October 22, 2019


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Transcript

(music)

[0:01] Narrator: The asteroid Apophis is performing a daring dance with Earth. In the year 2068, there's a slight possibility -- a one-and-a-hundred-and-fifty-thousand chance - it'll hit us.

First discovered in 2004, "Apophis" is the Greek name for the Egyptian god of chaos. The asteroid is estimated to be more than 1,200 feet across, or 370 meters - nearly as tall as the Empire State building. An asteroid that size could obliterate a city, crashing into us at a speed of more than 40 times faster than a rifle bullet.

Earlier predictions had given Apophis a three percent chance of hitting Earth ten years from now -- on April 13, 2029: a Friday the thirteenth. Despite the auspicious date, three percent doesn't seem very likely. But it was the biggest chance for a large asteroid impact on Earth since NASA had started keeping track. Thanks to radar measurements and sleuthing through sky-image archives, astronomers got a better grasp on the asteroid's path through the solar system, and ruled out the 2029 impact. We now know it'll cruise 19,000 miles above us, closer than some satellites. Flying at 16,000 miles per hour -- 30 times faster than the average airliner -- it'll cross over the Atlantic Ocean in an hour and a half.

Astronomers will use this close approach to get a more detailed view of the asteroid. They also hope to further hone down the already slim possibility it'll hit us in the future.

There are over two thousand potentially hazardous asteroids out there - large space rocks like Apophis that zoom around the Sun like swarms of speedy drivers. They each stay in their lane, but there are no traffic lights, signs or cops - so over time, collisions are bound to happen.

The superhighway of the solar system is so vast, none of these potential threats to Earth are likely. In fact, the odds are vanishingly low. But the chance is still there.

NASA has a Planetary Defense Coordination Office focused on asteroids that come near Earth. If a large asteroid ever hit our planet, it would be a disaster of historic proportions. So they recently conducted an asteroid-impact exercise, working with many different scientific groups and government agencies.

If we saw a big space rock heading our way, what would, or could, this group do to save us all?

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[3:00] Narrator: We're "On a Mission," a podcast of NASA's Jet Propulsion Laboratory. I'm Leslie Mullen, and this is Season Two, Episode 3: Bracing for a Crash.

(music) [3:17] Narrator: Lindley Johnson is in charge of Planetary Defense for NASA. His office coordinates all the agency's efforts regarding near-Earth asteroids, especially those that have a chance of hitting us. Lindley is tall and unflappable, with the demeanor of a sheriff in the Old West. He even has a mustache. He gives me the sense if there was an asteroid heading our way, he'd coolly draw his pistol and knock it clean out of the sky. Part of this impression might be due to his background.

Lindley Johnson: As a lieutenant in the Air Force, I was an orbital analyst in Cheyenne Mountain, tracking all of the objects in Earth orbit. It was called the Space Defense Operations Center back then. It was tracking satellites, debris, anything that was up there, both to know what the satellites were doing, what their purposes were, and also to protect important assets from potential collision with space debris.

We started a more intensive effort for tracking debris and predicting close conjunctions with operational spacecraft, back when the Space Shuttle started going up in the early 80s, and set up what we called the collision avoidance program. The Space Shuttle, being quite a bit larger spacecraft than anything else that we were putting up, the potential for collision was greater, and so it was decided we probably should pay attention to that.

When I was in the Air Command and Staff College, back in the early 90s, I was involved in a study that was looking at what the Air Force should be doing in the year 2020, it was called Spacecast 2020. And I had been involved with some of the astronomers already in tracking near-Earth asteroids. And so I decided that I would write my paper as part of this study on the subject of hazardous asteroids and potential collision with the Earth. And I was looking for a term that would bring together the astronomers and the Air Force, and so I came up with the term, "Planetary Defense."

[5:17] Narrator: The 1994 report, titled, "Preparing for Planetary Defense: Detection and Interception of Asteroids on a Collision Course with Earth," was the first time the words "asteroid" and "defense" had ever been used together. After Lindley retired from the military, he moved over to NASA and soon began developing the Planetary Defense Coordination Office. That office divides an asteroid threat into two stages: pre-boom, and post-boom. NASA focuses on pre-boom, when we see an asteroid heading for us.

Lindley Johnson: In the case of an asteroid impact to the Earth, pre-boom is figuring out what we could do about it. So NASA is involved in determining if there is any potential for impact of an asteroid, and then determining how big is the object, what's its composition, to try to determine how bad the impact effects could be.

In most cases, we can determine the object's quite small, and the Earth's atmosphere will break it up and there won't be any effects on the ground. But, a larger object, several tens of meters in size, could survive the entry through Earth's atmosphere and cause effects on the ground, or at least, blast effects from it detonating up in the Earth's atmosphere.

[6:31] Narrator: Post-boom is concerned with the result of a large asteroid impact. That's the purview of government agencies involved with emergency response, like the Department of Homeland Security, in particular the Federal Emergency Management Agency, or FEMA. And so the Planetary Defense practice drills involve all of these groups.

Lindley Johnson: Most of these exercises with FEMA, we set up a hypothetical situation where we've detected an asteroid that's on a potential impact trajectory. And in most cases, the exercise period is several years, because we would like to be able to detect these things several years in advance so we have time to prepare for them.

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[7:12] PDE Announcer: 2019 Planetary Defense Exercise, Day One. April 29, 2019: The International Asteroid Warning Network has announced that a recently discovered near-Earth asteroid could pass very close to the Earth eight years from now, on April 29, 2027. There is a small chance - 1 in 100 -- that it could impact our planet. Based on the apparent brightness, astronomers estimate the asteroid is roughly 100 to 300 meters - or 330 to 1,000 feet -- in size.

Lindley Johnson: We acquaint them with how we might know that there is a possible impact several years in the future, to help them understand how we detect and track these things, and observe them over the course of time.

And also the fact that, initially, we may have not certainty whether there will be an impact or not, because of the uncertainty of the asteroid's position several years in the future. And then the tracking of the object over time, because it's in a different orbit about the Sun, it goes through periods where it is observable by Earth observatories, and other times where it's not, where it's either too far away, or even on the other side of the Sun.

[8:27] PDE Announcer: 2019 Planetary Defense Exercise, Day Two: Three months later; July 29, 2019.

Based on months of observations, the International Asteroid Warning Network reports that asteroid 2019 PDC now has a one in ten chance of impacting Earth on April 29, 2027.

The asteroid will remain observable for the next six months, and observers around the world will continue to track the asteroid until it moves out of range early next year. Astronomers have narrowed the estimate of size of 2019 PDC to roughly 140 to 260 meters, or 460 to 850 feet. Based on this size estimate, if this asteroid were to impact Earth, it could release 100 to 800 megatons of energy, possibly producing serious devastation over a large region.

Space-capable nations should begin development of space missions to characterize the asteroid, and be prepared to deflect the asteroid if it is on a collision course with Earth.

Lindley Johnson: In another time period in the exercise, we get more observations that increases our precision of where the object is going. And so the probability of impact for these exercises then begins to grow. It may go from 10 percent to 80 or 90 percent.

[9:48] PDE Announcer: 2019 Planetary Defense Exercise, Day Three: Two years and five months later; December 30, 2021.

A reconnaissance spacecraft that flew by asteroid 2019 PDC has determined with certainty that the asteroid is on a course to impact near Denver, Colorado on April 29, 2027.

NASA and other space agencies around the world are ramping up work already begun on a fleet of spacecraft that will be launched to the asteroid to deflect it off its impact course with Earth. The asteroid is large enough to cause major damage over a large region around the Denver area.

Lindley Johnson: As we simulate learning more about the object and its orbit, and its size and composition, we then start talking about what the effects could be of this object impacting the Earth. And if it is large enough and solid enough, what could the size crater be?

And so, we are also talking about ways that we could mitigate such an impact. If enough time is available, we might be able to divert the asteroid in its orbit. But of course, we don't want the emergency responders to get too comfortable that NASA's just going to take care of this, because that is a challenge, and we're only beginning to test capabilities to deflect asteroids in space.

[11:06] PDE Announcer: 2019 Planetary Defense Exercise, Day Four: Three years later; September 3, 2024.

Three kinetic impactor missions have successfully deflected asteroid 2019 PDC's main body, and it no longer poses an impact threat to Earth. But a large fragment broke off, and remains on a collision course with Earth on April 29, 2027.

The International Asteroid Warning Network is organizing an observing campaign to track the asteroid fragment once it moves away from the Sun's glare into the nighttime sky, and becomes visible to large telescopes two months from now.

The asteroid fragment is estimated to be 50 to 80 meters in size, or 165 to 260 feet. The exact location for the impact is not yet precisely known, but the Eastern U.S. and Atlantic Ocean are currently at risk.

Lindley Johnson: With these exercises quite often, although we might be partially successful in diverting the asteroid, maybe a piece broke off, then we will simulate with them a piece of this asteroid impacting and doing some localized damage in a city-wide area. So they then have to think about how do they prepare for that, how do they prepare the citizens and infrastructure in this area to take the hit, so to speak.

[12:25] PDE Announcer: 2019 Planetary Defense Exercise, Day Five: Three years later; April 19, 2027.

The 60-meter, or 200-foot fragment of asteroid 2019 PDC is predicted to impact over the Central Park area in New York City, just after midnight on April 29, 2027 -- 10 days from now.

The small asteroid will enter Earth's atmosphere at 19 kilometers per second, or 43,000 miles per hour. This will produce a very large fireball, and the airburst is predicted to release the equivalent of 5 to 20 megatons of energy.

FEMA's National Response Coordination Center has nearly completed evacuation of residents and critical infrastructure. FEMA is also working with the International Asteroid Warning Network to define a temporary flight restriction zone around the impact area, to coordinate pre-impact access to the area by scientists placing sensors to monitor the impact, and to prepare for any casualties and, ultimately, recovery.

(beep-beep-beep)

[13:31] PDE Announcer: This has been a test of the Asteroid Impact Warning System. In the event of an actual asteroid impact threat, this signal would have been followed by information and instructions. This concludes this test of the Asteroid Impact Warning System.

(movie trailer: Deep Impact) "Last summer, two comets were discovered that are on a collision course with Earth.

"Oh my God."

"The smaller comet will hit first, creating a tidal wave over three thousand feet high. The larger comet..."

[14:02] Narrator: Movies like "Deep Impact" dramatize the terrifying consequences of a large asteroid or comet hitting our planet. News reports of asteroids flying past Earth try to shock and scare us. NASA's approach to the threat of asteroids is calmer, and more systematic. As we heard in episode one, part of that approach is to canvas our neighborhood, using telescopes to see what's out there. But we don't see them all. Many, especially the really small ones, can slip through our net. So like cosmic detectives, the Planetary Defense group hunts for clues, the tell-tale fingerprints of a small asteroid entering our atmosphere.

Lindley Johnson: Earth is impacted by smaller objects, a meter or two in size, several times a year. And these objects enter the Earth's atmosphere and break up. And we use weather radar. Weather radar of course was designed to detect raindrops in the Earth's atmosphere, and so when these objects get down low enough, the weather radar can pick up these smaller rocks.

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You can go out any clear night and see a meteor going through the sky, that's a small piece of dust, grain-sized object entering the Earth's atmosphere. The Earth accumulates some 100 tons of matter from space every day. The small stuff burns up higher up in the atmosphere, and so it doesn't come down low enough in the Earth's atmosphere for the radar to see it. It's only the larger stuff that gets down within 5 or 10 miles from the Earth's surface before they get picked up by the radar.

[15:33] Narrator: Lightning monitors also see the bright flash that occurs when an asteroid enters the atmosphere. And sensors meant to keep tabs on nuclear bomb tests hear the sound waves caused by an incoming asteroid.

Rob Landis: The infrasound. We can't hear it. But there are sensors all around the world to detect, to make sure folks are abiding by the test ban treaty. These things pick it up and sometimes you'll see an echo that will go around the Earth from it, depending on the energy of the event.

[16:02] Narrator: That's Rob Landis. He helped organize the International Asteroid Warning Network, also known as IAWN. This is a partnership of space agencies and astronomical observatories in different countries to prepare for any possibility of an asteroid impact. Because such an event can happen anywhere, regardless of a nation's boundaries, a true alien invasion. It's "a problem without a passport."

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[16:31] Narrator: Rob says figuring out the international response to an asteroid strike is vital, not only for big asteroids that could decimate a country, but for small ones that take us by surprise. For instance, last year a small asteroid blasted through the atmosphere and exploded over the Bering Sea, near the east coast of Kamchatka, a Russian peninsula not that far from North Korea.

Rob Landis: You can imagine if the Kamchatka event occurred over the Korean peninsula or over Pakistan and India right now, other nuclear powers that are not perhaps as sophisticated to distinguish between a manmade event and a natural event, and unleashing something that was wholly unintended. That's a much more realistic thing then the big one coming in on us. A smaller one, 10, 20 meters across, coming in and then being misinterpreted.

One of the things I like to think about with this is there's perhaps no greater gift that the space agencies of the world could do for humanity, then to know the time and place of an impact event, and prepare our response to it.

[17:27] Narrator: In 2013, an asteroid over Chelyabinsk, Russia blew up in the sky and shattered windows for miles around. In a sense, that asteroid was a test of whether a nuclear power could recognize the difference between an asteroid and a missile attack. What made it even more risky is that Chelyabinsk is a military town.

Rob Landis: It's like their Los Alamos. It's where the nuclear weapons research goes on. The initial YouTube videos I'd seen, you hear that, "Are we under attack?" It's in Russian. And also, those YouTube videos, these are amateur people. "Is this a meteorite?" "Is it a missile?" So there is that positive in there, the idea that it might be a meteorite. This thing, you could just tell, holy cow, we don't have anything that goes that fast, missile-wise. The Russians have nothing like that to shoot something like that down. Neither do we. These things can be, 50, 60 kilometers per second.

[18:21] Narrator: Besides the speed, a nuclear strike differs from an asteroid because it generates an X-ray flash and an electromagnetic pulse, not to mention the radiation. Perhaps many Russians are aware of the differences because the country seems to get more than its fair share of asteroids. There was the Tunguska event of 1908 that flattened hundreds of miles of forest; one of the largest asteroid events in recorded history.

Rob Landis: There was another event in Russia, just south of Moscow over a city called Efremov, releasing more than three kilotons equivalent energy. And we didn't see it coming. It happened during day time, early in the morning. But there's security cameras, some dash cams, Russians have dash cams for insurance purposes on their cars. It came almost straight down, and meteorites were collected from that as well. Russia's not particularly targeted. Russia just covers like 11 times zones, so it's the biggest landmass on the planet.

[19:14] Narrator: For the asteroids that we didn't see coming, it can take some time to collect all the evidence and piece together what actually happened.

Rob Landis: With Efremov, Russia, it was probably within a couple of days. With the Kamchatka event, it was a couple of months because we didn't believe the size of the event. For infrasound, there's no witnesses, there's no video imagery or anything like that. The sensors were actually designed to pick up the thermal signature of an ICBM launch. There might be other sensitivities with that, because this would be down range of North Korea for an ICBM attack on North America.

So we want to make sure we've got the facts straight. Due to the other security sensitivities and hey, maybe we have to pinch ourselves and pinch ourselves again. Did this really happen, or is it a faulty sensor? And I'm kind of glad that it was done that way, to make sure the facts were absolutely crystalline, before misreporting anything.

[20:14] Narrator: NASA and IAWN work with the State Department and the United Nations to keep other nations up to date on the latest asteroid discoveries and potential threats. Rob says some nations, like North Korea, might be wary of these advisories, seeing them more as a ploy to reveal a country's nuclear secrets.

To keep everyone on their toes, the Planetary Defense exercises have imagined asteroid impact scenarios over politically sensitive regions.

Rob Landis: One of our impact exercises, actually the impact event, the risk corridor took it over the Korean peninsula out over Japan. I like it because it's kind of real world in a way, because given the political situation, these are things we really face. Well, huh, the asteroid now has gone on the other side of the Sun as seen from Earth, we'll have to wait till it emerges from the other side of the Sun when we can see it next. "Oh my God. It's not just one asteroid, now it's three asteroids. One fragment's 20 meters in size. The other fragment's 50 meters in size. The other one looks like a rubble pile. What do we do now?" kind of a thing.

Now in the scenario as it played out, there was a number of space missions launched that diverted the remnant that it came through out over the Pacific Ocean, and there may have been a mild tsunami or something. So yay, world saved and whatnot. But the events leading up to it... and by God, Paul Chodas is the devil when he plans these things. He's very clever. I just, I hate him, but I also love him because he does such a great job of planning these wonderful exercises with a good dose of realism.

[21:45] Narrator: Here's Paul Chodas, the devilish mastermind behind the Planetary Defense scenarios.

Paul Chodas: I intentionally make them difficult because otherwise, you're not going to learn anything. It's kind of a "what if," right? What would we know, and when would know it?

[21:59] Narrator: Paul is also the director of JPL's Center for Near Earth Object Studies, known as CNEOS.

Paul Chodas: We are a NASA center for computing the orbits of the near-Earth objects and determining where they will be in the future, and determining whether they could hit the Earth or not. So a large part of our job has to do with uncertainties in the orbits. Because when you project an asteroid into the future, it's based on limited data now, and there will be some uncertainty in the future. And in fact, that uncertainty will be much bigger than the size of our planet.

[22:30] Narrator: CNEOS keeps a running tally of over 20 thousand near-Earth objects orbiting the Sun: asteroids, comets, even a few spent rockets and other interplanetary space-age debris.

Paul Chodas: Most of them are asteroids, and the definition of a near-Earth object is simply one that can come into the inner solar system, so it's a pretty generous definition. Most of the asteroids are way out in the asteroid belt, and they stay out there.

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[22:55] Narrator: The asteroid belt is between the planets Mars and Jupiter, and generally marks the border between the inner and outer solar system. Even though those asteroids don't currently pose a danger to us, the CNEOS program keeps an eye on them, and many other objects far beyond Earth too.

Paul Chodas: We are part of a larger program, the solar system dynamics group. And in fact, use the same software to calculate absolutely everything in the solar system. So we're getting close to 800,000 objects. We keep track of them all. It's really cool.

The historical rationale for our group at JPL is for tracking anything we might want to go to in the solar system, which means tracking where are the planets going to be. Then, went on to comets and then to asteroids.

I came to JPL to work on Halley's Comet in the 80s under Don Yeomans. His initial NASA project was to track Halley's Comet and predict where it would be when it returned in 1986. We were expecting it, but didn't know exactly where it would be and when it would be, so we were computing orbits for that. So wow, Halley's comet, that's a very special one, you know, once every 76 years. So that was exciting.

I remember an astrologer calling me up and said, "You compute Halley's comet's orbit, can you tell me when it will be closest to the Earth?" This is pre-email, so things are done on the phone. "Oh, sure, on this date." "No, no, no, no. We want to know the exact minute that it will be closest to the Earth." "Okay, that's not something I had thought was any importance to calculate but sure, I can tackle that." And then, printed out its positions and close times, and calculated the exact minute that it would be closest to the Earth. The astrologer was really happy about that, and so this is one instance of many where it became important. Well, how close will an object get to the Earth? So I said, fine, well, we'll just put that in the software so that it automatically detects that and reports it.

So that was the start of close approach tables. And then, computing uncertainties of the close approach is another step, and then another step on top of that is how close is it coming? If it's within the radius of the Earth, could it hit? And then the impact probabilities on top of that. So things kind of build on each other.

[25:03] Narrator: What started as an astrologer's request now is a comprehensive list of asteroids with a close approach to Earth. And more are found nearly every day.

Paul Chodas: Congress' original goal given to NASA to find 90 percent of the near-Earth asteroids that were one kilometer and larger, and that was assigned back in 1998, 20 years ago.

In 2005, Congress assigned us a new goal to find 90 percent of the near-Earth asteroids 140 meters and larger. So that's what we have been working on since then.

First of all, how do we know how many asteroids are in the total population if you haven't discovered them yet, right? And that's like fishing. If you're in a small lake and you catch fish and you tag them and you throw them back, and then, you're fishing so long that 90 percent of all the fish you catch are tagged, then you know that you have found 90 percent of the population of those fish. So that's kind of like what it is for asteroids, although we have to bin them by size.

I have to say that although our telescopes have improved, and we're finding more than ever before and scanning the skies more frequently than ever before with larger telescopes, that's not large enough to reach the goal that Congress has assigned us in any time soon. With our current technology, this is going to take 40 years maybe.

Our telescopes aren't powerful enough to see things that are much bigger than ... in the past, it was 10 meters and now it's one meter, unless they come really close to the Earth.

[26:34] Narrator: The asteroid that caused a global mass extinction 66 million years ago, ending the age of the dinosaurs, was about ten kilometers across. Astronomers have found only a handful of near-Earth asteroids that large, but none of those are headed our way. But we could get hit by smaller asteroids that are still big enough to hurt us.

Paul Chodas: Several asteroids have a chance, a very tiny small chance, but we can't rule out probability for some of the bigger asteroids. That's a disquieting feeling. (laughs)

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We have a system we call Sentry, which projects asteroid's positions into the future 100 years, for all the asteroids, and looks at the ones that could cross the Earth's orbit. We have 800 asteroids on this list, but most of these are very, very small impact probabilities, down at one in a billion, one in 100 million kind of level, really, really tiny. But we want to drive those to zero. The way you do that is by continuing to monitor those particular asteroids.

A lot of these objects you just have to keep tracking with time. So if you only tracked it for a few days, you can't really project ahead a year. Or if you've only tracked it for a few months, it's going to be hard to track it five years from now with certainty. And so you really need to track these objects for years and in fact, decades. And most of them have an orbital period that's a few years. So if you track it for a few years, you've seen it all the way around its orbit. Then you'll get a much better fix on the orbit and be able to predict it pretty well.

[28:08] Narrator: Time is the biggest challenge for asteroid defense. Time to find them, time to observe them, time to make a plan and then carry it out.

Paul Chodas: If an asteroid is discovered, most of our warning and calculations are making the assumption that it's just passing by and it could impact years or decades from now. But if it's on its final plunge towards the Earth, then we want to have an automated and expedited system to notify everyone that this is an important asteroid.

We do have a system, which we call Scout, which is monitoring the common web page where observers send in their potential new discoveries. We'll run our trajectories and detect the fact that it's on an impact trajectory, possibly. That's now automated and we have observers get a rating on these potential new discoveries, sometimes only within half an hour of discovering the object. If there is something heading for the Earth, the automation will detect that and send us emails or text messages. And we did have the one in Botswana last year. That was detected 12 hours or so before impact, or even less. Again, not much time to respond.

So time is important. So that's why we make predictions over 100 years into the future and we try to detect any possibility of impact 50 years from now. That's plenty of time to do something about it. The key thing is to find it early, and to go through these little exercises where we think about what we would do and what the steps would be.

[29:38] Narrator: Rob says the International Asteroid Warning Network is slowly growing, and he hopes it evolves fast enough to be able to handle a future asteroid emergency.

Rob Landis: It takes things like Chelyabinsk or the Kamchatka event for us to, okay, well, hmm. How can we improve on that? And part of it is because it's a volunteer effort. It's not set up like the DEW line, the Defense Early Warning system for North America. It's not set up like NORAD. I wish it was.

(music: "Skyfall," Adele)

There's a certain giggle factor associated with it until something bad happens. When you hear a politician or a comedian saying something, "Ah, you have as much of a chance of that happening as an asteroid hitting you." Well, one hand, it's kind of funny, but actually these things do hit us. Impacts are a fact of life. You can take a look since before spacecraft arrived at the Moon and Mars, and in the span of their lifetimes in orbit about those bodies, they've seen new impacts occur.

("Skyfall" lyrics) Let the sky fall When it crumbles We will stand tall Face it all together At sky fall...

[30:55] Narrator: Astronomers have used the last two Planetary Defense exercises to make observations on real asteroids. This way they get to train on how to react quickly and efficiently in the event of an emergency, while also gaining some new asteroid data and insights. And Rob says even though the Planetary Defense exercises are made-up scenarios, they've been helpful in other ways too.

Rob Landis: Okay, we're faking it. We have a fictitious asteroid that we see and it's going to do this. I think the first such exercise, I want to say it was in 2013 with FEMA, and the idea was six weeks before impact, what can you do? Can you mount any kind of mitigation mission or disruption mission? It turns out, we couldn't.

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The next exercise we had seven years until an impact event. And that gave us more time to figure things out. We put all the conference goers into this scenario and we start subdividing out, okay, who's going to handle communications? Who's going to be handling emergency response? Who's going to handle space mission planning? And that kind of a thing. It gets people to start thinking. And even though you may have a plan, are people going to follow it? It's still going to be chaotic, as governments and institutions jockey for position.

Then for the future, what are the next steps? We have a variety of experiences in our quiver of arrows, so to speak, to draw upon and be more efficient about it in the future.

The other thing these observation campaigns teaches us what interfaces we can touch on. If it was a real thing, I almost guarantee you every observatory in the world will be looking at it. Hopefully someday in the future, five, ten years or wherever from now, people might remember, "Oh yeah, back then we did it this way." So you have that relationship, knowledge and experience as well.

Now, honestly speaking, in our lifetime, do I think we'll see something like this we have to prepare for? Probably not, but maybe our grandchildren will have to, or great grandchildren will have to, and it's probably the right amount of insurance to have.

[32:59] Narrator: Special thanks to Whitney Haggins for acting as the Planetary Defense Exercise announcer. Whitney knows how to keep calm in an emergency in her regular job at JPL, which includes communicating critical information technology and computer security issues.

Next time - let's say we see a big asteroid coming our way. Rather than duck and cover and hope for the best, what if we do have enough time to send a space mission out there to do something about it?

Excerpt from Episode 4: Deflecting Disaster Andy Rivkin: If you're on train tracks, then the way to avoid getting hit by the train is to step off the tracks, it's not to try to outrun the train. Here, the way the physics works, you want to change the speed of the asteroid, and then that will take care of moving it out of the way.

[33:45] Narrator: If you like this podcast, please subscribe, rate us on your favorite podcast platform, and share us on social media. We're "On a Mission," a podcast of NASA's Jet Propulsion Laboratory.

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