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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 鈥済ravity tractor鈥� 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鈥檙e trying to protect Earth for a change, instead of wrecking it. Alive Planets Society, if you will.

To help save the world, they鈥檙e joined by planetary astronomer and asteroid expert Andy Rivkin at Johns Hopkins University in Maryland. Instead of sending something out to the asteroid, they鈥檙e thinking about how to save Earth while staying relatively nearby. Could we design a net to catch an asteroid? Or use听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.听Introducing: the asteroid gong.

Dead Planets Society is a podcast that takes outlandish ideas about how to tinker with the cosmos 鈥� from snapping the moon in half to causing a gravitational wave apocalypse 鈥� and subjects them to the laws of physics to see how they fare.

To listen, subscribe to 麻豆传媒 Weekly or visit our podcast page here.

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Transcript

Leah Crane: I want to alert the population every time we鈥檝e 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鈥檙e 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鈥檓 Chelsea Whyte, senior news editor at 麻豆传媒.

Leah Crane: And I鈥檓 Leah Crane, physics and space reporter at 麻豆传媒.

Chelsea Whyte: And today we鈥檙e protecting the earth.

Leah Crane: It鈥檚 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鈥檛 worry, I can鈥檛 imagine we鈥檒l get away without ruining anything.

Chelsea Whyte: No, absolutely not. We鈥檝e 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鈥檛 worry too much. There鈥檚 very little danger to actual Earth.

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

Chelsea Whyte: Great. But scientists are tracking these asteroids and, Leah, you鈥檝e 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鈥檝e written a lot about it and we鈥檒l put some links to some of those stories in the show notes.

Chelsea Whyte: But today we don鈥檛 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鈥檛 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鈥檛 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鈥檚 pretty similar. That method鈥檚 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鈥檛 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鈥檚 probably the most realistic one but you鈥檙e 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鈥檚 one where we haven鈥檛 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鈥檙e actually in, like, Hollywood territory? Like, we have no time, this huge planet-destroying asteroid is on its way. Could we make, I don鈥檛 know, like, a huge net? Like, just catch it before it hits our atmosphere?

Leah Crane: I don鈥檛 think so, but what I do think is it鈥檚 time to ask a professional. So we talked to Andy Rivkin at Johns Hopkins University about that net idea.

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

Chelsea Whyte: Sure.

Andy Rivkin: So you can鈥檛 just put it in front, you鈥檇 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鈥檛 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鈥檙e still going to potentially have a rain of rocks.

Chelsea Whyte: Yes, because it sounds like we鈥檝e got, like, this rubble pile coming through a net, it鈥檚 like you鈥檙e trying to sieve water, it鈥檚 not going to really work all that well.

Andy Rivkin: Some of the pieces are going to be moving fast enough that they鈥檙e going to escape, and again, depending on how you鈥檝e set it up it may just come apart. And maybe that鈥檚 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鈥檇 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鈥檚 just a trampoline, right?

Chelsea Whyte: Cosmic slingshot, let鈥檚 get Mars鈥�

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鈥檛 be stationary, right? Like, it would be orbiting Earth a lot. Like we鈥檇 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鈥檚 going to hit but now it鈥檚 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鈥檓 picturing something quite large in comparison to Earth. But then we really are blocking out a lot of the light.

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

Chelsea Whyte: Yeah, maybe even bigger.

Andy Rivkin: I think what you鈥檇 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鈥檛 have to because, you know, if you disrupt them now you鈥檝e got a zillion pieces to keep track of. And as I said once, as others involved have said, you know, you don鈥檛 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鈥檚 one kilometre in size, which is big enough to, we think, you know, destroy civilization, then you don鈥檛 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鈥檛 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鈥檛 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鈥檚 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鈥檚 like Pong a little bit.

Chelsea Whyte: Yes.

Andy Rivkin: Yes, and now I鈥檓 wondering whether it would be more like, you know, Captain America鈥檚 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鈥檚 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鈥檒l make a sound. Like, I want a large gong, really, out there because, I don鈥檛 know, that sounds interesting to me.

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

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

Andy Rivkin: Yes, well, we don鈥檛 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鈥檇 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, 鈥楬ere鈥檚 the sound of this pulsar鈥� or whatever. You know, you could say, 鈥楬ere鈥檚 what鈥檚 hitting and the frequency spectrum.鈥� And then, you know, have that Tweeted out or played over your, you know, everyone鈥檚 phone.

Chelsea Whyte: Gong saved us again.

Andy Rivkin: Right, but it鈥檚 also funny because you would also have for every, 鈥楬ey we鈥檝e saved you from鈥�, you know, 鈥榃e鈥檝e saved the Los Angeles area, we鈥檝e saved the Johannesburg area鈥� or whatever, from destruction, you would have an extremely large number of, 鈥極h, that was a shooting star that-,鈥� you know, 鈥楬ere鈥檚 a sand grain.鈥� You know, 鈥楬ere鈥檚 another sand grain, here鈥檚 another sand grain, here鈥檚 another sand grain.鈥� And then, you know, a few times a year it would be, 鈥極kay, we鈥檝e saved you from something the size of your laptop. Or the size of your chair.鈥�

Leah Crane: I think we omit that information, we just say, 鈥榃e saved you.鈥�

Chelsea Whyte: 鈥榃e saved you, you don鈥檛 need to know what it was from.鈥�

Andy Rivkin: 鈥榊ou鈥檙e welcome.鈥� Just you鈥檙e welcome, you鈥檙e welcome, you鈥檙e welcome.

Leah Crane: Gong-gong-gong-gong, you鈥檙e welcome.

Chelsea Whyte: I do think that鈥檚 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鈥檙e going out, if this doesn鈥檛 work, it鈥檚 not going to work well, at least-

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

Andy Rivkin: Yes, Nights In White Satin was the obvious one I was thinking of, that鈥檚 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鈥檚 not to say that it鈥檚 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鈥檚 going to happen all that often. But yeah, this would really, like, work them right out of that, wouldn鈥檛 it? They鈥檇 be like, 鈥楴ever mind.鈥�

Leah Crane: Like, 鈥榊ou鈥檝e got two options. Gong or meteor.鈥�

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鈥檝e 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 鈥楪ong or Death鈥� 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鈥檚 monthly space newsletter at 麻豆传媒 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鈥檇 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鈥檙e going to be wishing for the sweet meteor of death.

Leah Crane: Because of the gong sound.

Andy Rivkin: They鈥檙e like, 鈥楾his is not worth it.鈥�