Why Venus May Have Lost Its Moon Forever | Space Nuts: Astronomy Insights & Cosmic Discoveries

[00:00:00] Hi there, thanks for joining us. This is Space Nuts, where we talk astronomy and space science and dogs and cats living together and just about anything. Really, there's no topic that is ever ignored. Even when you don't want us to talk about it, we'll talk about it. Actually, we've got one of those stories in this episode. Not the first one though, because we're going to discuss Venus. Now, in many ways, Venus is just like Earth, except for one striking difference, aside from the world.

[00:00:30] weather, it doesn't have a moon. Why not? Well, yeah, there's probably a very dark reason for that. Satellite pollution. We're not talking about satellites in orbit, polluting our skies and making life for astronomers very difficult. We're talking about when they come back into the atmosphere and literally pollute our atmosphere. We'll see what's going on there. And the United States Space Force uniforms have been unveiled.

[00:00:59] At least one concept. And it's got some tongues wagging, some chins wiggling and some people scratching their heads. We'll talk about all of that on this episode of Space Nuts. 15 seconds. Guidance is internal. 10, 9. Ignition sequence start. Space Nuts. 5, 4, 3, 2. 1, 2, 3, 4, 5, 5, 4, 3, 2, 1. Space Nuts. Astronauts report it feels good.

[00:01:25] And he's back once again. It's Professor Fred Watson, astronomer at large. Hello, Fred. Hello, Andrew. You mean we're not going to cover migraines again this week? Why not? We can do that if you like. We've talked about that before. Yeah, we did. I mean, we've reached that age where the first topic, because I'm the captain of the veteran golfers at our local club.

[00:01:52] And the first topic whenever you sit down is your health. And what have you had done this week? Well, yes, I'm sure that's right. Because I'm a little bit older than you, my topics are even more interesting. So I was at a presentation last night where they were talking about coffins made out of mushroom fibre. Oh, my goodness. Yeah. Okay. That is different. It's different. Yeah, different. But apparently it works. Well, it'd be a lot cheaper, wouldn't it?

[00:02:22] Yeah, they don't last very long. Two days, I think, is the time it takes to decays. Wow. No, actually, I think it might be a bit longer than that. A very interesting presentation, though, from the Symbiocene Institute, which is looking at the ways that humankind can live more comfortably with its own planet, rather than being the terrible colonial species that we've been to date.

[00:02:50] Yeah. The problem with that is you've got to get everyone to agree. Exactly. And that was going to be my point, which I never really got to raise, but that's all right. Yeah. People come up with all these wonderful ideas about how we can do things right. But, you know, some countries will go, well, you know, we don't want to do that. Yeah.

[00:03:11] So I think just as an idea, though, and as a concept, I think this has much to approve of. Mm-hmm. And the reason what took me there was Marnie was part of a panel discussion yesterday. Excuse me. I'm sorry. Sorry, Marnie. I sneezed in the middle of your promo there. She was part of a panel discussion at which one of the other guests was an advocate.

[00:03:39] In fact, the founder of the Symbiocene Institute. Well, I think if you go to try to make those kinds of changes in the psyche of humanity, it's going to be a multi-generational approach. It's not going to be something we all just go to do, you know, the next day. Okay, we're now doing this. Yeah. Yeah. It just wouldn't happen. No, you're right. Humans don't work that way.

[00:04:07] But hopefully with enough panic from climate change, some things will change. Yes. Yes. Certainly needs to happen that way. Indeed. Shall we get down to business? Well, why not? All right. Our very first question is focusing on our twin planet. When we say twin, we're the good twin. It's the evil twin. We're talking about Venus.

[00:04:35] I mean, size-wise, it's similar to Earth. In fact, everything about it is similar to Earth. Size, mass, gravity, that kind of thing. Except it's got a god-awful weather pattern and it doesn't have a moon. And that's the subject of this particular story because they're trying to figure out why. Indeed, that's right. Yes, often referred to as Earth's ugly sister. Yes. Because of all the things that you've mentioned, the similarities.

[00:05:03] And as we're recording, it's very prominent in our evening skies at the moment. I really can't fail to see the planet Venus as it approaches its greatest angular distance from the Sun. In fact, it may even have passed it. I've kind of lost track with my confinement to hospitals and things of that sort recently. But it is still very spectacular in the evening sky.

[00:05:26] Anyway, a planet about the size of ours, of which we know a lot, thanks to orbiting spacecraft, which have carried with them radar equipment in order to be able to map the surface. Because the atmosphere, of course, is largely opaque. You can penetrate the atmosphere down to the surface in infrared.

[00:05:46] That was done actually by one of my former colleagues at the Anglo-Australian Telescope, David Allen, back in the 1990s, I think, or maybe 1980s, using infrared radiation. And it's to see the surface of Venus, which is quite a spectacular outcome. Yeah. But the best way to do it is with radar. And from that, we can see the topography. The jury, I think, is still out on whether Venus has plate tectonics because we see conflicting results.

[00:06:15] But the one thing that we do know for absolute certain is that it doesn't have a moon. Mercury and Venus, the only two planets in the solar system that do not have satellites, at least do not have natural satellites. So the question that you would ask as a scientist is, is that significant?

[00:06:38] Is that, you know, is it just happened, just the fact that the planet happens not to have a moon? Or whether it is a situation where Venus once did have a moon, given that moons are pretty common throughout the solar system, perhaps. There was a similar formation event to the event that formed our moon, when Thea, the object size of Mars, clouded the Earth in the early history of the solar system.

[00:07:08] And eventually that coalesced to form the moon. Which, by the way, I read a headline not very long ago that looks as though that formation of the moon from that debris cloud might have happened very, very quickly. And I can't remember how quickly it was, but it was surprisingly quickly. You might have seen that too. I think Jonty and I did actually do that story. Okay, great. Yeah. So, yeah, I was trying to find it actually through my notes. See my notes?

[00:07:38] These are all past episodes, all my notes. But I couldn't find it. Very nicely filed. Yeah, well, it's just a neat pile. It's not file. But I couldn't find it. But, yeah, I was trying to remember what we did about Venus previously and that was it. Yes. Okay. Anyway, so, yes, so Venus may have had the same experience. What would have happened, though, if Venus had had a moon? Why isn't it there now?

[00:08:07] And so this is the thesis of a group of scientists led by Stephen Cain, who's at the University of California, Riverside. He and his colleagues have looked to see, you know, what might have happened had Venus had a moon. So it's all done by modelling, of course.

[00:08:34] Their comments, more or less as we've just related, this is a comment from Stephen. Venus undoubtedly experienced large impacts, just as Earth has, and so has had as much, if not more, opportunity to form a moon similar to what we see in our own skies. So, all right, put a moon there in your modelling and see what happens.

[00:08:57] And this is the interesting bit because there is a really very neat explanation for why Venus doesn't have a moon that comes almost straight out of the modelling. And it's all about what they describe as the gravitational tug of war between Venus, a hypothetical moon, and the sun.

[00:09:20] And if you track this over billions of years, what you get is a situation opposite to what we've got on planet Earth. And that is that the laws of physics dictate that because there is basically an impulse given to the moon from the Earth's rotation slowing down, it means the moon is drifting away from Earth.

[00:09:49] And that's something we've talked about. It's well known, well established. One of those phenomena that we recognise as being scientific facts. But what they found, what these researchers found when they put the same sort of analysis into Venus and a moon, the moon would go the other way.

[00:10:10] It would basically, eventually, it would start to drift inwards towards Venus and spiral towards the planet, eventually passing within the Roche limit, which is where you can't have something staying together because of the competing gravitational pull on one side and the other, what we call the tidal effect. So it would break up.

[00:10:40] And, you know, even a big moon would not necessarily survive. In fact, one of the comments that Stephen Cain makes is an interesting aspect is that a heavier moon is destroyed faster, since a massive moon would drain Venus's spin so efficiently that it hastens its destruction. And so that is the basic outcome of this work.

[00:11:09] I think, in fact, I'm sure that they looked at a whole variety, these researchers of different scenarios. And one of the questions they addressed was, are there any circumstances under which a Venusian moon could actually survive? And the comments that Stephen Cain made on this are, survival came down to two main things.

[00:11:35] Venus had to be spinning fast when the moon formed, with a day shorter than about 12 hours. And the moon couldn't be too massive, up to roughly the mass of our own moon. In that narrow window, the moon migrates outwards and stabilises, much as the Earth's did. Outside that range, the moon is unfortunately doomed to be consumed by Venus.

[00:11:58] So a surviving moon would have to be modest in size, orbiting a rapidly spinning early Venus, which are conditions that don't match what we think the early Venus was actually like. And so, you know, the upshot of this is maybe indeed Venus did have a moon, which eventually was essentially gobbled up by Venus.

[00:12:24] It was drifted inwards, was torn apart, and the debris essentially rained down on the planet. The next step would be essentially to look for any, what you might call geological evidence on Venus that would give you some hints that this is what happened.

[00:12:51] And forgive me, Andrew, because I think I'm about to sneeze. Yeah, I've been fighting one for the last few minutes too. Why are we both sneezing? It's the time of year. That's right. Let me quote again Stephen Cain. Finding direct observational evidence is pretty tough. A moon lost billions of years ago would leave little to no direct trace we can point a telescope at today, so we can't observe the event itself.

[00:13:19] However, there are indirect avenues. For example, if a moon was destroyed and its debris rained down on Venus, it could have left a chemical fingerprint in the planet's surface or atmosphere. And upcoming missions to Venus, including NASA's Da Vinci, will measure the atmospheric composition in detail. So it is possible that we might eventually find something.

[00:13:46] One other comment from Stephen Cain is there's a broader test beyond our solar system because our results predict that slowly rotating Venus-like planets around other stars should generically lack large moons. So as astronomers begin searching for moons around exoplanets, that's a prediction that can eventually be checked against real data. So, yeah, it's a very nice piece of work, I think. A very interesting outcome as well.

[00:14:13] Yeah, and it sort of harps back to a story from a few weeks ago about how they do think they have found continental-sized anomalies deep in our crust that suggest parts of Thea exist. Might be parts of Thea, that's right. Yes, indeed. So, yeah, you can draw a similarity there. And so, yeah, there probably is evidence if that's indeed what happened. But, yeah, how do you find it?

[00:14:43] Well, we're very resourceful in that regard, I think. I think scientists, particularly astronomers, because they've got... All they've got is what comes in usually on electromagnetic radiation, apart from a few satellites going here and there. But, yes, it's... I think we might, well, get some hints as to whether this has happened in the past or not. Yeah. Okay.

[00:15:11] If you'd like to read up on that story, great article at space.com, or you can see the pre-peer-reviewed paper on the repository site archive. This is Space Nuts with Andrew Dunkley and Professor Fred Watson. Time to take a short break from the show to tell you about our sponsor, NordVPN. And if you're looking for a simple way to add more privacy and security to your time online,

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[00:16:33] go to this special URL, www.nordvpn.com slash Space Nuts. That's nordvpn.com slash Space Nuts. And don't forget the code word Space Nuts. Roger, your alarm's still here also. Space Nuts. OK, let's get close to home. In fact, we're getting right down and dirty into our own atmosphere with this story, and it's got to do with satellite pollution.

[00:17:02] Now, the number of satellites that are starting to appear in our sky is somewhat disturbing when it comes to optical astronomy. In fact, I saw a photo the other day where this problem was exhibited, where they'd done a little bit of time lapse, and the satellite tracks across that image were horrifying, if you're an astronomer. They were probably really interesting for other people,

[00:17:30] but it looked the same as, you know, the contrails that you see airliners leaving the sky. But it was actually the light reflection images of the satellites. But the other problem with them is when they come back down, they burn up. And what happens to all that stuff? And that's the nuts and bolts of this story, because they've chased a couple down to try and figure out

[00:17:56] what happens to, you know, everything that burns off them. Exactly so. And it is a... This, essentially, experiment is very well-timed, because at the moment we're with the Starlink constellation, which I think is kind of already past 12,000 spacecraft, not all of them functioning, those are re-entering at about one a day. That's the current rate.

[00:18:25] And every time one of those re-enters the atmosphere, it burns up at about 90 kilometres or thereabouts above the Earth's surface. And its contents, its metallic contents, become part of the upper atmosphere. And we already are seeing higher levels of certain oxides of aluminium and things of that sort that are probably the result of these re-entering satellites.

[00:18:52] So, the European Space Agency has, I think, in collaboration with a number of other organisations, what they've done is they have decided that they're going to check this out directly. And the way they've done that is by hiring a private jet, as you do. And it's using that private jet,

[00:19:21] they've basically chased a pair of re-entering satellites, which both were due to re-enter at about the same place, I think, a day apart. And so, what they've done is actually basically followed these in a jet which is festooned with spectrometers, images, and all of the equipment that we use to try and learn about what's happening when things burn up in space.

[00:19:51] And so, essentially, the satellites were tracked in detail. I like the spacecraft that they chose because there was a constellation called Cluster, which I think we might have talked about many years ago, European Space Agency constellation, which had four individual spacecraft, which were named after well-known dances.

[00:20:20] Tango, samba, rumba, and salsa were the quartet of the cluster spacecraft. And they actually were studying the way the Earth's magnetic field interacts with the solar wind. And they were launched back in, I think, back in the 90s. It's a long, long time ago. But their orbits were decaying. And in fact, rumba and salsa, I think, decayed quite some time ago.

[00:20:48] So, what was in question here was, since these spacecraft are still sending telemetry back, so you know what their velocity is, you know when and where these things are going to re-enter the atmosphere. And it was Tango and samba, which were basically, they had controlled re-entry, and it was basically that re-entry that was observed by this mission using a chaser jet,

[00:21:17] if you can put it that way, over the South Pacific Ocean. So, what we've seen, I think, is that this was successful. There's been a bit of a report saying that the outcome of the experiment was successful in that they got the data that they wanted. I'm not sure whether we yet have the details of what that analysis was, you know, in terms of what the exact effects on the atmosphere

[00:21:47] and the by-products that came from the re-entry of these two spacecrafts. So, I think those results are still yet to be described. But at least the experiment worked. Apparently, there were eight scientists on board this aircraft, and they observed the satellites from about 90 kilometres down to something like 65 to 70 kilometres when they stopped, basically stopped burning up.

[00:22:16] So, they were then completely vaporised. So, these details, as I said, we hope we will find a little bit more as the results come from that group of scientists. When they've finished analysing the data and start publishing, it could turn into something quite controversial because if they reveal that there's some really nasty stuff coming out of all of this, you know, a handful of satellites doing this,

[00:22:46] probably no big deal, but we're going to be talking over decades to come tens of thousands burning up. Probably more. Yeah. When it's one a day, which it is now, then you're potentially in trouble. And you're absolutely right, Andrew, because, you know, one of the possibilities is something we thought we'd licked back in the 1980s, and that's ozone depletion. Yeah. That's one of the possible outcomes of this.

[00:23:14] And that would then become a really hot potato politically, given that you've now got people saying, well, we've got all these pollutants that are actually starting to affect the behaviour of the upper atmosphere. And on the other side of the coin, you've got people saying, well, we need Starlink, because it's actually a vital service. It's vital infrastructure now on so many fronts. You've got a really quite interesting situation emerging, I think. Sure have.

[00:23:42] And yeah, where do you point the finger, if you want to put it that way? How do you curtail these effects and whose responsibility does it become? Yeah, you start looking, I think, at what you make your spacecraft out of. The Japanese have demonstrated that you can make wooden spacecraft and operate them successfully. Yeah. And I think wood is one of the more benign

[00:24:11] materials that would burn up. Of course, you've still got soot and carbon coming off that, but it might not be the aluminium that is certainly the biggest constituent of what is coming from present satellite re-entries. Yes, indeed. So yeah, it's a case of watch this space. We will probably learn more about this and we'll tell you all about it when that day comes. But they'll be analysing the data at the moment

[00:24:40] and we hope it's good news, but I've got a feeling it won't be, Fred. Yeah. I think you're right. Okay. That is a story you can also read at space.com. This is Space Nuts, Andrew Dunkley here with Fred Watson. We've been tranquility base here. The Eagle has landed. Space Nuts. Now, final story, Fred,

[00:25:08] takes us into the realm of science fiction, at least in part. They have just unveiled what might be the new United States Space Force uniforms. And they've got tongues wagging because they've drawn some similarities between the uniforms. And when I first saw them, my mind immediately went to SS uniforms of World War II. Exactly.

[00:25:36] And that is the controversy because they do not sort of, I mean, it's the first thing that comes to mind when you look at these designs, which have just been unveiled. And just to clarify where this has come from, it's come from Truth Social. It's one of the President Trump's, basically one of his posts on Truth Social. The as yet unconfirmed design is how it's being described. But yes,

[00:26:06] that was my thought too. When I looked at this, I thought, wait a minute, I've seen that sort of thing before. But you are probably aware as well of the sort of science fiction links that there are with this, where this uniform is said to have come from. Yes. This, back in the 90s, the late 90s, 1997, there was a movie released based on a book called Starship Troopers. And anybody who's watched that film, and I've watched it multiple times,

[00:26:36] it's a bit tongue in cheek. There's a lot of, to use the Australian vernacular, jingo is a minute. But it portrays a human society that is very, very authoritarian, very, very super aggressive, very competitive, lots of, it would be a very tense place to live if Earth, as we know it,

[00:27:05] was the way Starship Troopers portrays human life. And they're at war against the bugs who live on a planet called Clan Dathu. Like, you know what's sad about this, Fred? I'm doing it all from memory. And they have been shooting asteroids at Earth. And in the movie, they destroy the city of Buenos Aires. And that's sort of causes the humans to up the ante in terms of trying to eliminate the bugs.

[00:27:34] And so it goes on. But what's striking about it, not only the authoritarian nature of the military in this film, is the uniforms. They are dead set, just like the uniforms that have been suggested as the new US Space Force uniforms. I did a bit of research on this, Fred.

[00:28:00] The uniforms in the 1997 film, Starship Troopers, were deliberately designed by a costume designer, Ellen Mirajink, to evoke fascist aesthetics. So they're basically designed around the Nazi military uniform. That was deliberate. That was done on purpose. And now we're seeing these new uniforms, 2026,

[00:28:30] being unveiled based on the uniforms from Starship Troopers and Star Wars. If you remember, the Empire uniforms were of a similar ilk. They are, look, don't get me wrong. They're quite striking, quite striking. But they immediately put you in a mindset of going, whoa, what? You're not,

[00:28:59] you're not impressed. You're just going, hello, what are we thinking here? What are we, why are we doing it this way? That's, that's kind of the reaction I had. And me too. Um, when, when I saw, it was the boots I noticed first, I thought, wait a minute, I've seen that sort of thing before. Yeah, jack boots. Yeah, exactly. More or less. Yeah. Yeah. They're quite, um, I mean, I think uniforms are an amazing thing. Uh,

[00:29:27] I don't know where they originated. I, I did look it up once and I, I, I think it was the British or, no, the Romans, the Romans, um, that invented uniforms, but, um, everybody has them now. And, and some of them are incredible. I mean, uniforms for some reason make human beings look better somehow. Um, and these ones, I don't know if you're going to get the right kind of psychological reaction.

[00:29:56] Ha ha ha. If they go down this road and that's a, that's a big if, I guess. Hmm. I, I don't know where this story is going really, Andrew. And, um, you know, what, what we are likely to see coming out of the space force itself rather than just coming from the president's fertile mind. Uh, but, um, yes, I, I didn't find it something that cheered me up particularly. I, uh,

[00:30:24] I thought it was very much along the lines that you've described, something that we could probably well do without. Possibly so. Yeah. Yeah. And, what I would say to, uh, space nuts listeners is have a look for yourself and, but, you know, be your own judge. Don't you don't have to believe what we think. Um, we're just, uh, as soon as I opened the story that Fred sent me, I went, what is this? What, what, before I read a thing, I saw the picture and went, what, what are we looking at here?

[00:30:53] And then I read the caption and went, no, seriously. Uh, anyway, have a look. Uh, you can see it at, uh, space connect online.com.au. It's, um, yeah, or just do a, uh, a search through your favorite search engine of United States space force service dress uniform, I think is what it's called. Um, and yeah, well, we'll, we'll leave it to you to decide what you think.

[00:31:24] Uh, it's a, it's a difficult one because, uh, it, it's so divisive. Just, just that look in itself without saying anything, um, would be instantly divisive. I, I, I'd venture to say. Yeah, you probably rise. Um, yeah, it, um, yeah, for to me, it just portrays arrogance of a kind that, um, we could do without. Yeah, possibly so. All right. Uh, yeah, as I said, uh,

[00:31:52] space connect online.com.au if you want to check that out. And I think we are just about done. Fred, thank you so much. It's a pleasure, Andrew. Always interesting to chew the fat over these issues, no matter what they are. Yeah. With the uniforms, it's not often we talk about, uh, fashion in terms of, um, you know, space fashion, if I can put it that way. Well, that's what it is, isn't it? Really? Space fashion. Yeah. Well, we've talked about the flight suits. Certainly. Yes,

[00:32:22] we have. And when they've done major upgrades on those and, and their incompatibility between space agencies. So that, you know, there's always controversy somewhere, even in fashion. Uh, thanks, Fred. We'll catch you on the next episode. Sounds great. Thank you. Professor Fred Watson, astronomer at large. And don't forget to visit us online between episodes at space nuts.io or space nuts podcast.com. And you can send us messages there through the, ask me anything link up the top,

[00:32:50] or you can visit the shop where you can sign up for the astronomy daily newsletter, uh, and whatever you like. And if you want to become a supporter, you can hit the supporter button and see how you can do that too. And thanks to all our supporters, uh, for getting behind us with a cup of coffee and a, and a cream bun. Uh, and thanks to Hugh in the studio, uh, who couldn't be with us today. He wanted to be, uh, wanted to be the first in line for a space force uniform. And he's still waiting. And from me,

[00:33:20] Andrew Dunkley, we'll catch you on the next episode of space nuts until then. Bye bye. Space nuts. You'll be listening to the space nuts podcast. Let's complete this. Available at Apple podcasts, Spotify, iHeartRadio, or your favorite podcast player. You can also stream on demand at bytes.com. This has been another quality podcast production from bytes.com.