Theia's Fate, Galaxy Mergers & the Mysteries of Mars' Atmosphere | Q&A

Hello again, thanks for joining us on a Q and a edition of Space Nuts. My name is Andrew Dunkley, and today we will be I won't Fred will be answering questions about the former planet known as Fear Galaxy. Mergers have come up. We go back to Mars with a theory about Olympus mons and why only hydrogen? That is a question that comes from a believer, a five year old. We'll deal with all of that today on this edition of Space Nuts fifteen in channel ten nine ignition sequence Space nuts or three two space nuts as can I reported Neil Goods. And to solve all of those little riddles, we're joined again by Professor Fred Watson, Astronomer at Large. Hello Fred, Hello Andrew, very good to see you again. Good to see you too. We've got a bit of weird noise on your line. I think it's probably just the Internet being the Internet, so hopefully that'll go away. In fact, it just did, so yeah, there you go, solved itself. It must have heard me winging all as well. I assume. Yep, we're doing fine. Thank you. It's good to join you on the questions episode of what's this called again? Oh Space Nuts? That's right, space idiots, space nuts. Yes, yeah, they're all good people. We might as well jump in straight away to our first question, and it comes from one of our regular contributors. It's Rusty today, Fred and Andrew, It's Rusty in Donnybrook. I've been listening to your latest episode where look at the relationship between Sea and the Earth before the collision, and I just want to make sure I've got the story glory straight, so I put it in my own words. The Earth had a buddy named THEA who came a little too near. She hit with a splash, then made off with a dash. But there's no mooning for THEA around here, So what happened to THEA after the collision? The theories prior to this revelation said THEA had enough kinetic energy to leave the Solar System all together. But if the orbits were so close, that doesn't seem likely. So it seems to me there's three possibilities that THEA fell into the Sun, which would be another amazing feat to get that sort of precision. After the collision, Sea picked up a little slingshot energy and moved out further and became Mars, and Mars is a Mars size object after all. And the third possibility I can think of is that it picked up an unlikely amount of kinetic energy and became planet nine. So if it did become planet nine, it would have a highly eccentric orbit because it's too far away from us to actually see at the moment. But would this orbit then at some stage bring it back to the Inner Solar System of its origin? That's it? How you guys? Well, jeez, thanks, Rusty, hope you're will two over there in w A. What happened to THEA? He's come up with some interesting theories, quite a few ideas. I'm guessing they can't all be true. I think that's right. There's actually a fourth possibility I did to the three that that Rusty has proposed, and I think that's the one that's usually accepted, and there's kind of evidence for that. The fourth possibility is that basically was absorbed into the Earth. The remnants of thear actually in the Earth's mantle, And in fact, there's something called and there are two of these, a large low sheer velocity province in the Earth's lower mantle. And the hypothesis is that that is the remnants of thear so that we still see the evidence of that collision by anomalies basically in the Earth's mantle, which we investigate, you know, with seismology. That's how we know about what's going on in the mantle of the Earth. It's how we know about large low sheer velocity provinces. I'm kind of just using the words here because I'm not somebody who knows about the inside of the planet other than you know, the sketchiest outline of a core, a mantle, and a crust. But the mantle we know has significant structure and in fact money. And I have a good friend who Nick Petford, who is a volcanologist, and he's somebody who looks at these velocity structures in the in the mantle of the Earth and you know, the upwelling of material to form volcanoes and things like that. Next time we see Nick, I will ask him about these large scale low velocity shear areas and their relationship to THEA. But I think that's the consensus, rusty that the impact basically resulted in an explosion which shed something like I think one of the suggestions is about seventy percent of the mass of the Moon may have come from THEA. I'm actually I think that might. Let's put it this way, THEA is responsible for seventy to ninety percent of the total mass of the Moon. Under the classic giant impact scenario, where THEA is considerably smaller than a proto Earth, which it would have been, the Earth was still kind of Earthish sized. THEA was Mars ish sized, but the Earth would have probably grown a bit by absorbing the debris from THEA. Remember that the mass of the Moon is about one eightieth of the mass of the Earth, so it's a significantly large body compared with the other moons in the Solar System, but it's clearly smaller than you know, it's not Mars sized, And so Rusty's right in that the you know, the remnants of THEAR had to do something, but the current theory is that they were absorbed by the proto Earth, and we can still see evidence for them. Yeah, okay, so yeah, definitely not likely to be P nine. That would be a very odd kind of occurrence, wouldn't it. Yeah, well, yes, I think that kinematics don't work. You you know, you can't give it enough velocity and you need you need a lot of velocity for it to fall back into the Sun as well, too much energy. That's quite an energetic process, is getting rid of the orbital velocity of a body to make it fall into the sub It's you know, you need as much energy as you do to get it pushed out to the outer planet. So, yeah, didn't we talk about it once before and suggest that remnants of it just probably speed off into space never to be So again. I'm sure there would have been an element of that. Yes, you know that that debris cloud that eventually formed the Moon probably lost some of its some of its material content, and there may even be stuff wandering around in the form of neuroth asteroids now that are bits and pieces that are left over from that. But remember this was you know, this was within the first couple of hundred million years of the history of the Solar System. So you're talking about things that happened a very long time ago. Yeah. Indeed, I'm wondering, Fred, why we've just got this sudden influx of people asking questions in POM. This is just I'm blaming Martin for that. Martin Berman Gorvine, you started this and now it's so I think. I really liked Rusty's one there about the thought that was very nice. Yeah, I don't know. I think he pushed it a bit on one of those one of those rhymes. Although there there was a regular guest, and I'm sure you know who I'm talking about, col Wilson, who used to join us on the radio once a week to do bush poetry, Blew the Shearer, and he often got asked to do shearing demonstrations and he had to tell them, look, I'm not a shearer. I can't the sheer a sheep that saved my life. It's just my show name. But he used to actually invent words to create rhymes. It was one of his wonderful traits. And yeah, I used to spend a lot of time with Collie as a terrific bloke. I think we've dealt with Rusties theories and they were all wrong. Thanks for Rusty. Takes Rusty great to hear from you. Let's take a break from the show to tell you about our sponsor in Cogny. 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And here's the kicker, sixty percent off if you use the code word space nuts. That's in Cogni dot cog slash space nuts sixty percent off if you use the code word space nuts. Enjoy a peaceful online existence without digital disturbance with anguality. Here the land space nuts. Let's move on to our next question, and this one I've lost here it is. This comes from Lena. I am a new listener and not as hardcore as Spacenut as most of your audience. It's probably a good thing, but I saw an article today talking about merging spiral galaxies. If the universe is expanding, how does something as large as a galaxy move toward and merge with another galaxy? It seems they should be moving further away from each other. That comes from Lena in British Columbia in Canada. I think we've had questions of this ilk before, but it's always good to go over it again because there's a lot more going on in the universe than just you know, spreading out like school children playing what's that game where you don't know, I don't know what you call it? Something that you throw a ball and try and hit someone in the head. Anyway, go on, that's cricket, isn't it? Dodgeball? Dodgeball? And there's a bunch of games like that, like Red Rover Crossover. Did you ever play that? Oh no, we mustill have a lot of fun with that. Anyway. Look, Lina's question is a great one, and I guess the simplest answer here is that, yes, galaxies are big, but they're tiny compared with the universe, And so the expansion of the universe is something that we look at on very large scales. You know, you're looking out billions of light years and seeing this expansion. It's actually, with today's technology, it's one of the easiest observations that you can make that the universe is expanding, discovered back in nineteen twenty nine by Edwin Hubble. So, yes, So if the universe is expanding in space, is getting bigger and naturally carrying things further and further apart, why are some galaxies coming towards each other? And it's because on the scale of a galaxy, the expansion of the universe is miniscule, and that by far the dominant the dominant process is gravity. So galaxies, which yes, are being carried gradually apart by the expansion of the universe, when you put them close together, their own gravity gives them a force that pulls them together that's much greater than the expansion. And we actually give that a name. We call this the peculiar velocities of galaxies, because it's a velocity peculiar to an individual galaxy. And the usual way that we describe it, and I think we've talked about this before on Space Nuts, is if you imagine a river flowing, which represents the kind of expansion of the universe, and then somebody in a boat is moving around on the river. They're being carried downstream by the river's movement, but they've got their own movement provided by the boat on the water. And it's a bit like that with galaxies. They're being carried along by the expansion of the universe, but a far bigger effect is the way gravity pulls them together. So that's what's pulling our galaxy and the Andromeda galaxy together. It's the gravitational force between them. And on the scale of the distance between Andromeda and our own galaxy, which is about two and a half million light years, the expansion of the universe makes virtually no difference. You only start really noticing it when you get to much bigger, bigger scales. Yeah, they will come a point in time where all these galaxy mergers will finished, They'll be done and dusted, and the universe will keep expanding and eventually it'll just be darkness. There'll be nothing. Yeah. If that's assuming dark aage big crunch, right, yeah, I mean dark energy. We're now just starting to see the first signs that maybe over the last few billion years it's decreased. And so the acceleration of the universe it's still accelerating. The expansion is still getting faster, but it's getting faster at a slower rate, if I put it that way. So the acceleration itself looks as though it's declining. And that's why some people are still talking about the big crunch or they're going to have gibb again. It's it's because if the acceleration eventually goes away and becomes a deceleration, then yeah, you're going to get a big crunch. Yeah, yeah, it's you know, could go either way at this stage the way they're talking. We we have witnessed some galaxy e mergers, haven't we. It doesn't. Our own galaxy actually contain a couple of other galaxies that have been sucked into our void. Yeah, two quite big ones. Actually, what the things we call the large and small Madrilanic clouds. They are satellite galaxies of our own and they're being stripped of their stars by our own galaxy. It's gravitational pull and will eventually be part of the halo of our own galaxy. But we see we also see examples in deep space of big galaxies actually merging. The most famous is the Antenna Galaxies, two galaxies which are merging and pulling off spiral arms off each other. Quite it all happens in slow motion, though, doesn't it. And and when people, you know, think about galaxy merger merges, they're thinking all this drama and collisions and generally doesn't turn out that way. Well, you're talking about processes that take millions of years, and yeah, and you know it's and and in fact, galaxies probably when they collide, you don't get stars actually colliding because there's so much space between the stars. But what you get is the effect of clouds of gas colliding, and that spawns new star formation, so you might get lots of hot young stars being born in a galaxy collision. All right, here's my horrible attempt at poetry. It's more of a dance than a glance. I like that. Yeah, yeah it is. Actually that's exactly what it is. Yeah, there we go. All right. I hope that answers your question. Lena, Thanks for sending it in and thanks for listening to Space Nuts, which is what you're doing right now with Andrew Dunkley and Professor Fred Watson. We choose to go to the moon and this decay and do the other thing not because they are easy, but because. They are hard, these nuts. Our next question comes from Kevin, and he said, I've been listening with much learning and enjoyment to all the previous podcasts. I'm about halfway through them, so he's at around two hundred and nearly three hundred, I imagine, so let's just wait for him to catch up. He says, your discussions of Mars and its lack of atmosphere made me wonder if perhaps what must have been an enormous eruption of Olympus Olympus Mons is what might have killed the planet, or at least its atmosphere. That comes from Kevin, So, yeah, I'm very impressed by Olympus Monds because it is the biggest volcano in the Solar System, and it's staggeringly huge. But could an Olympus Mons eruption have stripped the atmosphere of Mars? Probably not, the I mean the eruptions of Olympus Mons would certainly have sent a lot of gas into the atmosphere. Olympus Mons has probably taken a long long time to grow. It's you know, it will have had eruptions kind of like some of the bigger volcanoes on Earth, and they took a long long time, so it's not like one big explosion. And that's why Olympus Mons is so high. It's because it's over a hot spot in Mars's mantle that just keeps on pushing out material, or did for a long period of time, and without the plate tectonics that carry the surface crossed over the hot spot and results in a chain of volcanoes like we see in Hawaii. It all built this one big volcano. So it's a process that took a long time, and maybe it did play a role in the changes in Mars's atmosphere. But we think the main reason why Mars lost its atmosphere is because it is a world that is too small to sustain plate tectonics. It doesn't have a magnetic field, so the subatomic particles from the Sun bombard the atmosphere continuously, and we think that's one of the main reasons why why it eventually lost lost its atmosphere. I mean, it's not most altogether. It's still got zero point six of a percent of the Earth's atmospheric pressure at the surface. That's enough for winds to blow and you know, to sort of blow dust clouds onto solar panels of spacecraft and things of that sort. But it's certainly not an atmosphere that we would recognize as being similar to Earth's. So I think, I think it's a good question. Actually, I think Olympus Mons and the neighboring volcanoes, there's there's more than one big volcano, the Olympus Mons is the biggest. They probably would have affected the atmosphere of Mars, but they're probably not the root cause why the atmosphere drifted into space. Yeah, it's more likely it was because Mars just couldn't hold itself together. Basically, it didn't have the gravity. It's yeah, it doesn't have the gravity to keep it hot enough to sustain plate tectonics or a magnetic dynabo basically, which is a magnetic field. Yeah, but Olympus Mons is fascinating for a few reason, So correct me if I'm wrong. But I think right now, as Mars is Olympus Mon's summit actually peaks out of the atmosphere. Is that right? It's sticking up that high? Yeah, it's certainly. I mean the atmosphere is like Earth's atmosphere. It gradually disappears as you go higher. But yeah, I mean effectively the summit is the pressure will be considerably lower there than it is delm what you might call the surface of Mars. This is one honking big shield volcano, though, isn't it like twenty one point two eighty seven kilometers in height thirteen point two miles or sixty and forty feet. Someone's going to climb that one day and stick a flag in it. It's two and a half times the elevation of Mount Everest. And this is something about Mars that astounds me. It's a smaller planet, but all its features geographically just make ours look like tidley wings. And it span is six hundred kilometers six hundred kilometers wide. Yep, that's that's extra. I just can't imagine it. I'd love to be able to stand there and have a look in my last five seconds of life, because I didn't take my breathing apparatus. But it is an amazing world. It's got cliffs as well around its base which are pretty spectacular. I think they're killing meters as well, so you know, it's quite quite, quite an extraordinary world. Yeah. Well, the Coldera itself is fifty miles across, and you compare that to Kilaweo, which is like a couple of miles across. It's amazing. No. I love that question, and yeah, good thinking, but probably not. And it sort of brings back the same argument on Earth that people say our global warming is caused by volcanoes and cows. It's got nothing to do with the billions of cars that we're driving around every day. But I think they've proven that's just not the case as far as i'm aware. Thanks for your question, Kevin, lovely to hear from you. Our final question comes from Yuki Hi. I'm Yuki. I am five years old and I live in Canberra. We listen to your podcast nearly every day. My question is why is hydrogen the only element that isn't made in stars? Why was hydrogen the only element around just after the Big Bang and not others? Yeah, that's a great question. Yeah, and congratulations to your ki on being able to even think of a question. Like that at the age of five, because I certainly wouldn't have. Been now I wouldn't either. I was still trying to fix the wheel on my conquered toy. Yes, that's right. I think I was at that level, and that look, the the bottom line is that hydrogen it was created in the aftermath of the Big Bang. I think sort of three minutes after the Big Bang, the temperature had cool enough that you could start to form atoms. And the atom that was was produced was the simplest it's one proton. It's the simplest atomic nucleus. And so that was what basically condensed out of the of the of the aftermath of the Big Bang. As as energy became matter, you got protons forming, and hydrogen is protons. In fact, in that period you also got the start of the process that does produce other elements in stars, what we call nuclear synthesis, where the nuclei of atoms, the centers of the atoms stick together, and it did. That process did start. So I think it come from the percentage it's something like twenty percent. I think of the aftermath of the Big Bang is helium, which is the next most complex atomic nucleus, and formed by hydrogen atoms coming together, but then the temperature dropped far enough that you didn't get the extension of that process into the formation of other atoms. So it basically had to wait until stars started to form because of the gravitational pull of these clouds of hydrogen together that raised the temperature again enough to start forming other elements. And so that's basically what it's all about. It's just the simplest of atoms is the hydrogen atom. That is why that was created. And you know, we nearly got more elements being created in the Big Bang, but only helium. Actually there's a bit of lithium and other stuff as well tiny amounts of other nuclei. But it's true to say that the star formations, star formation, and the interiors of stars is what led to the huge array of elements that we see now, all the elements of the periodic table. That's a fantastic question. It is. When you look at the list of the top ten gases in the universe by order of concentration, hydrogen is far and away the most dominant, with seventy four to seventy five percent of what they did scrub is baryonic mass helium at twenty four to twenty five percent, which leaves almost no room for anything else. Oxygen is less than one percent carbon, less than half a percent, neon, less than point one and then it just dwindles away. At number ten, you've got sulfur at point zero zero point zero four to four percent concentrations. They're staggering numbers when you're really. Yeah, so you go down the list. The bottom line is that the Big Bang hydrogen is still around. In fact, it it makes up quite a large percentage of the items in your body as well. Yeah. Yeah, well it's everywhere, isn't it. And that's the bottom line. And the way the Big Bang happened and everything that went on afterwards, you know, one smidgy little thing didn't happen, we probably wouldn't be here. Yeah, that's right. It's a scary thought. But then again, there's so much we don't know. U People believe in multiverses because they say, you know, the conditions are exactly right for life to form in our universe, and they might not have been. Yes, maybe there are lots of other universes where life didn't form. Well, yeah, the mathematics supports the theory, doesn't it. Oh gosh, the brain hurting part of the show just happened. So anyway, Yeah, it just keeps us thinking and it keeps us looking for answers, and that's what it's all about. Yuki. Great to hear from you, and hope all is well in Canberra. And a reminder, if you would like to send us questions, we welcome them with open arms. You can send them through our website space nuts dot io and just click on the ask Me Anything link at the top. It says a M A and we will do our best. Don't forget to tell us who you are and where you're from, and we will put your question on if we haven't had it before, and even if we have, we might revisit them. We do that from time to time. Keep them coming. And if you haven't asked a question before and you've always wanted to, please send it in. We'd love to hear from you. And we're just about done. Fred, thank you very much. Great pleasure. Andrew Or was good and hopefully we'll chat again soon. I hope, so that'll be good. Professor Fred Watson, Astronomer at Large. And thanks to Hu in the studio who didn't have a hydrogen problem, but he did have a methane problem. But he'll be out of an emergency surgery very very soon, hopefully for next week's episode. And from me Andrew Dunkley, thanks for your company. Catch you on the next episode of Space Nuts. Bye bye. You'll be listening to the Space Nuts podcast. Available at Apple Podcasts, Spotify, iHeartRadio, or your favorite podcast player. You can also stream onto the at fights dot com. This has been another quality podcast production from fights dot com.