burn up. And that was the same fate that the Galileo spacecraft suffered. That was back in 2003. And in the case of Galileo, you know, one of the reasons we did that was to make sure that the spacecraft never landed in the pristine environments of places like Europa, the moon of Jupiter, which has a liquid water ocean under the ice.

IRA FLATOW: Because you don’t want to contaminate it?

MICHELLE THALLER: Exactly. Yeah, we need to be very careful about that.

IRA FLATOW: But you will be collecting data as it goes down?

MICHELLE THALLER: Oh, absolutely, yes. There’s actually a number of wonderful sort of Viking burials coming up. We have the Cassini spacecraft, as well, that will be doing a planned entry into the planet Saturn. And both Juno and Cassini, of course, we want to know as much as we can all the way down.

IRA FLATOW: Wow, you know, because that Cassini– that’s been– what a workforce has it been.

MICHELLE THALLER: It’s been amazing. And you know, that the images are so beautiful that I always have to sort of stop people and say, “Oh, this is not a special effect. This is not computer generated.” We have had this amazing spacecraft around Saturn for more than 10 years.

IRA FLATOW: And so when will we start seeing pictures and data coming back from Juno?

MICHELLE THALLER: So that’s the thing that we’ve been trying to make sure everybody understands. The orbit insertion, which happens July 4th, is a risky, really high tension maneuver. And the cameras on the science instruments have all been shut off into a protective mode. So we’re not going to get images back immediately. We hope to have some images that the camera took, which is called Juno Cam, as it approached Jupiter. We have one image that we’ve already released. We hope to have maybe a movie of the moons of Jupiter going around. But then the real action starts later in the summer. In late August, we will begin to release some images of the poles of Jupiter. And this will be the first time we’ve had a clear view of the north and south poles and the giant auroras of Jupiter. And then come November, we’re going to go into main science operations and we’re actually going to ask the public to help us decide where we should aim the camera.

IRA FLATOW: Oh, come on.

MICHELLE THALLER: Absolutely.

IRA FLATOW: Are we voting? How do we vote? I mean, are you going to give us a choice of where to go?

MICHELLE THALLER: Yes.

IRA FLATOW: How does that work?

MICHELLE THALLER: On NASA’s website, there will be several different locations that we think there’s really interesting stuff to look at. And we’re going to have the public vote on what they would most like to see. So absolutely, you have a chance to help us choose where to aim this wonderful camera that will be taking the highest resolution images of Jupiter ever taken.

IRA FLATOW: Wow , wow. I’m waiting for that. I’m going to go on the website. And I understand that Juno’s been doing some new things for our NASA missions, certainly. You have movie like trailers out. Trent Reznor of Nine Inch Nails made a soundtrack, right?

MICHELLE THALLER: Yes, yes.

IRA FLATOW: And as you say, people can vote where to point the camera. There are also LEGO figurines on board?

MICHELLE THALLER: There are–three.

IRA FLATOW: What is that?

MICHELLE THALLER: Yes, three LEGO figurines. There’s a LEGO figurine of Jupiter, of course, the god Jupiter, you know, the namesake of the planet. And also Jupiter’s wife, Juno. Juno is named for Jupiter’s wife. The other moons of Jupiter tend to be named after Jupiter’s lovers. So we’re sending his wife out to keep an eye on him. And then the other LEGO minifigure is Galileo. And there’s a wonderful quote in an excerpt from Galileo’s first observations of the moons of Jupiter, all along for the ride. The little figures are actually in spacecraft grade aluminum. And there’s a wonderful collaboration with the LEGO company to bring LEGO minifigures out to Jupiter.

IRA FLATOW: Do you have a camera on them so we can see them while they’re out there on Juno?

MICHELLE THALLER: Well, you won’t be able to see them when they’re on Juno. We certainly have pictures of them that you can look at online. So if you just Google, “Juno Lego minifigs,” you can see them there.

IRA FLATOW: Now I’ve been following NASA’s missions for a long, long time. But I don’t remember trying to get the public this involved in so many different ways on a mission to a planet before. What’s the idea? Are you trying to make the public realize how exciting this is?

MICHELLE THALLER: Well, absolutely. I mean, you know, I really have always been inspired by how much the public likes NASA, and I’m so lucky that I get to go out and give talks about this stuff and kind of get that [INAUDIBLE] from people. But this really is, all of us on the planet are in this together. And science is not something that an isolated group of people that are doing off in some ivory tower. You know, I think that as– especially as younger scientists– you know, I’m always on social media. I’m always connected with all my friends. It feels odd to me that there be a large segment of the population that wouldn’t be participating in this, be with us. And so that’s why we’re doing that.

IRA FLATOW: That sounds great. I want to thank you, Michelle, for taking time to be with us today.

MICHELLE THALLER: Oh, it was wonderful, Ira. Thank you so much.

IRA FLATOW: You’re welcome. Michelle Thaller, astrophysicist and NASA Deputy Director of Science Communication. She’s the Juno mission spokesperson out there at JPL in Pasadena, California. I want to bring on another. There’s so much going on in the solar system now. So much exploration. Let’s turn to another close dwarf planet, close to Pluto, Ceres. You know, Ceres is the giant of the asteroid belt. And last year, NASA’s Dawn spacecraft arrived at Ceres to get our first close look. And now research, published in Nature, suggests that liquid water– again, more water we have out there– has played a role in the planet’s geology, perhaps very recently. Here to explain these findings and other news from Dawn is my next guest, Carol Raymond, Deputy Principal Investigator of the NASA Dawn mission to Ceres and co-author of two research papers concerning Ceres, Welcome to Science Friday.

CAROL RAYMOND: Thank you. I’m delighted to be here.

IRA FLATOW: I had to do everything I could not to play the Four Seasons music when you came on, but I’m sure you’ve played that yourself a few times. You understand what I’m talking about?

CAROL RAYMOND: Not exactly.

IRA FLATOW: You’re not old enough to remember “Dawn,” a song that they–

CAROL RAYMOND: Ah, yes, of course.

IRA FLATOW: Of course. OK, I’ve got that trivia out of the way. Tell us about this mission. What makes this so special? What are you trying to accomplish there?

CAROL RAYMOND: Well, Ceres is actually more than an asteroid. It’s really a– it was designated a dwarf planet, but it is a protoplanetary remnant, left over from the very first epic of solar system formation. So when the small planestesimals were accreting and they were merging to form protoplanets, and then those protoplanets were going on to form the planets that we know today, there were many, many objects in the solar system that were probably similar to Ceres. But Ceres is the only object that we know of in the inner solar system, which is a large primitive protoplanet. And so by going to Ceres and studying it, we’re able to look back in time and better understand what processes were going on during the time of the planet formation.

IRA FLATOW: What makes you say it’s primitive? How do you distinguish primitive from a more mature one?

CAROL RAYMOND: So primitive is a relative word, of course. The far reaches of the outer solar system contain the most primitive material from our solar nebula. But in the inner solar system, we use that term to describe a body which is rich in volatiles. And of course, volatiles are just light elements. And the most familiar one for to us is water– and the most important one, perhaps. So we’re looking for water rich, carbon rich, and organic rich bodies, which are retaining a lot of that initial material that was around when the planetesimals were forming. And Ceres is that type of object. And we knew that before the Dawn spacecraft went out to visit it because we knew how big it was. And we knew how massive it was because of how it perturbs other bodies around it, other asteroids. And so we knew that its density indicated it wasn’t made of solid rock. It was made either of a very porous rock or a mixture of rock and lighter elements, like ice.

IRA FLATOW: Got you. I’m Ira Flatow. This is Science Friday from PRI, Public Radio International. And so, you know, this is a unique then object that we’ve never studied this kind before.

CAROL RAYMOND: That’s right.

IRA FLATOW: And what’s the best picture we can paint so far of what Ceres looks like? We’ve talked a lot about Pluto, which is, if I were to look at or be there, what would the terrain be like?

CAROL RAYMOND: Well, what you see is mainly a very dusty surface. It’s covered with what we call a lag deposit. And the lag is what’s left over after volatile sublimates. So this is like what’s left over when the snow bank melts on the street of Washington, DC. And so this is a kind of a dark and dusty material. But in addition to that kind of background, we’re seeing the most fantastic formations of bright material dotting the surface, mostly associated with impact craters. But also, curiously occurring along fracture patterns in the surface. So we’ve got a surface which has many very interesting geological features. I mentioned the fractures there are large troughs on the surface. And then, there are many smaller fractures in sort of chaotic radial patterns, as well as concentric ones, which follow the circular outlines of the impact craters.

So those are the main elements of what makes up the surface and the sort of geology of the surface. And then we have, also, two major highlands and then two major lowlands. So there is some relief on Ceres. And we’re still puzzling out what that might be telling us.

IRA FLATOW: You know, while you look at them, we haven’t gotten close-ups. So now we get closer to them. They don’t just look like little rocks out there. They look like real places.

CAROL RAYMOND: This is a geological world. It is a small planet. And what we’re understanding now, based, in part, on the research that was published yesterday, is that this appears be a geologically active world. The deposits of very bright material that we were able to see as soon as we got in the vicinity of Ceres– these were the blinding bright spots that captured everybody’s attention– turns out that these are bright areas in the floor of a young crater, about 80 million years old, called Occator. And if you look, in detail, at that bright material, it’s a very curious domed structure that’s in a pit in the middle of the crater.

IRA FLATOW: Wow. Wow.

CAROL RAYMOND: And it has a radial fracture pattern on top of it. And so, just looking at it, it is giving you the impression that materials coming up from below and pushing the surface up.

IRA FLATOW: Dr. Raymond, I’ve got to go. This is quite exciting. Carol Raymond, Deputy Principal Investigator of NASA’s Dawn mission. Have a great weekend.

CAROL RAYMOND: Thank you.

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