08/09/2019

The Not-So-Great Red Spot

34:31 minutes

panoramic view of the swirls on jupiter with the great red spot, against a black background
Jupiter, with the Great Red Spot visible on the right. Image data: NASA/JPL-Caltech/SwRI/MSSS
Image processing by Kevin M. Gill, licensed under CC by 3.0

In the summer of 1665, astronomer Giovanni Cassini was peering through his telescope at the heavens. A friend, Eustachio Divini, had just tipped him off to an unusual spot on the planet Jupiter. And Cassini had observed, to his surprise, that this spot seemed to be permanent, spinning like a cyclone, in the southern tropics of Jupiter. 

Today, we know that swirling storm Cassini spotted was most likely the Great Red Spot, a storm system wider than the diameter of Earth. But now, after centuries of observation, the long-lasting storm appears to be shrinking—becoming less “great.”  

In this segment, Ira and his guests Scott Bolton and Tracy Becker of the Southwest Research Institute in San Antonio will catch up on the latest Jovian science, including a recent fly-by of the Great Red Spot by the spacecraft Juno. And they’ll discuss upcoming missions to Jupiter and Saturn’s moons, like the Europa Clipper mission and Dragonfly

And to have a little fun this week, we asked our listeners to weigh in on which planet was better: Jupiter or Saturn? And boy, did you all have opinions on this. A planetary smackdown ensued. 

Transcript: Nathan: Jupiter’s unequivocally better. With all those wonderful bands and that angry red spot in the storm on the surface. Plus it’s bigger. You know Saturn is not only substantially smaller but its surface is relatively bland. It does have rings I’ll give you that… Gibson: I think Jupiter is better than Saturn because one of its moons Europa may possibly have life on it and has sparked the imagination of scientists and sci-fi authors for decades… Peter: I don’t understand how this is even a question. Jupiter’s clearly Superior. It has the Galilean moons which showed Galileo that there were things orbiting planets not just the Earth. Jupiter cleared out all these asteroids so we don’t have to live with impacts every day on Earth. Jupiter has the Trojan group which are fascinating and under-explored. The solar system is the Sun, Jupiter, and various errata. Errata like Saturn.”

Ouch! Tough love from Nathan Hunter in Vancouver, Washington; Gibson in Denver, Colorado; and Peter Barber in New Zealand. But the smackdown didn’t end there. You weighed in on Twitter as well… and Saturn got a little more love this time around.

Jupiter’s swirling abyss—particularly this view of a jet stream showing a vortex that has an intensely dark center—provided fodder for those on Team Jupiter. Credit: Enhanced Image by Gerald Eichstädt and Sean Doran (CC BY-NC-SA) based on images provided Courtesy of NASA/JPL-Caltech/SwRI/MSSS
Those on Team Saturn frequently invoked the planet’s rings. This wave structure here results from the same process that spawns spiral galaxies. Photo by arun17kumar2002/flickr/CC BY-NC-SA 2.0

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Segment Guests

Tracy Becker

Tracy Becker is a planetary scientist at the Southwest Research Institute and Co-investigator on the UV instrument on the NASA Europa Clipper mission. She’s based in San Antonio, Texas.

Scott Bolton

Scott Bolton is Principal investigator on the Juno mission and a Co-investigator on the Cassini mission. He’s Associate Vice President at the Southwest Research Institute in San Antonio, Texas.

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow. I want you to come back with me now to the summer of ’65, 1665. Astronomer Giovanni Cassini is peering through a telescope, as one does on summer evenings. A friend has just tipped him off to an unusual spot on the planet Jupiter. 

Cassini observes and concludes that this spot seems to be permanent. A giant spot spinning like a cyclone in the southern tropics of Jupiter. Well, today we know that swirling storm Cassini saw was probably what we call the Great Red Spot, a storm system two planet Earths could fit inside. 

But you know what? For some reason, after hundreds of years of observation, that long lasting storm now appears to be shrinking. And luckily we are in the right place at the right time to observe the planet, a lot closer than Cassini was. Our observation point, the Juno spacecraft, which just zoomed over the Red Spot to study it. 

So for the rest of the hour we’re going to be talking about what it found and the many new missions in the works to uncover the mysteries of Jupiter, its neighbor Saturn, and their dozens of moons. And if you have a question about Jupiter or Saturn, you want to sound off on which of the two giants is your favorite– because people keep debating this all the time. Give us a call. Our number, 844-724-8255, 844-SIDETALK. Or you can tweet us at @scifri. 

Let me introduce my guests. Scott Bolton is principal investigator of the Juno mission and a co-investigator on the Cassini mission, named of course for Giovanni Cassini. He’s also associate vice president at the Southwest Research Institute. He joins me here at the studios of Texas Public Radio in San Antonio. Welcome back to Science Friday, Dr. Bolton. 

SCOTT BOLTON: Thanks very much. Great to be here. 

IRA FLATOW: Nice to have you back. Also with us is Tracy Becker, a planetary scientist at the Southwest Research Institute and co-investigator on the UV instrument on the upcoming NASA Europa Clipper mission. She’s also here at TPR. Welcome, Dr. Becker. 

TRACY BECKER: Thank you very much. It’s great to be here. 

IRA FLATOW: Nice to have you. Scott, Juno just flew over the Red Spot a few weeks ago and the spot is changing. Is that surprising, that it’s shrinking a little bit? 

SCOTT BOLTON: It is surprising, especially since it’s been observed since the days of Cassini. And maybe it was there earlier. So you’ve got this great storm sitting there for 300 years or more and now all of a sudden it’s changing. So that was a big surprise to us. We’re watching it shrink. 

And we flew over, as you say, just a few weeks ago. We’ve done it before, but this time we were doing a very special experiment where we were trying to detect to see if we could see a sense of the gravity field that might be tied to it, so that we could try to make an estimate or constrain how deep that storm went. 

It’s too early for me to give you the answer that. We’re still combing through the data trying to figure out what it means. But what we’re searching for is how deep did that root go? 

IRA FLATOW: Because it’s a ball of gas, right, it could go pretty deep? 

SCOTT BOLTON: It’s a giant ball of gas. I mean it’s, like a hurricane or a tornado. It must be working differently than that because it’s Jupiter and there’s no sea or land underneath. But it’s a giant funnel cloud of some kind, and the question is, is there some signature? 

IRA FLATOW: I’m trying to wrap my head around a giant funnel cloud the size of two Earths. Wow. 

SCOTT BOLTON: And very deep. So it’s going to look pretty ominous if you were flying through the atmosphere. 

IRA FLATOW: If it’s shrinking, is it shrinking quickly? Is it going to disappear in our lifetime or is it just really slowly going to disappear? 

SCOTT BOLTON: Well, it’s shrinking. And I would say that it’s quickly in the sense that we can detect it over a few decades. Since the days of Voyager, it’s definitely shrunk in size. 

Is it going to disappear? There are people that extrapolate that shrinking and try to make an estimate of when it would disappear. But I think that’s a little bit like getting up in the morning and weighing yourself, and say, wow, I lost 10 pounds. So how long before I disappear? 

IRA FLATOW: Dr. Becker, let’s turn to Saturn now. One of the things you’ve been studying are Saturn’s rings. What have you learned about them that we didn’t know? 

TRACY BECKER: That’s right. So the Cassini mission was orbiting Saturn for about 13 years, and it collected a lot of data about Saturn’s rings. One of the things that I was most interested in were the particle sizes that make up Saturn’s rings, so trying to find some of the smallest stuff. 

And what we did was use this really cool technique that instead of staring at the rings themselves and looking at the reflected sunlight, we actually pointed our instrument at a background star and let the rings come in front of that star. And using that, we can say a lot about the actual structure of the rings and what the particle sizes that make up the rings look like. 

IRA FLATOW: Can you say how many rings Saturn has? Is that a trick question? 

TRACY BECKER: So they’re all named. The main rings are the A, B, and C rings. Those are the ones that you can see with a regular telescope. And then there’s some more diffuse rings, like the D ring, the E ring, the G ring, and a very skinny, exciting ring called the F ring. So there’s a handful of rings. 

IRA FLATOW: I remember watching Voyager go past Saturn when they discovered the F ring and how weird it was. 

TRACY BECKER: Yeah, so the F ring is a super exciting place. It’s kind of at the edge of where Saturn’s gravity has more power or less power to destroy objects as they form. So it’s kind of at the edge of where the self gravity can actually start to allow objects to start to accrete. 

But then Saturn’s gravity still interferes. There’s a lot of collisions, really exciting collisions, happening in that area in that particular ring. And so you see all of these collisions and building up of the ice particles. So you can really see how stuff forms, and then gets destroyed, in a fun way. 

IRA FLATOW: So let’s talk about, why is there stuff? If Saturn is a gas giant, why does its rings have stuff that are made out of, what, ice or particles? What are they made out of? 

TRACY BECKER: So the rings look like they’re this place that maybe you could go ice skating, but that’s not the case. It’s all made up of individual particles that range in sizes of micron-sized dust up to house-sized boulders, pretty much, and then a handful of objects that are bit larger than that. 

And at first there was always this thought that maybe these rings formed right around the time Saturn formed. But recent results from Cassini, at the end of the mission, started to really show that these rings probably formed only about 100 million years ago by some sort of breakup of maybe an icy moon or some comets that came by. 

IRA FLATOW: So if you were a dinosaur you could have seen that? 

TRACY BECKER: That’s right. If they had figured out how to use telescopes or binoculars they could have seen it happening. 

IRA FLATOW: And do we know where this stuff came from? Was it captured by Saturn, or where did the material come from? 

TRACY BECKER: So that’s sort of the underlying question still. Was it a moon of Saturn’s that kind of moved in its orbit and somehow got disrupted by Saturn’s gravity, or was it incoming comets? Those are still areas of active research. 

IRA FLATOW: There was a paper published, maybe last week or a week ago, about the Earth and the moon. And maybe at one point our moon was formed as it started out as a ring around the Earth. Possible? 

TRACY BECKER: Well, so the leading idea there is that there was some sort of a collision event that happened with the Earth early on. And that would have spewed out a lot of material, and probably did form some sort of a disk before it was able to coalesce into the current moon that we have today. 

IRA FLATOW: That is quite interesting. Scott, why is it that Saturn has such spectacular rings but Jupiter has such wimpy rings? Uranus has a ring too, kind of a wimpy ring. 

SCOTT BOLTON: It’s true, and very little about Jupiter is wimpy. But the ring might be– 

IRA FLATOW: No insult meant. 

SCOTT BOLTON: The ring might be one of them. No, I’m not– I’ve worked on Cassini too. So I like both planets. 

IRA FLATOW: Do you have a favorite? 

SCOTT BOLTON: I don’t. My favorite’s actually Earth, and it might be sort of tied to the fact that I’m here. I also like to ski and surf and snowboard. We got it all. But anyway, you asked about the rings. 

IRA FLATOW: But getting back, right, getting back to the rings. 

SCOTT BOLTON: So there’s a theory that was proposed some time ago, called ring rain, which Cassini, at the end, has seen some evidence of. And it has to do with the magnetic field interacting with the ring and causing things to get pulled out of the ring and back into the planet. And the question is, how much of that material disappears? 

And we saw some evidence at the very end of Cassini. We sent the spacecraft into the upper part of the atmosphere, and we were able to measure, with the Ion and Neutral Mass Spectrometer, some of this material. And it looks like the ring rain idea is possibly true. 

And what that ring rain idea has– it sounds like you would just say, well, I’m raining stuff out of the ring, which is exactly what you’re doing. But it’s all connected to the magnetic field and the tilt of the magnetic field and the strength of the magnetic field. And, you know, Jupiter’s strong sometimes and wimpy in other ways, like the ring. 

And Saturn is a wimp with respect to the magnetic field. It has really a weak magnetic field, perfectly aligned with the body. We don’t understand that. 

We have no theory that really explains how that magnetic field comes about like that. But the fact that it’s so aligned and so weak may be tied to why it is able to sustain a ring. And if it had a magnetic field like Jupiter, that ring might not be there. 

IRA FLATOW: Quite interesting. And that’s one of the reasons why, with Juno, it dives in from millions of miles away, to within just a couple of thousand miles of Jupiter, and then goes back again because that magnetic field’s so strong it might destroy the– 

SCOTT BOLTON: No, well it might, but that’s not why we do it . It’s tied to the magnetic. Because of the strength of that magnetic field, Jupiter is surrounded by radiation, really incredibly high radiation particles that are moving very close to the speed of light. Those are really dangerous to a spacecraft. 

The magnetic field is as well. But it’s the combination of those two. The magnetic field enables this force field that’s super strong, packed with radiation weapons, basically– to a spacecraft or a life. And so we dart in and dart out as fast as we can. 

We come screaming through, barely touch it if we can. And then we go out where it’s safe, lick our wounds, and then go back in for another shot. 

IRA FLATOW: We have listeners calling in. Let’s go to the phones. Let’s go to Joe in Florida. Hi, Joe. 

JOE (CALLER): Hello. Question, why are the outer planets giants and the inner planets rocky small planets? I’m curious. 

IRA FLATOW: Good question. You want to tackle that one? Why are the inner ones like us, rocky, and the outer ones are gas giants? 

SCOTT BOLTON: So that’s a question that people that are trying to study solar system formation ask all the time. And one of the reasons is that the early inner planets, like us, may have started with a little bit bigger of a gas envelope. And we lost it because we didn’t have enough mass. 

We were closer to the sun, so things were warmer, and the hydrogen and helium would have escaped. Whereas Jupiter was big and massive, and so were the other outer planets, and they were able to hold onto it. That’s one idea. 

But there’s other reasons, in the sense that Jupiter may have formed first. And then the outer planets form, and they grab all this material, this gas. And we may or may not have started that way. 

Although, I would not be surprised. We may not have built a big enough mass at the Earth to grab all of that light element gas because it’s hot when it’s this close to the sun, and it’s moving quite fast. So you need a big gravity field to grab on to it. 

IRA FLATOW: Interesting. Dr. Becker, you’re working on an upcoming mission to Jupiter’s moon, Europa, called the Europa Clipper. Why is Europa of such interest? And what’s the mission going to do? 

TRACY BECKER: Yeah, so Europa is this icy moon of Jupiter. It’s one of the Galilean satellites. It was detected by Galileo back in 1600s. And it has an icy shell. It actually has a liquid water ocean underneath that shell. And there is actually more liquid water ocean there than in all of the Earth’s oceans combined. 

And so whenever we think about water in the solar system, we naturally start to think about the potential for life. So NASA’s Europa Clipper mission’s main goal is to assess the habitability of Europa. So the idea of, could life, at least as we understand it, have lived there, currently live there, or potentially live there in the future in those oceans. 

IRA FLATOW: I’m Ira Flatow. This is Science Friday from WNYC Studios, coming to you from San Antonio, Texas Public Radio, talking about Jupiter and Saturn. What about Enceladus? Doesn’t it have liquid water on it too? 

TRACY BECKER: It does. 

IRA FLATOW: How do you make the choice between them? Do you take a vote? 

TRACY BECKER: So Europa’s ocean has been known about for longer. The Galileo spacecraft that orbited Jupiter in the 1990s was the one that first detected that liquid water ocean. With Enceladus, we didn’t know for sure that there was a liquid water ocean there until Cassini arrived there in about 2005, 2004. 

And when that detection was made, it took a few flybys and a little bit more data to understand that there was liquid water. And the way they found it was that it was actually spitting out that water in these water vapor plumes. It was basically like water volcanoes on Enceladus. 

So works were already there to go to Europa first. But there are plenty of people who would love to go back to Enceladus and see if they can better explore that moon as well. 

IRA FLATOW: Mm-hmm, go to both places. 

TRACY BECKER: Hey, I’m for it. 

IRA FLATOW: You know what I always find interesting when I talk about this, especially about Jupiter, is how science fiction writers have known that Jupiter is the place to go to to find the interesting stuff. Most recently, Arthur C. Clarke, 2001. 

When you went to the moon, they found the monolith. It was beaming its stuff out to Jupiter. Right? And in 2010, a quote from the book, “all these worlds are yours except Europa. Attempt no landing there.” Are you familiar with that quote? 

TRACY BECKER: Yes. 

IRA FLATOW: What is the romance about the moons of Jupiter? I mean, do you have that same feeling? 

TRACY BECKER: Oh, yeah, definitely. And all of the moons of Jupiter are fantastic. I mean, you have Io spewing out volcano material. It’s the most active volcano world in our solar system. Europa probably also has these water vapor plumes that we’ve detected. 

And from early on, you could tell by how bright these moons are, like Enceladus and Europa, that they are mostly water ice on the surface. And so that, of course, just leads to that intrigue of what else is there. 

IRA FLATOW: Not to leave Saturn out, Tracy. What about the mission to Titan called Dragonfly. How did that get its name? What’s going on? 

TRACY BECKER: I’m not directly involved in that mission. But the idea, I think, behind the name of it, is the fact that there will be something flying around on Titan. So NASA recently selected that mission to go and explore Titan. It’s the largest moon of Saturn. And what makes it so exciting is that it has a hydrological cycle just like the Earth has, except that it’s with methane instead of with water. 

It’s too cold for water to be in the forms of lakes and clouds and rain. But methane, which is a gas here, is at the right temperature at Titan. And so you actually have an atmosphere. You have clouds, you have rain, and you have lakes made out of that methane. 

IRA FLATOW: And so what’s the mission? Are we going to fly a little robot around? 

TRACY BECKER: That’s right. 

IRA FLATOW: Is there enough atmosphere? 

TRACY BECKER: Yes, and that’s what makes it so exciting. It’s sort of like a quadcopter, but there’s eight propellers to fly it around. So it will be able to explore different very interesting locations, fairly easily, because it can pick back up, fly to the next location, and look there as well. 

IRA FLATOW: So there’s not a companion rover that’s going to go any place? You don’t need one if you can fly around. 

TRACY BECKER: That’s right, yeah. 

IRA FLATOW: And how soon do we think this will happen? 

TRACY BECKER: So again, I’m not part of that mission. I think the launch date is in the early 2020s. Scott? 

SCOTT BOLTON: Later. 

TRACY BECKER: 2030s? 

SCOTT BOLTON: Early 2020s. Is that what you said? 

TRACY BECKER: Yeah. 

IRA FLATOW: That’s close enough. 

SCOTT BOLTON: It’s a drone, basically. 

IRA FLATOW: It’s basically a drone flying around. 

SCOTT BOLTON: And, you know, what’s great about it is that Titan– we already know from Cassini, which dropped a probe there called Huygens– that the Europeans built. But we saw coastlines– 

IRA FLATOW: Wow, wow. 

SCOTT BOLTON: –mountain ranges. And so you’re going to have a drone flying around coastlines. I mean, it’s going to be spectacular. And it can move around and check different samples and also investigate the habitability of another ocean world. 

IRA FLATOW: This is Science Friday. I’m Ira Flatow coming to you from the studios of Texas Public Radio in San Antonio. We’re talking about exploring giant planets Jupiter and Saturn this hour. And we have lots of great pictures of Jupiter’s swirling atmosphere and Saturn’s rings up at sciencefriday.com/planets. And it’s really excellent stuff. 

And we had fun this week, we had a little fun. We asked you to weigh in, on the Science Friday VoxPop app, about which planet was better, Jupiter or Saturn, a planetary smackdown. A few of you chose Saturn, like Mindy in Hilo, Hawaii. 

MINDY (FROM THE APP): I think Saturn is better than Jupiter just because of the amazing beautiful rings. They’re the icing on the cake. 

IRA FLATOW: You can hear the frogs chirping in the background. That was great. Thanks, Mindy. But the real surprise was that almost all our listeners on Science Friday VoxPop app weighed in for team Jupiter. Let’s take a listen to that side. 

PETER BARBER (FROM THE APP): Jupiter is unequivocally better, with all those wonderful bands and that angry red spots, the storm on the surface. Plus, it’s bigger. You know, Saturn is not only substantially smaller, but it surface is relatively bland. It does have rings, I’ll give you that. 

GIBSON (FROM THE APP): I think Jupiter is better than Saturn because one of its moons, Europa, may possibly have life on it. It has sparked the imaginations of scientists and sci-fi authors for decades. 

NATHAN HUNTER (FROM THE APP): I don’t understand how this is even a question. Jupiter’s clearly superior. It has the Galilean moons, which showed Galileo that there were things orbiting planets, not just the Earth. 

Jupiter cleared out all these asteroids so we don’t have to live with impacts every day on Earth. Jupiter has the Trojan group, which are fascinating and underexplored. The solar system is the sun, Jupiter, and various errata– errata like Saturn. 

IRA FLATOW: Ooh, errata. Saturn is an errata, error– tough love from Nathan Hunter in Vancouver, Gibson in Denver, and Peter Barber in New Zealand. And if you want to join in and let us know what you think– are you team Saturn or are you team Jupiter? Download the Science Friday VoxPop app, and leave us your voice comment. And if there are any die-hard Saturn supporters out there, let your voice be heard now on the Science Friday VoxPop app. 

Now, it’s time to bring my debate back to my studio debaters here with me, Scott Bolton and Tracy Becker. Scott Bolton is principal investigator on the Juno mission. He is from the Southwest Research Institute here in San Antonio. Also with us, Tracy Becker, planetary scientist. She’s on the NASA Europa Clipper mission. Scott, tough love for Saturn on that one. 

SCOTT BOLTON: Yeah, I really felt bad for it there. 

IRA FLATOW: I have to say, having a backyard telescope of my own and having looked at Saturn and Jupiter, each one– I mean, I’m not trying to smooth this smackdown over. But when you look, on a nice night, and you can see those Galilean moons of Jupiter out there, you have the same little rush, I think, that Galileo had. They’re just sparkling out there. They’re lined up in a row sometimes, sometimes there’s a little shadow across Jupiter. 

And the same thing with Saturn. When the rings are tilted just the right way, it’s mind blowing. 

TRACY BECKER: Yeah, the first time I saw Saturn through a telescope, I could have sworn someone was dangling a little silhouette of a planet with rings, just a sticker, in front of the telescope. I couldn’t believe how picturesque it was through a telescope. 

IRA FLATOW: You thought Ed Wood was out there dangling that little– yeah, it’s great. Scott, let’s talk about Ganymede, another unique moon, is it not? 

SCOTT BOLTON: Ganymede is very unique. It’s the only moon that we’ve actually seen that has its own magnetic field. So in that sense, it’s almost like a planet. It has its own magnetosphere. It’s the only one we’ve ever seen that has that. 

We discovered that with Galileo, when we were flying around, and we got close to it. And I was on one of the teams, on Galileo, that actually detected what looked like a magnetosphere. We were looking at plasma wave signatures and there it was. 

IRA FLATOW: That’s cool. Let’s go to Birmingham, Alabama. Chris in Birmingham, Hi, welcome to Science Friday. 

CHRIS (CALLER): Hi. Yes, my question is just about– thanks for taking the call. The major moons around Saturn, are they going to be there forever, like, orbiting the planet? Are some going to disappear? 

TRACY BECKER: So the moons should be pretty stable around all of the planets. Just like Jupiter’s moon should stick around for a while, Saturn’s rings should also be there for a long time. 

IRA FLATOW: Well, it took 100 million years for Saturn’s rings to get there, right? 

TRACY BECKER: Yeah, so again, the rings are sort of this unique thing. Most of the moons, at least, have probably been there since the beginning. And the rings, a lot of people did think that they were there from the beginning too, until some of the most recent results from Cassini. 

IRA FLATOW: There was the theory, Scott, a while back, and maybe it’s still a theory, that because the gas giant Jupiter is so big, and it has so many satellites, that it was a little solar system that never got started. Jupiter never turned into the sun. Is that still thought of that way? 

SCOTT BOLTON: Yeah, I mean, they’ve evolved the theory now that Jupiter– it used to be if it was just 40% more massive, it would have ignited fusion. But I think now they realize it needed to be more massive than that. But it is just shy of being able to have ignited, like a star, and we would have been in a double star system. 

But even if it doesn’t ignite, Jupiter and Saturn are like mini solar systems. I mean, they have these moons. They have relatively big moons close to them that are going around. Jupiter, in particular, has the four Galilean moons. And it’s like a mini solar system. 

And when Juno was approaching, we made a movie where we took a picture every 15 minutes for about two weeks, and then put it together. And you can actually watch the satellites go around, and it looks just like a solar system. In fact, we don’t have any pictures of our solar system like that. It must be the way we look. 

You watch these things, and the ones that are closer in are moving around faster. The ones that are further out are moving around slower. And it’s sort of what Galileo must have seen and imagined. 

I mean, he was a brilliant guy. He saw this, and he looked at it and realized, oh, my God, these moons are going around a planet. And his view was, these things are going around something else out there. That means Earth’s not the center of everything. It changed our perspective of ourselves forever. 

IRA FLATOW: Interesting. Let’s go to Twitter, because lots of Twitter folks, a lot of planet geeks are checking in. Helen, for example, asks, does Jupiter exercise a rotational torque– I told you we’ll get to the geeks– rotational torque on other planets the way Earth does on Venus? Scott? 

SCOTT BOLTON: Well, it definitely exercises a torque, and in effect, gravitationally. Whether it’s meaningful enough to stop the rotation of other planets, no– or even interact with it, because it’s pretty far away. But it does do that to its own moons. And just like our moon is kind of locked in, we’re always looking at the same face, if you’re close enough to Jupiter, that’s what’s going to happen to you. 

IRA FLATOW: Let’s go to Troy in Gold Canyon, Arizona. Hi, welcome to Science Friday. 

TROY (CALLER): Hey, thanks for having me. I’m definitely pro-Saturn. Being an amateur astronomer doing sidewalk astronomy, I get a lot more oohs and aahs showing the “Lord of the Rings” than I ever do showing Jupiter. 

IRA FLATOW: You don’t get turned on by the moons of Jupiter? 

TROY (CALLER): I do, as an amateur astronomer, but from the sidewalk astronomy experience, most people are much more impressed when they see Saturn than they are when they see the moons around Jupiter. 

IRA FLATOW: Yeah, I actually would have to agree with that. Thanks for calling in with that. I mean, you really can’t match those rings, can you? 

TRACY BECKER: Yeah. 

IRA FLATOW: When they’re tilted the right way, and you see them. 

TRACY BECKER: And when you see them up close too. With Cassini for example, the rings are so broad, but they’re so thin. And it’s so fascinating to be able to see them up close, as Cassini was able to do. 

And earlier we were talking about the idea of the moons going around Jupiter kind of looking like a solar system in itself. Saturn’s rings also represent this really unique opportunity to understand planet formation. So the way that the ring particles interact with each other, the outside moons, the moons buried in the rings– all of those gravitational influences actually really show scientists how planet formation started, potentially our own. And it also looks a lot like– if you look at ALMA images of distant planetary discs that are forming around distant stars, it kind of looks a lot like Saturn’s rings. So there’s a lot of cool science to be done there. 

IRA FLATOW: Speaking of distant, our next call comes from Ukraine. Michael in Ukraine, hi, welcome to Science Friday. 

MICHAEL (CALLER): Hi, greetings. My choice is Titan. I’m absolutely gobstruck at the place. It’s the most amazing thing in the solar system. It’s the only Earth-like atmosphere at all in the solar system, with nitrogen and whatever. 

It has 1.5 times the pressure, so it’s the only place the astronauts wouldn’t need a pressure suit. Now, they’d need some real, real good thermal suit because 180 minus centigrade would tend to make you a little crisp. But everything about it is just insane. It’s like an alternate universe with rocks of ice and rain of methane and ethane and maybe nitrogen, oceans of methane and ethane. 

It’s just almost inconceivable. Rains or snows of mixed organics– I mean, it’s just so cool. I mean, I always wanted to go to Europa. And I’d volunteer to go one-way, which some people might cheer. But now I’m really, really hot on Titan. I just think it’s just such an incredible place. 

IRA FLATOW: Thanks for the call. Tracy Becker is nodding and smiling at the same time. 

TRACY BECKER: Well, the good news is that we get to go to both. NASA’s Europa Clipper mission will be there in the late 2020s and then Dragonfly will be arriving to Titan not long after that. 

IRA FLATOW: He waxed so poetic. Was he right about Titan, the things that he said and the way he described it? 

TRACY BECKER: Yeah, it’s an incredible place. 

SCOTT BOLTON: Yeah. In many ways it’s sort of showing us the history of Earth. When Cassini was going there, one of the arguments was that maybe this is what Earth was like when life was just getting started. And it is full of these lakes. They’re methane, so it’s a little a barbecue waiting to get lit. 

IRA FLATOW: Oh, I have a vision now. You’ve given me a vision that I can take with me. That’s quite interesting. We always talk about these scientists, like Galileo and Cassini, gazing at the planets and the moons. And I’m always wondering, how did they have the spare time to do this? 

I mean, somebody is picking up their tab for their rent and their food. And today we think there are great universities, or whatever, picking up their bill, paying them. Is that the same thing that happened with these ancient astronomers, Galileo and Cassini? 

SCOTT BOLTON: Absolutely, although, I don’t think it was just their spare time. They were dedicated in the sense that Galileo, he was really the first, right. He was really the first to take a telescope and turn it into some sort of a scientific instrument. And he pointed it up. Now, that was his game and what his goal was. 

The way he sold it was he took something that wasn’t very high quality and couldn’t be used and was able to improve it so that the optics actually worked, and you could see stuff. And he started going to the doges and the royalty in Venice. You know, at that time, there were big city-states. And he basically said, look, if you pay for this and you help me, you can use this telescope and see the merchant ships that were coming in. At that time, you can imagine, they don’t even know when the ship’s coming or what it’s got. 

But I think, more important, they could see war mongers or somebody coming that might be doing some damage. And so he sold it that way, and then took it and did what he wanted, which was look up. And he looked at all the brightest objects, right, the moon, Venus, Jupiter. It was really natural. 

And with Cassini, science was already getting started a little bit. And so the scientific method, which basically it started with Galileo, was a little bit on the right road. 

IRA FLATOW: Interesting. 

SCOTT BOLTON: So he was really doing science for the sake of science. 

IRA FLATOW: Let me just tell everybody that this is Science Friday from WNYC Studios. So who funded Cassini’s work? 

TRACY BECKER: Cassini was an Italian astronomer, scientist, and mathematician. And King Louis XIV, I believe it was, actually hired him to start up the Paris Observatory and was kind of his astronomer/astrologer on-site. So I think a lot of the funding came from, the French Royalty to actually pay and support him through his astrology methods. 

And then at the same time, he was really getting more and more involved in the astronomy as a result. And ultimately, in the end, he didn’t really adhere to most of the ideology behind astrology, by the end of his career. 

IRA FLATOW: We only have a few minutes left, so much to talk about. Let me see if I can get a phone call and a tweet in. Tweet from Twitter says, when you look at the night sky and see Jupiter, I say a silent thank you for being our guardian and keeping many large objects away from the Earth. I guess that’s true too. Let’s go to– let’s stay right here in Texas. Let’s go to Natalie. Hi, Natalie. Welcome to Science Friday. 

NATALIE (CALLER): Oh, my gosh. Hi, thank you for having me on. 

IRA FLATOW: You’re in Del Rio, right? 

NATALIE (CALLER): Yes. 

IRA FLATOW: Yes, go ahead. 

NATALIE (CALLER): OK. So I’m a 7th grade science teacher, and we were gathering information from a couple of videos that we saw, One Strange Rock. And we were also listening to the news saying how the French scientists have found that Europa has these currents. And my kids kind of combobulated all of the information together, and they asked me a really great question. They said, could there possibly be life on Europa? And I said, there could be a possibility of life that we don’t know yet. 

IRA FLATOW: OK, good question. That’s why we’re going there, right, to find out the possibility? 

SCOTT BOLTON: Absolutely. In fact, that is one of the main goals. The life that you would see at Europa is probably under the water, so under the ice shell. But almost everywhere we look on the Earth, we see life where there’s water. 

And in particular, you go to these big deep vents, thermal vents that are coming out of the deep ocean, and you see that it’s full of life, these things they call black smokers. And in Europa’s case, the belief is that that water may be in contact with the rock underneath, which is a thermal energy source. And so you might have something very similar to what we have in the deep seas of Earth. 

And eventually, you need a submarine to go in there. But maybe some of the hints will spray out from water volcanoes that spray out. And the spacecraft of Clipper may be able to detect some of the evidence of that. 

IRA FLATOW: Sounds like some of our best days are ahead of us in planetary exploration. 

TRACY BECKER: Yeah. And these are the goals of the Europa Clipper mission, to look at how salty the water is. Also if there are these plumes there that we think we’ve seen, can we fly through them? Can we sense any of the materials that would indicate that there is possibly some sort of hydrothermal activity? 

IRA FLATOW: I can’t wait. You’ll all come back to Science Friday with the results when they happen years from now? 

SCOTT BOLTON: Absolutely. 

TRACY BECKER: Definitely. 

IRA FLATOW: Scott Bolton, principal investigator on the Juno mission, co-investigator on the Cassini mission. Tracy Becker, planetary scientist at the Southwest Research Institute, also where Scott Bolton comes from. And she’s co-investigator on the UV instrument on the NASA Europa Clipper mission. Thank you both for this really terrific conversation. 

TRACY BECKER: Thanks for having me. 

IRA FLATOW: Thank you. 

SCOTT BOLTON: You’re welcome. 

IRA FLATOW: And next week, we’re going to be talking about lightning, in all its shapes and sizes, and want to know what questions you have. Let us know what you’d like to know about lightning by downloading the Science Friday VoxPop app. Tell us what you want to know about lightning. That’s Science Friday VoxPop app, wherever you get your apps. 

And you asked us your sunscreen questions last week, remember? And we have the answers. Go to sciencefriday.com/sunscreen for the science on sunscreen. You can also say hi to us on social media– Facebook, Twitter, Instagram. Every day now is a Science Friday. 

Want to thank all the folks here at Texas Public Radio in San Antonio. We love to visit your city, and thank you for welcoming us and for taking care of us while we’re here. I’m Ira Flatow in San Antonio.

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