Short Wave - A Mission To Redirect An Asteroid

Episode Date: November 22, 2021

In movies, asteroids careening towards Earth confront determined humans with nuclear weapons to save the world! But a real NASA mission to change the course of an asteroid (one not hurtling towards Earth), the Double Asteroid Redirection Test (DART), is about to launch. NPR science correspondent Nell Greenfieldboyce joins the show to talk about what it takes to pull off this mission and how it could potentially protect the Earth in the future from killer space rocks. Email the show at [e-mail]. See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. Hey everybody, Emily Kwong here. So we know that in the past, rocks from outer space have struck Earth and caused destruction, sometimes mass destruction. And the idea of having to deflect an incoming asteroid is a staple of science fiction. It's what we call a global killer. The end of mankind. It doesn't matter where it hits. Nothing would survive, not even bacteria.

My God. That's a clip from the movie Armageddon. It came out the same year as the similarly themed, yet scientifically more plausible flick, deep impact. Now, we get hit all the time by rocks and meteors. Some of them the size of cars, some no bigger than your hand. And then there's Meteor from 1979. It's five miles wide.

It's traveling at a speed of 30,000 miles per hour. And there is no place on Earth. And these three movies all have something in common when it comes to how they deal with this potential threat. NPR science correspondent Nell Greenfield Boyce is here. I'll bet she knows what it is. I assume it's nukes, right? Nuclear weapons? Yes, Hollywood's favorite counterstrike, the nuke. Yeah, you know, Hollywood loves to go after asteroids with nukes.

But, you know, if people really care about planetary defense, they say that is just generally way too messy and uncontrolled. and, you know, suboptimal for all kinds of reasons. You might end up with, like, lots of smaller but still deadly asteroids heading your way. Yeah, it might create a whole other problem. And now this is the expertise we crave on this show. You're here to talk about ways to really redirect an asteroid. And a very real NASA mission that is scheduled to launch this week for this very purpose. My understanding is that this will be the first time with this mission that NASA has ever tried to change.

the movement of an asteroid. Yep, it is indeed NASA's first test mission for planetary defense. That makes it a big deal and it's kind of unusual. Nancy Chabot is at the Johns Hopkins University applied physics laboratory. A lot of times when I tell people that NASA is actually doing this mission, they kind of don't believe in it at first. Maybe because it has been the thing of movies. She's the coordination lead for the double asteroid redirection test, or DART. So DART is demonstrating asteroid deflection. It is absolutely not asteroid disruption, which is how it goes a lot of times in the movies. The plan isn't to blow up an asteroid, but just to give one a little nudge to see how it reacts.

Okay, so today on the show, what it takes to give an asteroid this kind of scooch. and how this subtle maneuver could potentially inform future efforts to protect us from killer space rocks. You're listening to Shortwave, the Daily Science Podcast from NPR. All right, now, Hollywood aside, how much of a threat are asteroids to our planet really? I mean, does NASA really need to test out ways to protect us from space rocks? It's enough of a threat that NASA set up a planetary defense coordination office back in 20, its goal is to find potentially hazardous objects out in space, track them, understand what they're like, figure out deflection methods, and also to coordinate with departments like FEMA, you know, the Federal Emergency Management Agency. FEMA? FEMA's involved in this in asteroid disaster planning.

Oh, totally, yeah. I mean, depending on how much notice the Earth had, the best option might be to just evacuate a geographic area to save lives. So FEMA would be working on that. NASA and FEMA and a bunch of other agencies regularly hold these kind of tabletop exercises, these kind of fictional but realistic scenarios to think about what would need to be done if telescopes ever spotted a rock that was headed our way. So what have NASA and other space agencies found up there? Telescopes have found and tracked more than 90% of the really big asteroids that scientists think are out there. So, you know, like a kilometer across or larger, the kind of huge asteroid that could cause extinction events.

And, you know, there's no threats like that in the foreseeable future. But we know less about smaller asteroids. Okay. How small are we talking? Well, like around, you know, 400, 500 feet across. If one of those struck the Earth, it could make a crater that's miles wide. And it would devastate a whole region. It could take out a city, you know, just cause mass.

mass chaos on the western or eastern seaboard. Nancy Chabot told me, of the ones like that that we know about and have tracked, none are on a path that would threaten Earth in like the next hundred years. Okay. I'm relieved to hear that. That's some good news. But she also told me that more than half of the ones that size that scientists think should be out there haven't been found and identified and tracked yet. And that's why that's such a priority for planetary defense. Uh, yeah. Keep in mind, compared to planets or moons, asteroids are really, really small. They can be really dark.

It's just hard to spot them. Yeah, not super comforting that there are asteroids of this size that we don't know about somewhere, you know? Take comfort from the fact that just this year NASA gave the go-ahead for work on a new space telescope that's designed to find those kinds of asteroids, you know, the ones that could wipe out a city. Okay, let's say one was found and it was on a collision course. what could NASA do? The basic idea being tested in the upcoming DART mission is that if you can find some kind of threatening asteroid when it's still far out in space, you could do something relatively minor that would alter its trajectory and make it no longer a threat. For example, you could just ram a spacecraft into it. Wait, that's NASA's grand plan here to just smack an asteroid with a spacecraft.

The fancy name for it is a kinetic impactor. It's a kinetic impactor test. But yes, they're just going to hit the asteroid with a spacecraft that's going 15,000 miles per hour. Okay. No nukes, just good old-fashioned kinetic impactors. So what asteroid does NASA plan on ramming into with this mission? It is not one that's threatening Earth in any way. So they're sending the dart spacecraft out over 6 million miles away to a well-known asteroid system that's got two asteroids together.

That's the double. in the name of this mission. It's the double asteroid redirection test. And Nancy Chabot says there's this big asteroid that's orbited by a smaller one. So there's the larger asteroid dittimose, which is 780 meters in diameter. And there's this smaller moon demorphose

that goes around it every 11 hours and 55 minutes. So, you know, 780 meters, for those of you who are not into the metric system, that's about 2,500 feet, so like half a mile. Okay. That's the big one. And remember, it's the small one, demorphist, that NASA wants to hit. And this asteroid, the target, is about 500 feet across.

And the dart spacecraft is about the size of a golf cart. So it'll be like ramming a golf cart into like the Great Pyramid. And will that be enough to noticeably change dimorphus, this asteroid's movement around its bigger buddy asteroid? Yeah, basically the dart spacecraft will hit it head on. And this is expected to show. Shortened the time, the asteroid will then take to travel around its larger companion. So maybe its orbit will go from 11 hours and 55 minutes to 11 hours and 45 minutes. It'll change just a little bit, but it should be measurable.

Proving this idea. But how are they going to track that? Because I assume once the spacecraft hits the asteroid, I mean, that craft is gone, right? Well, it'll be in pieces, yeah. So let me back up for a minute. I mean, no one has ever seen the little asteroid that they're going to hit. No one knows what it looks like if it's smooth or has big boulders or what. What telescopes do is watch the bigger asteroid and see it dim as the little orbiting one passes in front of it.

So, you know, they'll be able to watch this asteroid system in the wake of the collision. And they'll be able to see if the timing of this dimming changes. So, you know, they're only going to get pictures of, you know, this target. at asteroid in the final seconds of the mission that the dart spacecraft will be sending back and sending back and sending back. They'll get all these pictures and then the pictures will just stop because the spacecraft has crashed into it. That is Hollywood-level dramatic.

Okay. But you just said now that asteroids are hard to see. And it seems like this one they're trying to hit is pretty small. Is there any chance they're going to like miss the bullseye? I talked to Elena Adams about that. She also works at the Applied Physics Laboratory. She's the mission systems engineer. And she says this spacecraft will use the kind of automatic navigation and tracking systems

that were developed for missile defense, which is another situation where you're trying to hit a small moving object at high speeds. She told me in the last four hours of the mission, the spacecraft will be flying itself under its own control. During the first three hours of its autonomous operations, it only sees didemos, the bigger asteroid. And so the whole time is just watching this larger asteroid and trying to steer itself towards it. And by the time it detects the smaller asteroid demorphus, it's going to switch. It's going to say, now I'm guiding myself into the smaller body. And she and the other mission managers and scientists and engineers will have nothing to do at that point but just watch and wait. It is four hours of watching paint dry, but kind of terrifying.

Yep, nerve-wracking. And I know, now, the mission's launch window is a lot of. about to open up this week, but when will the dart crash into this asteroid? Yeah. So after launch, it takes like 10 months to get to the asteroid system. And that means the impact will occur in late September, early October next year. It depends just on exactly when it launches. And if it hits, how soon will they know the mission was a success in shifting the position of the asteroid? So it'll take weeks of telescope time, probably, to do telescope observations. You know, they might be going on for months.

They'll also be able to get some photos coming back from a small cube satellite that'll be sort of riding along with the spacecraft for a while. It'll carry this with it and then it jettisons it about a week before the impact. So this little tiny satellite will be sort of separate and it'll be able to spy on the impact and send back pictures of how much debris got kicked up and all that sort of thing. And then in 2024, so in a few years, the European Space Agency is actually sending a mission called Hera to the. asteroid system. And that should be able to, you know, see the impact crater and take all kinds of measurements. And no, not to be nervous, but is there any chance that the upcoming DART test could send the asteroid careening off? I don't know, towards Earth, towards us? I actually asked Nancy Schabaut that exact question. There is absolutely no way that the DART test is a threat to

the Earth. It's far away. I mean, you can just rest assured on that one. It's not going to come for us. Okay. All right. Will you come back and see us next. year and we can talk about what happens with this mission? Oh, absolutely. Absolutely. Assuming the launch goes okay and the solar panel is unfurl and, you know, the spacecraft works. Way to be positive, Nell. I've just seen a lot in my years of covering it. So no assumptions till it's on its way. 100%. Nell, thanks for coming on the show with us. Thanks for talking asteroids. The story was produced by Eva Tesfai and Thomas Liu and edited by Giselle Grayson. Margaret Serino checked the fact.

The audio engineer was Patrick Murray. I'm Emily Kwong, and you are listening to Shortwave, the Daily Science podcast from NPR.