Is an enormous shield the worst way to protect Earth from asteroids?

Protecting Earth from any huge asteroid that might come our way is complicated. If you break the space rock into pieces, that could create a hellish rain of shrapnel. However, smashing something into an asteroid without breaking it well before it nears Earth could change its trajectory, as could the “gravity tractor” technique of parking something massive right next to the asteroid. But those protective measures only work if we know about the asteroid far ahead of its projected landfall.

Researchers have been working on this problem for decades, but our hosts Leah Crane and Chelsea Whyte have some new ideas. In this episode of Dead Planets Society, they’re trying to protect Earth for a change, instead of wrecking it. Alive Planets Society, if you will.

To help save the world, they’re joined by planetary astronomer and asteroid expert Andy Rivkin at Johns Hopkins University in Maryland. Instead of sending something out to the asteroid, they’re thinking about how to save Earth while staying relatively nearby. Could we design a net to catch an asteroid? Or use a tighter mesh material that might act as a trampoline to chuck the asteroid towards Mars?

The idea of a huge shield orbiting the planet is a tantalising one, not least because any impacts it takes might make a sound and could serve as an alert system every time the planet was saved. Introducing: the asteroid gong.

Dead Planets Society is a podcast that takes outlandish ideas about how to tinker with the cosmos – from snapping the moon in half 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: I want to alert the population every time we’ve saved them with our shield. I want them to be alerted by a loud gong sound.

Chelsea Whyte: Why the loud going sound? Well, we’re saving the universe from the scourge of asteroids. Welcome back to Dead Planets Society.

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.

Chelsea Whyte: And today we’re protecting the earth.

Leah Crane: It’s a bit of a different vibe from our usual chaos and destruction.

Chelsea Whyte: A little bit of a zigzag there.

Leah Crane: Yeah, but don’t worry, I can’t imagine we’ll get away without ruining anything.

Chelsea Whyte: No, absolutely not. We’ve spent a lot of time over the years talking about near Earth asteroids like Bennu which was visited by the Osiris Rex space craft a couple years back. And also their potential for destruction, you know, I would say, listeners, don’t worry too much. There’s very little danger to actual Earth.

Leah Crane: I would say there’s no danger to Earth as far as we know.

Chelsea Whyte: Great. But scientists are tracking these asteroids and, Leah, you’ve written a lot of stories about planetary defense.

Leah Crane: Yeah, there are a lot of fairly reasonable ways to deal with any asteroid that happens to be heading towards Earth, and scientists have studied that a lot. We’ve written a lot about it and we’ll put some links to some of those stories in the show notes.

Chelsea Whyte: But today we don’t really care about reasonable, do we?

Leah Crane: Never have, never will, but it is a good place to start.

Chelsea Whyte: So, then what are some of the best ways we have now to protect against, you know, terrible asteroid destruction?

Leah Crane: Evacuate?

Chelsea Whyte: Yeah, okay, I mean, evacuation would work if it was a small asteroid but not something huge, not like something that killed off the dinosaurs. In that situation leaving major cities isn’t really going to do us much good, is it?

Leah Crane: No, in that case we just die.

Chelsea Whyte: Okay, well, terrible. But what about the, sort of, Armageddon approach? What if we get, you know, Bruce Willis and his merry band of drillers and they go up and put a nuke in an asteroid? Is that at all realistically possible?

Leah Crane: So, something sort of similar has been proposed where we put a nuke next to an asteroid and use that detonation to push it off course. Unfortunately it probably doesn’t require any Bruce Willises.

Chelsea Whyte: Oh, bummer. But much easier, I assume. It sounds a little bit like the DART mission that NASA did recently, right? The one where they went to the asteroid Dimorphos and just punched it in the face. Is this, like, a bigger punch?

Leah Crane: Yeah, it’s pretty similar. That method’s called the kinetic impactor, where you just slam something in to the asteroid and the key there is to move it without breaking it, because you don’t want a hail of tiny asteroid bits.

Chelsea Whyte: Yeah, it makes sense. And DART did work, right?

Leah Crane: Yep.

Chelsea Whyte: But in a real scenario would we have enough time to use that method?

Leah Crane: Of all the methods they have it’s probably the most realistic one but you’re right, we would need a fair amount of lead time to get the spacecraft built and launched and all that, but for really all the methods lead time is really, really crucial. And there’s one where we haven’t actually talked about yet, which is my personal favourite, which is the gravity tractor, where you just park something really huge next to it and let that gravity pull it into a different trajectory.

Chelsea Whyte: Cool. I love that but, okay, so what if we’re actually in, like, Hollywood territory? Like, we have no time, this huge planet-destroying asteroid is on its way. Could we make, I don’t know, like, a huge net? Like, just catch it before it hits our atmosphere?

Leah Crane: I don’t think so, but what I do think is it’s time to ask a professional. So we talked to Andy Rivkin at Johns Hopkins University about that net idea.

Andy Rivkin: So, there’s a few things. You know, we get hit from all directions.

Chelsea Whyte: Sure.

Andy Rivkin: So you can’t just put it in front, you’d have to put it on all sides.

Chelsea Whyte: But, like, if we knew it was coming and we had a very large amount of a net, and we had some idea of its trajectory toward Earth, could we stop it with a net?

Andy Rivkin: Well, how fine of a mesh do you want to make the net? As we saw in Dimorphos and some other asteroids, assuming you could make a net strong enough, which perhaps we can for our purposes-

Chelsea Whyte: Yeah, a magic net.

Andy Rivkin: Right, so, if you made the mesh, you know, even yea big, you know, there might be material that makes it through, it looks, you know, from Dimorphos, Didymos, and Itokawa, and Bennu, and they all don’t look like single rocks, right, they all look like collections of smaller pieces and gravel. So you might end up, depending on how springy you want to make the net, I guess, you know, whether it would, kind of, hold them in and then spring you back. Whether some of it would make it through the mesh. Whether the process of it hitting would make it splash.

Chelsea Whyte: And then just hit everywhere, yeah.

Leah Crane: So it seems like a net might be kind of a bad idea, we’re still going to potentially have a rain of rocks.

Chelsea Whyte: Yes, because it sounds like we’ve got, like, this rubble pile coming through a net, it’s like you’re trying to sieve water, it’s not going to really work all that well.

Andy Rivkin: Some of the pieces are going to be moving fast enough that they’re going to escape, and again, depending on how you’ve set it up it may just come apart. And maybe that’s okay for your purposes, maybe part of the plan of a net would be to kind of slow it down, but then it seems like you would need to have enough springiness in the net that basically you’d be putting an enormous of energy in to the net to, kind of, have it, I guess, be trading brittleness for springiness.

Leah Crane: Well, at that point it’s just a trampoline, right?

Chelsea Whyte: Cosmic slingshot, let’s get Mars…

Leah Crane: What if we use something rigid? You know, historically the best way to protect something is to use a shield, so what if we did Captain America shield but real big?

Chelsea Whyte: Yeah, huge. But this shield, it wouldn’t be stationary, right? Like, it would be orbiting Earth a lot. Like we’d make a second sad moon.

Leah Crane: A second amazing moon. Andy had some thoughts about this idea too.

Andy Rivkin: In some ways you have some of the same thing, right, it’s going to hit but now it’s supposed to hit and stop all at once, and so now it would splash against this vibranium shield.

Chelsea Whyte: Yeah, depending on how big it is it could splash, I mean, I’m picturing something quite large in comparison to Earth. But then we really are blocking out a lot of the light.

Leah Crane: I’m picturing, like, the size of Australia.

Chelsea Whyte: Yeah, maybe even bigger.

Andy Rivkin: I think what you’d get is something similar to the disruption ideas that people have in planetary defense. Typically we think about wanting to move things all in one piece, right, we would rather not disrupt them if we don’t have to because, you know, if you disrupt them now you’ve got a zillion pieces to keep track of. And as I said once, as others involved have said, you know, you don’t want to miss a thing. Yes, well, you could do a badum-tss for that. But if you have to disrupt it then, you know, there are cases where you just have to suck it up. So then the question is where you disrupt it, and can you disrupt it enough so that most of the pieces are going to miss the earth. Or, if you have something that’s one kilometre in size, which is big enough to, we think, you know, destroy civilization, then you don’t want to break it into a bunch of pieces, any one of which might still wreck a continent.

Leah Crane: Right, but on the other hand if those pieces are heading away from Earth maybe we don’t care that much.

Andy Rivkin: Right, or if you did enough in advance that you could say, we can keep track of them.

Chelsea Whyte: Yes, somehow we didn’t know about the asteroid until a couple days out but we did have this mega shield already built. This is the scenario.

Leah Crane: We were already building it for other reasons.

Andy Rivkin: Right, so it turns out that, you know, unnamed billionaire has among their other projects had the giant shield that nobody knew about.

Leah Crane: Let’s be honest, probably the CIA.

Andy Rivkin: Sure. In that case basically the question is going to be the sideways speed, you know, how far ahead of time do you do this compared to the sideways speed, and is that going to let you let stuff miss the earth?

Leah Crane: It’s like Pong a little bit.

Chelsea Whyte: Yes.

Andy Rivkin: Yes, and now I’m wondering whether it would be more like, you know, Captain America’s shield or more like the tip of the Washington monument, or something, you know, some pyramid, you know, some design to maximise your-

Chelsea Whyte: Oh.

Leah Crane: I like that.

Chelsea Whyte: Yes, that’s a really good idea about the shape of it. But I do want it to be flat for one reason, and that is that I want to know if it’ll make a sound. Like, I want a large gong, really, out there because, I don’t know, that sounds interesting to me.

Leah Crane: Well, I want to alert the population every time we’ve saved them with our shield. I want them to be alerted by a loud gong sound.

Chelsea Whyte: Okay, but wait, that’s a good question. Would the sound enter the atmosphere if it were, like, how loud would it be?

Andy Rivkin: Yes, well, we don’t hear things hitting the moon, and so I imagine that if you wanted the sound it would be a very, very late stage thing, or you’d have to hook it up with sensors that could, you know.

Leah Crane: We could put a contact mic on it.

Andy Rivkin: Yes, yes, so just like people do the whole, like, ‘Here’s the sound of this pulsar’ or whatever. You know, you could say, ‘Here’s what’s hitting and the frequency spectrum.’ And then, you know, have that Tweeted out or played over your, you know, everyone’s phone.

Chelsea Whyte: Gong saved us again.

Andy Rivkin: Right, but it’s also funny because you would also have for every, ‘Hey we’ve saved you from’, you know, ‘We’ve saved the Los Angeles area, we’ve saved the Johannesburg area’ or whatever, from destruction, you would have an extremely large number of, ‘Oh, that was a shooting star that-,’ you know, ‘Here’s a sand grain.’ You know, ‘Here’s another sand grain, here’s another sand grain, here’s another sand grain.’ And then, you know, a few times a year it would be, ‘Okay, we’ve saved you from something the size of your laptop. Or the size of your chair.’

Leah Crane: I think we omit that information, we just say, ‘We saved you.’

Chelsea Whyte: ‘We saved you, you don’t need to know what it was from.’

Andy Rivkin: ‘You’re welcome.’ Just you’re welcome, you’re welcome, you’re welcome.

Leah Crane: Gong-gong-gong-gong, you’re welcome.

Chelsea Whyte: I do think that’s all very annoying and worth it because when the big one comes, I do want us all to time it out to play a piece of music that ends with a gong, like, at the right time so if we’re going out, if this doesn’t work, it’s not going to work well, at least-

Leah Crane: Like Pachelbel’s Cannon with our planetary defense gong.

Andy Rivkin: Yes, Nights In White Satin was the obvious one I was thinking of, that’s the one that ends with a gong that I could think of.

Chelsea Whyte: Bohemian Rhapsody, any way the wind blows.

Andy Rivkin: Oh Bohemian Rhapsody, what my problem? Yes, of course, yes, of course.

Chelsea Whyte: I think people do have an outsized worry about being hit by asteroids. It’s not to say that it’s not worth doing planetary defense and figuring out what we can do about them, but I think sometimes people get a little over-worried because the odds are just not that it’s going to happen all that often. But yeah, this would really, like, work them right out of that, wouldn’t it? They’d be like, ‘Never mind.’

Leah Crane: Like, ‘You’ve got two options. Gong or meteor.’

Andy Rivkin: Yes, no, this is where I come in and I of course say that the planetary defense programme, you know, the international planetary defense programme is of course all about providing additional options besides gong or death. But-

Chelsea Whyte: I’ve never been happier that we have a planetary defense system and people looking into this because gong or death is, like, pretty bad options.

Leah Crane: I want a t-shirt with ‘Gong or Death’ on it.

Leah Crane: We promise we have no plans to actually build a death gong.

Chelsea Whyte: Thanks to Andy Rivkin for joining us today.

Leah Crane: And thanks to you for listening to Dead Planets Society.

Chelsea Whyte: And if you enjoy our podcast you might also enjoy Leah’s monthly space newsletter at New Scientist called Launchpad. Check it out at newscientist.com/launchpad.

Leah Crane: And finally, if you have any cosmic object you want us to figure out how to absolutely wreck, let us know and it could be featured in a later episode of our podcast. Our email is deadplanets@newscientist.com, and if you just want to chat with us about this episode or wrecking the cosmos more generally we’d love to that and you can find us on Twitter at @chelswhyte and @downhereonearth. Thanks again for joining us.

Chelsea Whyte: Bye.

Andy Rivkin: They’re going to be wishing for the sweet meteor of death.

Leah Crane: Because of the gong sound.

Andy Rivkin: They’re like, ‘This is not worth it.’