A Mission To Save The Planet (From The Next Asteroid)

17:37 minutes


NASA’s giving the go-ahead to a mission designed to test our ability to deflect asteroids that could hit or shave by Earth. The Double Asteroid Redirection Test, or DART mission, is now in the preliminary design phase. If it’s built and launched, the refrigerator-sized missile would be aimed at a 160-meter asteroid called Didymos B, which will approach Earth in 2022 and 2024.

Such a missile impact would only knock the rock slightly off its trajectory, says DART co-investigator Andy Cheng, but the change should be enough to minimize the asteroid’s threat. Cheng joins Science Friday to discuss how this test is a key step in improving our understanding of how asteroids might respond to deflection efforts.

[These are some facts about asteroids that rock.]

Of course, targeting an asteroid requires advance notice. How adept are we at identifying and tracking the asteroids that may come too close for comfort? Lindley Johnson, NASA’s Planetary Defense Officer, updates us on the progress in locating asteroids, especially those smaller, harder-to-spot ones.

Listen to a science-themed parody of Aerosmith’s “Don’t Want To Miss A Thing” from the movie, “Armageddon.” Vocals and lyrics by Rachel Bouton and produced by D Peterschmidt.

Segment Guests

Andy Cheng

Andy Cheng is Chief Scientist of the Space Department at Johns Hopkins University Applied Physics Lab. He’s based in Laurel, Maryland.

Lindley Johnson

Lindley Johnson is the Planetary Defense Officer in the Planetary Defense Coordination Office, based at NASA Headquarters in Washington, D.C.

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow. Do you remember the movie Armageddon? If you don’t, let me remind you. It starts out a little bit like this, with an asteroid with Earth’s name on it.


– How big are we talking?

– Sir, our best estimate is 97.6 billion–

– It’s the size of Texas, Mr. President.

– Yes, sir.

– What kind of damage are we–

– Damage? Total, sir. 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. What do we do?


IRA FLATOW: Oh, you’ll have to see the movie. And while the movie does come with some Hollywood exaggeration, the problem of an asteroid hitting the Earth is not fictional. In 2013, a small meteor exploded over Russia. It was only 20 meters across but an estimated 1,500 people were injured as a result of the shock wave.

According to my next guest, it’s not asteroid the size of Texas that we should be worrying about, rather those smaller ones. Under 200 meters, which are far more numerous and also mostly still undiscovered. What would we do if such a menace is found? NASA has a solution, which may also sound a bit like the plot from Armageddon.

Launch a missile about the size of a refrigerator and slam it into the asteroid. But do not try to break it into pieces as they did in the movie. Hope the force of the impact can change that asteroid’s path just enough to keep it hitting the Earth. NASA’s DART Mission, now in a preliminary design phase, will try to do just that.

Joining me now to explain the DART mission and why it’s necessary are my guests. Andy Cheng, co-leader for NASA’s DART Mission and Chief Scientist of the Space Department at Johns Hopkins University Applied Physics Lab. Welcome to Science Friday, Andy.

ANDY CHENG: Yes, glad to be here.

IRA FLATOW: You’re welcome. Lindley Johnson is Planetary Protection Officer for NASA. Welcome.

LINDLEY JOHNSON: Yes. Yeah, Lindley Johnson. That’s Planetary Defense Officer, by the way.

IRA FLATOW: Defense Of– Well, tell us why there is a Planetary Defense Office.

LINDLEY JOHNSON: Well, the hazard of asteroids crossing Earth’s orbit and being a potential for collision and impact with the Earth is a real thing. And so our job is to try to find any of those before they find us.

IRA FLATOW: Hmm. Andy, you know, a lot of people don’t think about this. Should they be thinking more about it?

ANDY CHENG: Well, we should definitely be doing both finding the asteroids before they get us. You have to find the threat. And then we have to do something. So finding them doesn’t do any good if we’re just not going to do anything anyway. And developing a mitigation method doesn’t help us if we don’t find them. So we’ve got to do both.

IRA FLATOW: All right, let’s talk about if everything goes as planned, what’s going to happen when the DART Mission launches?

ANDY CHENG: Well, when the DART Mission launches, the DART Mission is a technology demonstration. It will demonstrate the method of deflecting an asteroid by running a spacecraft into it and changing its orbit.

So we launch. We actually first spiral out of Earth, we have to get out, get away from Earth. Then we’re going to use a long-range telescope, find the target, and use that telescope as they get close to discriminate. Our target is actually a binary asteroid, where our target is orbiting another larger asteroid.

We have to separate the two in the telescope, figure out which is the one we want to hit, and then the telescope is used as a homing sensor to home in on it. And we will run the spacecraft into it at about six kilometers per second, which is about nine times the speed of the bullet from an AK-47.

And so that impact will change the orbit. It’ll basically deflect the target and change its orbit around the other asteroid. And then we’ll measure the effect of that change, we’ll measure that change in the orbit from Earth with Earth-based observations, telescopes, astronomical observations.

IRA FLATOW: Why do you need to choose? Why do you choose an asteroid where one is orbiting around the other?

ANDY CHENG: So we can– Well, there’s two reasons. First is, that way, we can measure the effect of the deflection. We can show that we deflected the asteroid, we can show the change, that the orbit has changed, and we can measure the amount of the change.

And we can do that from Earth with ground-based observations. That’s the one reason. The other reason is because this asteroid is orbiting another one, we are not going to be changing the orbit of the system around the sun to any appreciable degree.

IRA FLATOW: So that’s a safety measure, then? So you don’t accidentally knock it into a different orbit?

ANDY CHENG: Well, yes. We’re not going to knock it into a dangerous orbit.

IRA FLATOW: Lindley, what kinds of asteroids are NASA most worried about? They worry about the not-the-size-of-Texas one?

LINDLEY JOHNSON: No. All the ones the size of Texas have been found and they are safely in the main belts of asteroids between Mars and Jupiter. We are worried about those that come within 30 million miles of the Earth’s orbit and have the potential to cross Earth’s path around the sun.

So our program, its first priority is to find all these near-Earth asteroids. Sort out the ones that are potential hazards to Earth, those that are really coming close to Earth’s orbit. Determine their size and other characteristics so that if one is on an impact trajectory, we have the information that we need to mount a deflection mission like DART.

The whole principle of deflecting an asteroid from an impact of the Earth is just to slow up its speed or speed it up, one of the two, so that when the Earth reaches that point in its orbit that it would impact, the asteroid would have already passed because we sped it up or it would not be there yet because we slowed it down. So the DART mission, slamming the asteroid into it at the right angle and speed, is designed to slow it down.

IRA FLATOW: How many asteroids do we know about versus how many we think there might be out there that might hit us?

LINDLEY JOHNSON: Yeah. OK, well, it depends on size. The population of all sizes of asteroids that might come near Earth is probably in the millions. Our first objective of our program was to find all those one kilometer and larger. And our population estimates for that, so there was a little under 1,000 of those. And we have found 93% or so of those already.

So our current objective is to find those down to 140 meters. And we think the population of those is somewhere around 25,000. We’ve only found a little under 7,700 of those, so we’ve only found about a third of that size so far. The total number of near-Earth asteroids in our catalog though is approaching 17,000.

IRA FLATOW: And how much time and effort and money do we spend on looking for these asteroids?

LINDLEY JOHNSON: Well, for the detection and tracking and characterization, it’s a larger part of our program. That is in the $35 to $40 million a year range. The total amount of our program, including the preliminary development for DART and some other capabilities is, this fiscal year, 2017, was $60 million.

IRA FLATOW: $60. Is that a lot of money?

LINDLEY JOHNSON: Well, not relative to a lot of other things that are done. But it’s a good amount of money for doing the ground-based portion of our program. And we are doing what we can with the money that is appropriated.

IRA FLATOW: How much time, how much lead time do you need to find an asteroid, and if it’s dangerous, you want to make sure you can intercept it?

LINDLEY JOHNSON: Well, we certainly want to find it as far ahead of time as we can. We would certainly like to have years, maybe as much as a decade to be comfortable that we have the time to build the spacecraft or spacecrafts. It would be a mission campaign against the asteroid.

We’d first like to get a spacecraft out to get a good look at it so we know exactly what we’re dealing with before we attempt a deflection like DART or some other technique. So 10 years is a good amount of time. It could be less than that, but the shorter amount of time you have, the less options you have to deflect it.

And even if it’s a small object that is only a few months out, just knowing when and where it will impact is an advantage to the emergency response community. They rarely get a chance to know about a disaster that’s going to happen before it does. So we would still want to know about it to be able to evacuate people and secure down the infrastructure before the impact.

IRA FLATOW: Two or three months out, you could be pretty sure of where it’s going to hit?

LINDLEY JOHNSON: Given enough observations of it, yes. We are able to pretty precisely determine where and when it will impact because the timing of it can be very accurately established.

IRA FLATOW: Andy, for discovering and deflecting the dangerous asteroids, can technology advances like imaging or propulsion or something else help this happen faster and more smoothly?

ANDY CHENG: Well, certainly technology advances can always help. And, in fact, DART is a technology demonstration, so we are demonstrating the technology to be able to do this.

I wanted to comment on one thing, about the amount of damage, the kind of disaster that we are talking about averting, even from one of the smaller asteroids, a few hundred meteor asteroid impact. If we’re talking about something like that over a metropolitan area, you’re talking many billions of dollars of damage and potentially millions of casualties. So we are really talking about a major disaster that’s being averted here.

IRA FLATOW: So you’re saying that we’re not spending, if I read the tea leaves, they’re not spending enough money to save all those lives.

ANDY CHENG: No, probably. They’re not spending– Well, it’s an unlikely but very dangerous event that you are now spending, I would say, a modest sum of money to be able to do something about.

IRA FLATOW: Go ahead, I’m sorry, Lindley.

LINDLEY JOHNSON: Yeah, well, a couple of examples of what Andy is talking about. The crater, meteor crater it’s commonly called, in eastern Arizona, it’s a crater that’s over a mile wide.

That was created by an object that is estimated to only been about 50 meters in size. Now, it was an ARM asteroid, so its ability to penetrate the Earth’s atmosphere and hit the ground was greater. But even so, that’s not something you’d want to have happen in your backyard.

Another more recent event, in 1908 in Tunguska, Siberia, was an object only about 40 meters in size. It did not reach the ground, it exploded a few miles above the surface. But even so, the blast wave knocked down some 2000 square kilometers of Siberian forest. And you would not want that to happen over a metropolitan area.

IRA FLATOW: And how big was that? The Tunguska? Do we know?

LINDLEY JOHNSON: About 40 meters in size, is the estimate.

IRA FLATOW: Yeah, and that really did some damage, it knocked the whole forest down. Didn’t it?

LINDLEY JOHNSON: Right, yeah. Now, had it happened maybe three hours later, that would have put it in the vicinity of Moscow.

IRA FLATOW: Wow. Do we know why? What’s so special about Russia, why they got the last two big events? The one that we’re talking about?

ANDY CHENG: Russia’s a big country.

LINDLEY JOHNSON: Russia has the largest landmass within its set borders.

IRA FLATOW: So let me give you my blank check question. If you had a blank check, I know you never get this. I don’t have one in my back pocket, just letting you know. And you want to spend it and create the ideal system for tracking and tracing and then maybe moving asteroids headed our way, what would it look like? Let me ask you, Lindley, first.

LINDLEY JOHNSON: Well, the things that we need to do to find them, track them, and then demonstrate capability to deflect one. You know, the most frequent case would be a smaller sized object of 100 meters or so in size.

That kind of a program could be done on a yearly budget in the $200 to $250 million a year range. It’s really fairly modest. You know, this is not something that we need to be spending billions of dollars on. But we do need to have better capability than we have today.

IRA FLATOW: I’m Ira Flatow. This is Science Friday from PRI, Public Radio International. Of course, you know, sometimes popular culture can help people get things going. They’re not always accurate. I mean, in the film, I think they broke up the asteroid. That’s not a good thing to do because you get a lot of little asteroids coming in that are going to be harder.

LINDLEY JOHNSON: That’s right. We’d like to keep it intact if at all possible.

IRA FLATOW: Yeah. And I want to thank you both for taking time to be with us today. Do you have any advice for anybody who’s listening? Anything to do immediately? Andy?

ANDY CHENG: Advice, no. Sorry.

LINDLEY JOHNSON: Well, we need to continue to pursue this program at a reasonable pace. NASA’s certainly working with our administration and Congress to determine what the right amount is. We are also working with our international partners in this.

We work with the European Space Agency, the Japanese Space Agency. Russia, as well, Roscosmos and the Academy of Sciences in Russia. It’s a worldwide problem, you know. You never know where an asteroid is going to strike. It could strike anywhere. So it’s a good area for not only a national capability but for international collaboration.

IRA FLATOW: All right. Thank you both for taking time to be with us today. Andy Cheng, co-leader for NASA’s DART Mission, Chief Scientist of the Space Department at Johns Hopkins University Applied Physics Lab. Lindley Johnson, Planetary Protection Officer for NASA. Have a good weekend and thank you both for taking time to be with us today.

LINDLEY JOHNSON: Thank you for your interest. Thank you.

IRA FLATOW: You’re welcome. And because all great adventures need an heroic theme, here’s a musical tribute written and performed by our own Rachel Bountin, produced by Danielle Peterschmidt. The most scientifically accurate Aerosmith parody you might ever hear. Take a listen.


RACHEL BOUTON: I could end all life and boil all your oceans. I could make so many awesome explosions. But you just want to push me away with Newton’s laws of motion. I don’t want to change my course, don’t want to be pushed away, ’cause I’d miss ya, babe, and I don’t want to miss the Earth.

‘Cause even if I’m hit by DART, you know that you’re still in my heart ’cause I’d miss ya, babe, and I don’t want to miss the Earth. I could spend my life hurtling toward you. I could stay on this trajectory forever– Sorry. Trajectory just sounds so dumb.

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