Mighty Jupiter Revealed

Mat Kaplan: Mighty Jupiter returns, this week on Planetary Radio. Welcome. I'm Mat Kaplan of The Planetary Society, with more of the human adventure across our solar system and beyond. Scott Bolton is back, the leader of the Juno mission that has spent nearly five years orbiting and revealing Jupiter has great science to report. Scott is also going to tell us a story about Carl Sagan that you don't want to miss. The fun and fascination continue with Planetary Society chief scientist Bruce Betts drops in with another report on the night sky, where there is a lot to marvel at and you might earn a Planetary Radio T-shirt.

Mat Kaplan: Listening to the podcast version of Planetary Radio? If so, you may notice a change. You asked for it, we have delivered. No more commercials. We're on our own now. We may hear about opportunities from The Planetary Society but that's it, and you're welcome. But if you really want to thank us, please leave a review or rating in Apple Podcasts, and share the good news about the solar system and beyond by telling your friends about our little show. Thank you.

Mat Kaplan: Here are a couple of headlines from the May 28th edition of our weekly newsletter The Downlink. We're pretty certain that a vast ocean of liquid water is under the kilometers of ice that blanket Europa. A new computer model of the Jovian moon now points to underwater volcanoes, much like the ones at the bottom of Earth's seas. And you know what's found surrounding those energy sources on our planet, right? Extraterrestrial tube worms, anyone?

Mat Kaplan: Mars science rover Curiosity has delivered tantalizing but still inconclusive evidence for organic salts on the red planet. If they are there, they could be leftovers from extinct lifeforms, or not. Don't you wish we'd get clear data indicating past biology? So does every Mars scientist I know. This has not yet made it into The Downlink, but President Joe Biden's budget request includes a big boost for NASA. You can bet this will come up when Casey Dreier and I bring you the June space policy edition of Planetary Radio.

Mat Kaplan: Dr. Scott Bolton is associate vice president of the space science and engineering division at the Southwest Research Institute in San Antonio, Texas. He is also principle investigator for NASA's Juno mission to Jupiter. He doesn't just oversee Juno, Scott led concept development for the mission's microwave radiometer experiment that peers deep below the swirling clouds of our solar neighborhood's biggest planet.

Mat Kaplan: He spent 24 years at NASA's Jet Propulsion Lab before joining SwRI but he has never ended his deep collaboration with JPL where, for 24 years, he worked on missions, including Magellan, Galileo, Cassini, and as you'll hear if you stay for his delightful story about Carl Sagan, even the Voyager grand tour missions. He received Smithsonian magazine's American Ingenuity Award in 2018.

Mat Kaplan: Scott Bolton, welcome back to Planetary Radio and congratulations on this extensions of the Juno mission. You were about to celebrate your fifth anniversary at Jupiter, 10th anniversary of launch. Now we can congratulate you on the extension to September of 2025, richly deserved.

Scott Bolton: Thanks so much. It worksheet really exciting to hear about that extension. Just putting it together was just an amazing experience because we were looking at the orbit and of course we had all these discoveries that we wanted to address and do more of and get closer to the northern hemisphere. Then we realized that we had the opportunity to go close to the satellites and the rings and the whole mission opened up. I mean it was just like, we're really a full system explorer, it's awesome.

Mat Kaplan: Did you have any hope that things would go so well, that you'd be able to turn away from Jupiter and examine Europa and some of the other moons and those rings?

Scott Bolton: We knew we had the capability when we were launching it originally but we weren't getting very close, in fact we were purposeful staying far away, we didn't want to disturb our orbit and get too close to those, the orbit changes. So we did some distant observations during the prime mission of both the rings and the satellites, we got some interesting images of Ganymede and Io, but I don't think...

Scott Bolton: I mean, I'd love to take credit but I did not have the vision that we would actually completely transform the mission like this. A lot of it is we're basically built like an armored tank. Of course, we were nervous and worried about the radiation environment and eventually hurting the spacecraft, and we really haven't see any hints of any damage yet and everything's working perfectly and that's really what opened the door.

Scott Bolton: So yes, I had a hope that maybe the radiation wouldn't get to us and we'd just keep going around and we'd do more and more Jupiter, but I did not realize that we would have the opportunity to flyby really close to the satellites. And of course, part of that was because we stayed in the orbit that we originally went into.

Scott Bolton: We were in this, originally the plan was to go into this big orbit that was 53 days long and then shrink it down to an 11 or 14 day orbit. That would have eliminated this possibility. Of course, we wanted to do that, and we saw some hints in the rocket system and the fuel system that said there was a little bit of a risk there. We said, "Well, the whole mission will work with this bigger orbit, let's just leave it alone." That opened the door for this extension. Sometimes things happen and you make lemonade out of lemons.

Mat Kaplan: I was going to ask you if staying in this longer orbit had proven in some way to be a blessing in disguise? Well, obviously it has been, but what about for your observations of Jupiter? Have there been other advantages to staying in this orbit?

Scott Bolton: Absolutely. Before we got there, we didn't know that we're going to have polar cyclones covering both poles. When that was discovered, not only are they amazingly beautiful and intriguing, but it's not clear how they're made or how long they are able to be maintained and does the configuration change? Having this longer orbit has allowed us to monitor those over the years, and we've seen things that look like they were going to change there, where a new one was going to come in and sort of opened up, another cyclone had formed, and space started to open up between two.

Scott Bolton: And we thought, wow, there's going to be a new configuration, we're watching one get made. Then we went around again and then by the time we went around again the new one had been booted out. Evidently it's a very exclusive club.

Mat Kaplan: They really do, it's like the existing almost permanent cyclones kick out newcomers, blackball them.

Scott Bolton: Maybe, I'm not sure what it is. We're watching them evolve and one of the exciting things about the extended mission is we have this instrument, the microwave radiometer that actually gets to see below the cloud tops and sort of see the routes of these storms. In the original mission, we're not close enough to the poles, we're close to the low latitudes, but when you go over the poles we're at a larger distance away from the planet. So these microwave instruments don't resolve the storm itself. It sort of mixes it with the surroundings.

Scott Bolton: But during the extended mission, we get much closer to the northern hemisphere and the north pole, and so at some point we'll actually get the beam or the resolution of the microwave instrument to be smaller than the cyclone that we're looking at. So then we'll be able to compare the routes of that with other cyclones and other vortex storms across Jupiter. We'll learn about what's underneath them, which will be fascinating. Not to mention, I mean you already are going to be able to keep monitoring them and learn about how they're structured, how they are made. It's very exciting new science. All based on an unexpected discovery.

Mat Kaplan: Seems to be how it works. Often enough, certainly glad to hear it's happened this time as well. We're going to probably come back to those views of the poles as I ask you about some of the recent science, but I find it just wonderful news that you're not seeing the effects of the radiation that as you said, you feared so much. This must be causing enormous sighs of relief among your colleagues at JPL who are starting to build the Europa Clipper, which is going to face the same challenges.

Scott Bolton: Absolutely, of course they have a different orbit so the radiation that they'll see is a little bit different, but we're in close touch with them, giving them input about how we see the radiation, the fact the lack of us seeing effects from it. We don't see much impact on the solar cells, you also kind of thought that those might degrade. So all of this was sort of an experiment. They're modeled after us, they have a vault, they have the solar cells. So it's really good news to them.

Scott Bolton: Then on top of that, because of the orbit, we're going to actually cross through the region that they actually are going to orbit. Before, we'd been much closer to Jupiter than they would get, so if we measure the radiation it doesn't really help them that much because we're in a different place.

Scott Bolton: But both Clipper and JUICE, the European mission that goes to Ganymede, we're looking at the radiation environment and measuring it and we have very sophisticated fields and particles instruments, so we're going to be able to really characterize the environment for both missions around Ganymede and around Europa. And of course, we'll share that with them and they can update their models, and of course we'll get observations of the moons themselves, which will kind of complement their measurements.

Mat Kaplan: JUICE, of course, the Jupiter Icy Moons Explorer, as you said, from the European Space Agency. Let's go on to some of your own science that is still underway of course. I want to note first, you finished the 33rd pass last April. You must be getting ready for number 34?

Scott Bolton: We are. I think it's June 8th.

Mat Kaplan: Not long.

Scott Bolton: On the 33rd one, we completed our goal for the magnetic map. What we were trying to do was pass by very close to Jupiter at different magnetic longitudes in order to make a map. So the map itself is divided into 32 sections. We had two spare orbits, in case something went wrong we were able to make up a longitude. We used up one spare, back when we were going to change our orbit and fire the engines, and we didn't do it. And we never used up the second spare.

Scott Bolton: So we actually completed that map on the last orbit, which was kind of a celebration that we had finished that. Of course, the next one still gets us great data and we're still going to go by and we're getting incredible images now as you get closer and closer to the poles, the geometry's changing, and you see all these things. So we're very excited about one, completing the 33rd orbit, it's on its orbit, and still not having any radiation effects, we're getting great measurements. And on the 34th one, even though we're still in our primary mission, we've already adopted the orbit because we no longer have to go into Jupiter. Originally, the planetary protection would say if you were ending the mission you should then fire the thrusters and enter into Jupiter in order to protect yourself from crashing into Europa.

Mat Kaplan: As Cassini did?

Scott Bolton: That's right. And we're not going to do that now. Instead, we're going to fly close to Ganymede on June 7th.

Mat Kaplan: Wow. Will you, I know you've got all those other instruments as well, but will JunoCam be able to get some shots as you fly by?

Scott Bolton: Absolutely. Now, of course, we're different than Cassini and Galileo, we don't have a big scan platform, we don't have a telephoto lens or a wide angle. We have JunoCam, which produces incredible imagery for Jupiter but that's what it's designed for. When we go by Ganymede, we will get Voyager/Galileo level resolution images of that surface. I expect it to be spectacular, but we won't get the far away shot that you normally would get because the spacecraft's pointing toward the Earth and Ganymede's literally not in the field of view. But we do get closeup pictures on June 7th which will be really exciting, and we get a lot of other science. We go through the magnetosphere and we fly by in a snapshot, coming from the south going toward the north, so we see something that nobody's really seen before.

Scott Bolton: We'll look at the effects of sputtering on to the moon, we'll go by pretty close, 1000 kilometers away from the moon. So it's closer than the Galileo spacecraft really did. And we'll get spectacular science, we'll also make a map with the microwave radiometer, of the ice. And nobody's ever seen that before, the closest thing we have are radar and VLA type observations of Ganymede from far away a long time ago but they're very low resolution. We're going to make a map at six frequencies and basically interrogate the top 5 or 10 kilometers of the ice.

Mat Kaplan: That's thrilling. I will settle for closeups from JunoCam.

Scott Bolton: We even do a radio occultation.

Mat Kaplan: Oh, no kidding?

Scott Bolton: So we'll look at the ionosphere.

Mat Kaplan: And that, of course, remains to me, still one of the most amazing things that spacecraft are able to do, and to be able to do it from as far away as Jupiter and even further as Cassini did at Saturn, just blows me away. Let's talk about what's happening at those poles. I did read a little bit about the work that's being done on those auroral storms. It's almost romantic, auroral storms at dawn. There are some beautiful, beautiful images and actually sort of a low frame rate video I guess on the Juno site that we will link to, along with a lot of other things that we'll be talking about on this week's show page, at planetary.org/radio. Can you tell us about these beautiful auroras that are so much like what we see at the poles of our planet and still quite different?

Scott Bolton: Yeah, they're spectacular, and we're getting great images, both in the ultraviolet and the infrared. And of course, we have the particle instruments and the plasma wave and the magnetic field so when we go over them we're really looking to match the flux of particles that are going into the atmosphere with the emission that we see in the aurora. So you have this beautiful structure, you see an oval kind of like what we see at the Earth, but then you see these umbilical cords or whatever, these things that are associated with the moons.

Scott Bolton: So they're linking and they're making their own spots in the aurora and we're getting close up and one of the exciting things is as we go closer and closer to the poles over the course of the primary mission and into the extended mission, we're lowering our altitude over those auroral regions.

Scott Bolton: We were surprised, even though we thought we were close enough, the amount of light coming out of the aurora did not match the particles that were precipitating into the atmosphere as far as acceleration goes. And so we believe that it must be below us and fortuitously we're going to keep measuring closer and closer, and eventually we're going to probably be able to see that or explore that region and that's a little bit different than the Earth.

Scott Bolton: There are significant differences between the Earth's aurora. We thought it might be between Earth and Saturn and it seems to be its own beast, but it's quite exciting. We also see the effects of the aurora in the microwave, which was sort of a serendipitous thing. We can actually measure and see it reflecting into the microwave instrument. We are getting to the point in the extended mission where we'll be going over the night side so you would actually be able to make visible light images of that as well.

Scott Bolton: So there's a lot of incredible stuff with the aurora and they're just naturally beautiful. If you ever get a chance to see the Earth's and go up to Alaska or anywhere in the north and you get to see those during the winter and it's dark, it's just dancing lights. I can only imagine what it must be like to hang out in Jupiter's atmosphere and what it must look like looking the other way.

Mat Kaplan: That's a view I would love to see. It sounds like you would too. I get to cross off our own aurora on my bucket list not too long ago and it was spectacular, I recommend it everybody. When you talk about these threads, threads of energy between the auroras at the poles of Jupiter stretching out to the moons, the Galilean moons. Can it be thought of almost like those fun plasma balls you can get at knickknack stores and you touch it and there's a string of energy, glowing plasma between your finger and the center of that evacuated globe?

Scott Bolton: Yeah, it's a little bit like that. I mean, what's happening is, is Jupiter has a gigantic magnetic field and magnetosphere, but the magnetic field lines come out of the poles and go in through the other pole. They go out pretty far away from Jupiter. So the moons are orbiting there.

Scott Bolton: When the moons orbit or the magnetic field is actually going around at about 10 hours and the moons are going around, Io's about a day and three quarters, Europa's a little bit longer. But they're going around in days, let's say. So what happens is is the field spins past them. When the field line connects to the moon, they can transfer particles, literally, back and force, and currents. And those currents and things like that can accelerate particles right into the atmosphere.

Scott Bolton: It works a little bit the same way at the Earth as well, although we have a lot of effects from the solar wind. Jupiter's got a lot of energy internally to its magnetosphere because it's spinning so rapidly around. It's like an engine. What's interesting is you have, in the moons of Jupiter, you have Io which is spewing out volcanoes. You have Europa, which may be outgassing things like water and maybe geysers.

Mat Kaplan: Fingers crossed.

Scott Bolton: And then you have Ganymede, which has its own magnetosphere and magnetic field. So all of those are interacting a little bit different from each other. Ganymede essentially has its own aurora, and we'll look at that. We've seen it already on the 29th orbit. We looked in the UV and saw the glow coming from that. We'll get a little bit closer and get higher resolution in the next few months.

Mat Kaplan: Mind-boggling. Let's talk about lightning, specifically shallow lightning and mushballs, which my colleague at The Planetary Society wrote a really good article about on May 4th, my colleague, Rae Paoletta. Also fascinating and accompanied on the website by this knockout animation, which a lot of people contributed to. We have credit to... Well, I'll let you give credit to them, you know the one I'm talking about right?

Scott Bolton: I do. Of course, I'm always afraid I'm going to leave out a name. I saw that article that your colleague wrote, it was fantastic.

Mat Kaplan: Oh, good, I'll let her know, thank you.

Scott Bolton: In fact, I spoke with her a little bit about it as one of her sources of material but she talked to lots of people. It's a fascinating topic. The link between the lightning and mushballs is fascinating by itself because they were independent efforts. We were working on trying to explain how the ammonia and the atmosphere could be changing so deep in Jupiter, way below where you would see the condensation.

Scott Bolton: Once ammonia reaches a temperature where it all evaporates, it no longer condenses into liquid and no longer has ice, then most theories have it say and most people had assumed that once I get below that I'm kind of below the weather layer, it's just going to mix up, it's a gas. I'm not going to have it turn into liquid anymore, it's too warm.

Scott Bolton: Yet, we see variability in ammonia really deep, and we're trying to figure out how can that happen, what's happening in Jupiter? We were playing with that and there were people trying to play around with it, at first with rain and the rain couldn't do it enough because the rain would only go down until it evaporated and you couldn't really mix it in very well. And I thought, well maybe if we use solids because I live in Texas and you've got hail all over the place and I'm thinking it's very warm and I see a piece of ice laying on the ground and bounce around. In fact, it will break a hole in my table or knock out a roof or dent your car. So it's a very real thing here.

Scott Bolton: So I thought if you made that, it might go down further, so we started looking at that and the scientist that was leading that effort was Tristan Guillot from France. Very brilliant guy and he put together the whole story and had this idea of how you could actually create this. And around the same time that we were presenting that for the first time, Heidi Becker who leads our Stellar Reference Unit, which is the SRU and it's basically a low light camera that we use to navigate, but she uses also to do radiation monitoring.

Scott Bolton: She had taken some pictures of Jupiter and detected lightning. And because we were closer and she had higher resolution than any lightning imager had had before, she detected small lightning. It was smaller than what anybody had seen before.

Scott Bolton: Lightning is just assumed, they calculate the depth of the lightning based on the size of the flash, how big of an image of the light do you see and you assume it starts small somewhere in the cloud where lightning happens and then it just grows as it goes out, like from a flashlight, goes out spherically.

Scott Bolton: So you can see how big it is on the cloud top or wherever you are able to see it and then you can propagate downwards and say well this is where it is. So most of the lightning that Voyager had seen linked to the water clouds, wasn't a big surprise. That's where we expected it to happen.

Scott Bolton: Heidi's detection were smaller, and it was above where the water clouds were and in fact it was above where liquid water could exist, it had to be frozen. There are theories that suggest that in order to get lightning you need three phases, you need the liquid, the ice, and the gas to get the charges right. You can make lightning without it but not at these levels of energy.

Scott Bolton: So I'm looking at that and we're realizing okay, it must be higher up, so what's happening? There's a liquid further up. It must be ammonia, is mixing with the water ice and acting like an antifreeze. And literally creating a new solution, a little bit like Windex, but the old Windex. The new Windex isn't ammonia and water but the old one was. It's an antifreeze.

Scott Bolton: So then I went over, I said, "I think this might be linked to the mushballs, it's another piece of confirmation, sort of a consistent story." And indeed, in the mushball theory you had water ice shooting up in narrow jets and hitting the ammonia and the ammonia is melting it, creating sort of a slushy liquid that then gets made into hail and falls back down. The mushball theory was saying that you needed big storms to do that, but we didn't think that you would have lightning generated from these, that there'd be some other liquid cloud or something.

Scott Bolton: But then when they put in the mushball theory and put in a factor for storms, they more or less reproduced our data pretty well. So these two theories came out around the same time. Heidi put together her paper on the shallow lightning. We call it shallow because it's higher up in the atmosphere, right? And put together this video to try to explain it to people.

Mat Kaplan: Don't you love it when the model fits the data?

Scott Bolton: Yeah. It's amazing. Often you get more questions when you start to do that, and we still have questions and we'll now be able to, in the extended mission, make more and more observations. Also from the night side but we'll get statistics on the shallow lightning and how small it is and that will fold into the theory for mushballs.

Scott Bolton: We also notice, when we look at lightning, because we look at it in different ways. We can see it with the plasma wave instrument, we can see lightning with the microwave instrument, and we can see it with the cameras. We've noticed that it's more prominent in the northern hemisphere than the southern for some reason, it's one of the asymmetries that we've seen, and on top of that it's at fairly mid to high latitudes, there's more of it. So that's right where we're going with the extended mission. It's a beautiful connection.

Mat Kaplan: Absolutely. Stay with us, Scott Bolton has more fresh science from Jupiter, and one of the best Carl Sagan stories you'll ever here.

Bill Nye: Bill Nye the Planetary Guy here, the threat of a deadly asteroid impact is real. The answer to preventing it? Science! And you. As a Planetary Society supporter, you're part of our mission to save humankind from the only large scale natural disaster that could, one day, be prevented. I'm talking about potentially dangerous asteroids and comets.

Bill Nye: We call them near-Earth objects, or NEOs. The Planetary Society supports dedicated NEO finders and trackers through our Shoemaker near-Earth objects grant program. We're getting ready to award our next round of grants. We anticipate a stack of worthy requests from talented astronomers around the world.

Bill Nye: You can become part of this mission with a gift in any amount. Visit planetary.org/neo, and when you give today your contribution will be matched up to $25,000 thanks to a Society member who cares deeply about planetary defense. Together, we can defend Earth. Join the search at planetary.org/neo today. We're just trying to save the world.

Mat Kaplan: I mentioned that video, I only wish we could show it. It's one of those times when I regret this being merely an audio podcast radio show. But we can at least share a bit of the music that backs this fairly short video, although there's a longer clip as well, a flyover of Jupiter. And I do want to give some credit to some of the people behind all of this.

Mat Kaplan: Beginning with that composer, I think we'll use it at the very end of today's show and most of you out there probably have heard of the person behind it, Vangelis. You got him to compose some music for you, your mission, and Jupiter.

Scott Bolton: Absolutely. Well, I've been friends and a colleague of Vangelis for over 25 years. Way before Juno came along. We were already doing stuff together, because I kind of have another hat that mixes science and art and music together. So we were friendly and he had already done things, like he worked with Carl Sagan on Cosmos and shown other music like that.

Scott Bolton: So it was a natural for him but we've stayed friendly. I literally call him up and say, "Hey, we've got this video, what do you think?" He'll say, "Send it on," and the next day we'll put the music out and we'll play around with it. The music's spectacular, he just creates it, he's inspired by what we're sending him literally.

Mat Kaplan: I'd be surprised if he wasn't. And apologies to Vangelis, I guess a lot of people make that mispronunciation.

Scott Bolton: Actually, he's living in France and the way you pronounce it is Vangelis there, or Vangelis.

Mat Kaplan: Of course.

Scott Bolton: So, everybody pronounces it differently. I simply pronounce it the way it's introduced to me in Greek, when we visited him Greece originally, and it's actually a very common name in Greece. When I went to meet him for the first time, there were like three or four people in the house all named Vangelis. It was very confusing to me.

Mat Kaplan: I do want to give credit to a couple of other people who contributed to that.

Scott Bolton: Koji.

Mat Kaplan: Yeah, Koji.

Scott Bolton: And Heidi Becker.

Mat Kaplan: And Kevin Gill.

Scott Bolton: And Kevin Gill, absolutely.

Mat Kaplan: So Koji did this gorgeous animation but some of it was based on images which pop up all over the place, images largely taken from JunoCam, that have been processed by this so-called amateur Kevin Gill, who happens to be a computer software guy at JPL but does this on the side. I have seen other work by Kevin that reveals just how amazingly powerful JunoCam seems to be.

Scott Bolton: Absolutely. Kevin is gifted and has a great eye and is obviously very technically competent, and he's made some incredible contributions to us. We take all the data, the JunoCam data, and we post it for citizen scientists to play around with. Some of them are technical backgrounds like Kevin, although he isn't an imagining analyst, he does that for fun. And that's what's beautiful about the whole JunoCam experience, is you're giving people from all walks of life a chance to go play around and make images. What we post is not an image at all because we're a spinner and it doesn't look like a picture at all, you have to actually figure out how to create it.

Scott Bolton: There's a whole bunch of people like Kevin. Kevin's one of the best but we have a number of people, Gerald Eichstädt, there's a whole list of them. I mean, we literally have thousands of people playing around with the images. Some of them are artists and they're making an image that doesn't necessarily look like Jupiter. It's their image of it or vision and the colors are stretched or the whole image is changed. I've got ones that people have sent me that look like a heart for valentine's day or it looks like a cat, or has astronauts put into it or spacecraft put into it.

Scott Bolton: They literally have poetic license to do what they want, and some of them are made also scientifically correct or with science in mind and we literally use them for that. We've invited people from that, those citizen scientists, to be on papers because they're doing science.

Mat Kaplan: The power of citizen science. Let me bring up one other example of Kevin Gill's work, which was recently published on the website. There are two different views, there's one from 2020 and one from just last April, and it has to do with this thing called Clyde's Spot, discovered by yet another amateur, this time an amateur astronomer, Clyde Foster in South Africa and I saw both of these were also processed by Kevin, and it is absolutely fascinating to see what, I don't know, a year and a half apart, something like that, the development of this storm on Jupiter.

Scott Bolton: Yeah, it was amazing. We have a large effort to coordinate amateur and professional ground-based and Earth-based astronomers to help us. They're watching Jupiter when we're not able to see it or they're seeing it from a different angle and it's been a really successful effort, it's led and coordinated by one of our co-investigators who I asked to do this because he himself was a great astronomer named Glenn Orton, he's at JPL.

Scott Bolton: So Clyde was one of the people that was helping us and doing these things, and he sent out a notice saying, "I discovered this spot, it was kind of near the Great Red Spot, but it was clearly a new storm that nobody had seen." We happened to be flying right over it a couple of days later, and got a closeup view of it. And Kevin and others all analyzed that, it was a beautiful storm, and had this incredible oval shape, and then about a year later, a little more, we went over the same thing and it had changed dramatically in its shape and its contour. It's got all these folded filaments that are sort of folding in on each other, and it's still beautiful but in a different way.

Scott Bolton: So we put together a press release that showed both, then and now, and we involved Clyde again and of course Kevin was involved, and it's amazing that we're lucky to be there that we can get closeups and watch how these things evolve. The Great Red Spot itself is changing while we're there. It's shrinking and things are changing and you're seeing how that happens, but Clyde's spot was a spectacular example of the advantage of having Juno there seeing how Jupiter really works.

Mat Kaplan: And we'll include a link at planetary.org/radio. Great Red Spot, sure. What's up with this cousin of the Great Red Spot, the Great Blue Spot?

Scott Bolton: Yeah, so that's actually a magnetic feature. So when we map out the magnetic field, we saw this feature that was almost serving almost like a pole. It had a lot of flux going in, so we called it the Great Blue Spot. It's near the Great Red Spot, in the sense that it's just a little bit south, but of course the Great Blue Spot moves around with Jupiter's rotation. The magnetic field basically defines Jupiter's spin, so it's moving around the whole planet every 10 hours or so. So it's tied to a specific magnetic longitude, if you will.

Scott Bolton: The Great Red Spot is literally blowing in the wind and so it moves with respect to the Great Blue Spot, it doesn't stay in the same place relative to it.

Scott Bolton: But one of the more amazing things about the Great Blue Spot is as we got closer and closer and got enough passes that went over it, we mapped it out magnetically, and you could see that in the north it was sort of treading between two jet streams, one going to the right and one going to the left, or one going east, one going west. And you could see that as you got better resolution of that Great Blue Spot, that the one that was tied to the jet stream that was moving easterly was distorting the magnetic spot in that direction, it was being sheared. And the one on the bottom, which was tied to a jet stream going the other direction, was being sheared the other way. When we discovered that and realized it, it was really direct evidence that the deep atmosphere was messing with the magnetic field.

Mat Kaplan: Which just sounds crazy, how can wind be changing the magnetic field? Well, you have a theory about that, right, or a hypothesis?

Scott Bolton: That's right. Well, what you need is you need the wind to be penetrating down deep enough into Jupiter where the atmosphere becomes conductive. So eventually, I go down and the atmosphere has enough conductivity. In fact, at some point, that's where the magnetic field is getting generated, but probably deeper than we're seeing. And this is deeper than what we can see with the microwave radiometer.

Scott Bolton: But we'd already detected that the zonal jets go down at least as far as we could see with the microwave, and the gravity field was able to see the asymmetry of the zones and belt structure sort of was mirrored in the gravity field and we estimated 3-4000 kilometers and below that maybe Jupiter was rotating around as a solid body and above that it had these cylinders.

Scott Bolton: But somewhere, you get into a region where it's conductive, where there's enough charged particles in the atmosphere to literally conduct electricity, electromagnetic fields, and the winds must be penetrating down at least that deep.

Mat Kaplan: What a world. This captures most of the most recent stuff that I've been able to discover coming out of your data and these amazing images. What have I missed before we go on to a couple of other less Jupiter-related questions I have for you?

Scott Bolton: Well, there's the puzzle of the dilute core, which I think we've talked a little bit about before.

Mat Kaplan: Yes, we have.

Scott Bolton: But we continue to model that. It's very puzzling. The theorists are a little bit behind the data in the sense that we see the evidence in the gravity field that the core must be fairly large and dilute without sharp boundaries. We were originally set out to figure out whether there was a compact core of heavy elements in the center or none, and it was going to help us understand how Jupiter formed. Did you form it by creating a bunch of asteroids or rocky things and then have the atmosphere collapse on top of it?

Scott Bolton: And instead, we see this diluted core, sort of fuzzy, and it's quite large and it's not clear how you make a Jupiter like that. It's not clear that you could start with a compact core and have it evolve to that. So it's kind of a puzzle. One of the theories is that maybe Jupiter was hit pretty hard early on, enough to shake up its core a bit. And to me, I don't find that hard to believe because I think things are probably hit often throughout the history of our solar system. Certainly we think that happened with the Earth and moon.

Scott Bolton: But hitting Jupiter and you've got to hit it with a big enough piece that you've affected its core, and Jupiter's pretty big, so it had to get hit pretty hard to do something to it. And recently, people have started looking at Saturn and doing seismology with the rings and there's a paper out there that suggests it might also have a dilute core. So maybe we're learning something about giant planets in general, they're not like we think. That's, I think, a theme of Juno is rewriting the book on Jupiter because when you get up close, the deep atmosphere didn't work how we thought, the poles didn't work the way we thought, the aurora doesn't work the way we thought, the magnetic field doesn't seem to work.

Scott Bolton: So we kind of had to eat some humble pie and say okay, from far away it looks like one thing and when you get up close those theories don't always hold up. So the dilute core I think is still a field of active research, even though we suggested it a while ago, it's a new result to this day and there are models still going on trying to match it out and understand the equation of state. We're right at the edge of our understanding of even how hydrogen behaves under great pressure and temperature. We're but umping into our knowledge of fundamental physics, basically.

Mat Kaplan: Ain't science great? The only thing that would have surprised me would be if there hadn't been any surprises revealed by Juno. Let's come back to Earth as we go into the home stretch here. I introduced you upfront as associate vice president at SwRI, the Southwest Research Institute, which is a name that comes up pretty frequently on this program and elsewhere. You head that division, the Space Science & Engineering division. Can you tell us a little bit about SwRI and what your division does?

Scott Bolton: Absolutely. It's Space Science & Engineering, we do a lot of both, all related to space exploration. Besides Juno, obviously there's a whole team of scientists that are working on different fields. They've built a couple of instruments that were on Juno, the plasma instrument which we call JADE, and the ultraviolet instrument, which is called UVS were built at Southwest Research Institute in San Antonio.

Scott Bolton: They have a copy of that, copy of the ultraviolet instrument, on the ESA mission JUICE that goes to Ganymede. They have another copy of it, also on the Europa Clipper. I say they're copies, they're not exact copies, but they're similar. Sort of the next evolution of the instrument. They also built the mass spectrometer on Clipper, one of the most important instruments that are going to measure the composition of Europa and see how the organics and the potentials for life there.

Scott Bolton: So they do quite a bit of science. They also run the science team for the Magnetospheric Multiscale Mission called MMS, which is orbiting the Earth. A lot of our work studies the magnetosphere and the aurora of the Earth and they've done quite a few missions and contributed to different things that orbit the Earth and study the heliosphere, the magnetosphere of the Earth.

Scott Bolton: Then we have another office in Boulder, and of course that's where New Horizons, the mission that went to Pluto is led out of. They also do some Earth orbiting stuff, there's a mission being developed there called PUNCH, that's fantastic. And in fact, we also did some of the first small spacecraft where we have a mission that studies the hurricanes, and we have a constellation of very tiny spacecraft that are all invented and built in one of our engineering divisions. So that's a very broad organization and services NASA in a lot of different ways.

Mat Kaplan: Busy place. I want to turn to your earliest days at the Jet Propulsion Lab, we mentioned upfront that you had years there of course before going to SwRI, and of course you still work closely with JPL on the Juno mission. But I want to take you back to the very beginning and a story that we have tried to tell in the past on this show, which is going to be as delightful to a lot of folks out there who are Carl Sagan fans as it was to me when you first told it to me. I think you first told it to me sitting in a lunch room at JPL. Tell us about this interaction that you had as a very young scientist with Carl?

Scott Bolton: Yeah, that's a fond memory of mine. So, I graduated with an aerospace engineering degree out of University of Michigan, and I went to JPL in the summer of 1980. I was attracted there because somebody came and gave a talk at the University of Michigan about Voyager, and I wanted to go to another star and I went, we that place is going the furthest, I got to go there.

Scott Bolton: So I went to work there and of course I got there just in time to see Voyager going past Saturn. I might have missed the first one but I got in time for the second one, I don't remember the exact timing, but it was very quick. Of course, the place was on fire with press. I mean, I would drive in and there would be trucks with antennas and things all lined up outside, it was a real heyday for the press and the media and I was amazed at what was going on, and you'd go in in the middle of the night and you could go into the cafeteria and watch the pictures of Saturn.

Scott Bolton: They would publish what picture was coming down when and I would go in in the middle of the night with friends and we would just watch them and it was amazing. And of course, everybody... I wanted pictures, I wanted to get my own versions of the pictures, and I found out where the laboratory was to actually make the photos and I would hang out there and I would get some that way. Even though there was always a shortage of photos because almost everything they were making went to the press and media.

Mat Kaplan: This is pre-digital, of course.

Scott Bolton: Well, it wasn't pre-digital but it was the early days of the internet and so you didn't have the same thing. When I first got there I was still programming in Fortran and you didn't really have email, they were just starting to make these networks. So yeah, everything was hard copy and certainly all media people weren't using computers yet. I'm old, right? There were no cellphones back then. I wasn't very far from typing in on cards in order to run a program, and the computers were big and heavy. The calculators were big and heavy even.

Mat Kaplan: Yeah, I remember.

Scott Bolton: This is something my kids have no concept of. So anyway, I'm there and I'm trying to get these pictures and I'm sneaking around and it was hard to get them. Eventually I found where the media offices were, which were in the administration building almost up on the top floor, one of the higher floors, and they were saturated, they would have boxes and boxes of these photos and lithographs that they would hand out to the press and media.

Scott Bolton: So I would hang out there hoping I could pick up a scrap or something that tore and nobody wanted or got folded or whatever it was. But I didn't always follow the rules completely, so I found myself in there in the middle of the night one night. The lights were out and the door was unlocked and I walked in and I'm looking around in the dark because there's guards around and I didn't want to get in trouble but I thought well maybe I'll find some photos that nobody wants or something laying on somebody's desk and I'll get a souvenir and I'm going to be able to see the pictures.

Scott Bolton: Even if I didn't take it, I just wanted to look at them, right? And there's no phone, I've got an old fashioned flashlight and I'm looking around trying to stay quiet. I hear a noise out in the outer office, and I'm already in the inner ones, and I'm like oh no, I'm going to be in trouble. So I hide behind a desk. Turn off the light and I'm waiting.

Scott Bolton: And I hear somebody shuffling around, also no lights are on. They're doing it with a flashlight too. So eventually I get enough confidence that I'm thinking, this person's not supposed to be here either or they would just turn on the light. They're not going to get me into any trouble. And maybe they know where something is, you know?

Scott Bolton: So I finally get enough courage to step up and I said, "Oh, you must be looking for pictures too." And the voice comes back and said, "Yes I am," but it wasn't an ordinary voice. Right away, I heard that it was Carl Sagan, and I knew. When I heard that voice I was like oh my gosh. So I said, "Are you Carl Sagan?" We're still in the dark. And he said, "Yes." And I said, "Oh my god, I'm a huge fan of yours. What are you doing here?"

Scott Bolton: He goes, "I'm looking for pictures." I said, "But you can get anything you want?" He goes, "No, I can't, they all go to the press and I have all these interviews in the morning and I can't get them, I'm trying to prepare." And he goes, "And they won't give them to me." I said, "Are you kidding?" I said, "Well here, here's some I found." He's looking through them and he goes, "Well, here's some I found."

Scott Bolton: And we started comparing notes and trading pictures, and I said, "I can't believe you're up here in the middle of the night." He goes, "Yeah." And he said, "So tell me about yourself?" I said, "Well, I'm an aerospace engineer but I'm starting to go back to school, I'm going to study physics at Caltech, I'm going to try to be a scientist, I started working on Halley comet missions."

Scott Bolton: He said, "Oh, that's what you should do, go back to school as soon as you can, get as much degree as you can as early as possible." He goes, "You're doing the right thing here, this is great." It was an introduction kind of in a funny way but we stayed friends after that, it was such a bizarre introduction. He stayed in contact with me, checking on me. And when I went to take classes and I was at Caltech for a while, then I was thinking okay, the advisor I was working with moved and left, and I said, "I'm thinking of going up to Berkeley," and I talked to him about it and he goes, "Oh yeah, that's good, you should go up to Berkeley, they're fine. Caltech's great too, you could be at either one."

Scott Bolton: In fact he even said, "What about Cornell, have you thought about that?" I said, "I'm trying to stay close to JPL so I can go back and forth." But he stayed in touch with me and we traded science papers and different things. He was a great advisor and incredible friend. The funny thing was is later I started working with Vangelis, who had worked with Sagan, and the whole time I was talking to Sagan Vangelis never came up. It was just a coincidence that we both ended up there. It's a great story because it was Carl Sagan and who would think you would meet him in the dark?

Mat Kaplan: With flashlights. Scott, if that isn't the best Carl Sagan story ever it's right up there. I have to think that Carl would be very proud to see how rather than forcing people to skulk around with flashlights in the dark, you are making data and images available of this magnificent planet for all to see and work with and I am so glad that it's going to continue for many more years, at least until September of 2025.

Scott Bolton: Thank you very much, yeah. That's it. I want to share it with everybody.

Mat Kaplan: Thank you Scott, it's always a delight to talk and I look forward to checking in again as Juno continues to whirl around that big world.

Scott Bolton: Thank you, it's always a pleasure to chat with you.

Mat Kaplan: Same here. Scott Bolton is a Southwest Research Institute associate vice president and principle investigator for the Juno mission. Time for what's up on Planetary Radio. Here is the chief scientist of The Planetary Society, Bruce Betts. Welcome.

Bruce Betts: Hey Mat, good to hear you.

Mat Kaplan: I have a message that you'll like, it came from Brandon Gaskins, he says, "I just moved across the country from Mount Rainier to Acadia National Park area in Maine. Listening to you and Bruce definitely made it an easier drive."

Bruce Betts: Oh, how nice. That sounds like a lovely place.

Mat Kaplan: Yeah, road trip. He took us across the country with him. But do you know what's even better? I'm going to be visiting Maine and Acadia National Park for the first time in October. I'll see you there, Brandon, because I'm sure we're bound to run into each other.

Bruce Betts: Do you just plan your trips based upon listeners' emails?

Mat Kaplan: Just now, just in the last few minutes, yes.

Bruce Betts: "I've moved to the seventh circle of hell." Oh, I'd love to vacation there.

Mat Kaplan: I hear the air conditioning is out most of the time but otherwise it's okay. Hey, what's up?

Bruce Betts: So anyway. As I attempt to recenter my brain. We've got good stuff to look at in the evening sky over in the west. Venus getting higher and higher, it's still low so you want to look soon after sunset, low in the west, Venus as usual. Super bright. And Venus is, as it gets higher, will be hanging out next to the moon, the crescent moon on June 11th, and then on the 12th the crescent moon will be between Venus and the much dimmer, reddish Mars, and on the 13th crescent moon hanging out next to Mars.

Bruce Betts: Mars has a fun lineup going up, looking reddish and like a kind of bright star. It will actually, on June 7th, but in a nice line with Castor and Pollux, the twin stars of Gemini, all about the same brightness, Mars much redder.

Bruce Betts: We've also got, for some of you in the world, an annular solar eclipse. So where the moon does not completely cover the sun but if you're in the right place you get the outline of the sun around it. Please use safety glasses, it is never safe to look at an annular eclipse without them. That'll be on the 10th of June and visible from... at least partial eclipse will be visible from central and eastern portions of Canada, Greenland, Russia, and northeastern US and Europe, and Europe's also going to get some of the partial. The actual annular eclipse is pretty limited to northern Canada across Greenland and Russia. That's June 10th, check it out or if you don't live there I'm sure there'll be some lovely webcasts.

Mat Kaplan: Have fun, folks. Wear that protection.

Bruce Betts: Pre-dawn still got Jupiter and Saturn, Jupiter looking really bright, Saturn looking yellowish and there hanging out over in the southeast, in the pre-dawn. We move on to this week in space history, 50 years ago Surveyor 1 was launched, the first soft landing on the moon by the US leading robotic precursors to the Apollo landings later on. And in 2003, Mars Express launched on its way to Mars and it's still working, still doing great for the European Space Agency.

Mat Kaplan: Just amazing, amazing longevity. And it sounds like, from what Scott Bolton was telling us, Juno may have the same kind of luck, at least until it runs out of gas.

Bruce Betts: Yeah, that's great. We'll have a related fact in just... What, right now, random space fact! So Juno, which you may have heard of moments ago, has big giant solar arrays, which you may have heard about a little bit recently. The active solar cell area of the solar arrays is just slightly under 50 square meters. That is for the completely Planetary Society obsessed among you, 55% larger than LightSail 2's solar sail, the sail at 32 square meters, just the solar cells are bigger for Juno.

Bruce Betts: Now, Juno is over 300 times more massive and out at Jupiter where there's 125th-ish as much sunlight. It's not doing a lot of sailing but it gives you a comparison, they're big. Big, big solar arrays.

Mat Kaplan: I love it, I love all of that, that's fantastic. And man, they may just keep spinning around up there and generating power for a long time to come. So yeah, good stuff.

Bruce Betts: Good stuff. Well, let's continue the good stuff and go on to the trivia question. I asked you what is the most massive star within 10 light years of Earth.

Mat Kaplan: Our winner, first time I think, is Cody Roxwald. Cody Roxwald, in Florida, said that it's Sirius A, Alpha Canis Majoris A, the dog star. Little bit more than two solar masses. He adds, "Thank you or making me learn more about the known universe, can't wait to learn about the unknown." Congratulations, Cody. You're getting a Planetary Radio T-shirt from chopshopstore.com where The Planetary Society has its store. And Bruce is modeling it for me right now. You'll just have to imagine how stunning it actually looks on him.

Bruce Betts: Oh my.

Mat Kaplan: I've got more. Devin O'Rourke in Colorado knew how to get to us. "Sirius A, although you and Bruce are pretty big stars to me." We're within 10 light years. Bert Caldwell in New York, "Our sun, Sol, would be in fourth place with Alpha Centauri A in second and Sirius B in third." Several people, not a lot, but a few mentioned the sun, but you did say the biggest star within 10 light years, so you did just fine.

Bruce Betts: Actually I said the most massive star, the massive star.

Mat Kaplan: Ah, okay, that's better. Matthew Eastern in Virginia gave us a long list with Wolf 359 at 11th place. Wolf 359 I guess is going to have to wait for the year 2367 to be know to for anything important. That's just a little gift for you Trekkies out there.

Mat Kaplan: Torsten Zimmer in Germany, obviously is reading Andy Weir Project Hail Mary, he says, "All in all a nice star, but like so many in the neighborhood, it will soon be infected by astrophage which will significantly bring down the real estate value." You have to read the book, you've got to read the book.

Mat Kaplan: Thomas Pue in Virginia, "I seriously had a ruff time finding the answer to this one. I had to hound my computer for the answer, but in the end it was a doggone good star. I give it a solid A."

Bruce Betts: Well, I'm wagging my tail at that one.

Mat Kaplan: I thought you'd like that one. Hey, in the space poetry corner this week a first time entry from very long-time Planetary Radio listener, Homer, who lives in Ionia, Greece. "Sirius rises late in the dark liquid sky on summer nights, star of stars. Orion's dog, they call it. Brightest of all. But an evil portent bringing heat and fevers to suffering humanity."

Mat Kaplan: Okay, that excerpt is from The Iliad, it was actually submitted by the very much alive Christopher Beck, also in Virginia. Virginia well-represented. But we went classical for the poem this week.

Bruce Betts: Yeah, it got really dark in a hurry. That's what makes it a classic.

Mat Kaplan: Boy, Star Trek and Greek classics in one what's up segment. We're ready to go on to another contest.

Bruce Betts: I'll try not to add anymore popular or classical culture while I do this but you never know. So as of now, June 2021, how many of the nine spacecraft that have visited Jupiter are still communicating with Earth? We've had flybys, we've had a couple orbiters, technically if one dropped a probe you could consider that 10. But of the spacecraft that have visited Jupiter, how many are still communicating with Earth as of now? Go to planetary.org/radiocontest.

Mat Kaplan: I think I could do this one. I might enter. You have, and so do I-

Bruce Betts: I keep telling you you're not eligible.

Mat Kaplan: Oh, yeah. All right, you have until Wednesday, January 9th at 8:00 AM pacific time to get us the answer, and win yourself one of those aforementioned Planetary Radio T-shirts. That's it, we're done.

Bruce Betts: All right everybody, go out there, look up at the night sky and think about why Mat keeps getting the trivia contest wrong every time he enters. Thank you and goodnight.

Mat Kaplan: I'm never giving up. It's only been 1004 shows? I'm never giving up. He's Bruce Betts, the chief scientist of The Planetary Society who joins us every week here for what's up. Planetary Radio is produced by The Planetary Society in Pasadena, California, and is made possible but its jovial members. Join our party at planetary.org/join. Mark Hilverda is our associate producer, Josh Doyle composed our theme, which is arranged and performed by Pieter Schlosser. Ad astra.