Why NASA’s first planetary defense mission sent a spacecraft crashing into an asteroid

Last night, NASA completed a first-of-its kind mission to steer a spacecraft into an asteroid.

In this case, the asteroid was not hurtling toward Earth threatening to wipe out civilization, and the aim was not to blast it to smithereens “Armageddon style,” but rather to just give it a good bump — enough to slightly change its course.

The Double Asteroid Redirection Test, or DART, took aim at a small asteroid called Dimorphos, which is about 11 school buses wide. It’s orbiting a bigger asteroid called Didymos, about 7 million miles from Earth.

Marketplace’s Meghan McCarty Carino spoke with Nancy Chabot, DART mission coordination lead at the Johns Hopkins Applied Physics Laboratory, about why this mission was the first of its kind.

The following is an edited transcript of their conversation.

Nancy Chabot: Well, one of the main challenges with this DART test is that you are targeting a small asteroid in space that has never been seen before. And you’re doing this at high speed — the spacecraft travels at 14,000 miles per hour — and it collides with that small asteroid 7 million miles away from the Earth. One of the main things with this is not just to see how effective this technique might be at deflecting an asteroid, but developing this technology to target an asteroid where you have limited information about it.

Meghan McCarty Carino: So what does success look like for this mission? How quickly can you measure it? And what sort of complications are you watching for?

Chabot: Well, success was those final DRACO images that appeared on everybody’s screen live when we saw the surface of the asteroid when we’ve never seen it before, and really dramatically told the final moments of the DART spacecraft, because really just targeting this small asteroid is an important part of the test. Now we’re to the point where we want to think about how good is this kinetic impact or technique at doing this. So the Italian spacecraft LICIACube, the Light Italian CubeSat for Imaging of Asteroids, made its close flyby three minutes after DARTS impact and collision and captured some images. And those are starting to come back now these days later, in these weeks later. But that’s just a [flyby] as well. And so we’re actually actively using telescopes here on the Earth and in space in order to observe what happens, and they’ll be busy for weeks in order to measure how much the asteroid moved, how much we deflected this smaller asteroid that orbits around a larger asteroid.

McCarty Carino: I’ve heard the DART spacecraft described as like a battering ram. I’m struggling to picture that. I mean, how would you describe this spacecraft?

Chabot: Well, I have a lot of fun describing this spacecraft is a very human-sized spacecraft. Actually, it’s got really long solar arrays that stick out about the length of a school bus. But the main mass is sort of like a small golf cart. And so this small golf cart runs into an asteroid that’s about the size of the Great Pyramid or the Roman Colosseum, or really pick your favorite sports stadium and insert it there. But this is definitely just giving it a small nudge. And you would do this years in advance so that this small nudge adds up to a bigger position with that time so you wouldn’t be on this collision course. It definitely is not asteroid destruction. This is all about deflection, not destruction.

McCarty Carino: So this type of mission is just one part of what would need to be a larger defense system for asteroids and other near Earth objects.

Chabot: You know, the foundation of planetary defense or any defense system there for these natural objects that hit the Earth and have been for billions of years and will continue into the future is knowing where these objects are. Of the asteroids that have been found, currently, none are a threat to the Earth for the foreseeable future. And we always stress that. But asteroids the size of the Dimorphos, those Great Pyramid-sized asteroids, we actually have found less than 50% of that population. And things like this could be devastating on a regional scale if they were to hit the Earth. So along with developing techniques like DART to deflect these asteroids if we needed to, we also really want to be finding all of these asteroids so we have that warning time.

McCarty Carino: All right, you said that this is not likely to happen in the near future. What is the near future? And, you know, how much certainty do we have about tracking these things?

Chabot: Large asteroids that hit the Earth and cause devastation are thankfully quite rare. This is the good news. And there’s more good news there, actually too. Things that are about a kilometer and larger, NASA and other space agencies around the world have found more than 95% of the asteroids that size. So none of these extinction-level, dinosaur-killer ones are headed towards us for decades. So really planetary defense has turned a lot of focus to these smaller objects, these few 100 meters in size, like the asteroid that DART targeted. And these, if they were to hit the Earth, could cause devastation for tens to hundreds of miles or so. And you can imagine if this is over a heavily populated area, like a city or a small state even or a small country, just how devastating that effect would be. So they’re very, very rare. And what we really need to do is find all the asteroids so we have the warning time, and then we’ll be able to do something about them.

McCarty Carino: Are there any other applications for this technology beyond deflecting asteroids?

Chabot: One of the things that is most challenging with this mission was for the final hours, the DART’s spacecraft was flying itself to target this small asteroid that had never been seen before. And so this autonomous navigation, this smart spacecraft, if you will, is an exciting technology and its own that could have future applications.

McCarty Carino: All right, I read that you have an asteroid named after you.

Chabot: I do, I’m very proud of it.

McCarty Carino: How did that come about? And can you guarantee that it won’t hit Earth?

Chabot: I can guarantee that asteroid Nancy Chabot is on no way a collision course for the Earth, which is good news. They don’t give those names out to ones that are in the near-Earth-objects sort of population that could become a threat. So a lot of us in the asteroid community, the science community, are lucky enough and honored enough to have these objects named after us. It’s definitely an honor.

McCarty Carino: And I’ve got to ask, do you have a favorite asteroid-hitting-Earth movie?

Chabot: You know, I’m a big fan of all science fiction, actually. I know some of my colleagues are maybe a little more harsh and a little more critical of science fiction, but I still credit, like, “Star Wars” for a lot of being a space scientist today. I think being able to dream things without the reality closing you in really makes us imagine new things and innovate new things to create a future where we can potentially prevent this.

Related links: More insight from Meghan McCarty Carino

Nancy Chabot kind of hedged on this question, but let us know your top asteroid movie. I know it’s hard to pick a favorite — they’re all so … bad.

But you can check out this comprehensive list of asteroid-themed movies if you want to watch a few.

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