#433: Marsquakes Surge & Parker Probe's Record Speed

[00:00:00] Hi there, thanks for joining us again. This is Space Nuts. My name is Andrew Dunkley. Thanks for your company. Coming up, we will be looking at a couple of things. Marsquakes. Looks like they're

[00:00:10] happening at a faster and more furious pace than ever thought. And that's because we can detect them now with much more accuracy. Also the Parker Solar Probe has made the news again. It is skimming

[00:00:25] around the sun almost literally, but it's doing it at a thunderclap race pace. And we'll also be looking at a supernova first seen in 1181. But now we know all about it, or at least more than

[00:00:39] they did back then. That's all coming up on this edition of Space Nuts. 15 seconds, guidance is internal. 10, 9, ignition sequence start. Space Nuts. 5, 4, 3, 2, 1. Space Nuts. Astronauts report it feels good. And here again to furnish us with his knowledge or at least help my

[00:01:04] son move furniture because he's got a new apartment in Sydney is Professor Fred Watson, astronomer at large. Hi Fred. Thanks Andrew, just let me know and yeah we'll be there helping. Yeah we're planning the trip down. He hasn't quite got it yet, all the legal stuff you know.

[00:01:24] Whereabouts is it? What suburb is he in? Campsy. More specifically a place called Clempton Park which is very pretty leafy little suburb. And best of all he's not on a main road whatsoever so no traffic. Very hard to do in Sydney, very hard to do.

[00:01:43] We're quite proud of him because he's managed to do this all by himself in the second most difficult real estate market in the world. Which I think is really impressive. It is. So ladies, he's a catch.

[00:02:01] There you go. Well let your friends know. Yeah yeah. Now before we get into our stories, you've just come back from a little trip to South Australia where you took a tour group around to

[00:02:15] show them rocks and things. It must have been exciting. It was. It was a lot more exciting than you make it sound. So it was a round trip really. We started off in Adelaide, headed up to Port

[00:02:29] Augusta and then to Coomber Pedy via Woomera which is a name I've had in my vocabulary since I was about six. Because it was always in the news, was Woomera, when I was growing up in the 1950s

[00:02:46] that this was the spaceport for British rocket tests and all kinds of other things. And it was all happening very much front of mind, very prominent in the media. But I've never been

[00:02:59] Andrew. Never visited Woomera until now. And it's worth a look. Look, you would enjoy it too. There's a lot of vintage space stuff there, reminiscent of I guess the Kennedy Space Centre, but an earlier generation when rocketry was in its kind of, the modern era of rocketry was

[00:03:20] in its infancy in the post-World War II period. Lots to see, some really interesting aircraft missiles, rockets and all the rest of it. Yeah. Is Australia's first ever rocket still in that chuck shed? Probably. I didn't see it there. It's there somewhere apparently. Yeah, it would be.

[00:03:43] But of course it's still an active site. I think it's the RAAF that operates now. The Woomera prohibited area, it's a huge area of South Australia. I don't know how many thousand square kilometres it is, but they still do launches and people in the area, the station

[00:04:02] dwellers, station holders, people have got sheep stations and things like that. They get told every so often, oh, we're going to evacuate you for a day. So, well, they do something. And it's very

[00:04:12] secret. So we didn't find out about any of that, but we did talk about the history and it was great. Then I should mention the reason it's called Woomera is because that's an Aboriginal device

[00:04:27] to launch a spear. It is, gives you a spear, much greater reach. An extra kick. Great name. You met some space nutters too. We did, yes. We followed the path around to places like Williams Creek and Maree. Maree is interesting because it's got a man,

[00:04:50] the Maree man, which when you see it from the air is an Aboriginal elder probably. He's got a long beard and he's four kilometres long. And nobody knows how he got there, but it looks as though

[00:05:04] he's done by bulldozers or something like that. And then down to Arcarula, a place where there's a dark sky park and to a place called Nilpena. And in fact, the Nilpena Ediakara National Park. Ediakara is the name of the hills in which some very interesting fossils were found

[00:05:26] some years ago. And these are the fossils of the first animals, basically the first things that moved around on beds of microbial mats in shallow seas. And we met the chief ranger there, Kim Goyer,

[00:05:44] I think is the way his name is pronounced, who flashed his space nuts t-shirt at us as soon as we arrived, which was great. So it was good to see him and talk to him. And then a bit further on,

[00:05:56] we met another space nut case down on the Murray River. We were at a place called Manham at the time, but we had a lovely dark sky event. All the locals came out and we did some talks and

[00:06:10] everybody dressed up in stars and spacey kind of stuff. One of our tour guests came fully clad in an astronaut suit, which apparently needed a pump to keep the air blowing through it so he

[00:06:23] didn't die. Fantastic stuff. But there we also met Tracy Hill, who's another space nut. And Tracy was very gracious in the fact that she took part in a charity auction,

[00:06:40] which was to buy a copy of a book called Why is Uranus Upside Down? That had something to do with me. So she paid a handsome price for that. And Tracy, well done. There was a slight mix up with Tracy's

[00:06:53] name when the winner was announced. So I had to rewrite the inscription in the book, but it was great to meet Tracy. We had a nice chat and we'll stay in touch with both Kim and Tracy because

[00:07:04] these are people who are passionate about the district they live in and passionate about the things that they can show people. Wonderful. All right. Hello, Kim. Hello, Tracy. And thanks for being space nuts followers. They're all over the world. I think you'd be hard pressed not to run

[00:07:20] into one these days, the way things are going. It would be nice to be like that, wouldn't it? I didn't run into any in China though when I was there a few months ago. Yes, we've never had a question from China, I don't think.

[00:07:35] More than welcome. More than welcome. Yeah. So you're back down to earth now, so to speak and back to normal for a little while. But Space Nuts continues and we're going to talk about Marsquakes now. And this is a really interesting story because we have talked about

[00:07:52] Marsquakes before and they've been investigating them courtesy of the InSight mission, but now they're starting to come up with numbers that are a little bit bigger than they expected. That's correct. The analysis of this, Andrew, comes from a spacecraft that's no longer operational.

[00:08:16] Our old friend InSight, which was fitted with a seismograph, seismometers to measure Marsquakes. And the bottom line with this story is that some of the Marsquakes have been misinterpreted, which is easy to do when you're looking at a record of, I guess, little tremors

[00:08:46] that you don't really have much of a clue with that tremor as to where they come from. We did talk about this recently, actually, because some people said when you've only got one seismometer,

[00:09:00] how do you know where these tremors are coming from? And there's various signatures in the tremors that you can interpret as to what the path that these tremors have taken through through the Martian crust, what that path is. So this is work that has been carried out by

[00:09:22] scientists at ETH Zurich, which you might know is the university that Einstein attended, and Imperial College London. And I once did a course there. So there you go. It's a common ground for us in the world of astronomy. So these scientists, what they've done is they've

[00:09:40] essentially made a kind of estimate from the seismic data from InSight as to the global meteorite impacts. And that gives them a number of somewhere in the region, they've caught between 280 and 360 meteorites striking the planet each year, forming impact craters greater than eight

[00:10:09] meters, which is about 26 feet. So these are impact craters that you could detect from space, you know, with the various Mars orbiting spacecraft. And indeed they have, they've managed to link and I think this is the crux of the matter, they've managed to link some of the

[00:10:30] seismic traces with what are obviously newly excavated impact craters, so that you can tell by the color, if you're looking down from an orbiting spacecraft and you see something that has a particular color against the red of the Martian dust, you can get a clue as to whether

[00:10:55] that crater is a new one or not, whether that is the result of a recent impact. And in fact, I think they've been able to tie down some of the seismic traces with a particular new

[00:11:11] impact feature. So basically what it means is that it's, I think it's something like five times the number of impacts that we thought were hitting the surface is what is now estimated from this new research. And what the conclusion they come to, actually let me quote Geraldine Zenhuisen

[00:11:38] from ETH Zurich, who says, the rate was about five times higher than the number estimated from orbital imagery alone. Aligned with orbital imagery, our findings demonstrate that seismology is an excellent tool for measuring impact rates. So there's that link between what you can see from

[00:11:58] orbit and what the seismograph is telling you. I'm fascinated by this because they're giving us numbers in the hundreds, but Earth gets hit to the tune of thousands a year. And we don't seem to

[00:12:15] see those sorts of cratering effects. What's the difference? Is it because Mars atmosphere is so thin and can't be traced? Yes, that's right. So, you know, if we had the same atmospheric density as Mars, two or 300 eight metre craters every year would be headline making news.

[00:12:42] Because you wouldn't really want to go anywhere without experiencing the risk of something hitting you on the head that could cause an eight metre crater. And so that's, you know, that's the crucial part is that Mars atmospheric pressure is 0.6%,

[00:13:05] 0.6% of Earth's atmospheric pressure is less than 1%. So there's much less of a breaking influence by the atmosphere on Mars than there is on Earth. And by breaking that's B-R-E-A-K-I-N-G. So what it means is that these meteorites always hit Mars' surface at very high velocity,

[00:13:35] what they call hypervelocity impacts. And it's that that really betrays the to orbiting spacecraft that reveals that something's happened recently, because they apparently cause a debris zone around the crater, which is more than 100 times bigger than the

[00:13:57] crater itself. So they stand out from orbit, you've got a crater maybe eight metres across, and that's pretty big, but with something 800 metres around it that tells you that there's something's happened there. So actually the points made in the paper that they've written,

[00:14:19] knowing the number of impacts is going to be really important for the safety of any exploring spacecraft, whether they're robotic or whether they've got humans on board. And I suppose there'd be no pattern to this. So I guess if you had the time to analyse it,

[00:14:38] you might be able to figure out where and when these things might happen. But it increases the risk. I mean, if this was Earth, our insurance policies just wouldn't be... we couldn't afford them. But when you're talking space missions in an environment that's

[00:14:56] hostile and we're not built to suit Mars's atmosphere, you'd want to collate as much data as possible to try and avoid these situations, I imagine. Yes. So it's obviously something that will be taken into account in future mission planning. It's a bit of a warning really that

[00:15:19] Mars is a rather more hostile environment than we expected. At the same time, it's not going to rule out Mars exploration. I think it's safe to say that we've had how many rovers on Mars? It's probably

[00:15:38] 10 if you include the Chinese rovers, you include not just Spirit and Opportunity and Curiosity and Perseverance, they're the big four. But there were rovers before that, Pathfinder was one of them. Maybe it's not 10, but perhaps six, seven or eight, something like that. Rovers on Mars, none of them

[00:15:57] as far as we know have been zonked by an incoming meteorite. So it's a risk, but it's a low risk. Yes, yes. And I suppose we should also say that not all these Earth tremors that have been picked

[00:16:12] up over the course of this mission are caused by meteorites. Yes, that's correct. There's been other factors as well and some of them are still a bit of a mystery. Yes. So that's really the

[00:16:25] I guess the whole point of their argument that they've been able to isolate the ones just by their characteristic signature, they've been able to isolate the ones that are caused by meteorites rather than by tectonic activity. There isn't much tectonic activity on Mars in that regard,

[00:16:43] its core is much cooler than the Earth's and so it doesn't drive the tectonic activity that we have. Okay, if you want to follow up on that story, it's being published in the journal Nature Astronomy. This is Space Nuts, Andrew Dunckley here with Professor Freer Watson.

[00:17:01] You're okay and I feel fine. Space Nuts. This next story is interesting too, Fred, in that we've been hearing about, well we've heard about this once before but it's happened again, the Parker Solar Probe which is orbiting the Sun

[00:17:19] and has been since, oh gosh, what was it? It's been up there for five or six years, I think, something like that. It's just achieved or equalled a speed record during one of its recent orbits and we're talking numbers that are just mind-blowing. I mean,

[00:17:41] hundreds of thousands of kilometres an hour. That's amazing. It is. So the Parker Solar Probe is interesting. It's one we haven't talked about much but it has been active, as you've said, for some years. It's just completed its 20th close

[00:18:01] approach to the Sun and that's telling you that this is the spacecraft that comes closest to the Sun of all the solar orbiting spacecraft that we have launched. This one is the closest

[00:18:17] and in fact its 20th close approach was on the 30th of June 2024, not very long ago. Its distance was 7.26 million kilometres from the solar surface and by that we mean the photosphere, the bit beyond which you can't see. The Sun doesn't have a surface because it's a

[00:18:37] ball of gas. That's about 4.51 million miles. So it's, you know, in terms of cosmic distances, that is grazing the surface of the Sun. It's very, very close and Kepler's laws tell us that

[00:18:52] the closer you get to the body that you are orbiting around, the faster your velocity is. It's how it works and that's why we've got this record speed. In miles an hour it's 394,736 kilometres per hour. It's 635,266 kilometres per hour, which let me do it in my head,

[00:19:16] is somewhere under 200 kilometres per second. I haven't got a calculator handy but it's in that region. You divide it by 3,600 to get kilometres per hour into kilometres per second. So it's in the region of 200. That's a phenomenal velocity and at that speed

[00:19:40] you've really got to take relativity into account, not just because of the speed but because of the gravitational potential that you're in. You know, you're in a strong gravitational field and both of those things mean that Einstein's two theories of relativity, the special theory which is about

[00:19:57] speed and the general theory which is about gravity, those two absolutely start dominating your calculations. So really interesting stuff for all kinds of reasons. The Parker Solar Probe is fitted with heat shields that seem to be withstanding the stresses and strains on the

[00:20:16] spacecraft that come from being so close to the Sun and we look forward to hearing what data have been collected during that 20th close approach to the Sun. Yeah, it seems to operate in a very complex orbital pattern because it uses gravity assist

[00:20:33] from Venus in some situations. It just depends on what's available at the time I think, but it would all be mapped out. But it will be doing its next pass on the 24th of December and they expect it will probably crack near 700,000 kilometers an hour in that pass.

[00:20:54] And that's just unthinkable isn't it? This has got to be the fastest thing ever. Yeah, well that's right. It's not the fastest that was launched but because it's been wound up by all these gravity assists to push it so near the Sun, yes it

[00:21:11] probably is the fastest spacecraft ever. I wonder how it survives the environment that it's exposed to. I mean just the radiation that's bombarding it for one, but it would be exposed to tremendous heat wouldn't it? Yes, that's right. So it's got a pretty substantial heat shield which

[00:21:32] if I'm remembering correctly, I think the spacecraft is turned so that when it's closest to the Sun, the heat shield is doing all the work. And while the spacecraft kind of behind the heat shield is making the measurements. So yeah, very intriguing and very, very successful

[00:21:52] mission actually. So I think it's got, is it four more or three more close passes to the Sun? I think it's three more. And actually, no, it's four more. It's got four more close passes. So

[00:22:10] the mission is sort of coming to its closing phases, but we will no doubt hear more about it. We probably should do a nice story on the Parker Solar Probe at some time down the track when we

[00:22:22] see some of these results. Yeah, I just found that the final pass will be next year, the 24th flyby of the Sun. So its mission comes to an end in 2025, but I mean that's how long it takes to

[00:22:35] sort of work its way into position to do a pass because it's going so fast. It can't just sort of stop and go back. It's got to go out and do another lap around whatever it can do,

[00:22:47] a lap around Mercury would be involved I imagine. But yeah, it's quite extraordinary. What a fascinating mission. And yes, we should talk more about it when they start releasing some of the

[00:22:58] data, I guess. Who knows what they could learn? There's so much we don't know about the Sun, which makes it such an interesting thing. And it is the nearest star to our planet. So

[00:23:08] we can learn a lot about things that are so far away and untouchable just by observing what's right next door. Yeah. Fred, let's get on to our final story. This one I also find intriguing. And this one dates back to the year 1181 when there was a supernova recorded.

[00:23:28] But we're only now starting to learn more about it. Yeah, that's right. 1181, it's a time... We often associate these supernova, ancient supernova explosions or observations with Chinese scientists. And in fact, probably the best known is the supernova of 1054,

[00:23:52] which was observed by Chinese scientists. If I can call them that, they were certainly assiduous observers of the sky. That 1054 supernova is what produced the Crab Nebula, one of the most famous supernova remnants in the sky in the northern constellation of Taurus,

[00:24:10] the bull. The Crab Nebula is well studied. And in fact, we've in the last few months seen some extraordinary images of it from the James Webb Space Telescope. But this one is different. The supernova of 1181 was recorded throughout Asia, but mostly in Japan. Japan was, again, the

[00:24:37] home of people who were very, very clever and careful sky watchers. And it's a time actually when Japan was at war with... As often was the case in past history, it seems to be still the

[00:24:58] case today. But Japan was at war and there were records kept of that time, which were put in a kind of... It's what's described by our old friend phys.org, which is the website that's carrying

[00:25:18] this story. It described as in diary format. So, you know, it's like a journal, I guess, called the Azuma Kagami. I hope I'm pronouncing that correctly, which chronicled what was going

[00:25:33] on. The events taking place mostly to do with the war. This was all not very far from modern day Tokyo. But other things, including this appearance of the new star, they are called

[00:25:50] a guest stars in those ancient texts because they're just a guest in the sky that then goes away. And indeed, there is a note here that this one was also observed in China and Korea as well,

[00:26:06] and was bright enough to be quite noticeable. It wasn't a daylight supernova, which we think the 1054 one was, but it's comparable in brightness to the planet Saturn, which is certainly noticeable.

[00:26:21] It's not the brightest of the planets, but it's up there with the ones that you really do notice in the night sky. Apparently, it was visible for about 180 days, and then dimmed away and was lost. And it took a long time for modern day scientists to find it.

[00:26:47] What's happened is that basically using the text of this diary record of the supernova, the Azuma Kagami, people have narrowed things down to the constellation of Cassiopeia, which is another far northern constellation in the northern sky. We

[00:27:14] see it certainly from the latitude where I am in Sydney. So that gave the scientists enough of a clue to look for a remnant from this explosion. And it's quite different from the remnant from the

[00:27:33] Crab Nebula, which is just like a tangle of material dust and gas that's obviously got shockwaves propelling through it in all different kinds of directions. This is something quite different. First of all, it's visible in X-rays. And what we have is an X-ray image from the XMM

[00:27:57] satellite with some infrared components as well from an infrared spacecraft called WISE. So we're looking at this in two different wave bands. And what we can see in the structure is, first of all, it's a spherical object, which has some really detailed

[00:28:21] what we might call contours in it, where you've got things like, first of all, in the middle we've got the wind bubble. This is coming from the paper about this. Then there's going outwards a wind termination shock, and then a region of unshocked ejecta.

[00:28:39] That's material that's come from the explosion but hasn't had a shockwave going through it. And then there's something called a reverse shock, and then a forward shock. And all this complexity can be sort of seen in the X-ray image. And... That sounds like my golf game.

[00:29:00] Got forward shocks in it. Too much wind and too much shock. Can just see you doing a reverse shock with your number five iron or whatever. Anyway, but that study has given enough detail that scientists can now work out what this supernova

[00:29:20] was. And it's a very rare one, something that does not normally happen. Two white dwarf stars. Now white dwarf stars are what our Sun will end up as. It's basically a thing the size of the Earth

[00:29:37] with the density, with the mass of the star. So very, very dense and very hot. That's how the Sun will end its days in a few billion years time. But two of these objects apparently have collided.

[00:29:49] And that's what has caused this very unusual type of supernova. A lot of the work has been done with computer modeling, of course, and analyzing the observations. And the rarity is this double shock formation that we've just spoken about. The forward shock and the reverse shock and then

[00:30:09] the inner shock. And so there is a sort of footnote to the story though, that comes from these observations. The sort of winds that blow from this event, what we call stellar winds, they are

[00:30:28] thought to be relatively recent in their formation. So that they say, perhaps only within the past 20 or 30 years, these high speed stellar winds have been blowing from the surface of the star, which is quite extraordinary, really. Just we happen to be looking at it at the right time

[00:30:46] to see some of the action. Yeah, indeed. And we get very lucky sometimes with observations, but I suppose we could also suggest that these things are happening so regularly. Maybe it's not

[00:31:01] luck, we're just picking them up because they're happening at a rate of a dime a dozen. But this one, this one's different. This one's been quite unusual and a very lucky discovery indeed. My hope

[00:31:14] Fred, one day is we do get to see one for real in our lifetime. Betelgeuse being the optimum candidate, I suppose. Yeah, that's correct. We don't want one too close, Andrew. But yeah, Betelgeuse is

[00:31:30] about 700 light years away, I think, which is far enough away that we would certainly see something visible in the daylight sky, it would be very bright, but is not going to be lethal to life

[00:31:50] on earth, which a nearer one might be. Yeah. And in recent discussions, we've talked about things that have happened so far away from us that have actually affected our atmosphere. So yes, that's right. It is really mind boggling to consider that there's so much influence out there

[00:32:11] is so far away and we think we're all safe and well, and we are, but you just always got to consider the possibilities, I guess. But yeah, that story was published in the Astrophysical

[00:32:23] Journal if you're interested in finding out about the SN1181 supernova. Fred, we've reached the end of the program. Thank you so much. Well, it's a great pleasure, Andrew. It's not a pleasure to

[00:32:37] have reached the end, but it's always a pleasure to talk about these things. The end is nigh. Yes, I'm sure. No problem. We'll see you on the next episode. Sounds good. Thanks very much, Andrew. Take care and we'll speak soon. Fred Watson, astronomer at large, and thanks for

[00:32:54] listening. Don't forget to follow us on social media or if you're on YouTube, hit the subscribe button and don't forget to visit our website, spacenutspodcast.com. Oh, and thanks to Hugh in

[00:33:06] the studio who couldn't be with us today, but all the best to his wife who's dealing with some medical issues as we all are when we reach this age. And from me, Andrew Dunkley, thanks for your company. See you on the next episode of Space Nuts. Bye-bye.