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  • As many a late '90s film suggests, the Earth could be in a bit of trouble

  • if a sufficiently-sized space rock were to slam into us.

  • And astronomers around the world are totally on top of it, monitoring potential threats

  • and developing methods to avert a hypothetical Armageddon.

  • Which is why last week, a sort of asteroid impact drill was conducted

  • at the International Academy of Astronautics's annual Planetary Defense Conference,

  • which demonstrated what might happen if an asteroid hit us within the decade.

  • Over five days, the conference attendees played out what could happen after the discovery of a hazardous,

  • but in this case totally fictional, asteroid.

  • And it demonstrates some of the problems we might face

  • if we had to tackle an asteroid threat for real.

  • NASA's Jet Propulsion Lab created the initial scenario concerning a fictional asteroid dubbed 2019 PDC.

  • In the real world, JPL's Sentry and the European Space Agency's CLOMON systems

  • would calculate the chance of an impact, and refine those estimates over months of monitoring.

  • But that can get tricky, sometimes an asteroid is too close to the Sun in the sky to observe,

  • and other times its orbit takes it too far away,

  • so it's too dim for our dedicated telescopes to pick up.

  • According to the scenario, it was determined after one month of observation

  • that 2019 PDC had a 1% chance of striking the Earth in 2027,

  • and the asteroid was between 100 and 300 meters across.

  • A rock that size, with an impact chance of that magnitude,

  • is listed as a 2 on the Torino Scale for impact hazards.

  • Which is a scale that we have, by the way.

  • But that's mostly because of the relatively low risk.

  • A three hundred meter asteroid could ravage an entire continent

  • if it actually hit the Earth in the right spot.

  • Hence the continued monitoring.

  • The second day of the conference corresponded to 4 months of theoretical observations,

  • after which the risk of 2019 PDC's impact increased to 10%,

  • and its size was narrowed down to between 140 to 260 meters.

  • Analysis of its orbit using computer simulations pinned down where it could possibly hit:

  • a 70 kilometer wide band stretching from Hawai'i to Africa.

  • Yes, that is a big swatch of the planet.

  • Including quite a bit of ocean.

  • So, the Space Mission Planning Advisory Group, or SMPAG, a real-life group that monitors asteroid threats,

  • made some recommendations.

  • That included two different methods for knocking an asteroid off its current orbit that we could actually use:

  • a kinetic impactor, which would be a large spacecraft that rams into an asteroid really fast,

  • or a nuclear detonation.

  • Yes, nuke the asteroid.

  • If you detonate a nuclear bomb near an asteroid, some of its surface will vaporize,

  • and it will recoil and hopefully get knocked off its collision course with Earth.

  • Either way, we'd have to get working pretty soon.

  • Because we'd have to change the asteroid's orbit before 2025

  • for the relatively small deflection caused by the blast to actually make 2019 PDC miss the Earth.

  • And it'll take one to two years for a craft to actually get there.

  • On top of that, just like our missions to other distant space bodies,

  • you really only get one launch window a year, if not fewer.

  • So basically, we'd only have a couple of years to get the plan figured out.

  • But one problem that would very likely come up in the real world, and did in the fictional scenario,

  • is that we don't have enough data on the asteroid to know exactly how much we need to deflect it,

  • and therefore what exactly we need to hit it with.

  • Rather than just sit and wait over a year for it to get close enough to observe again,

  • we could send a reconnaissance probe to it.

  • But that would take precious time,

  • and it would leave not much wiggle room to analyze that data and then launch the deflector.

  • It's conference day three now, and we did decide to send a recon craft.

  • It arrived just before new year's of 2022,

  • and the extra data from it told us that 2019 PDC is going to hit Denver.

  • We were also able to learn more about the rock's makeup.

  • It appears to be a giant rubble pile, 140 to 220 meters in size.

  • Based on that, the asteroid would explode 6 to 9 kilometers above the Earth's surface,

  • creating a blast one hundred times the size of the Tunguska impact back in 1908.

  • That space rock leveled 2000 square kilometers of uninhabited forest, 80 million trees,

  • and shattered windows in villages up to 60 kilometers away.

  • Only one human reportedly died, but many a reindeer got crispied-up.

  • To prevent this far worse hypothetical disaster, NASA, the ESA, and the Japanese, Russian,

  • and Chinese space agencies planned to launch six separate kinetic impactor crafts.

  • They'd launch in mid 2023.

  • Based on estimates of the asteroid's mass,

  • it should only take three such impactors to nudge it off course.

  • The others would be backups.

  • Which seems smart, since we're talking about losing Denver.

  • But as a separate backup, NASA could send another recon probe carrying a nuclear device.

  • There is one problem with that plan, which is that launching a nuke into space

  • is a violation of international agreements.

  • So we'll have to navigate that political problem if it ever comes to it.

  • But in this scenario, they actually decided against using a nuke.

  • Day 4 of the conference corresponds to September 2024.

  • Denver's safe; the kinetic impactors worked,

  • but chipped off a 50 to 80 meter chunk of the asteroid, and that bit is still headed to Earth.

  • Perhaps luckily, it's got about a 50% chance of hitting the Atlantic.

  • Unfortunately, observations are on hold for a few months because the rock is behind the Sun.

  • Nukes came back into the discussion,

  • with the SMPAG suggesting we use one to break up the fragment into even smaller pieces,

  • most of which would hopefully burn up in the atmosphere.

  • On the last day of the conference, corresponding to ten days from impact,

  • it was announced that a 60 meter fragment will explode 13 to 15 kilometers over Central Park in New York City.

  • One thousand Hiroshima bombs worth of energy, inflicting serious damage within 33 kilometers.

  • And none of the attempts in the intervening years had managed to stop it.

  • Since it's hitting one of the largest cities on the planet,

  • over ten million people would need to be evacuated.

  • And the impact would render the city unlivable, leaving millions without homes even if they survived.

  • The estimated damage exceeded $70 billion in the local New York and New Jersey area,

  • which could expand to a loss of over $2 trillion worldwide.

  • Which was a pretty grim end to the scenario,

  • although they were able to theoretically prevent an even worse disaster.

  • Lucky for us here in actual 2019, there are not any asteroids we've detected that have

  • even a 1% chance of hitting us in the next several centuries.

  • As such, no object has above a zero on the Torino scale,

  • and we've got plenty of time to develop our anti-impact plans.

  • I mean we have been hit by some pretty nasty space rocks in the past,

  • so it is bound to happen one day.

  • Just probably not when any of us are alive to see it.

  • Thanks for watching this episode of SciShow Space News.

  • If you can't get enough of science-y goodness, reminder that we also have a podcast and it's very good!

  • I love it.

  • SciShow Tangents is a collaboration between Complexly and WNYC studios.

  • It's hosted by me, and a bunch of other awesome people who work for SciShow including:

  • SciShow co-host and producer Stefan Chin,

  • SciShow producer Sam Schultz (he is standing behind the camera right now),

  • and Crash Course editor Ceri Riley.

  • Which isIt's just a great group humans!

  • They're really smart and funny.

  • Every episode, we get together and try to blow each other's minds with amazing science facts,

  • and try not to go on tangents, and totally fail at that.

  • We also play Truth or Fail, where we try to stump each other with two made-up facts and one real one.

  • And there's poetry.

  • There's poetry!

  • Join us every Tuesday for episodes wherever podcasts are downloaded.

  • And thank you for listening!

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