Planetary Defense (Part 1)

In 2013, a house-sized asteroid exploded over Chelyabinsk, Russia, with the force of 30 atomic bombs. A century earlier, an asteroid impact flattened 830 square miles of Siberian forest. In this episode, we uncover how planetary defense has evolved from theory to reality—why asteroid threats are more real than most people think—and what it will take to stop a civilization-ending impact. Because the next asteroid isn’t a question of if—but when.

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  On a frigid morning in Russia, February 2013, the skies suddenly burst open.

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  Then, a bright flash.

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  A sonic boom. Windows shattered across the city of Chelyabinsk as a house-sized asteroid exploded in the atmosphere 14 miles above the ground. And released energy 30 times more powerful than the atomic bomb dropped on Hiroshima.

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  Thousands were injured and shocked as the heavens revealed one of the Earth's oldest threats: an asteroid traveling at 40,000 miles per hour delivering a cosmic warning. Without warning. The explosion was equivalent to 440,000 tons of dynamite. It generated a shockwave that blew out windows over 200 square miles, leaving the city blanketed in glass. More than a century earlier, in 1908, another asteroid blast flattened 830 square miles of forest, deep in the Siberian wilderness. An area roughly the size of Houston.

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  This explosion was known as the Tenguska event. The shockwave was so powerful, it circled the globe twice. Despite its massive energy, no impact crater was found because the asteroid disintegrated entirely in the atmosphere before reaching the ground.

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  Folks who are listening should not be worried in their day-to-day life about these kinds of events, but when something occurs once every 500 years, that doesn't necessarily mean that it'll be 500 years before the next one hits.

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  While scientists estimate that tens of millions of asteroids the size of Chelyabinsk or larger linger within our solar system, only a fraction of their trajectories have been catalogued or monitored by astronomers. Their elusive nature underscores their danger. These ancient wanderers of the cosmos hover overhead like a hidden menace. Unpredictable and uncharted, they can slip past our satellites unnoticed. A team of scientists at Lawrence Livermore National Laboratory are spearheading the fight against cosmic threats with cutting-edge technology to deflect asteroids and defend Earth from potential devastation.

• 3:25Speaker 02

  It's one of the only natural disasters we actually have the power to prevent through science and technology, and so why not try? I think it's worth it.

• 3:40Speaker 00

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  Hollywood has historically portrayed asteroid threats with nail-biting, high-stakes drama. It was called Orpheus, the meteor. Like in the movie Meteor from 1979. Its power is greater than all hydrogen bombs. And Armageddon from 1998. It's what we call a global killer, the end of mankind. Or Don't Look Up in 2021. We discovered a very large comet.

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  Oh, good for you. It's headed directly towards Earth.

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  This comet is what we call a planet killer. In these "save the world from disaster" movies, heroic figures race against time and the unknown. In reality, defending Earth from asteroids is a calculated, methodical process where the real heroes are the scientists. Before diving into what it takes to save the world from these threats from above, let's begin with the fundamentals. What exactly is an asteroid? Asteroids are rocky fragments left over from the formation of the solar system. They orbit the Sun like planets but are smaller, ranging from tiny pebbles to city-sized boulders.

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  While most are clustered in the asteroid belt between Mars and Jupiter, some venture closer to Earth, crossing our path as they fly through space.

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  Asteroids are not these perfectly smooth surfaces. They're very collisionally processed. They have rubble pile structures, so lots of boulders of different sizes. There's lots of smaller sized ones and fewer big ones.

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  Megan Bruck-Syle is a physicist and former leader of the Planetary Defense Program at Lawrence Livermore National Laboratory.

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  Asteroids are pretty dark. They don't reflect a lot of light. And so we have a really good idea of where all the bigger ones are, things that are a kilometer or larger that would be at dinosaur level extinction.

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  There are roughly half a billion asteroids in our solar system, with over 30,000 classified as near-Earth asteroids, meaning they travel within 4.6 million miles of the Sun and occasionally pass through Earth's orbit. What began with early stargazers marveling at celestial bodies has evolved into a sophisticated science of tracking and understanding objects that approach Earth. At Lawrence Livermore National Laboratory, a dedicated team is at the forefront of what is called planetary defense, working to detect, track, and divert potentially dangerous asteroids.

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  Planetary defense is the field of study concerned with how to protect Earth from hazardous comets or asteroids. And that can include observing them ahead of time so that we know where they are and when they might impact Earth, how to mitigate by preventing them from impacting Earth at all. It's typically staged as either a deflection, a gentle nudge so it misses the Earth, or disruption when you break it up into lots of little bits. And lastly, if we don't have time to completely prevent an impact, we can still mitigate the effects of the impact by being able to advise on emergency response. So if we know what kind of... Damage is going to be felt here on Earth.

• 8:07Speaker 02

  We can advise on evacuations and securing of critical infrastructure. There's a ton of work in planetary defense to have full preparedness for the threat that we know awaits us. As an example, NASA was given a mandate to find 90% of asteroids 140 meters or larger by 2020, and they're only at 45%. So there's a lot of threats out there that we don't know where they are or if and when they're going to be a threat to us on Earth.

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  More than 100 large asteroids pass dangerously close to Earth every year. Close, meaning within 28 million miles of our planet's surface. On average, a car-sized asteroid enters the atmosphere about once a year, creating a spectacular fireball that burns up before reaching the ground.

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  You can visualize, okay, the sun is at the center of our solar system. Earth is orbiting around it. And then if you go out past Mars, you get to the asteroid belt between Mars and Jupiter. And the near-Earth asteroids are perturbed inward from the asteroid belt, and they have these orbits that can intersect Earth's orbit. And some of them are more circular-looking, some of them are more elliptical-looking, some of them are higher inclination, so they're at an angle relative to the plane of the solar system. There's millions of them if you go down to the smaller sizes, but there's tens of thousands have been discovered already, and they discover them at the rate of about 2,000 to 3,000 a year.

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  With thousands of near-Earth asteroids discovered every year, the need to understand their potential risks is important. They vary in shape, size, density, and composition, from solid rock to loose clusters of rubble. These factors can dramatically change the way we attempt to redirect or destroy them.

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  If you hit something too aggressively... You're trying to deflect it and keep it all in one piece, but you're a little too aggressive and it starts to fall apart. Well, that's not great because then you have something that it's harder to predict what the two big fragments are going to do over longer time scales. If you want to break it into lots of pieces, it's better to do it with feeling, like really aggressively break it into lots of pieces that are well dispersed and don't pose any threat to the Earth.

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  So what happens when we know an asteroid is on a direct collision course with Earth? How do scientists act decisively to alter its path or neutralize the threat entirely? One solution is something called kinetic impact. Kinetic impact involves hitting asteroids with a spacecraft at high velocity. The impact changes the asteroid's trajectory and momentum, which in turn changes its orbit. And in 2022, this idea became reality. Here's design physicist Katie Kumamoto, who currently leads the planetary defense program.

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  For a kinetic impact, the most conservative case we can think of has just a momentum transfer. So we have momentum in the spacecraft. We hit the asteroid and we, at the very least, will transfer that momentum to the asteroid. Now, the asteroid's much bigger, so even though our spacecraft was going really fast, it was much smaller. And so we only apply a small velocity change to the asteroid. But depending on the properties, the mechanical properties of the asteroid, we actually get this extra push from any ejecta that we produce. When you hit this kind of pile of rocks, you spray a bunch of damaged rock material back in the direction that the spacecraft was coming.

• 11:39Speaker 02

  For the average near-Earth asteroid orbit, if you give it a 1 centimeter per second change in velocity, 10 years in advance, that's enough for it to then miss the Earth. And you don't want to give it so big of a shove that it starts to come apart accidentally. And so whether it can sustain 1 centimeter per second, 10 years in advance is another question, depends on the size. If you had 20 years warning, you could get away with a gentler nudge, so a half a centimeter per second. And gentler is better because then we don't have to transport as much mass if we're doing kinetic impact.

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  Asteroid deflection is a delicate balance. Too much force, and you risk fracturing the asteroid into hazardous fragments. Too little, and you might not shift it off course in time. So preparation is critical. Simulations and exercises are vital, allowing experts to practice calculated deflections with the right amount of force. But for a long time, this was just theory. Concepts and calculations that only existed in the realm of computer models. To truly test these techniques, scientists needed more than just simulations. They needed to try it on a real asteroid.

• 12:56Speaker 00

  Lawrence Livermore National Laboratory is hiring. If you're passionate about tackling real-world challenges in science, engineering, business, or skilled trades, there's a place for you at the lab. Right now, positions are open for a Senior Guidance, Navigation, and Controls Engineer and a Senior Business Operations Specialist. These are just a few of the more than 100 exciting roles available. At Lawrence Livermore, you'll work on projects that matter, from national security to cutting-edge scientific advancements. Join a team that values innovation, collaboration, and professional growth.

• 13:36Speaker 00

  Explore opportunities at llnl.gov/careers, where your next career move could make history.

• 13:53Speaker 00

  The DART, or Double Asteroid Redirection Test Mission, was NASA's first full-scale test of planetary defense, designed to see if a spacecraft could alter the course of an asteroid by directly impacting it. In 2021, the DART spacecraft targeted Dimorphos, a small moonlet orbiting a larger asteroid, Didymos.

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  It's humanity's first attempt at altering the motion of any celestial body.

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  The DART mission was the first full-scale planetary defense application test, where what we did is we had the DART spacecraft and we just sent it hurtling at an asteroid to strike it and change its velocity in space.

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  Protecting Earth from potentially deadly objects in space.

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  And so this was just a test. The target of the DART mission was not a threat to Earth, but we were proving that in the event that an asteroid was on a collision course, we would be able to move it by just hitting it really, really hard.

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  DART was launched in November of 2021.

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  NASA is about to intentionally crash a spacecraft into an asteroid, and they're going to do it right here on live television.

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  And 10 months later, DART collided with Dimorphos at high speed.

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  Everybody's watching on the TV screens because we're getting live images streamed back about one per second.

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  14,000 miles an hour.

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  And so we can see, oh, we've successfully targeted Dimorphos. Oh, we can actually see Dimorphos for the first time as more than a pinprick of light.

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  See it getting closer and closer. We're here just in the final few seconds.

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  And the signal that we actually hit Dimorphos was actually, we get this final partial image where the spacecraft got destroyed before it could send back the full image. And when that popped up on the screen, the like screaming and elation of we actually did this.

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  First planetary defense test was a success, and I think we can clap to that, everyone.

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  We have successfully moved an asteroid. That's incredible. It was electrifying.

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  This mission demonstrated that a kinetic impact could be used to deflect an asteroid's path.

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  NASA's DART spacecraft has successfully crashed into an asteroid.

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  Potentially keeping it from hitting Earth if detected early enough.

• 16:03Speaker 03

  The DART spacecraft successfully struck Dimorphos, which was its target asteroid, and it changed its velocity by close to 3 millimeters per second, which doesn't sound like very much, but for deflecting an asteroid for planetary defense purposes, that's actually a sweet spot.

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  DART was proof that we can, in fact, redirect a celestial danger. NASA has been able to show that they can potentially save life as we know it. The success of the DART mission not only demonstrated our ability to redirect a potential cosmic threat, but also underscored the importance of understanding the complex variables at play. Beyond the celebration of impact and deflection lies the meticulous work of predicting how different types of asteroids, each with unique shapes, compositions, and structures, might respond to such an intervention. Modeling these variables isn't straightforward. For instance, the goal isn't to destroy the asteroid, but to deflect it.

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  Achieving this reliably depends on understanding how the asteroid's specific characteristics influence its response to impact. These same characteristics can also influence how an asteroid reacts to atmospheric interaction, if it remains on a collision course with Earth.

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  Some of this high-fidelity modeling is very early in maturity, so what we were trying to do is develop very descriptive simulations of the solid object coming into the atmosphere and breaking up in the atmosphere.

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  Jason Pearl is a physicist with the Planetary Defense Group at Lawrence Livermore National Laboratory. He focuses on modeling asteroid airbursts, events where smaller asteroids break up in the atmosphere before reaching the ground. The energy released during an airburst is comparable to a nuclear explosion, with potentially devastating effects. Accurate modeling involves predicting how an asteroid might break apart in the atmosphere, and depends upon how different asteroid types behave. Rubble pile asteroids, for example, present unique challenges. These loosely bound clusters of rocks and dust may fragment more easily than solid asteroids,

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  but their debris can disperse unpredictably, spreading over a much larger area.

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  I think it's very early in this line of research. There's a lot of work to be done. Most of the work so far in the airburst side has been making sure that we're doing our due diligence, figuring out if we're modeling things correctly.

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  One example of this work came from analyzing the Chelyabinsk event, a near-Earth asteroid that exploded in the atmosphere over Chelyabinsk, Russia back in 2013. Jason's team used high-fidelity models to simulate the asteroid's behavior, and their results suggested the Chelyabinsk asteroid possibly entered Earth's atmosphere as a single, solid piece. Many asteroids in near-Earth space are thought to be rubble piles, so this was significant. Understanding whether an asteroid is solid or a rubble pile is critical, as it influences how an asteroid would respond to impact or deflection.

• 19:12Speaker 01

  When these explode, it's on the order of kilotons to even megatons of energy. These objects, what are these made out of? What kind of shapes are they? How are these things arranged? You might have something that's like a solid chunk, you might have something that's composed of the buckshot, or it's just a pile of gravel. So there's a whole range of different materials, too.

• 19:31Speaker 00

  Every fragment and detail matters. Each high-fidelity simulation allows scientists to account for a range of possible scenarios before a real asteroid is in sight. And while Jason's team has made strides, modeling asteroid behavior remains a frontier in planetary defense research, requiring ever-more-precise simulations and an understanding of complex physics.

• 19:55Speaker 01

  You could have something like a comet where it's composed of ice. You could have a variety of other materials, they're called chondrites, but it's essentially this composite of different materials, kind of like rocks. When they come in, it's roughly like on the order of 20 kilometers per second, so it's Mach 60. It's very quick, and so the whole event might be order of a few seconds. And when it comes in, a shock wave forms, and you get some superheated gas on the surface of the object, and this will start to melt and vaporize the surface, and eventually the object will fragment or break up.

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  The incredible energy and variety of these space objects pose unique challenges for scientists. With each new discovery, they're faced with unknowns. From the materials asteroids are made of to the unpredictable ways they might break apart. But what if the biggest challenge isn't the asteroids themselves, but the tools we trust to deflect them? Scientists have found that every component of the design of the spacecraft matter. Each detail can affect the force delivered to the asteroid and how it reacts. For example, the shape of the spacecraft impacts how much force is transferred in a collision.

• 21:10Speaker 02

  Sometimes it's just a grind that you're making things better and better slowly. But then there are these surprises. An example of that would be how much the spacecraft geometry, the details of that matter for the deflection result for DART. So DART is not a sphere. It's a box with two giant solar panels attached to it. And the box part is about the size of a refrigerator. But for convenience, people often will model it as a sphere or just one box to simplify the geometry. And when you include all of that realistic engineering detail, it actually does affect the results and it's less effective by about 25% in how much momentum it delivers to the asteroid.

• 21:53Speaker 00

  A streamlined model might suggest one result, while a more realistic model, accounting for every solar panel and structure, might reveal something entirely different, ultimately affecting the asteroid's response. And then there are logistical challenges: timing, coordination, and resources. Planetary defense requires years, preferably decades, of advanced detection to prevent a potential impact. These challenges mean that planetary defense missions involve not only technical accuracy, but also long-term planning and international cooperation to prepare for a coordinated response.

• 22:30Speaker 02

  The DART mission was a nice microcosm of how we could collaborate internationally. We had a lot of European collaborators on that. For years, as part of the Planetary Defense Conference, which is international and moves all over, the next one's going to be in South Africa, which is the first time it's been in the southern hemisphere, actually. And South Africa has some really good telescopes they use for the DART mission as well. We collaborate there, go through the tabletop exercises together through these planetary defense conferences.

• 22:58Speaker 00

  Planetary defense is an international problem that could affect any country. This developing field will need continued research, refinement, and international cooperation. Every mission and model adds to our understanding, but there's still a long way to go before we have a fully tested, reliable defense system. Agencies around the world are working together to build a coordinated defense strategy. This includes data sharing initiatives, joint research projects, and conferences where experts from around the world come together to discuss new developments and run simulations on hypothetical impact scenarios. These collaborations ensure that the world is ready to act together if and when it's necessary.

• 23:43Speaker 02

  It's an international problem that could affect any country. There is a special responsibility on the spacefaring nations to advance our methods and technology to be able to protect not just ourselves, but any country that might be affected. There's a lot of discussion of the politics and law around planetary defense at these conferences, too, because if someone's gonna do something and they accidentally push it into another country, well, that's the big problem, right? That can create fear of touching anything, doing anything, and then just taking the hit, which would be bad for everybody to really embrace that mentality, just to take the hit. So we collaborate. It's a worldwide effort, and it brings a lot of different shared interests across different

• 24:25Speaker 02

  disciplines together, so astronomy, physics, geology, engineering.

• 24:30Speaker 00

  To face a threat as complex as an asteroid on a collision course, we'll need all the resources we can get. Future missions are essential, not just for practice, but for real-world understanding of how to approach these space rocks with greater precision. Scientists hope to learn more about asteroid composition, improve prediction models, and ultimately gain confidence in our ability to avert a disaster. In the end, planetary defense isn't just about the science. It's about preparation for the day we might need to act. The more we prepare, the better we can protect our planet from the cosmic threats that have been around for billions of years.

• 25:12Speaker 00

  These efforts are a reminder of both our vulnerability and our resilience, a testament to human ingenuity, and the determination to protect our world from forces beyond our control.

• 25:44Speaker 00

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