Ep. 594: Juno – Primary Mission Highlights

Pamela’s always loathed to talk about spacecraft until the mission’s in space and the science is rolling. NASA’s Juno mission just received a mission extension, adding Jupiter’s moons to the menu. Now, finally, we can talk about Juno.

Next episode: Planet Hunting (Updated)

Download MP3 | Show Notes | Transcript

Show Notes


NASA’s Juno Mission Expands Into the Future (NASA JPL)

New Frontiers Program (NASA)

Discovery Program (NASA)

Planetary Mission Program Overview (NASA)

Radioisotope Thermoelectric Generators (RTGs) (NASA)

Voyager (NASA JPL)

New Horizons (NASA)

Galileo (NASA)

Cassini (NASA)

Mars Curiosity Rover (NASA)

Perseverance Rover (NASA)

2018 Giant Dust Storm on Mars (NASA)

Opportunity’s Mission Is Complete (NASA)

Juno’s Solar Cells Ready to Light Up Jupiter Mission (NASA)

Juno Spacecraft and Instruments (NASA)

Junocam (SwRI)

Juno Solves 39-Year Old Mystery of Jupiter Lightning (NASA)

Seán Doran (Twitter)

Kevin M. Gill (Twitter)

Jason Major (Twitter)

NASA’s Juno Navigators Enable Jupiter Cyclone Discovery (NASA)

Jupiter’s Cyclones Exhibit Strange Rotations (PSI)

A Hot Spot on Jupiter (NASA)

Ganymede (NASA)

Jupiter’s Moon Ganymede (Universe Today)

Europa (NASA)


Juno Awards

Cataclysmic collision could explain Jupiter’s fuzzy core (Science Magazine)

‘Diamond rain’ falls on Saturn and Jupiter (BBC News)

Juno Data Indicates ‘Sprites’ or ‘Elves’ Frolic in Jupiter’s Atmosphere (NASA JPL)


Transcriptions provided by GMR Transcription Services

Fraser:                         Astronomy Cast Episode 594: Juno. Welcome to Astronomy Cast, our weekly facts-based journey through the cosmos, where we help you understand not only what we know, but how we know what we know. I’m Fraser Cain, publisher of Universe Today. With me as always is Dr. Pamela Gay, a Senior Scientist for the Planetary Science Institute, and the director of CosmoQuest. Hey, Pamela! How you doing?

Dr. Pamela Gay:         I’m doing well. How are you doing Fraser?

Fraser:                         I’m doing great. Same as it ever was.

Dr. Pamela Gay:         It is one of those groundhog day – I think it’s day 340 of March 2020 at this point.

Fraser:                         Yeah, exactly. Yeah, I’m even tired of just making the joke that time has no meaning, and that it is Groundhog Day. I’m so beyond it. We’re just getting through, rolling, getting work done, communicating the universe, having a good time. All right, here’s the show. I got no fancy announcements. Nothing interesting.

Dr. Pamela Gay:         Life goes on.

Fraser:                         Life goes on. Now, Pamela is always loathed to talk about spacecraft until the missions in space and the science is rolling. NASA’s Juno mission just received a mission extension, adding Jupiter’s moons to the menu. Now, finally, we can talk about Juno, which we will do in a second. But first, let’s take a break. And we’re back. Juno mission. What is it?

Dr. Pamela Gay:         It is a Frontier’s class spacecraft that is the furthest out solar-powered spacecraft we have so far launched, with some of the biggest solar panels made for an interplanetary probe. And it has journeyed its way across the solar system, put itself happily in orbit around Jupiter, and it’s sending back amazing data that reading through its science, I have to admit it just makes me smile.

Fraser:                         Mm-hmm.

Dr. Pamela Gay:         It’s exploring the innards, the outers, and the electrical fields around –

Fraser:                         Right.

Dr. Pamela Gay:         – Jupiter.

Fraser:                         All right, so I wanna talk about a couple of things that you mentioned first. So, you say that it’s a Frontier’s class mission. So, what does that mean?

Dr. Pamela Gay:         It’s the size of the budget it gets essentially. And when you look at missions that NASA funds, you have the Discovery class missions. These are often testing new concepts, doing high-risk things. You have the Flagship missions. These are the giant extraordinarily expensive things that we count on to advance science. And then the Frontiers missions are somewhere in-between. So, this is one of those in-between missions that’s made out of fairly mature technology with an expectation that it’s gonna succeed and do some awesome science. And you know what? It has done exactly that.

Fraser:                         Right. And then the second thing that you mentioned is that it has solar panels.

Dr. Pamela Gay:         Yes!

Fraser:                         And when we think of spacecraft, we think they all have solar panels. But this is very unusual for an outer solar system spacecraft. The first of its kind.

Dr. Pamela Gay:         That is an understatement.

Fraser:                         Yeah.

Dr. Pamela Gay:         We have sent all sorts of things out to the outer solar system, sending many of them before you and I were even born. And all those prior missions had some form of radio thermal generator. They had a radioactive fuel source that through its decay is releasing heat. And that is powering those spacecrafts. Now, for a long time, the US wasn’t producing the kind of radioactive materials that we need to power spacecraft like Voyager I, Voyager II, New Horizons. Even Galileo and Cassini all had these nuclear engines.

Fraser:                         Curiosity. Perseverance.

Dr. Pamela Gay:         Exactly. Now, Curiosity and Perseverance could have used solar panels. Mars is –

Fraser:                         Sure.

Dr. Pamela Gay:         – our boundary condition. But it’s because of that radio thermal generator that Curiosity has that it was able to survive the massive dust storm that struck Mars a couple of years ago, even though poor little Mars Exploration Rover Opportunity just wasn’t able to make it. Now, with Juno, we had that lack of materials to make another nuclear engine, and we have new innovations in solar power, new innovations in batteries. And, in designing this mission, they designed it with the biggest trio of solar panels put on something leaving Earth’s orbit.

Fraser:                         So, one thing that I find really interesting is that essentially, the amount of electricity that you can generate at the orbit of Jupiter is 1/25th the amount of power that you can generate at Earth. So, if you want solar panels – you think living in Canada is hard for you to power your house with solar panels, try living at Jupiter. So, in other words, if you want the equivalent amount of power, you need 25 times bigger. How big are the solar panels on Juno?

Dr. Pamela Gay:         I have absolutely no idea.

Fraser:                         They are the size of a tennis court.

Dr. Pamela Gay:         So, we have tennis court-sized solar panels on a spacecraft that my basement lights draw more energy than that spacecraft is able to generate. And so, here we are, out at Jupiter, five times further away from the sun loosely than the earth is, 25 times less solar radiation hitting you than at Earth roughly. So, with Juno, we have a mission that panel tip to panel tip, spans 20 meters with this trio of solar panels.

And those solar panels, while amazing and powerful, because this mission is roughly five times Earth’s distance away from the sun, because it’s receiving roughly 25 times less energy from the sun than we get here at Earth, those panels are producing less energy than it takes me to power all of the equipment in my basement studio.

Fraser:                         Yeah. Yeah, you would drain that spacecraft just running your computer and a couple of lights.

Dr. Pamela Gay:         And they’re able to do the most amazing things with everything that they do on this mission. They have plasma detectors. They have particle detectors. They have equipment for mapping the gravitational field around Jupiter. They have JunoCam that does optical images. They have sensors for doing microwave ultraviolet. Everything they do with all of those instruments, and all of the power necessary to send all of that information back to Earth on this antenna, all of that comes from those three magnificent solar panels.

Fraser:                         And you mentioned a bunch of interesting instruments. One that almost didn’t fly was a camera. But we will –

Dr. Pamela Gay:         Yes.

Fraser:                         – talk about that in a second. But first, another break.

Dr. Pamela Gay:         Hi, this break is being brought to you –

Fraser:                         By coffee! Hello to our friends on Twitch. This –

Dr. Pamela Gay:         All right.

Fraser:                         – episode is brought to you by people watching us on Twitch. Not to mention the people on YouTube. We always forget about the Twitch. And we’re back. You talked about the instruments – let’s talk about some of the science. So, what is the purpose then? What do scientists want to know about Jupiter? What questions will Juno help answer?

Dr. Pamela Gay:         So, Jupiter is designed to help us map out the interior of Jupiter, figuring out its structure, figuring out what is the content of the clouds at various altitudes? And to finally start to understand some of the things we saw with earlier missions like lightning strikes that didn’t match quite what we were expecting, because we were only catching parts of what was going on with the Voyager missions. So, what is the electrical environment in the clouds, and what is the structure beneath? None of which require pretty pictures to be taken.

Fraser:                         Right.

Dr. Pamela Gay:         Those were the original things that it was out to study.

Fraser:                         Right. And if people I’m assuming are pretty familiar with these absolutely gorgeous pictures of Jupiter that are shared on the internet, both from NASA but as well as just a huge group of citizen scientists. Seán Doran, –

Dr. Pamela Gay:         Kevin Gill, Jason Major.

Fraser:                         Kevin Gill, Jason Major, yeah. A lot of people who just do astonishing work with this. That mission almost didn’t go with a camera on board.

Dr. Pamela Gay:         It’s true. There was a somewhat last-minute decision made, that as part of the education and public outreach for this mission, they’d essentially toss on a optical color camera that they were going to allow – much like HiRISE does with its citizen science efforts – they’d allow everyday people to propose, “Can you please take images of.”

Fraser:                         Mm-hmm.

Dr. Pamela Gay:         And JunoCam would be used to take these images that could be used for education, and meteor relations.

Fraser:                         And not surprisingly, people figured out how to use it for science.

Dr. Pamela Gay:         And it’s a really lucky thing that this mission had that camera, because unlike Galileo and the Voyager missions, Juno is set up to pass over the pulse of Jupiter. It’s in a polar orbit. It turns out, the polar regions of Jupiter have strikingly beautiful cyclones that move and have color profiles that are like nothing we’ve seen elsewhere in the world. So, there are these beautiful blues and whites. And this is a reflection of the different chemistry that’s there. And it’s with JunoCam that we’ve been able to piece together counter-rotating cyclones in some places, where you have two cyclones side-by-side –

Fraser:                         Wow!

Dr. Pamela Gay:         – going in different directions as they’re in different bands. It’s using it that we’ve been able to start to piece together the relationships between different features, the hot spots and the storm fronts that we see. It became a science instrument.

Fraser:                         Yeah, and there’s an interplay between the citizen scientists, the people who are the image processors –

Dr. Pamela Gay:         Yeah.

Fraser:                         – and the scientists working back and forth, where the images are finding these really interesting features on the – you talked about the cyclonic action, these various –

Dr. Pamela Gay:         Yeah.

Fraser:                         – storms that are interacting with each other right along the edges of the storms. And then they’re putting this information back to the scientists. And then they’re looking through this, and they’re coming up with ideas, and then the image processors – I’m talking about human beings here –

Dr. Pamela Gay:         Yeah.

Fraser:                         – are highlighting those features. And you’re getting this really wonderful interplay between the two. Now, you talked about this orbit that Juno is doing, taking it above and below, I guess the poles of Jupiter. How is that different from traditional views that we get of a planet like Jupiter?

Dr. Pamela Gay:         Well, what we have historically done with Jupiter, with Saturn, is we’ve been in much more of an equatorial orbit, where we were focused on what is happening on the main body of the world. And in fact, here at Earth, the majority of our satellites are going round and around roughly the orbit. It’s often tilted a little way one or the other, so you’re going back and forth as that ellipse goes around the planet. With Jupiter, they simply put Juno in a highly inclined, and also a very elliptical, a strongly flat oval-shaped orbit. This wasn’t entirely intended, but it has the benefit of allowing us to get those close-in images, and then also be far out and get everything in context.

Fraser:                         Right. And avoid the horrible radiation environment that is close to Jupiter.

Dr. Pamela Gay:         Exactly. It’s a beautifully designed mission.

Fraser:                         Yeah. So, one of the things I think that encouraged us to put this on the docket was that Juno has now been at Jupiter since 2016. We’re four years into the mission now, and it’s time for its mission extension, which was announced just a couple of days ago.

Dr. Pamela Gay:         This is actually its second extension. It was originally extended until the summer of this year. And now, it has extended all the way out until September 2025. And with that extension, they’re going to be changing the orbit ever-so-slightly over time, allowing it to get more and more detailed images of some of these worlds we haven’t gotten to explore the way we wanted to. We’re going to be seeing the mission going in and getting better looks at Io, getting better looks at Callisto. All of these different worlds, it’s in one part a bittersweet set of orbits, because when it’s done, they are going to suicide the mission into the surface of Jupiter.

Fraser:                         Right.

Dr. Pamela Gay:         But as they decrease the orbit on this mission as they extend it over time, they’re going to be getting more and more detailed images of three particular of Jupiter’s moons. Ganymede, Europa, and Io. Ganymede is Jupiter’s largest moon. It’s one of the largest small bodies in our solar system. It’s actually bigger than the planet Mercury. It is thought to have significant subsurface water. And so, here is one of those places that just might have the stuff capable of life. Maybe.

Fraser:                         We mentioned this before. I’m of the opinion Ganymede is the new hotness. Ganymede is the new Europa. Everyone’s excited about Europa, but Ganymede has an intrinsic magnetic field. It’s the only other place in the solar – it’s the only other smaller object in the solar system. The only moon in the solar system with a magnetic field. You’ve got Jupiter and Saturn obviously, but – and Earth – but you’ve got Ganymede.

It has the same kinds of layers of ice and some subsurface ocean that Europa does. But it’s farther away from Jupiter, and it doesn’t have as terrible a radiation. Plus, it has a magnetosphere. It’s a very interesting place. And the last time that we saw it up close was, what? Galileo? And Galileo didn’t even have a good antenna to be able to communicate its findings back home to Earth.

Dr. Pamela Gay:         And Galileo ceased to be in the early 2000’s. We’re now essentially 20 years later.

Fraser:                         Mm-hmm.

Dr. Pamela Gay:         And now, we get to go back. And it’s not just Ganymede. For those of you who are still team Europa, I’m one of you. And this mission has your back. It’s also going to be getting up close and personal with Europa, and then of course that volcanic favorite Io, which with its position a little too close to Jupiter you might say, it’s basically an oozing lava ball of myriad volcanoes that are constantly erupting.

Fraser:                         Yeah.

Dr. Pamela Gay:         And we’re gonna get better images of that as well, before they finally crash the mission on purpose –

Fraser:                         Mm-hmm.

Dr. Pamela Gay:         – into the atmosphere of Jupiter to make sure they don’t contaminate any of these worlds that just might support life.

Fraser:                         Do you know what the name comes from for Juno?

Dr. Pamela Gay:         So, there’s debate on this. The Juno team claims that it is named strictly after Zeus’s wife.

Fraser:                         Mm-hmm.

Dr. Pamela Gay:         But there’s also rumors and apparently one NASA acronym sheet that says it’s an acronym. But I’m going to deny it its acronym goodness.

Fraser:                         Jupiter unusual…

Dr. Pamela Gay:         No, the U came from Jupiter itself.

Fraser:                         Jupiter… hmm… nice one.

Dr. Pamela Gay:         No, the U is actually from Jupiter –

Fraser:                         Okay, Jupiter. JU. Got it.

Dr. Pamela Gay:         And the N is from Near-polar, which they made –

Fraser:                         Right.

Dr. Pamela Gay:         – one word.

Fraser:                         Yep.

Dr. Pamela Gay:         And the O is for Orbiter.

Fraser:                         Got it. Okay, Juno. Juno’s actually a big – in Canada, Juno is our equivalent of the Oscars. So, our media awards are called the Junos.

Dr. Pamela Gay:         Okay.

Fraser:                         There you go. Little fact. Little thing you didn’t know. Well, I would like to dig more into some of the really interesting science findings from the Juno mission, and we’ll talk about that in a second. But first, let’s have a break.

Dr. Pamela Gay:         And I’m going to drink more coffee, ‘cause oh my God!

Fraser:                         I’m gonna drink some water.

Dr. Pamela Gay:         You have one of the recess glasses.

Fraser:                         I do! Yeah, I liked it.

Dr. Pamela Gay:         If anyone wants one of those, drop me an email. I still have a couple boxes of them up in my attic, and I’d be happy to basically send them to you for not very much money to get them out of my attic.

Fraser:                         Sounds good. And we’re back. All right, there’s just been mountains of science. And I would love to just talk about – we talked in general some of the overall science findings and some of the goals and stuff. But I’d love to just pick out some really interesting discoveries that Juno has made at Jupiter that have just really advanced our understanding of Jupiter, its environment, and what maybe that holds for other planets out there in the universe. Pick one.

Dr. Pamela Gay:         So, my favorite results of this mission is that Jupiter has a – depending on the release you read – either fluffy, or fuzzy core.

Fraser:                         Okay. What does that mean?

Dr. Pamela Gay:         What it means is that scientists had expected – the people who model the insides of these worlds – had expected that Jupiter would have this nice, highly dense rocky core that would’ve formed first, and then gathered all of the gas that formed Jupiter’s atmosphere in around it. But when they actually started mapping out the internal structure of Jupiter, they found that that core was less dense and much bigger than expected. Fluffy was the word they used.

Fraser:                         Okay.

Dr. Pamela Gay:         And it’s thought that this likely arose from a 10 Earth mass early solar system object bashing into what is now modern day Jupiter. And in the process, all of that energy that imparted fluffed out the core of what is now Jupiter. Now, it’s possible that there are things we don’t understand about planet formation, by which I mean there are definitely things we don’t understand about planet formation.

Fraser:                         Yeah.

Dr. Pamela Gay:         But it’s possible that there was some other physics that led to this fluffy core. But the idea of it coming up as the result of a collision is completely consistent with what we see throughout –

Fraser:                         Right.

Dr. Pamela Gay:         – our solar system. We know that Earth has been hit many times, we know that something knocked Venus on its head, Uranus got knocked over. We see the results of impacts on a regular basis. And it could be that Jupiter got knocked into being fluffy.

Fraser:                         But I don’t think fluffy – I mean, I know that’s sort of the term, but it’s –

Dr. Pamela Gay:         Yeah.

Fraser:                         – sort of surprisingly less dense.

Dr. Pamela Gay:         Yes.

Fraser:                         But still insanely dense. But I don’t think –

Dr. Pamela Gay:         This is true.

Fraser:                         Yeah. It’s harder than rock. It’s hydrogen, helium, that’s been compressed.

Dr. Pamela Gay:         It’s crystalline.

Fraser:                         Yeah, that’s been compressed to densities that you would have trouble picking up a chunk of it if it was in front of you, ‘cause it would be so heavy and dense.

Dr. Pamela Gay:         It may rain diamonds.

Fraser:                         Yeah. Temperature’s what, 90,000 Celsius? This is not some kind of fluffy, puffy, you know?

Dr. Pamela Gay:         It’s all a matter of perspective though, –

Fraser:                         Yeah, totally.

Dr. Pamela Gay:         – because when you’re expecting it to be much smaller and more compact, –

Fraser:                         Mm-hmm.

Dr. Pamela Gay:         – they actually use the words fluffy and fuzzy in various official –

Fraser:                         I know.

Dr. Pamela Gay:         – descriptions of these results, and it was fabulous.

Fraser:                         Yeah, it’s possible I was a little hesitant.

Dr. Pamela Gay:         You were annoyed, and I was excited.

Fraser:                         Yeah, I was a little annoyed that that was the terminology, ‘cause it just felt it was the exact opposite of what the inside of Jupiter is. I mean, just this idea of that hydrogen in Jupiter is compressed under so much gravity, that it is a metallic form of hydrogen.

Dr. Pamela Gay:         Yeah.

Fraser:                         But then it oozes like metal hydrogen juice.

Dr. Pamela Gay:         Mm-hmm.

Fraser:                         That flows around the core.

Dr. Pamela Gay:         The physics is weird.

Fraser:                         Yeah, I know. I know, it’s so weird. And that’s what causes the magnetic field, is hydrogen compressed into a solid, but still sort of squosen around the core of the planet. And that causes the giant planetary-wide magneto field that causes this horrible radiation. Give me another science result before we wrap up. Anything else that you found really fascinating that we did discover with Jupiter?

Dr. Pamela Gay:         So, there are sprites.

Fraser:                         What’s a sprite?

Dr. Pamela Gay:         So, we see these here at Earth. When you get really big lightning storms, you can end up with this amazing ultraviolet flash that goes upwards through the atmosphere. They’ll go up to 60 miles above the surface of our planet. Well, we see the same things associated with the lightning storms on Jupiter. The big difference there is while our lightning storms tend to happen around the equator, where we have a lot of instabilities in the atmosphere, Jupiter’s instabilities are more in the polar regions.

And so, its lightning storms are more in the polar regions. So, in these big water ammonia clouds that it has, you can get storms. And they have lightning in them the way we have lightning here on Earth. And they have sprites, which are ultraviolet. They look like jellyfish electrical discharges that go upwards through the atmosphere.

Fraser:                         And we know that we have them on Earth. And it was surprising to find them on Jupiter. And that was a fairly recent science result as well. We saw that three months ago. So, it’s sort of good timing. Awesome. I’m a huge fan of Juno, I love both the science results that are coming out, as well as just the gorgeous photographs. And whoever is working on any kind of mission, if you dare not put a camera on that mission, I just hope you see the lesson of Juno. Science will continue to get done. It’s worth it. See it through, put a camera on every mission. Pamela, that was awesome. Do you have some names for us this week?

Dr. Pamela Gay:         I do. As always, our show is supported through the generous contributions of people like you. While we now may appear on Houston’s Channel 21, we don’t yet have commercial sponsors. So, we rely on donations from everyday people to get everything we do funded somehow. So, I would like to thank David, ACUT-Patron, Joe Hook, Aurora Lipper, Catherine McCabe, Jeanette Wink, Burko Roland, Ramji Enamuthu, Andrew Poelstra, David Truog, Brian Cagle, TheGiantNothing, Venkatesh Chary, Burry Gowen, and Jordan Young. Thank you so much for everything you do that allows us to do everything we do.

Fraser:                         Thank you, Pamela! We’ll see you next week.

Dr. Pamela Gay:         Buh-bye!

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