Can we smash together all of the asteroids to build a new planet?

Let’s be honest: the asteroid belt is a bit of a mess. It is full of big rocks hurtling around at high speeds, occasionally getting tossed towards assorted planets, and generally causing a ruckus. On this episode of Dead Planets Society, our hosts Chelsea Whyte and Leah Crane have decided to embark on a solar system cleanup mission: to unify the asteroid belt into a single rocky world.

But it isn’t as easy as just stirring up the asteroid belt and hoping everything smashes together. For the asteroids to stick together instead of just creating even more asteroids, they have to collide at a relatively slow speed. A huge funnel might work to make sure they all get squished together. Or maybe an injection of aerogel across the entire asteroid belt could slow them down and eventually bring them to a gentle halt – though the ring itself could make it difficult to explore the outer solar system, and it could have some nasty effects on Earth’s wildlife, too.

Leah and Chelsea were joined for this episode by planetary astronomers Andy Rivkin at Johns Hopkins University in Maryland and Kat Volk at the University of Arizona.

Dead Planets Society is a podcast that takes outlandish ideas about how to tinker with the cosmos – from putting out the sun to causing a gravitational wave apocalypse – and subjects them to the laws of physics to see how they fare.

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Transcript

Leah Crane: This is a podcast where we imagine what it might be like if we were given cosmic powers to rearrange the universe.

Chelsea Whyte: I’m Chelsea Whyte, Senior News Editor at New Scientist.

Leah Crane: And I’m Leah Crane, Physics and Space Reporter at New Scientist. Today we want to talk about the asteroid belt, the stream of asteroids circling the sun between the orbits of Mars and Jupiter.

Chelsea Whyte: But we’re not going to destroy them. This time we wondered what would happen if we mushed them all together. Unify the asteroid belt.

Leah Crane: All for one and one for all. I want a new planet, making a planet from scratch is too hard, let’s make one from asteroids instead.

Chelsea Whyte: I mean, that’s a bit of a turn of course for you, but okay, new planet it is.

Leah Crane: It’s time to start fresh.

Chelsea Whyte: So, let’s get into it, I think we should call an expert because I have lots of questions. First, aren’t asteroids kind of a problem? I mean they’re so messy and they threaten planets and they seem like we should just, sort of, tidy them all up.

Leah Crane: I do think it’s going to be a little harder than just sweeping them up with a big cosmic broom. Especially because we probably want to do this in a way that doesn’t destroy the rest of the solar system.

Chelsea Whyte: Yeah, I mean, probably. We’re going to have to try some non-broom methods then I guess. Maybe some sort of colossal funnel. And then, how do we catch the debris? Maybe we could use some kind of cosmic jello mould.

Leah Crane: And the other question, what would that planet be like? We spoke to Andy Rivkin at Johns Hopkins University, who listeners may remember joined us to create the asteroid gong a few episodes back.

Leah Crane: We don’t want to blow up a planet, we’re not destroying anything in this episode, potentially.

Andy Rivkin: I hardly know you, who are these people?

Leah Crane: This is an improvement campaign.

Chelsea Whyte: Yes, a little bit of a tidy up of the solar system.

Andy Rivkin: Yeah, that’s borderline insulting to an asteroid scientist.

Leah Crane: Sorry. Sorry not sorry, help us get rid of the asteroids. What we want to do is take the asteroids and stop them from being separate and unite them behind a common cause, which is being a planet.

Chelsea Whyte: So, the question really is, (a) could we do that? And (b) would it disturb the solar system at all? Because it would have the same amount of mass in the same zone-ish. Would anyone else get out of sorts? Would Jupiter have a hard time, or Mars? Or, would it just sort of be like, ‘Eh, shrug, cosmic shrug.’

Leah Crane: Aside from the asteroid scientists being really upset with us.

Chelsea Whyte: Yeah.

Andy Rivkin: Disappointed, it’s more of a disappointment.

Leah Crane: Oh no, that’s worse.

Chelsea Whyte: Not all scientists are disappointed in the idea though. We also chatted with Kat Volk at the University of Arizona and she agrees that asteroids just aren’t that exciting.

Leah Crane: Asteroids suck.

Kat Volk: Yes, they’re boring.

Leah Crane: They’re all over the place, they’re like the dust mites of the solar system. And I think they’d be better if we turned them into a planet. Usually, I advocate for smashing things up, in this case I’m advocating the opposite. I think we should un-smash the asteroids. Could we just stir up the asteroid belt, would they eventually smash together?

Kat Volk: You need them to smash together at very low speeds to merge and also I’ve got some bad news about the total mass of the asteroid belt.

Leah Crane: Oh no.

Kat Volk: It’s even smaller than Pluto.

Chelsea Whyte: Oh, really?

Kat Volk: Yes, actually there’s a nice pie chart showing, like, Ceres and Vesta, if you just combined the two of them, that’s about a third of the total mass of the asteroid belt.

Leah Crane: That’s such a bummer.

Kat Volk: So, you’re going to struggle to get something much bigger than Ceres and Vesta.

Leah Crane: In case you don’t know, Ceres and Vesta and are icy dwarf planets in the asteroid belt, and they’re each way smaller than Earth’s moon.

Chelsea Whyte: Why does the asteroid belt loom so large in my mind. I feel like it’s so full and it really isn’t.

Kat Volk: I blame Star Wars.

Chelsea Whyte: Yes, that’s probably what it is.

Chelsea Whyte: So, then we had to ask, how can we collect all of these spread out rocks?

Leah Crane: So, I feel like there’s two ways to do this, one is put up a big road block and just let everything smash into it. And then sort of extrude it out.

Chelsea Whyte: Yes, like, maybe like a funnel.

Leah Crane: Yeah

Chelsea Whyte: You know, it all smashes into the funnel and then gets pushed through this narrow neck so that-

Leah Crane: Like a meat grinder.

Kat Volk: Yes, if you orbit the funnel so that things kind of make gentle collisions. Someone should make a cartoon.

Chelsea Whyte: And then we would just need, like, a slicer at the end of the funnel to chop off different planet sizes.

Leah Crane: This is the asteroid sausage.

Chelsea Whyte: Yes, this is the sausage factory.

Kat Volk: It doesn’t sound all that far off from some of our models.

Leah Crane: We have a special offer for our listeners, you can get four weeks of New Scientist free, followed by a monthly subscription price of 9.99, that’s in dollars or pounds. You’ll get unlimited access to our website and app, plus benefits including newsletters, essential guides and invitations to subscriber-only events.

Chelsea Whyte: Go to NewScientist.com/dpsoffer to start your free month of New Scientist.

Leah Crane: Alright, we’re back. I do love the cosmic funnel but it might get smashed if we just plop it down in the middle of the asteroid belt. But don’t worry, Andy had a plan.

Andy Rivkin: The way you would want to do it- so Ceres is the largest object, Pallas is the second largest, it’s the third most massive. Ceres and Pallas have orbits that are not super different from one another. So, I think what you would want to do is take Ceres and Pallas. You take Pallas, maybe you kind of slow it down, so kind of have a slow, slow docking with Ceres. You know, just approach very slowly so that you don’t make more debris and more stuff to clean up. So, I think that would be job one, that would get you most, mass wise, most of the way there. I think you’d then maybe need to go out to some of the asteroid families which are, you know, these collections of thousands and thousands of asteroids that have very similar orbits because they formed, you know, something hit a big asteroid and then the debris had enough speed to escape from the main asteroid, but not enough to really change its orbit around the sun too much. Then kind of, do the same thing, kind of bring those things back together. Maybe you could get down to a few dozen or a hundred objects out there in the asteroid belt. I think Vesta would be one of those, the Vesta family, if you could bring all those down to Vesta. Vesta is the third largest object and then just try to do the local clean up that way.

Chelsea Whyte: Right, bit by bit and then mush them together.

Leah Crane: I just had the stupidest thought and I really like it. You know how in the early days of the space programme, astronauts used to have all their food encased in gelatine so it didn’t make crumbs.

Chelsea Whyte: Oh, do we need a large jello mould?

Leah Crane: I just feel like we’ve been talking a lot about making sure these collisions are really slow so they don’t create a lot of crumbs, and instead of that, we could just coat all the asteroids in gelatine.

Chelsea Whyte: I like it, I think we would need a whole lot of jello.

Andy Rivkin: Yeah, I’m not- let me offer, as an alternative perhaps, if we’re going to do this. So, there is aerogel. aerogel is the kind of material that got used on the Stardust mission, to kind of collect comet dust as it zang through- zang? Zinged through. I don’t know what the past tense of zing is. Zinged, I guess. So, if you could, as long as we’re going in this direction, maybe the way to do it is to take Ceres and kind of puff it out to make it this really low-density, kind of, object, to put it in this low-density framework and then maybe that’s the way to do it. So, now you’ve got this, I don’t know, many thousand kilometre aerogel.

Chelsea Whyte: What do you mean, puff it out?

Andy Rivkin: I don’t know, I don’t know.

Leah Crane: I feel like if you want to inject a bunch of aerogel into it, right? So that it’s poofier and also can catch other things.

Andy Rivkin: Or, maybe you’d build the aerogel into it. Or, embed it in aerogel, or take Ceres and make itself into some aerogel. Because aerogel was just, you know, just kind of a low-density material, low-density silicone material as I understand it. I’m sure that all of my colleagues, if and when they listen to this, are going to be like, ‘This is not how it works Andy.’

Leah Crane: This how it works, we’re making a cosmic fly strip and we’re trapping all of the asteroids on there.

Andy Rivkin: Kind of like here’s kilometres and kilometres and kilometres of this aerogel material that will slow you down. Then you’ve caught your asteroid.

Chelsea Whyte: Yes, like a brake, like a gel brake. It’s like you put it up in front of the train and the train slowly goes into the jello tunnel and gets stuck.

Andy Rivkin: I would say exactly, not exactly, exactly. But yes. And then in fact, yes, you would just fill the asteroid belt with that, or fill parts of the asteroid belt with that. So, that might be- it’s not one object. It’s not gathering the asteroid belt into one object, but if you just filled the whole area with this aerogel, maybe you have a ring of this super low density material.

Chelsea Whyte: Jelly doughnut!

Andy Rivkin: Kind of filling the space between Mars and Jupiter. And then that, in principl,e might be able to get you the near-Earth asteroids too. Because a lot of them have aphelia out in the asteroid belt too, so once they retreat from the inner solar system, go out into the asteroid belt and they get stuck.

Leah Crane: I love doughnut, I love the space doughnut, it’s my favourite thing ever. Would that ruin the solar system?

Andy Rivkin: Well, it depends on your point of view, doesn’t it?

Leah Crane: I guess my question is, how would that ruin the solar system?

Andy Rivkin: It would make it also so that, I suppose, you could not spend spacecraft to the outer solar system.

Chelsea Whyte: Oh, yeah.

Andy Rivkin: Because you’d now get stuck, you know? Europa Clipper, or whatever else you want to send out there instead, just it would be a real hassle to get out there. Now, you might be able to limit that by, I don’t know, maybe you could, instead of having the space doughnut be a doughnut, maybe you could make it a disc and just limit it to a plane mostly. But then, you still need enough room to slow stuff down.

Chelsea Whyte: You’d still need wacky gravity assist to get up or over.

Andy Rivkin: Yes, so some might say that would ruin things, I guess.

Chelsea Whyte: Sure.

Leah Crane: But, that’s just ruining our stuff, not the solar system.

Chelsea Whyte: Yeah.

Andy Rivkin: Yes, I think as a whole, I don’t think that- from the point of view of the outer solar system, the asteroids are whipping around fast enough so that they kind of smeared out anyway, as far as Neptune is concerned, right? They have very little gravity and so I think most of the effects would be aesthetic ones, you know? Here’s this weird glow, from the earth.

Chelsea Whyte: I love it.

Andy Rivkin: It might change the heat balance, I guess, of things in a weird way, I’m not sure. Maybe not, because again the mass, I don’t know what the mass of aerogel would have to be to make this work, to make this work, compare to the mass of the asteroids, I don’t know if you now would have to put a huge amount of mass out there. So, whether it would just be like, ‘Oh, it’s the glow of the space doughnut.’ Or, if it would be like, ‘Damn, I hate the space doughnut, I can’t sleep.’ You know? All the migratory birds, all the moths are always flying towards the space doughnut, I have no idea. I have no idea.

Leah Crane: Okay, so Andy made it clear that the effects for Earth might be pretty rough and I kind of thought we weren’t destroying anything this episode.

Chelsea Whyte: Yeah, I man, Earth would still exist, we didn’t really destroy it, but it might be pretty unpleasant here, right? If the birds and the moths are all just going nuts. But Kat had another idea about how we might make an asteroid planet work.

Leah Crane: So, what I’m thinking is we take our asteroid world and put it somewhere else – potentially the habitable zone. I’m thinking asteroids have water on them, it seems like asteroid world might make a pretty good planet if we put it into a place where liquid water is allowed.

Kat Volk: Maybe, it would be a very small little world.

Leah Crane: Yes, sure.

Kat Volk: I don’t know.

Leah Crane: We could make it a moon even.

Kat Volk: Yeah, maybe we make it Venus’s moon, because Venus needs a moon.

Leah Crane: Yeah, it doesn’t have any.

Kat Volk: So, maybe that would be better. And, you know, there are arguments actually maybe that that would help make Venus habitable. There are arguments that the fact that we have a moon is part of why our climate is more stable, because the moon’s gravitational effects kind of helps stabilise the Earth’s spin axis.

Leah Crane: We could put our asteroid moon in orbit around Venus, that might help Venus out. The asteroid moon might potentially become a sort of Titan-y, potentially habitable moon, if we’re lucky.  But it seems like asteroid planet is good actually. I like asteroid planet.

Kat Volk: And then we wouldn’t have so many near Earth asteroids trying to hit the Earth either.

Leah Crane: Right? We wouldn’t have any near Earth asteroids, because we wouldn’t have any asteroids.

Chelsea Whyte: Two birds, one stone. Yeah.

Leah Crane: I, for one, think we’ve drastically improved the solar system.

Chelsea Whyte: I’d love to hear our listeners’ suggestions for what this asteroid planet should be named. Tweet at us, I’m @chelswhyte and Leah is @downhereonearth. Or, email us at deadplanets@newscientist.com.

Leah Crane: We’d like to thank Kat Volk and Andy Rivkin for joining us today and thanks to you for listening to Dead Planets Society.

Chelsea Whyte: And from our inbox, we had a listener submission from Richard Cameron that is quite timely given our recent moon destruction episode. Richard says he has always enjoyed looking at our moon, but he takes a sort of opposite approach than we did. He asked us, ‘What if we had more moons? How many could be added before we destroyed the Earth? And would they also destroy each other after tearing our world apart?’ These are some great questions Richard – we might have enough to do a Moon 2.0 episode.

Leah Crane: More moon. Bye.

Chelsea Whyte: Bye!