Saturn v Jupiter - Katherine Parkinson, Paul Abel and Michele Dougherty

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Speaker 12 Hello, I'm Brian Cox.

Speaker 1 And I'm Robin Ince, and this is the Infinite Monkey Cage. Now, as many of you will know, there is quite an overlap between the world of both theoretical and particle physics and also

Speaker 1 world and international wrestling.

Speaker 1 The The Large Hadron Collider was indeed inspired by a bout between Rowdy Roddy Piper and Hulk Hogan, where Peter Higgs, a very, very keen wrestling fan, saw the tremendous amount of energy that was expounded when the two went from a double-legged takedown into a camel clutch ending up with a pile driver.

Speaker 1 And it was at that point he thought, what if the origin of the masses of the W and Z bosons is electroweak symmetry breaking in the early universe?

Speaker 1 Perhaps the universe is metastable and we live in a false vacuum state. Take him down, Roddy!

Speaker 2 Are you okay? Are you okay?

Speaker 13 I'm fine. I'm wondering what a camel clutch is.

Speaker 14 I'm so glad it wasn't just me.

Speaker 2 I have no idea either.

Speaker 12 The physics actually was remarkably accurate there.

Speaker 12 What he was saying with the Z boson and the photon are essentially the same, apart from the fact that the Z is very massive and the photon is massless.

Speaker 12 I suppose by your analogy that means that the Z is Big Daddy, and Barry McGuigan is the photon or something.

Speaker 1 No, no, and I know people are already annoyed by that because that is you not merely mixing your metaphors but also mixing your different sporting splendors there.

Speaker 2 Right.

Speaker 12 This is a science show.

Speaker 12 Radio 4 is the last bastion of Rethian values in an increasingly trivial world.

Speaker 12 So today, I'm going to be sensible and tell you we're discussing the gas giant planets Jupiter and Saturn and the future plans to explore them.

Speaker 1 But at the same time, it is very important to remember how much wrestling and science have been combined for literally hundreds of years.

Speaker 1 Many of you who are also fans of Isaac Newton will remember that one of the most important statements in science is: if I have seen further, it is because I've stood on the shoulders of giant haystacks.

Speaker 1 In the red corner, we have Jupiter, a gas giant, weighing in at 2.5 the mass of all the other planets in the solar system.

Speaker 1 And

Speaker 1 in the slightly yellowish, perhaps more kind of puce through a smaller telescope, we have Saturn, King of the Rings.

Speaker 12 Jupiter and Saturn are each surrounded by their own mini solar system of moons, fascinating worlds in their own right, that are prime candidates for the search for life beyond Earth.

Speaker 1 So joining us to decide who leaves with the Kuiper belt are a space physicist, a theoretical physicist and someone who has been at the forefront of information technology. And

Speaker 1 they are.

Speaker 11 I'm Michelle Doherty. I'm a professor at Imperial College in London and a planetary scientist.

Speaker 11 And this place I would like to discover most I'm not going to tell you about right now, but we'll find out as the evening progresses.

Speaker 14 Hello, everybody. My name is Paul Abel.
I'm a theoretical physicist at Leicester University.

Speaker 14 My area of expertise is black hole thermodynamics, which has nothing whatsoever to do with what we're talking about tonight. But they asked me to do the show, and I was bored and said yes.

Speaker 14 So, where would I like to go? Well, I would like a planet to be discovered where the population

Speaker 14 has managed to unite quantum mechanics and gravity together.

Speaker 14 And they have a working quantum theory of gravity, because I think a world like that would be very, very different from this one and probably quite unrecognizable.

Speaker 14 The technological advancement would be astonishing. So I'd like to see that kind of world discovered, or a world where the oceans are made of gin.

Speaker 2 Might not be,

Speaker 2 surely.

Speaker 13 Hello, my name is Catherine Parkinson. I'm from the University of Show Business.

Speaker 13 And the planet I would most like to discover is the planet or habitable moon that I imagine ET to have come from?

Speaker 1 And this is our panel.

Speaker 1 Oh, I love that, Catherine, because that immediately made me think also of perhaps my favourite one, which would be the asteroid which the little prince is on, which has the rose that grows and which he has to protect and is so worried about.

Speaker 1 But let's get down to the real science of it. Who is your favourite wrestler? No, the I love Barry McGuigan.

Speaker 13 I know he wasn't a wrestler.

Speaker 1 he's a a boxer but my dad's from uh northern ireland and we barry was massive in my house growing up so um i i liked your uh reference to him now because you are the adjudicator today we have this kind of battle between battle of the planets between saturn and jupiter and what is your planetary knowledge generally your planetary science knowledge i live near the observatory

Speaker 13 Yeah, no, that is it.

Speaker 2 Right.

Speaker 1 That's why we chose you. We literally, we had a big map of where all of the people in entertainment lived, and we went, she definitely lives closest to the Greenwich Observatory.

Speaker 13 No, I am very interested in it.

Speaker 13 I remember when I was about 10, just wondering why we didn't learn more about the planets at school, and haven't seen that change as much as I thought it might with my children.

Speaker 12 We should start then. So, Paul, you're championing Jupiter.
Yes. So, give us the one-minute pitch.

Speaker 14 I've got it split into two things. Firstly, its place in history.
Jupiter was one of the planets Galileo turned his telescope to.

Speaker 14 And it has four very large moons, and you can see them with the telescope he built himself. And at that moment, Jupiter stopped being a star in the sky and became a world surrounded by moons.

Speaker 14 And that began the Renaissance with not thinking of the Earth as the center of the universe anymore.

Speaker 14 Because if there's moons orbiting Jupiter and the Earth is important, why aren't they orbiting the Earth? So that's the first point.

Speaker 14 The second point is, yes, everyone goes on about showing people Saturn through a telescope, but if you show people the first time Jupiter, they can see the gorgeous cloud markings changing in 10 minutes.

Speaker 14 It doesn't need a very large telescope. And as well as that, you've got the moons of Jupiter that pass in front and cast shadows.
And it really is almost like being in a spaceship approaching it.

Speaker 14 And then final point, Jupiter saves our lives by its immense gravitational fields sucking out comets and debris and stopping them from colliding with the Earth on a way that will be far more frequent than we have at the moment.

Speaker 12 It is worth saying, isn't it, that you you can see those moons and you can see it's a disk with any telescope. Yeah.
Essentially, so for an amateur astronomer, it's the easiest target.

Speaker 14 And you can do some very simple things.

Speaker 14 If you time how quickly the great red spot, which is this vast hurricane in Jupiter's southern hemisphere, you time how long that takes to go around the planet, you can work out how quickly the wind speeds are on Jupiter, and they're absolutely colossal, much more so than here.

Speaker 14 All you can do with Saturn is look at the rings, not that I'm biased.

Speaker 1 That is

Speaker 14 real physics with it.

Speaker 1 Very strong argument there that without Jupiter we're all going to die. So

Speaker 1 Michelle, Saturn.

Speaker 11 How can he choose Jupiter over Saturn? I mean, you look in the night sky and there's this gorgeous planet out there with fantastic rings around it, moons as well, you know.

Speaker 11 And if we go back in history, I can do that as well. Cassini had a look at Saturn through a telescope that he built.
And when he first saw it, it looked as if it was a funny shape.

Speaker 11 It wasn't a round ball. There were these two blobs on either side, and they changed shape every time he looked at it.

Speaker 11 It was only after a period of time that he realized there were these rings, and depending on how they were oriented, you could see the rings or you couldn't.

Speaker 11 So Saturn's much more interesting, and it's much further away, and it's got these fantastic moons.

Speaker 14 Jupiter has fantastic moons. Yeah,

Speaker 14 volcanoes. Big as Texas.
What would you want?

Speaker 12 So, Michelle, could you just... describe a bit more about the structure of these planets.
How big are they? What is their composition?

Speaker 11 You sort of look at Saturn or at Jupiter in the night sky or in fantastic images that you get from different telescopes. And it looks like it's a solid surface, but it's not.

Speaker 11 If you tried to stand on it, you'd fall all the way through. So there's a solid core, and then there's liquid above that core, and then there's gas.

Speaker 11 And they sent a probe.

Speaker 11 There was a probe that went through the atmosphere of Jupiter, and there was a probe that went through, well, Cassini spacecraft dived into the atmosphere of Saturn, and they broke up because of the large density in the atmosphere.

Speaker 14 There's also that metallic hydrogen. So

Speaker 14 you get to with Jupiter, you get to pressures where the hydrogen is squashed into a metal and it generates this enormous magnetic field.

Speaker 14 If you could see Jupiter's magnetic field in the night sky, it would be as large as the full moon. It really is, and it one of the most impressive structures.

Speaker 12 It's seen from Earth. Yeah, it's not.

Speaker 11 And seen from Earth, that's right. Yeah, yeah.

Speaker 14 It's an enormously... powerful structure.

Speaker 12 So if we were to slice through Jupiter, first of all, what's its radius? How big is this thing? And could you describe that cross-section through the planets as you dive down?

Speaker 14 Yeah, for Jupiter, you've got the upper atmosphere that we see.

Speaker 14 We think the darker cloud bolts are made of ammonium hydrosulphide, and the brighter zones are higher up, ice crystals, and various things.

Speaker 12 So it's ammonia.

Speaker 14 Hydrogen sulfide, I think.

Speaker 14 There is some still debate, even though we've got spacecraft out there, there's still considerable debate about the chemistry of the stuff we can see, let alone the stuff further down.

Speaker 14 Anyway, you've got these cloud bands, and then you go through a water layer, and I think there's supposed to be a methane layer. And then under that, you've got this hydrogen-helium layer.

Speaker 14 And it was thought for a long time that that went down quite a way before it was all squashed by the pressures and temperatures into this metallic hydrogen-helium.

Speaker 14 But the Juno spacecraft, which is flying around the poles of Jupiter, actually seems that the metallic layer is much closer to the cloud tops than we thought. And it's a complete mystery.

Speaker 14 And I've asked several of the very distinguished space scientists in our department, and all I get is a baffled look. So I don't really know.

Speaker 11 So, can I try and match the story about the metallic layers?

Speaker 12 Yes, because I was going to just say, because although you're advocating for Saturn in this rather artificial construct, you are on the Juno mission, aren't you?

Speaker 12 So the Juno mission that Paul referred to is one of the spacecraft.

Speaker 11 No, I'm not, but I'm on another Jupiter mission. So I'm very tawn tonight.
I'm very tawn tonight. I hope none of my Juice colleagues listen into this program.

Speaker 12 JUICE is the... I always think, you know, spacecraft, they're wonderful names usually.
Cassini and Galileo.

Speaker 11 well well I blame I blame the European Space Agency but could you say what JUICE stands for so I'll tell a little story before that so to begin with we were going to have a joint spacecraft mission NASA was going to build a spacecraft to go to Europa and Europe was going to build a spacecraft to go to Ganymede and then NASA said oh no we can't afford to do it so ESA turned around to us and said you've got three months to design an ESA only spacecraft mission and oh by the way you've got to change the name we didn't have time to think about a name.

Speaker 11 So, after a long day of planning the new mission, we went and sat in the pub. And I think we were three Ginantonics in.

Speaker 11 And we came up with a list of names. The first two, I can't actually remember them, but ESA said no other spacecraft had been called that before.
So, one of the names which we came up with was Meow.

Speaker 11 Moon Explorer of Ocean Worlds.

Speaker 11 Which we thought was great, but we didn't think we would be taken seriously.

Speaker 11 So, number four was Jupiter Icy Moon Explorer, and you've got to work a bit hard at that, but that's where Juice comes from.

Speaker 11 And Issa said to us, You can't call a spacecraft Juice, we're going to have to call it something else after launch. And I said to them, After launch, we're going to rename it.

Speaker 11 Oh, no, everyone likes Juice. So that's where Juice came from.

Speaker 13 Your story made me think of when I started drinking when I was 15.

Speaker 13 I was told that when I ordered a gin and tonic, I had to say gin and tonic supersonic. It was just some boys winding me up.
And I thought that's what you had to say to order a gin and tonic.

Speaker 13 I said, Can I have a gin and tonic supersonic?

Speaker 11 It's a good thing you weren't in the meeting where we chose the name.

Speaker 2 Good thing I was in the middle of the night.

Speaker 1 Similar wind-ups when dealing with astronomy, where a new student comes in and you create some form of fabrication which they must discover.

Speaker 14 I t used to, when I was very young and stupid, used to tell them equations were easier to solve if they were written in a colour red.

Speaker 14 Until my head of department said, stop doing that.

Speaker 14 So I changed it to green.

Speaker 12 So Michelle, so you're going to deviate from the colour for Jupiter. Yes.
You're not advocating for Jupiter. No, no, no.

Speaker 12 Can you describe this cross-section and this strange metallic hydrogen and what that is?

Speaker 11 So Saturn is something similar.

Speaker 11 We're still not quite sure what the interior looks like, but one of the things we plan to do with Cassini is we were responsible for the magnetometer instrument on Cassini.

Speaker 11 So that measures the magnetic field.

Speaker 12 So now we're around Saturn, look at that.

Speaker 11 We're orbiting around Saturn. And

Speaker 11 I said to everyone, one of the strange things about Saturn is all the observations that have been made so far seem to imply that the rotation axis of Saturn and the magnetic axis lie on top of each other.

Speaker 11 And planetary dynamo theory says that cannot be.

Speaker 11 And so I kept saying to everyone, oh, if we just get closer, if we spend more time there, we'll find out the answer. Turns out there isn't any tilt at all.

Speaker 11 It turns out that Saturn is much more interesting than Jupiter.

Speaker 14 Jupiter has a similar thing.

Speaker 11 Oh, yeah, well, but Jupiter doesn't have a secondary dynamo which masks the effect of the internal dynamo. So it's unique in the solar system.

Speaker 12 You could perhaps unpack that a little. Well, refer to the Earth.

Speaker 11 So, you know, we stand on the surface of the Earth and we've got a compass needle and it points to the north pole of the magnetic field.

Speaker 11 And the magnetic field of the Earth that's generated in the interior of the Earth protects us from the effects of the solar wind.

Speaker 11 So all these energetic particles coming towards us, we get protected by the magnetic field of the Earth. So Jupiter and Saturn also have these internal planetary fields.

Speaker 11 And Jupiter's field in some ways looks similar to the Earth's because there's this tilt between the rotation axis and the dipole axis.

Speaker 11 Saturn is unique in the solar system because it has this planetary dynamo in the interior, but there's a dynamo on the quite close to the surface, which is masking the effect of the interior.

Speaker 12 So there's something else creating a magnetic field. So it's not just

Speaker 12 the single thing in the cork.

Speaker 12 So that means that there are electrical currents flowing in the high atmosphere, presumably. So what would that be? You said it was there's ammonia up there and then there's whatever.

Speaker 2 So Saturn's atmosphere.

Speaker 14 It's a layer? It's more conduct. If you look at Saturn through a telescope, the banding is much more subtle.

Speaker 14 And I think it's because there's this petrochemical smog isn't there that obscures the the atmosphere so what you're seeing there because it is it's kind of a dull yellowy colour is probably referred to in the interview yeah that's that's just that really is haze in yeah it's petrochemical haze yeah why why it's there not on jupiter i don't know because if you look at voyager date and cassini images you can see the banding much more strongly than through an earth-based telescope just to

Speaker 12 that banding so jupiter the first thing you see when you look at jupiter through a telescope or any photograph are those bands bands, those clouds, which is unusual because you look at Earth's clouds and they don't go in these

Speaker 12 stripes around the planet. So why is it stripey?

Speaker 14 I think it's the winds, wind speeds.

Speaker 14 So the great red spot the storm I mentioned that's been going for 300 years, because you mentioned earlier there's no land, these storms can't break land and lose their energy and dissipate.

Speaker 14 So that just doesn't happen. Once they get started on these big planets, they go forever.
And for some reason, you've got these parallel wind jet streams that go around the equator and all the way up.

Speaker 14 And I don't really understand how this works, but you get these gases forming between those. And that's where the belts and zones come in.

Speaker 14 They seem to be constrained between these very, very fast jet streams. Yes.

Speaker 11 I still don't understand why the red spot is still there.

Speaker 14 It's nearly gone. When I started

Speaker 14 drawing Jupiter a long time ago, it was much larger and it's now shrunk.

Speaker 14 And no one knows really what's going to happen to it, whether it just becomes spherical or whether it'll disappear completely, or there might be some sort of global event that happens.

Speaker 14 Because the southern hemisphere of Jupiter is quite different to the northern hemisphere.

Speaker 14 And every now and then, the band that's in the south, the one you can see through your telescope, disappears completely. And the red spot gets really dark.
And then you get this.

Speaker 14 breakout of spots in the southern hemisphere and the band reforms and nobody really understands why this happens.

Speaker 11 So what was interesting is in the first couple of years of us being at Saturn with Cassini, there was a...

Speaker 14 Oh, the storm.

Speaker 11 There was a huge storm that was seen in the northern hemisphere. And over time, it spread itself out.
And so there was almost like a great red spot, although it wasn't red.

Speaker 11 And then as the planet rotated on its axis, it evolved and it moved around and slowly it dissipated. But it took about a year, I think.

Speaker 14 It did. The features in that part of Saturn remained disturbed for a couple of years afterwards.
Very, very unusual. And it was outside the usual spot cycle.

Speaker 14 Saturn normally has these big, big storms every 30 years. And this was outside that 30 years.
Yes, it was. No explanation for it.

Speaker 12 it's interesting Catherine isn't it that these the the time scales we speak of weather on these planets but as you said this storm is over 300 years old it's it's quite daunting it does sort of sound like a bad sort of spot that sort of takes a while to settle and then has some kind of damage around it that takes longer to settle it's three three times the size of the earth wasn't it it was initially much larger than now this is about five times the size of the earth now it's about a couple of times the size of the Earth.

Speaker 14 It's slowly shrinking.

Speaker 13 I mean, this is a serious question, even though it might not sound like one, but if there was extraterrestrial life and there was all this helium going on, would they speak in a high voice?

Speaker 14 I mean, I'll just say yes, so we can move on.

Speaker 2 Oh, we're not moving on now, Paul.

Speaker 1 We have literally found the peak of this show.

Speaker 2 Robin will remember, though.

Speaker 12 Do you remember Carl Sagan? I think it was in Cosmos. It was.
Had the idea of these floating organisms.

Speaker 14 The jellyfish. There was a painting done, I think, wasn't there? Yeah, showing these huge jellyfish type creatures in the atmosphere.

Speaker 12 Is there somewhere? So is there a region where you could, as Sagan did, where you could imagine some kind of life in those atmospheres? There must be a region. You said there's water vapor there.

Speaker 14 I would imagine it is possible. I mean, we look at the solar system and we long ago thought all the things that we thought were normal aren't.

Speaker 14 So I could imagine something, you know, it's very simple, like bacteria just exist in that region.

Speaker 12 Just in terms of the conditions, what kind of conditions are we speaking about in the cores of these two planets?

Speaker 11 Incredibly hot. What are we talking about? Plus 300 degrees Celsius.
More than that.

Speaker 2 More than that.

Speaker 11 Pressures at the kind of levels where on Earth we couldn't even generate them. Lots of material moving around.

Speaker 14 Even though we've got all these spacecraft and we can study these planets with telescopes, both in space and in our gardens, and in between, there's still considerable debate about the interior of these planets.

Speaker 14 And I think that's marvellous because it kind of gives amateur astronomy plenty to do.

Speaker 14 I know you professionals have got all the kit and the money, but whilst you don't know what's inside, we've still got a job to do.

Speaker 11 The last thing I wanted to mention is that really put me in my place.

Speaker 13 I'm interested in that Saturn's rings, and Jupiter has rings, but they're eroding. And because they think that they were caused by a moon getting

Speaker 13 too close, is there the potential for

Speaker 13 a long time ahead more rings to come?

Speaker 11 Potentially. Yes.
And one of the things that's also happening to the rings is they're being covered with water vapor from one of my favourite moons. I don't know if I'm allowed to talk about it yet.

Speaker 2 Type of the money. We can move on to the moon.

Speaker 11 But the rings are being covered all the time with water vapor falling on top of them. Ring rain.
Ring rain. Yeah, you know.

Speaker 11 She's been looking up scientific books.

Speaker 13 Nobody can forget that phrase.

Speaker 12 So those rings, so what's our current understanding? Because they're quite recently formed, I think, aren't they? That's the current view.

Speaker 2 Yes.

Speaker 12 Could you describe the current thinking as to how, as Catherine said, how did they form?

Speaker 11 Why did they form?

Speaker 11 Well, my understanding is, and the theory guru over there might tell me it's all wrong, but there were a moon or maybe two that got a little bit too close to Saturn and they were pulled apart by the gravitational force of Saturn.

Speaker 11 And because of orbital dynamics, all the bits that broke up now orbit around Saturn. So when you look at the rings, they look as if they're solid, but they aren't.

Speaker 11 They're made of these countless individual particles, each in their own orbit around Saturn. And there are some beautiful images which show moons right on the edge of the rings.

Speaker 11 And the moons orbit at the same time of the rings, and they make these beautiful wave structures on the rings.

Speaker 1 That bit where you see these patterns, and we are a pattern-seeking creature, and you know, to look at what appear to be the patterns in Saturn's rings, you know, that sense of wonder and awe.

Speaker 1 I know you have done some research, you know, when you knew you were coming on the show. Did you find yourself looking at certain things and just going, What a strange thing.
That's not just a mess.

Speaker 13 Yes, the thing of beauty, this subjectively beautiful thing, has come from sort of trauma, or potential trauma.

Speaker 12 I like that. Yeah, and the fact that it's so ethereal, temporary.
So, what what when do we think they will vanish from view?

Speaker 14 Do we have a yeah, they will eventually fade and then that'll be it.

Speaker 14 They're a very short-lived phenomenon, I guess, in the age of the solar system.

Speaker 11 But what I find so interesting is they really thin.

Speaker 1 So if we were thinking of it on a scale of Earth and Earth had rings, what would what kind of

Speaker 2 meter? Yeah, it'd be

Speaker 14 like a sheets of paper, really. It's just the ice that makes them so very visible.

Speaker 14 When Voyager was going to Saturn, they wanted to fly through the Cassini division, and Carl Sagan astronomers said, Perhaps not a terribly good idea because there might be stuff there we can't see.

Speaker 14 And as they got close up, there was the Cassini division, which looks empty from the Earth through birth-based telescopes, filled with rubble and dark material.

Speaker 14 The spacecraft had been utterly destroyed.

Speaker 12 We've had two Cassinis here, so Cassini the Astronomer, after which the Cassini spacecraft. The Trikish.

Speaker 13 But also thinking not to get obsessed with Saturn.

Speaker 14 I feel that it's already stacked against me.

Speaker 13 I feel like, you know, that cartoon in children's books when you had the Saturn with the ring in the bath and it being because it's not as dense as water.

Speaker 13 But I think I always thought it was like a rubber ring that you would have at a swimming pool. But is that the case that Saturn is less dense than water?

Speaker 11 Yeah, I think it is.

Speaker 2 I think it is.

Speaker 14 If you could find an ocean large enough, Saturn,

Speaker 11 you could just float. You could float Saturn on that.

Speaker 13 I just cannot get my time.

Speaker 2 I love that rubber ring thing, though.

Speaker 1 I love the idea that when the ring does finally disappear, Saturn just kind of drops.

Speaker 2 But oh, God, that was it.

Speaker 5 What does possibility mean to you?

Speaker 16 Um, that's a hard question. Something that you can strive for.

Speaker 15 I'm able to do anything I set my mind to.

Speaker 4 You're confident in yourself and you believe in yourself. Stuff that you could achieve.

Speaker 15 I feel it's signa. Anything is possible when you're more confident.

Speaker 16 Shoes are a huge part of that. They are the most important part of my style.

Speaker 4 You can like express yourself in the right shoes.

Speaker 2 Anything is possible.

Speaker 5 DSW, countless shoes at bragworthy prices. Imagine the possibilities.
Suffs, the new musical has made Tony award-winning history on Broadway. We demand to be home.
Winner, best score.

Speaker 5 We demand to be seen. Winner, best book.
We demand to be quality.

Speaker 5 It's a theatrical masterpiece that's thrilling, inspiring, dazzlingly entertaining, and unquestionably the most emotionally stirring musical this season. Suffs.

Speaker 5 Playing the Orpheum Theater, October 22nd through November 9th. Tickets at BroadwaySF.com.

Speaker 6 Want to stop engine problems before they start? Pick up a can of C-Foam Motor Treatment. C-Foam helps engines start easier, run smoother, and last longer.

Speaker 8 Trusted by millions every day, C-Foam is safe and easy to use in any engine.

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Speaker 9 Safe home!

Speaker 1 Was keeping it up.

Speaker 12 Why don't we go to Jupiter? Okay. And so, can you give us an overview of the moons that are there?

Speaker 14 Well, there's lots of dull ones, but there are four very interesting ones. These are the ones you can actually see.

Speaker 2 We could have just cut it there.

Speaker 12 There are loads of dull ones.

Speaker 2 Thank you. Saturn.

Speaker 1 How many dull ones are we talking about?

Speaker 14 I didn't come down to be here to be insulted, you know. I could have stayed at home on social media.

Speaker 14 There are the four main moons, which you can actually see.

Speaker 14 These are the ones that Galileo saw with his small telescope. Io, Europa, Ganymede, and Callisto.
Ganymede, the largest moon in the solar system, in fact, is larger than the planet Mercury.

Speaker 14 So these are actually kind of, if they were orbiting the Sun, they would be planets in their own right.

Speaker 14 But for me, the most fascinating one, everyone chooses the icy moons because, you know, potential for life. But for me, the most fascinating one is Io, because it's so volcanic.

Speaker 14 It's just a bit larger than our own moon, and the largest active volcano on Io is twice as big as Texas.

Speaker 14 And the reason it's this hot is because one side of Io is very close to Jupiter, and the other side you've got the other satellites pulling.

Speaker 14 It's like bending a paperclip back and forth, you get a lot of heat generated. And that's what's happening on Io.
It's being this tug of war which generates all this heat and all this volcanism.

Speaker 14 You're not going anything like that on Saturn. It really is a fascinating moon.

Speaker 11 There is a plan to hopefully send a spacecraft called IO Volcanic Explorer

Speaker 2 or Observer. IVO, it's called.

Speaker 11 That would be fascinating. We're going to try and propose to do that.
But we aren't going to go into orbit. We're just going to fly past.

Speaker 14 That's enough. If you need the money, we should all have a whip round.

Speaker 2 We can.

Speaker 12 So Europa, you mentioned Europa, though. Europa is the target of the Europa Clipper mission, for example, which as we record is going to be launched next week.

Speaker 12 So when we broadcast, it's either on the way to Jupiter or

Speaker 14 on its way way to the inner solar system. Very unfortunate.
Europa, it kind of looks like a white billiard ball. It's completely covered in ice and very, very smooth.

Speaker 14 And for a long time, it was suspected that the same mechanism by which Io is for so volcanic, that same sort of heat process can melt the interior of Europa. And we think there's this ocean on Europa.

Speaker 14 And obviously it's very difficult because we can't see through the ice to determine it. But what people did was they compared the Voyager spacecraft images with ones taken by Galileo.

Speaker 14 And there were subtle markings and changes on again.

Speaker 12 Galileo, the spacecraft, Galileo, not the Galileo.

Speaker 14 Galileo, the spacecraft,

Speaker 14 imaged that you're very pedantic today, Brian.

Speaker 14 And

Speaker 14 they were able to see these changes, which suggests that there is probably a deep ocean. Whether there's life in that, I don't know.

Speaker 14 Certainly, if we look at the Earth's deep sea vents, there's life down there that's quite different to what we see. So maybe there is.
I just hope we don't spoil it.

Speaker 12 So the JUE spacecraft, which is in flight, which you are a scientist on. Yes.

Speaker 11 So yes, we're going to fly past Europa twice. I think we have 29 flybys of Callisto, which is the one furthest out.

Speaker 11 We're also going to fly past Ganymede on numerous occasions, but then we're going to go into orbit around Ganymede.

Speaker 12 And why Ganymede?

Speaker 11 Because Ganymede is unique in the solar system,

Speaker 11 because not only do we think it has a liquid water ocean under the surface, but it's the only moon in the solar system that has an internal dynamo field.

Speaker 11 So if you stood on the surface of Ganymede and you had a compass needle, it would point to the north pole of the magnetic field.

Speaker 11 So as a magnetometer magnetometer person, where else in the universe would I want to go to other than Saturn?

Speaker 12 So, this is a world that, as Paul said, it's the biggest moon, it's a planetary-sized moon, and it's got a magnetic field and it's got a liquid ocean.

Speaker 11 And

Speaker 11 if there is organic material on the surface, it will be protected from the impact of the radiation from Jupiter because of the magnetic field.

Speaker 12 So, it's a potential target.

Speaker 11 It's a potential target. But Europa, we think the silicate mantle

Speaker 11 is in contact with the liquid water. And so organic material might be able to leak out into the liquid water, but we aren't sure about that with Ganymede.

Speaker 1 Catherine, we're over halfway through the show now, so we need to know roughly where you are in terms of

Speaker 1 which planet is going to be the victor, because as you know, the other one will be destroyed.

Speaker 11 Oh, really?

Speaker 2 I didn't know that. I'm sorry.

Speaker 1 I'm so sorry. I have to admit, we were deliberately hazy on that.

Speaker 11 I've got a a spacecraft going there. Can I change my mind?

Speaker 12 But yeah, listening to all these things.

Speaker 1 What is it that you've heard so far? Is it a sense of beauty, the possibility of life? Is it something different?

Speaker 13 I mean, I feel like Jupiter wins anyway in many ways. And that's why, of course.

Speaker 14 Saturn you'll choose, yes.

Speaker 13 I'm intrigued by the sort of fluffiness of Saturn, but with this obviously very unfluffy core. And I think its moons

Speaker 13 do excite one more. But yeah, at the moment, it's Saturn just because, you know, Jupiter is already the godfather.

Speaker 12 So we've had Jupiter's moons, so we've talked about Io, Europa, Ganymede, Callisto, the Galilean satellites.

Speaker 12 Over to Saturn, you mentioned, Catherine mentioned Titan, and you've mentioned obliquely this moon Enceladus. So could you go through Saturn's inventory of large moons?

Speaker 11 I lose track of how many moons Saturn. It's got a lot.
Every time they look, they're more. So the last count was about 68.

Speaker 14 You can see eight of them with a small telescope. Yes, that's right.

Speaker 2 Yeah, it is quite phenomenal.

Speaker 1 What is the size in which something will become defined as a moon?

Speaker 11 As long as something is orbiting around a planet, you can call it a moon. One of my favourites is Enceladus, and that's 500 kilometers in diameter.
And its surface is covered in water ice.

Speaker 11 And so it's a bit like Europa.

Speaker 11 If you fly over it, it it's white it reflects back at you and the reason I'm so partial to Enceladus is that we discovered a water vapor plume coming off from the south pole of Enceladus and so that's when there was a focus on Enceladus as a place where life could potentially form because you need four things you need four ingredients you need liquid water you need a heat source you need organic material and then you need those first three ingredients to be stable enough over a long enough period of time that something can actually happen.

Speaker 11 And for me, I think that's probably one of the most important realizations that planetary scientists have come to in, I don't know, the last 30 years or so, is that if you're looking for liquid water in the solar system, you don't have to focus on the inner solar system.

Speaker 11 You can look beyond us,

Speaker 11 but it's just not on the surface, it's underneath the surface.

Speaker 14 I think that must be the biggest change, mustn't it, in planetary science? Most people thought in the 60s that the moons of Jupiter and Saturn were just like our own moon.

Speaker 14 I think Carl Sagan had to really press for the moons of Jupiter and Saturn to be surveyed by Voyager because everyone thought they'll just be dead and uninteresting.

Speaker 14 And they turn out to be some of the most interesting places in the solar system.

Speaker 1 Both of you, in terms of when trying to get financed for missions, you know, there's so much to explore. There's a very small pool really of money.

Speaker 1 If you were going into a meeting to say, this is where we should be going, what are the things that will most excite whether it's ESA, NASA, whatever it might be?

Speaker 11 The search for potential habitability is how we sold JUICE.

Speaker 11 And I think if we hadn't made the discoveries on Cassini that we did, we wouldn't have been able to persuade the European Space Agency to fly JUICE. So it's the search for life.
Paul?

Speaker 14 I think that's exactly the same. I think that's the thing that seems to drive things, these space missions.

Speaker 14 I would love personally to see a space mission to Iapetus, the moon of Saturn, which is approximately half the hemisphere is really dark. Oh, yeah.
And the other half is really light.

Speaker 11 And there's that really high ridge that runs around.

Speaker 14 There is. It's very unusual.
And if you watch, you can actually see this satellite in a small telescope when it's on one side of Saturn.

Speaker 14 But as it moves around the other side, it vanishes because it's dropped in magnitude. It's so faint because the dark hemisphere is pointing towards us.
And it inspired Arthur C.

Speaker 14 Clarke to set 2001 initially on Saturn because that moon was part of the monolith and then they changed it to Jupiter.

Speaker 12 Cassini.

Speaker 14 but they changed it to Jupiter, right? Yes,

Speaker 12 the astronomer Cassini saw it, didn't he? And he thought it seemed to be vanishing, didn't he? He said, Yeah, just but it can't be.

Speaker 2 No, that's right.

Speaker 12 Because the laws of nature would not allow it to vanish. Yeah, so he correctly surmised, didn't he, that it was half very dark and half reflective.
That's right.

Speaker 13 Is Saturn

Speaker 13 is the day one hour longer on Saturn than Jupiter?

Speaker 11 We don't quite know how long a day on Saturn is.

Speaker 13 Let's just say yes.

Speaker 11 It's about 10 hours.

Speaker 11 Whereas on Jupiter it's just over nine hours.

Speaker 14 Here's a fun fact. If you start observing Jupiter early in the evening and about December and stay up till about five in the morning, you can see a whole day on Jupiter.

Speaker 14 It rotates so quickly.

Speaker 1 Right, Catherine, I'm now going to give you your loud one final question to Paul and one question, final question to Michelle, just before you make your decisions.

Speaker 2 Okay.

Speaker 13 Hypothetically, what would Jupiter smell like?

Speaker 14 A cross between a gentleman's lavatory and a farmyard.

Speaker 1 This could really swing it. Michelle,

Speaker 12 just say lavender.

Speaker 11 Hot chocolate.

Speaker 13 Like she knows me.

Speaker 1 So, Catherine, your decision then. It's Saturn or is it Jupiter?

Speaker 13 I mean, what brilliant, fascinating planets, but Jupiter's already massive, so Saturn.

Speaker 11 I knew I liked you.

Speaker 12 Just to finally frame that, because this is an important question because when we're talking about future missions, so is there any way really of deciding between these two systems?

Speaker 12 Because they're both.

Speaker 14 We shouldn't have to. Fascinating work.
We shouldn't have to. We should spend our money on the exploration of space.

Speaker 14 It's an important part of understanding who we are and the bigger picture of where we are.

Speaker 11 And there's this really cool mission going to Titan called Dragonfly.

Speaker 2 Oh, yes.

Speaker 11 And I was in Washington last week and I saw Dragonfly being built. It's a helicopter.

Speaker 11 And it's going to be dropped into the atmosphere and they hope like hell that the rotors will actually fire as they drop it. And it's going to fly over the methane lakes.

Speaker 14 And and the interesting as well, when the sun becomes a red giant, the habitability of Titan really increases.

Speaker 14 And if there is any organic material there, will the magic that converts that into self-replicating proteins, DNA, form there?

Speaker 14 It would be fascinating, which is why, again, it should be a protected environment. Even though it's four million years, billion years in the future.

Speaker 12 As you said, Paul, before we went out there, you'd think, okay, there's Earth and Mars, and that's pretty much it, right? Nowhere else.

Speaker 12 And then you find these worlds, like multiple worlds, three or four in orbit around Jupiter, three or four in orbit around Saturn, that may have the conditions that could support life.

Speaker 14 I was thinking that'd be somewhat ironic if that's where life is discovered first, not on an exoplanet, not on Mars, but deep in the moons of one of these gas giants, because no one would ever have thought of that.

Speaker 11 And one of the things I meant to mention, and I forgot, is that one of the other reasons we want to focus on Ganymede with Juice is that we think the internal structure of Ganymede is a water world structure, and we think a lot of the exoplanets which are being discovered are water world structures.

Speaker 12 Isn't that wonderful? It's a planet, really.

Speaker 12 I miss it in a sense.

Speaker 11 But Brian, I'm glad I didn't mention it earlier because it might have changed the vote.

Speaker 14 No,

Speaker 14 I could see you were biased when you were offering her brownies in the green room, so I know.

Speaker 2 Brownies? I knew, I think that's the main thing.

Speaker 14 I knew which way it was going.

Speaker 12 Paul, just before we finish it, you should show some of your sketches.

Speaker 14 Well, I've got all embarrassed now.

Speaker 1 I know this is radio. This is just for the...

Speaker 12 Because Paul is one of the last remaining old-fashioned astronomers. Dinosaur doesn't take pictures.

Speaker 14 No, I don't take pictures, and anybody who's seen me trying to operate Word will know why I don't. This shows the surface.

Speaker 14 You probably can't see it, but we've got the great red spot there. And on this particular drawing, I measured just how wide the great red spot was, just because I was bored and it was cold.

Speaker 14 And we also have the moons of Jupiter there. You can see perhaps their shadows being cast.
And you can watch, because the inner moons move quite quickly over a course of two or three hours.

Speaker 14 You can see this change. So it is quite spectacular.
And there's still a reason to do this. It connects us with the history of astronomy and science.
So I think there's still a reason to do it.

Speaker 1 Could you hold some of the drawings a little bit close to the microphone so that the audience are holding it?

Speaker 13 They're really, really good circles. Do you use a compass to make it?

Speaker 2 They are ellipses.

Speaker 2 I'll tell you what, Eversinoste.

Speaker 1 I don't think you two are going to get on so well now.

Speaker 1 In terms of in the acting world, if there had been a a similar kind of, you know, the competition, playwrights, actors, plays, whatever it might be,

Speaker 1 what is the green room of a theatre equivalent of Jupiter versus Saturn?

Speaker 13 Oh, I mean, that's really hard, but

Speaker 13 I suppose you could have a comparison of James Bonds or Benedict Cumberbatt versus Idris Elbert.

Speaker 12 Are you going to say Chekhov versus Shakespeare? Oh, sorry.

Speaker 13 Can we edit that? Can we edit that?

Speaker 13 I mean, for me, it would be Chekhov or Ibsen.

Speaker 1 I've spent a lot of time, because you were saying about how you came up with Juice, I've been working on an acrostic myself.

Speaker 1 And

Speaker 1 I came up with Jupiter ambulating, moving interplanetary explorer,

Speaker 1 looking eagerly, extraterrestrially, contributing, understanding regularly to interested species. And then you could call it Jamie Lee Curtis.

Speaker 12 I wonder why you were so quiet. We should do that.
If we did that every episode, look so wonderful.

Speaker 1 We can't say you're probably me saying anything when you've done all those different shows where you wander around with a parasol and explain some kind of orbit.

Speaker 1 We asked the audience a question as well, and the statement is, the planet I would most like to live on is...

Speaker 2 What have you got there, Brian?

Speaker 12 Mars, because on Mars every day I could work, rest, and play.

Speaker 2 That's for Malcolm.

Speaker 1 Now, the exciting thing here is waiting for the D-Reem pun that will probably be in it. Have you got the D-Ream pun?

Speaker 13 The planet I would most like to live on is Venus. She's got it.
Yeah, baby, she's got it.

Speaker 1 Oh, banana Rama before D-Reem.

Speaker 2 Very rarely happens there.

Speaker 1 Pluto, because I'd like to be irrelevant and forgotten.

Speaker 2 I'm glad you're here.

Speaker 1 That's what I'm going to say.

Speaker 2 So that's

Speaker 2 that.

Speaker 12 Pluto,

Speaker 12 nitrogen, glaciers, water mountains, and potentially

Speaker 12 liquid ocean. So there could be life

Speaker 2 on Pluto. So

Speaker 12 it's been unforgotten.

Speaker 11 So you see, you don't have to be a planet to have life on it.

Speaker 1 What's the next one you've got?

Speaker 13 Well, Mars, because it's made of chocolate, to repeat the joke. Right, yeah.
Yeah, that's a good joke.

Speaker 1 I've got that. This one's moved on from chocolate.
Mars, because that's where all the men are.

Speaker 2 That's too sally.

Speaker 12 Allison is extremely pragmatic. It's Venus because we wouldn't have to worry about the heating bill.

Speaker 13 The forbidden planet, because I'm just a rebel and I dream of being told off by Brian. That's not me, that's Debbie.

Speaker 13 As Debbie, although also me.

Speaker 1 Saturn,

Speaker 1 because

Speaker 2 rings can only get better.

Speaker 1 Anyway, thank you very much to our panel, Michelle Doherty, Paul Abel, and Catherine Parkinson.

Speaker 1 We are recording this in 2024. You are hearing this in 2025.
So at the moment, we have no idea what next week is going to be about, or even if there is, next week.

Speaker 1 So I decided the best way was to find out through scientific methods. So, I have consulted Brian's astrological chart to see what is the most likely subject for next week's show.

Speaker 1 So, Paul, how accurate do you think that will be?

Speaker 14 I think it will be 112% point three accurate.

Speaker 1 You're entirely right. According to his astrological chart, it just says bloody physics again.

Speaker 1 So, thanks very much for listening. Bye-bye.

Speaker 2 In the infinite monkey cage,

Speaker 2 in the infinite monkey cage,

Speaker 2 in the infinite monkey cage.

Speaker 1 Till now, nice again.

Speaker 10 Best medicine. Dissecting funny and fascinating medicine.

Speaker 12 I think pain management is the best medicine. Bibliotherapy.
Therapy by books. Sleep.

Speaker 2 Well,

Speaker 10 Spot the Comedian.

Speaker 10 Celebrating medicines past, present, and future.

Speaker 1 I think transplantation is the best medicine because it can completely change someone's life.

Speaker 12 Defibrillation.

Speaker 2 Oh, defibrillators. Okay.

Speaker 10 Amazing machines. That much is clear.
Sorry. Clear.

Speaker 10 That's the new series of best medicine from Radio 4 with me, Kiri Pritchard McLean. Available now on BBC Sounds.

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