The Supermassive Podcast - 50: Quakes in Space

Episode Date: February 28, 2024

Izzie and Dr Becky are exploring shaky ground, whether that’s on Earth, other planets and even on our neighbour the Moon. This month is all about quakes.  With special thanks to Mark Panning, the project scientist for NASA's InSight mission, and Dr Jess Johnson from the University of East Anglia. Join Izzie and the UK Space Education Office for Mars Day on Tuesday 5th March, sign up to the virtual event here.  Explore the North Tyneside Solar Trail and discover models representing planets from our solar system, 16 & 17 March 2024 The Supermassive Podcast is a Boffin Media production for the Royal Astronomical Society. The producers are Izzie Clarke and Richard Hollingham. 

Why do we get moonquakes? And it's sort of that snap backing and that's what gives us what we call a space quake. When the earthquake happens, it's completely random. It's the subject of very many bad disaster films. Hello and welcome to the Supermassive podcast from the Royal Astronomical Society with me, science journalist Izzy Clark and astrophysicist Dr Becky Smethurst. Yeah, hold on tight because this month we're covering shaky ground. This episode is all about quakes, whether that's on Earth with earthquakes or other planets entirely.

And even on our pal the moon. Yeah, moonquakes. Do you know what? I'm looking forward to getting into that later because it's just something that we bypass all the time. But anyway, Dr Robert Massey, the Deputy director of the royal astronomical society is here too so robert can you give us a basic definition of a quake is there one yeah as basic as i can so the british geological survey has a handy definition that it describes it's a sudden release of energy in the earth's crust in this case uh leading to waves radiating outwards and shaking the ground. Now, we see about, we detect about 200 or 300 moderate quakes each year, even in the UK, although only a small number are actually strong enough to be felt, about 10% of those.

I have to say that I know quite a lot of people who've felt earthquakes in the UK, but I'm not one of them. I've slept for them. I've been at my desk, you know, when an earthquake's happened, just didn't notice, you know. It's like, just doesn't happen for me. The only thing I remember about when earthquakes hit in the UK is all the news stories that are like, my wheelie bin fell over.

Yes. Yeah, exactly. My windows vibrated. Yeah, which is pretty much as strong as it gets. I mean, my wife actually felt quite a strong earthquake in Athens back in 1999. And that was known by those of us who saw the total solar eclipse that year because it was around the same time.

But not that there's a connection. But, you know, that was an example of someone. I do know people who felt them, just doesn't include me. I felt one. It was actually when I was observing. So I was using the Caltech Submillimeter Observatory, which no longer exists, sadly, but it's on top of Mauna Kea in Hawaii, which is obviously quite a geologically active place. But we were in this telescope that the whole control room moves with the telescope as you move the telescope to look at something else.

So we just felt the shift and we thought it was like, you know, like the tracking on the telescope catching up or something like the dome catching up with the tracking and then we were looking at all these cables swaying like rhythmically and repeatedly and we were like was that an earthquake and then we realized the telescope was not pointing where we where it was supposed to be pointing anymore so we realized that an earthquake had hit well maybe i'm experiencing one in the uk right now because just as you were saying about the wheelie bins the bin men arrived and i was like that's they're called bin men what which one is it um okay but where else in our solar system do we actually see seismic activity well we detect it in quite in a couple of places we detect it on the moon as he mentioned and on mars and i think we'll hear more about that later on and it's almost certainly present on venus because there's evidence for new features forming there it's just putting a seismometer on the surface of Venus is a challenge because even

robust Soviet space probes were destroyed within about an hour and a half it's just such a harsh environment however there's also this idea of detecting them from above with balloons and that's been done recently on Earth so it could be tried in places like Venus and we see geological features young ones on Mercury so it might suggest there's activity there too. And definitely on some of the active moons of Jupiter and Saturn, and it takes different forms. And the best example is Io with hundreds of volcanoes on its surface, but also Enceladus, Triton, which is a moon of Neptune, and Pluto. And all of those have what you could describe as cryovolcanisms. That's cold volcanisms.

It has features that are akin to flowing rock, but it's more about flowing ices of different kinds. And you have to stress as well, this is something that happens on planets and moons with solid surfaces. So if you have gas giants, obviously, you know, that's not a place where you're going to see a quake in that sense. You just see more of a weather disturbance in the atmosphere. Cheers, Robert. Then we'll catch up with you later in the show

for some more questions and obviously some stargazing too. So let's take a look at Mars. So as Robert said, we know that Mars has seismic activity and that's thanks to NASA's InSight rover. Launched on the 5th of May 2018, InSight made its way to the Red Planet to study the deep interior of Mars. The mission ended in 2022, but what did it find?

I spoke with Mark Panning, the mission's project scientist. One reason why we want to study Mars is that it's a big enough planet that it's held onto enough heat that it's had activity. It's had volcanoes that have erupted through the whole four and a half billion year history of the planet, including some that look like they've been erupting at basically the same spot for that entire amount of time. That's really interesting. But unlike the Earth, where we have this thing called plate tectonics that's moving stuff around and resurfacing the planet and constantly changing things so we don't

preserve really old signals. Most of Mars' crust is really old. The surface preserves billions of years of history. And so Mars is kind of in the sweet spot for kind of understanding how rocky planets evolve because it's big enough to be active, but small enough that it's not so active that it's erased its entire history. And so obviously you were incredibly involved in the InSight mission that went off to go and study all of this. So what were the aims of InSight? And can you tell us more about that mission? Yeah, so InSight is a pretty unique Mars

mission. It was the first Mars mission that was actually aiming to look inside Mars instead of looking at the surface or looking at the atmosphere. If you look up online what the inside of a planet looks like, inside of Mars, inside of Venus, inside of any of these planets. You'll see pictures where they show a cut in half planet and there's all the circular layers. But what you don't realize is when you look it up for other planets, a lot of that's really just guesswork. We don't know how big each of those layers are, which layers exactly are present. It turns out we know that really well for the Earth. And the reason why we know that really well for the Earth. And the reason why we know it really well for the Earth is we've been measuring earthquakes for a really long time.

And we can see how the waves go down in the Earth and how fast they go and what things they bounce off. And we have all the really precise measurements. On Mars, we have guesses based on gravity. We know when spacecraft fly by how much they move so that tells you how heavy the planet is and there's other things we could do to guess but it's not really well constrained so insight was going to go and take that cartoon guess and make it more like the earth where we actually know what all of those layers are how big they are yeah and so what was on board to be able to do that? Like, how do you, where do you even begin with that? Insight was trying to redo

the first, what we call geophysics. We're putting out a really, really sensitive seismometer, which was going to measure Marsquakes. And it did. We also wanted to know how much energy is coming out of the planet. Turns out you can kind of think of planets as heat engines. Everything they do is just trying to get heat out, right? And so if you could measure how much heat's coming out, then that tells you about the planet. So we had an instrument we called the mole that was supposed to go down three to five meters and measure the heat coming out. We actually didn't get that deep, but that was the plan. And then the last thing we were planning on measuring was actually, we called it an instrument. It was called the RISE instrument, but it was really just looking at the radio

communications direct to Earth and looking at, you know, tiny little frequency shifts of those, which tell you how fast the planet's rotating and how that varies. These really detailed measurements tell you like basically how the planet wobbles. And that's kind of cool too, because it's like if you shake a jug of milk and you can feel how it wobbles, you know how full that jug of milk is. So that's what we were trying to do with Mars and see how it jiggled. And then from that, figure out things about its deep interior its core okay so let's talk about some of the results what were the big findings from InSight well first order we did what we aimed to do we really figured out that cartoon we knew how big the core was we showed that the

core of Mars was liquid which is actually what we, but that was consistent with the data we saw. It turns out how big the seismic waves that bounce off the core depend on whether it's liquid or solid, and it looked liquid. And also those little wobbles I was talking about were also consistent with that. We showed how thick the crust was. And what about all of the seismic information? What did you find from also measuring the seismic waves we did see over 1300 quakes over four years which is a lot but they're mostly small and we would only see them during certain times of the year because it turns out that seismometers are really sensitive to lots of other things and And during the dust storm season on Mars, we just basically didn't see Mars quakes then

because they were too small to get above the noise of the dust storm season. But during the non-dust storm season, we saw lots of quakes. The biggest quake we saw during the mission is somewhere around something we'd call a magnitude 4. But suffice it to say, if you lived in California and there was a magnitude four event, you might not feel it. You probably would feel it. But it's not a giant quake. So that was the biggest one we saw. If you look at them, they look like earthquakes in a lot of ways. Seismic waves shoot out from where the quake happens, we actually see a lot that are related to impacts, which are meteorites coming down and hitting the ground. So the waves spread out from that.

On Mars, what we see is that there's some shaking that kind of follows out past the initial arrival. And that's stuff that's bouncing off of fractures and broken things in the crust. stuff that's bouncing off of fractures and broken things in the crust. The crust on Mars is old, billions of years old. And so it's a little more broken up than what we see on Earth, where most of the crust isn't that old because we are constantly resurfacing the Earth. What I call a surprise, and it was a surprise because one of our pre-mission guesses was right. And I expect it to be wrong because space always surprises us. Planets always surprise us. I expect things to be wrong.

And we went and before the mission we said, hey, we're probably going to see events at this place that's not that far from where we're landing called Cerberus Fawcett. And we said, we're probably going to see events there. And that was cool because people saw from orbit that there were rock slides that had fallen down the edges of these cracks that make up the area. And they argued that lots of these rock slides must have happened at the same time. And maybe that was evidence of a Mars quake. That sounded cool. And it looked like something we were going to look for. And then we got there and about half the events we ended up seeing actually were in that area.

That's just always shocking when a prediction is right. So what are the processes that are happening on Mars that drive these Mars quakes? It's a good question. We don't know all the answers to that yet. I will say going in, what we expected, what we modeled for what was going to be driving quakes on Mars was basically that the planet was slowly cooling and contracting. So it's like when things get cold, they shrink. Mars should actually be shrinking a little bit as it's cooling down. That puts stress on the crust, and that should lead to quakes. And that's what we expected to see.

But most of the quakes we saw were, over half of them were in this place called Cerberus Fosse, which is a place that has some of the youngest geologic evidence of volcanoes on Mars. So there's eruptive material that's less than 10 million years old. And in geologic terms, that's really young. And we see all these events associated with it. And actually, the way the quakes look, it looks like stuff opening up, like cracks opening up.

It's not what we expected, but it seems like there's at least a large fraction of the seismicity on Mars that we observed is related to ongoing remnant volcanic activity that's still happening on Mars. Maybe today we haven't seen eruptions while we've been observing Mars, but this stuff is pretty young and it looks like there's stuff happening underground that's associated with it. Thank you to Mark Panning. And very quickly on the topic of of Mars I'm going to be hosting Mars Day on Tuesday the 5th of March so this is a free virtual event with the UK Space Education Office the European Space Agency and the UK Space Agency will be exploring astronaut training the latest

missions and you can expect to have a few astronaut appearances as well that sounds fun where can you register is he that sounds great anyone can register at marsday.org.uk that actually sounds really fun people should totally go yeah i'm really looking forward to it i'll be in uh cornwall for it um but it's sort of oh like the the uk space like launch like goon hilly so and then it's um obviously just a virtual event for everyone else but yeah very very exciting let's bring this a little closer to home then becky we've talked about moonquakes but let's get into it yeah what's going on why do we get moonquakes well i mean it's exactly what it says on the tin isn't it it's shaking on the moon

i think what i love about okay that's it i like to say it moon. I think what I love about the idea of moonquakes is that they were like a just completely unexpected discovery. Like no one thought that there would be moon quakes because it really is just this solid looking blob of an object in the sky. But the Apollo missions left seismometers on the moon, which I'm glad they thought to at least do it but it was completely unexpected when they started detecting moon quakes i think they detected something like 12 000 over the span of about eight years so i think they they were operational until they were like turned off in like 1977 or something but in that time you know they they detected a lot of quakes and chandra in three as well the the isros the indian space research organizations

lander um that was on another moon back end of last year that also apparently detected a moon quake while it was there as well so we've got a lot of data on moon quakes but they're pretty weak though like the strongest moon quake is you know a lot weaker than the weak hang on the strongest moon quake is weaker than the weakest earthquake okay i'm with you all right that took me a minute but i got that but they do last longer because there's nothing to like damp a moonquake once it starts so it will just you know if you think about the fact that you've got like plate tectonics on earth you've got going from like rock to sea and everything but with the moon it's just a solid thing that can reverberate around for for a long

time there's a few different types of moonquakes that we think we've detected so the obvious one is just asteroid impacts are the things that are going to create the biggest sort of quake around the surface but then if you think about the fact that because the moon is tightly locked with earth you know what if you pick a pick a place on the moon it has two weeks of daytime and then two weeks of night time that we call like the lunar night so as that comes back round into sunlight you start to obviously heat up the surface and then it starts to crack and quake um after two weeks in the frigid cold of space basically then you have a couple of different what we've termed shallow and deep quakes on the moon so shallow being anywhere from like 50 to 200 kilometers below the surface and then deep moon quakes which are like

more than 700 kilometers below the surface and we think the deep quakes are essentially from the tidal pull between the moon and the earth you know how we get the tides in the oceans we get this bulging in the oceans which causes our high tides. And then where there isn't the bulge, there's the low tides. That's also happening on the moon as well to the entire moon. So that sort of pulling from the earth is what we think causes these very deep quakes on the moon. Nice. And I recently read that the moon is shrinking as well, which is causing more quakes. So why is that a problem for future missions to the

moon yes this shrinking is what we think causes the shallow quakes that i just mentioned as well so do you remember how we think the moon formed is a big old collision with a couple of objects and here we go here's the moon so it's actually it was a collision with the earth so we think like a proto-planet collided with the very early earth and then all of that material spewed off and it coalesced around the earth to form the moon and so if you think about very hot rock it's been completely vaporized in sort of a collision with the earth we think what happened with the moon was molten and then as it's um aged it's cooled and it's still cooling to this day as well. And so we think there is still a bit of a liquid interior in there. But as rock cools, it also shrinks as it solidifies as well. And that

causes the outer crust of the moon, which is already solidified, to then crack and cause one of these shallow quakes. And there was actually a paper that was published last month by Water and Collaborators that looked into this with the Lunarissance orbiter which is you know like a nasa orbiter that's been in orbit around the moon for ages now it's a real workhorse of our studies of the moon and it's found evidence for faults on the surface of the moon what are called thrust faults so if you imagine like two pieces of rock next to each other that have been caused to shake and then they sort of push each other up in the same way that sort of like mountain ranges are formed on earth with tectonic plates.

It's not tectonic. It's just sort of like stuff shaking next to each other because of the, of the, of the quakes. And those faults can be like 150 meters high. Yeah. So they're a pretty big deal. And so this,

this paper was looking specifically at the South pole, like the South pole region around it because that is where the artemis missions that nasa are planning you know the ones to send humans back to the moon that's the area that they're planning to land them and they're trying to pick out a region that would be like hey that looks like a good and flat enough region that we could land people and it would be fine and we want to go to the south pole because it is like a scientifically interesting area of the moon. You know, it's where we think there might be a lot of water deposits if they're there and stuff like that.

So we need to know the best place to land. And if it's a particularly active region where maybe the rock is weaker, so these quakes affect it more, then that really does pose a hazard if you've got 150 metres of rust faults just popping up. Yeah, just a slight. Obviously, if you've got astronauts on the moon for a short period of time you've got less of a risk but if you are also planning to put a permanent moon base up there which is sort of nasa's long-term plan then that's also a big deal

thankfully there is a plan to put some more seismometers on the moon now to study this in more detail because obviously looking at it from the surface you can see where things have formed but you don't know how necessarily often these might be yeah it's called the far side seismic suite the fss that's being launched in 2025 and then hopefully with that they can make a really informed decision on where to put sort of like things long term okay and so more generally how common is seismic activities on other moons and how do we know that so on our moon there is rarer than on earth so i think 12 like i said 12 000 quakes were detected by the apollo seismometers over eight years i tried to find a number to compare it to on earth and there is a very large disparity so There's a lot. So I found that the Earthquake Information Centre

says that there are about 55 earthquakes a day around the world that we detect. That makes about 20,000 a year. So that's obviously still more than that was ever detected in eight years on the moon. But the USGS, the US Geological Survey, says 500,000 detectable earthquakes in the world each year. 100,000 of those can be felt.

So anywhere from 20, to five hundred thousand that's a real astronomer's number i feel oh i this is something i mean the interview is coming up later in the episode but this is something i should have got jess who's one of our guests to like confirm because there's a thing that we're talking about is what are you defining as an earthquake? So that could be where that disparity comes from. Yeah, exactly. So, but either way, whatever number it is, it's over 20,000, let's say, which is well more than was detected on the moon.

But the earth is not like the most geologically active place in the solar system. That title falls to Io, Jupiter's moon, which is the Galilean moon, you know, the four Galilean ones that you can see if you have binoculars or a telescope and you look at jupiter it's the one that's furthest in towards jupiter so it gets a lot of pulling in terms of tidal forces again making it the most geologically active place in the solar system as robert said before it's over 400 volcanoes which is quite

crazy for a moon as small as it is it's smaller than our moon and it has very strong quakes and it has solid ground tides. So, you know, we were talking about the Earth's tides a minute ago with the bulges in the oceans. It's actual ground bulges because the tidal forces are that strong. We don't have any seismometers on Io yet, sadly, but I can imagine that quakes are very, very common there given the tidal interaction with Jupiter.

And we also had this incredible flyby from the Juno probe recently that's in orbit around Jupiter. It came about, I think it was just over a thousand kilometers above the surface and saw these incredible plumes of volcanic activity on the surface of Io. So that's going to be trying to work out if there is still a molten core on Io. And that should hopefully tell us more about perhaps if there is still a molten core on Io and that should hopefully tell us more about perhaps if we could make a model of it how many quakes there would be yeah and in preparation for this episode I came across the terms starquake and spacequake which I think are a little different from what we've covered so far so let's start with starquakes what's a starquake yeah you see both of these involve magnetic fields which is not an astronomer's favorite your favorite topic everybody avoids

this question um i'll start with starquakes because i think they're sort of the most similar to earthquakes so these happen on the surface of neutron stars so this is like the core of massive stars that's been left behind after they've gone super nova right and you've crushed all the matter down to the point where all you've got is neutrons right neutral particles that are as tightly packed as they can physically go and resisting gravity still like if if you get too many of them there all of a sudden you'll collapse down into a black hole but you can resist it for a while with neutrons and they're obviously incredibly dense objects it's all a fluid inside but then you do have like a solid outer crust still on a neutron star then you've got also intense magnetic fields around a neutron star and so if the magnetic fields get a little bit twisted and wound up because also the neutron stars are spinning so fast

then that can interact with this sort of solid crust also the neutron stars are spinning so fast then that can interact with this sort of solid crust on the neutron star and it can warp the crust itself and you get what's known as a starquake we detect that as a huge burst of gamma ray radiation so gamma ray light very high energy light which if it was near enough to isn't at the right angle could wipe out all life on Earth. So that's another one for everyone who enjoyed the end of the world episode. See January's episode, please. Thank you very much. There was one quite recently, but thankfully it was far enough away and everything

that there was no issue to us. I don't think we are in danger. I wouldn't lose sleep over it. I'm sorry I ever brought it up. And then if we go to spacequake, which love this as a word i always hear it as space cake i don't know why and then i'm like cake but space quakes are also to do with magnetic fields but it's to do with our magnetic field on earth so we have this magnetic field that you can think of it you know like um do you ever do that experiment as a kid in science where you put a bar magnet down in iron filings and you'd sort of see all the iron filings like line up around the magnetic field lines so picture that

around the earth right and but then also picture it being completely bombarded by the solar wind which is like particles that are just streamed off by the sun so it causes the side that's facing away from the sun to sort of stream out in like a tail like a comet's tail almost and what happens is if the solar wind is particularly strong in terms of like if there's been like a flare from the sun or something like a burp up of more particles from the sun then it's particles it's it's plasma right it's not gas it's sort of like very high energy particles like electrons and protons and stuff that are loose that we call a plasma that then interact with that tail and can actually break some of the magnetic field lines and then cause them to like snap back towards the earth and it's sort of that snap backing

and that reverberation of the plasma around the magnetic fields that gives us what we call a space quake and essentially it's just a huge variation in the what we call the electromagnetic field around the Earth, which then interferes with all of our electrical things. Satellites. And that goes back to what we said in last month's episode where you have a very strong like aurora where you can then interrupt like communications and electrical grids and all that kind of stuff. So like I think the energy in spacequakes is the same as sort of like a five or six mag like earthquake in terms of stuff. So like, I think the energy in spacequakes is the same as sort of like a five or six mag, like earthquake, in terms of comparison. So they are like a big deal in terms of energy. But again, it's more of the solar storms we have to worry about than the spacequakes. Our planet is made up of a number of large tectonic plates, which have been slowly moving since about three and a half billion years ago. Plates meet at fault lines and can move apart, move towards each other and

also in slightly different directions. But during this movement rocks sliding past each other can get stuck and then when they suddenly move that releases a bunch of energy which can be felt as an earthquake and it's worth mentioning that they can be devastating. You might have seen the pictures from last year's earthquake in Turkey and Syria where lots of communities were flattened and we've seen the devastation of earthquakes and we now know that 55,000 people were killed. I spoke to Dr Jess Johnson, an associate professor in geophysics at the University of East Anglia, who told me a bit more about earthquakes and the new ways to study them.

In those areas where the two plates are locked together because of friction, there's ground deformation. So if you sort of imagine if you had a piece of fabric and you moved one part in one direction one part of another you'd get ripples you'd get kind of wrinkles and that's sort of what's happening a lot of the time in the crust and so we can measure that strain that deformation and find out how much is kind of stored up there how much much needs to be released. When the earthquake happens is completely random. Okay. We cannot predict when the earthquake is going to happen. We can find areas where earthquakes are more likely to happen because of this strain and because of mapping places that earthquakes have happened before, but we don't know when the earthquake is actually going

to happen so the earthquake starts happening the the fault itself will kind of rip kind of almost like a zip so it starts in one place and then it propagates along the fault and therefore one part of the rock will move relative to the other part. And it's that sudden movement that creates those seismic waves that cause the shaking. And then afterwards, the stress is somewhat released in that particular area. But it sometimes passes stress on to further down the fault that maybe a section didn't fail. So it's not true to say that if you've had a big earthquake you're less likely to have another one. In some cases you're actually more likely to have another big earthquake because it's loaded stress onto another part of the fault.

And so what determines the magnitude of an earthquake? I feel like you know when we hear about it in the news, it's always like magnitude six, magnitude seven. How does that work? Well, the magnitude is based on the size of the section of the fault that fails. So you can have a very small fault and it will have a very small magnitude. A very large fault will have a very large magnitude. It's also proportional to how much relative movement there is. So that's sort of the physics of how energy is released. When we measure an earthquake, we measure it with something called a seismometer. We essentially look at the size of the vibrations that have reached the seismometer and look at the distribution of that energy and we

can kind of follow it back to the source and we work out how much energy has actually been released so that's how we define the size of the earthquake and then we can work out something about the fault from that okay and so you know when we've been talking about earthquakes here it's very much that model of tectonic plates and you know taking us back to school days but is that the only way that you can have an earthquake absolutely not i think because of the way that earthquakes are covered in the media when media say earthquake you automatically assume and they mean a damaging earthquake or an earthquake that can be felt. The magnitude scale is logarithmic and so we often hear about magnitudes five, six, seven, eight, even nine. Nine's sort of as big as you can get pretty much but magnitudes actually

go down into the negative numbers. How does that work? Because it's logarithmic. Well, okay. Yes. So, okay. So talk us through that then. If someone hasn't come across this term logarithmic, how does that work? It means that for every point on the magnitude scale, the earthquake is 10 times bigger. And so you can have something 10 times smaller and 10 times smaller again and 10 times smaller again. And if you stamp your foot on the ground, you are creating very energy that caused seismic waves. And I actually quite like that definition because it doesn't tell you anything about the source and it also doesn't tell you anything about the size. So an earthquake can be caused by anything that creates seismic waves. It can be caused by natural processes such as faults and those are the most common types

but it can also be caused by an explosion or a collapse. Mine collapses will often cause earthquakes. A landslide might cause an earthquake but also in terms of size as I've already said, we can go down to very, very small earthquakes. And if we talk about hydro fracturing, which is quite a controversial issue. And this is fracking, is this like fracking? Yes, fracking. When the media say it could cause an earthquake. Yes, it absolutely, it does cause earthquakes. That is the point of it. The way that fracking works is they pump high-pressure fluid with other stuff into the ground to try and cause tiny little cracks.

It's those tiny little cracks that are actually earthquakes. They're just not felt earthquakes. They're not big enough to feel. We can measure them, though, and we can map them, and that's how people or scientists keep track of the fracturing process. Yeah so actually I'd like to talk about this so how do you for example measure earthquakes? How are you collecting that information? Okay so earthquakes have been recorded or measured for a thousand years.

In ancient China, they came up with the first sort of seismometer and it was like a jug with some dragon heads on it with balls very delicately perched in their mouths. And around that jug, there were toads with their mouths open. And if that jug got vibrated slightly, then the balls would fall out of the dragon's mouth into the toad's mouth. And so people were measuring not only that there was an earthquake and the size of an earthquake, but also what direction the waves were coming from.

Particularly over the last hundred years, the sort of modern seismometer has been developed and essentially it's a mass or a magnet that is anchored to the ground but around that magnet is a coil which is suspended on a spring and because of the momentum that coil tries to stay in the same place but the magnet that is attached to the ground moves if the ground moves and the relative motion between the magnet inside a coil of wire creates a current yeah so there are these types of inertial seismometers all over the world measuring earthquakes all the time but there are new techniques coming in, aren't there, which are using something that we're all very familiar with. So talk me through this because I think it's brilliant.

Absolutely. Yeah. So we're all familiar with fibre optics. We get our internet using fibre optics, but there's this new way of measuring vibrations in the earth using the fiber optics and it's called distributed sensing so when the telecommunications company lay the fibers there are always some that are backups that are not used and they're called dark fiber we can use the dark fiber network to monitor vibrations in cities so the way this works is the glass fiber is laid out underneath the ground and we shoot a light down the fiber. Now because it's light it travels much much faster than seismic waves and there are natural impurities in the glass fiber that reflect some of that energy. We measure the reflection of the energy. And if there are changes

in those reflections, it can tell us that the fibre has been bent or stretched in some way. And so that corresponds with, say, like a movement in the earth, that reflection is measuring that change in the ground. Absolutely. Yeah. So if the ground moves, then the fibre moves with it. Absolutely, yeah. So if the ground moves, then the fibre moves with it. And we can pinpoint pretty precisely to sort of 20 centimetres, where that movement has happened, how fast that movement was, how much it's moved by. And so not only is that a completely new paradigm in the way that we're measuring ground movement but if we're measuring every 20 centimeters we can capture very very small very localized events and learn a lot more about what's going on in the subsurface prior to these catastrophic failures thank you to jess

johnson that was so fascinating it is like I mean it's studies like this that are so important because you know like finding out new ways to study them helps with like earthquake defences in the long run as well which you know we all want to see come through. Yeah absolutely and Robert can I bring you in on this part? It seems like this is quite an area where there's a lot of exciting new developments as well. I think I saw that the RAS gold medal in geophysics went to someone studying earthquakes and seismic waves. Can you tell us more about that? Yeah, I can. And it did. It went to Professor Mike Kendall from Oxford, who is a longstanding seismologist who's worked in this area for many decades.

We award our geophysics medals to people studying planets in the solar system, including the Earth. So quite a lot of those gold medal winners are to people who look or looked in the past at earthquakes. And Mike's work is on seismology in general. He's interested in things like the layer at the base of the mantle, the interior layer of the Earth, and also just generally how waves propagate from them. And I've known him for many years and he's a nice guy. So if he's listening, I want to offer my congratulations to him. He's a former vice president. And to look at his science.

So he spent his career, as I said, looking at seismic waves, 20 years in Africa studying because there's a place in East Africa where there's basically a new rift opening up. There's a lot of interest from geophysicists and seismologists there. And he's now looking at how to manage the world's energy demands, including in areas like sustainable resources. So things like looking for geothermal energy sites and working out how to monitor the sites where captured carbon dioxide should be stored. So if you wonder about the applications of geophysics,

there are some really important real-world ones that come from that. Just like at Iceland. They've got it all figured out, haven't they? Exactly. Yes, exactly. We just need to be living on Iceland to get as much geothermal energy as we want, I guess. I was just like, how can they have so many electric cars over here? And I'm like, oh, because their electricity is practically free. Exactly.

This is the Supermassive podcast from the Royal Astronomical Society with me, astrophysicist Dr. Becky Smethurst and science journalist Izzy Clark. Right. We have had more and more questions. I'm aware that the Supermassive mailbox continues to grow, but these are just the ones on quakes. At some point it'll reach critical mass, Izzy, and it'll collapse and you won't have to worry about it. You joke, but it's already starting to glitch on me. But anyway, that's a different issue. It's a starquake. Blame the starquake. Sorry, the Supermassive Mailbox having a starquake.

Didn't get your email, thanks. But no, obviously, Becky, we've mentioned that Mars doesn't have plate tectonics or, you know, at least that we know of. So what about elsewhere in the solar system? Because longtime listener Martin Gregg asked this question. He says, is it still thought to be the case that Venus doesn't have tectonic plates? elsewhere in the solar system because long-time listener martin greg asked this question he says is it still thought to be the case that venus doesn't have tectonic plates yeah martin most people agree that no it doesn't which is a little bit confusing when we think about like that there

has been some surface changes okay so it's something internal to venus it's causing those and things on the surface do maybe look akin to like tectonic activity on Earth, you know, sort of like those fault lines and things like that. But people think it's more likely to be explained by ancient volcanism on Venus, it doesn't seem to have tectonic plates. However, I looked into this, and there was actually a paper by Weller and collaborators last year that used a supercomputer to model venus's atmosphere so particularly like the nitrogen content of venus's atmosphere and they said that could only be explained if there were plate tectonics billions of years ago now i am not a venus venus geologist i don't geologist geo means earth i don't know

what they call themselves if they're like a venus geologist but anyway i don't get geologists. Geo means earth. I don't know what they call themselves if they're like a Venus geologist. But anyway, I don't understand how they could have got that from there. Maybe I need to go read that paper in more detail. But I think it's a really interesting idea. But I think the agreement is that now there is no tectonic activity on Venus. There's a huge raft of arguments about whether there's current volcanism on Venus as well. There was like a paper that came out last year like comparing images that were taken of venus's surface that says oh look this has changed so it's got to be volcanic activity and people don't agree and people argue

about that so i think the bigger question is is volcanoes first and most people agree there's no tectonic activity okay and robert Robert Carl Lump Dunn says, I know axes can change due to quakes, but can orbits be affected here on Earth or elsewhere? Can we just start the axis part of that question? How do quakes change an axis? Quakes change an axis. He's like, do I have to worry about that?

We can't just gloss over that. Everyone else will just be like, sorry. It's the subject of very many bad disaster films, isn't it? This is a nice question to stretch my brain in the morning as well. But the answer is that the axis in space doesn't shift, but the distribution of mass around the Earth does, and that can introduce wobbles in the way that the Earth rotates and the way the axis behaves.

And you also, by the way, get that effect as well as some earthquakes and things like glacial rebounds, so the long-term changes in the shape of the Earth. And that does have an effect on things like the length of the day, and it leads to lengthening and shortening. So these little leap seconds that we get every so often, how often they come depends on those shifts to some extent as well. But for an orbit to change, I mean, for the axis, the rotation axis in space to shift itself, you need an external force. Unfortunately, that's extremely unlikely. And the same applies to the basic parameters of an orbit as well. So the mean distance to the sun, the distance from the Earth to the sun is not going to change except down to an incredibly catastrophic internal force so

some awfully large event so back to that end of the world episode again to think about that but that shouldn't be confused with what you get these cyclic changes going on and so the shape of the earth's orbit does change a bit due to its interactions with the other planets over time now in the very very long term if you wait billions and billions of years, then the sun is slowly losing mass because it's consuming its nuclear fuel infusion from hydrogen to helium. And as a result, the mass is going down. And so the gravitational pull to the Earth and the other planets is very, very slowly weakening. And so they're slowly drifting away. But that's on an enormously long timescale. So quite separate to anything in the short term,

like earthquakes. I just had a crazy thought while you were saying that robert right i was thinking like how could you physically change the orbit of something and my brain went back to io and i was like imagine that there was a like a volcanic eruption on io that was so large that it created some sort of mass ejection in one direction. Yeah, that's true. That then propelled the planet somehow in another. Could that change the orbit? Like a rocket engine. Like Iron Man, like Rocket Hand style, you know?

So yes, I suppose. I mean, I'm not publishing this in a paper. Don't put my name to it. Oh, I don't know. I think you should. Or get it under a pseudonym. April 1st paper, right? Yeah. Oh my gosh, that would be incredible. put my name i think you should or get it and get it under a pseudonym april first paper right yeah oh my gosh that would be incredible and becky our next question is from north tineside solar trail

but let's just give them a shout out first yeah so this is a model of the solar system at one to one billion scale that's going to be displayed along the north tineside coastline that's so cool yeah i'm just looking at the website now. So if anyone's up in that part of the world, northtynesidesolartrail.co.uk. It starts at Tynemouth, passes through Colourcoats and Whitley Bay, and it finishes at St Mary's Lighthouse. I love the Northeast Coast.

So I am like, yes, let's put a model of the solar system. It's essentially like a six-kilometre walk. Oh, nice. Sounds great. That's on the 16th and 17th of March, 2024. Lovely. But they have also sent in a question. So let's do that.

Oh, cool. What did they ask? I got so distracted. Before you're looking at the walking route. It's like, does solar system space combine with a beach walk? I'm there. So their question is, do earthquakes affect gravity? Oh, good question.

Yes, the local gravity, but not the global gravity, which I guess comes back to what Robert was just talking about because if it did, I would be worried. Because if you think about it, the local gravitational force that you feel from the Earth actually depends on the mass distribution in your general area. How much matter is actually there in terms of like are you near to like denser rocks and therefore like you will feel a larger pull ever so slightly you know from from gravity um so it's like if you're nearer to

a mountain range right there's just more stuff there that's you know gonna be pulling on you than if you're near like the mariana trench for example in the middle of the atlantic where there's like stuff missing um and so earthquakes like we talked about how they generate these waves in the earth themselves which are like density waves and they can actually sort of change the density of the rocks themselves and therefore gravity just for a little bit right for a short time and so the earth's gravity does sort of oscillate to some extent like in sync with the waves from the earthquake traveling around the globe but globally the pull of earth's gravity stays the same like the moon wouldn't notice like a difference with a strong earthquake for example right okay that makes sense and robert jade and mark has a question about io and jupiter

they say volcanoes are often talked about on io but how does jupiter's tidal force influence its seismic activity well i mean becky mentioned uh io in some depth earlier on but the simple answer is it's not that simple is that io is a small world next to a very big planet with a very strong gravitational field. And also a lot of relatively small, but still quite big for moons nearby. So the effect that happens on Io is that you get a tidal stretching from both Jupiter's gravity and to a lesser extent from the other moons. And that means that it heats up the interior and that's what drives those incredible eruptions that we see and you know presumably as Becky was saying lots of Io quakes as well so it's not the only example actually we also think that Enceladus which is a moon around Saturn that's well known for having plumes of water is experiencing the same thing but

this time associated with Saturn and if you go out from Io to Europa, that's another what we think is an ocean world, where there's a deep ocean under an ice crust. And the assumption is, too, that it's Jupiter's gravity and the other Galilean moons stretching that as well. So where you see that happening, you do get this heating effect. And, you know, it's really very dramatic in the case of Io. I should say as well, actually, you know, those volcanoes, like you mentioned, they were discovered by space pros. I think by Voyager 1 was the first one to see the volcanoes and i right back in about 1979 1981 around that time uh but we can now see them with good telescopes on earth as well because telescopes have got so much better in the last 40 years yeah i think jdwst detected it as well

recently didn't they detected plumes of from enceladus i'm not sure if they've detected volcanism from ioyabist they've no i i check this here they have also seen the plumes are from Enceladus. I'm not sure if they've detected volcanism from Io Ebbest. No, I checked this. Yeah, they have also seen the plumes on the volcano. So it's fantastic to be able to see this stuff. Yeah, it really is. Or near the Earth, anyway. Do we know if it's cryovolcanism on Io? I don't actually know.

Yeah, I think the assumption is we probably need to get an Io experiment on, don't we? We could do a whole podcast on Io. Do you know, it's so crazy. Add crazy to the list right i'm writing this down so ios yeah so i must be like hot volcanism but when you go to places like you and when you go to places like europa there's heating to melt the water and then these moons further out so enceladus is sort of like cryovolcanism because it's ice and water but the moons that are really far out like triton and they're also no longer planet pluto and they must have other weird processes going on that melt these ices so not not water so much but things like methane and so on and that flows and erupts in

a weird way i guess whatever juno results show us in terms of the interior will give us some sort of density so we can work out if it is actually sort of like a magma that we're used to on Earth or not. Yeah. So we really need to do a podcast on IO, Izzy. This might be my inner eight-year-old talking that just loved the page on IO in my Facebook because it looks so pretty, but I feel like we need to do a podcast on IO. Okay, it's on the list.

It's on the list. But thank you to everyone who sent in questions. And if you'd like to send one in for a future episode, then you can email podcast at ras.ac.uk or find us on insta it's at supermassivepod okay so let's finish with some of the usual stargazing robert what can we see in the night sky this well not the night sky but we are slowly seeing long days on the 20th of march we've got the spring equinox or the autumn equinox if you're in the uh the southern hemisphere so slow changes in the length of the day yeah this time of year it's not bad actually it's a good time to see pretty much the largest number of bright stars at least for us in

the northern hemisphere because Orion is still there pretty good in the evening sky right into April but you should look out as well for the fainter spring constellations like Cancer the Crab really quite faint but it does have things like Messier 44 or Precipi the Beehive a fabulous open cluster that looks brilliant binoculars and Messier 67 another one nearby Ursa Major including the plough gets really high in the sky in the spring as well and it's a fantastic signpost too if you follow the slightly unfeasible tail of the bear or the plough you run that down towards the bright star Arcturus which is very very obvious in Boötes the herdsman herdsman even and then the plough itself the middle star of the handle or the bear's tail if you prefer is Mizar on our course it's a sort

of visual double star pick and prepare binoculars and you'll see that well with a third one and if you have a small telescope you can see that Mizar itself, the brightest star, splits into two as well. I don't mention double stars enough really, but if you've got small telescopes, they're really nice targets. And under, as a major, you've got Leo the Lion and, you know, also Hydra,

which is mainly notable for being the biggest constellation in the whole sky, but it stretches all the way from not that far from Orion next to Manosra as the unicorn, all the way along the sort of horizon for us to under Virgo, which is visible later in the night. Now, in terms of objects to look out for, two come to mind this month. One is, which we mentioned before, a previous podcast,

Comet 12P Pondsbrooks, which is one that goes around the sun every 70 years. And it's at its best this month and into April. It's still quite faint, but it's been going through these weird outbursts, and we're just wondering, it's at its best this month and into April it's still quite faint but it's been going through these weird outbursts and we're just wondering it's just possible if it has another outburst then it might go from being something that's just about visible with the naked eye to something that's easily visible we just don't know so it's worth keeping an eye on with a with an app like Stellarium or something similar it'll be an Andromeda it's moving into Pisces and Aries and the crucial thing is that means it's over in the west and northwestern sky.

So you need a good horizon. You need to wait for it to get quite dark, but not completely dark. So the longer you leave it, the lower the comet will be. And just have a look. But the expression about this is that comets are described as being like cats. They've got tails and they do exactly what they want. And Robert, aren't there some people that are really keeping their fingers crossed that it's gonna brighten a little bit have cat zoomies i guess the equivalent of cat zoomies for a comment because if if if it does

there's the eclipse coming up on the 8th of april that goes across like most like a good chunk of the us and if it's bright enough you you might be able to see it during totality of the eclipse which is just an absolute bucket list moment. It makes me so much more annoyed that I'm now not going to see the eclipse like originally planned. Oh, you and me too. No, there are historical examples of this as well, where there were comets seen near eclipse sun,

and it must be an incredible sight. I mean, a total eclipse is impressive enough already. By the way, I should say I'm not going either, but good luck to those who get to see it. I think isn't Richard going? Richard, our producer Richard is going to be in Pennsylvania,

so probably clouded out, but hopefully seeing it and can report back for us if he does. Well, it's not much consolation, but the eclipse, I think there's a tiny bite out of the sun

visible from the UK. Oh, nice. I'll look out for that then. Like a few percent. So yeah. Through the clouds, I will look out for that like a few percent so yeah so the clouds i will look out for the tiny light um the final thing i'll mention is that mercury is at its best

in the second half of march and that's you know a type this small planet near the sun always quite hard to see but if you look for it in the right place it can be a lot more obvious and that's one of those examples so if you look in the western sky after sunset probably start about half an hour after sunset because it needs to get dark enough again use an app but those two weeks in the second half of March it'll be there above the western horizon doesn't look like much to the eye but if you get a small telescope pair binoculars makes it easier to see but if you get a small telescope you will see as well that it has phases and it's best it tends to look like a small half moon, so like a first quarter moon.

And that's one of the pieces of evidence that showed that the planets were going around the sun, that they were changing their position with respect to the Earth as we found out hundreds of years ago. Well, I think that's it for this month. We'll be back in a few weeks with another bonus episode. And then after that, we're going into interstellar space to explore interstellar

objects i am very excited so this is objects that are not from our solar system they've come from somewhere else and they're passing through passing through the neighborhood hey friends bye very quickly but hi bye and of course contact us if you try some astronomy at home it's at supermassivepod on Instagram, or you can email your questions to podcast at ras.ac.uk. And we'll try and cover them in a future episode if the mailbox doesn't collapse before that. TBC.

Until next time, everybody, though, happy stargazing.