AILSA CHANG, HOST:
Today marks the beginning of the 2019 Planetary Defense Conference. Experts from around the world have gathered outside Washington, D.C., to discuss how to protect the Earth from the threat of a devastating impact from a giant asteroid just in case. And a big part of this week-long meeting is working through a detailed simulation of an asteroid strike - whoa.
NPR's science correspondent Nell Greenfieldboyce is here with us now to tell us about this asteroid exercise. Hey, Nell.
NELL GREENFIELDBOYCE, BYLINE: Hello.
CHANG: So what exactly happens at a conference on planetary defense?
GREENFIELDBOYCE: OK, so this is just a gathering of people from China, Russia, the United States, France, all over. They're scientists. They're engineers. They're people who know how to, you know, calculate trajectories to see what's coming our way...
GREENFIELDBOYCE: ...People who know how to design missions or know how to use telescopes to find these things. And also people from the Federal Emergency Management Agency...
GREENFIELDBOYCE: ...So you know, decision-makers.
GREENFIELDBOYCE: It's all the kind of people that we would depend on if there was an actual threat from an asteroid. They come together. They hold one of these events every couple years, and they have these drills. So so far, they've had, like, three drills at the conferences. And then NASA and FEMA have independently had their own exercises.
CHANG: I had no idea this was going on. What does an asteroid impact exercise look like? I mean, how does one simulate the collision of an asteroid and the Earth?
GREENFIELDBOYCE: So basically it's a tabletop exercise.
GREENFIELDBOYCE: You're not actually simulating the collision.
CHANG: Good to hear.
GREENFIELDBOYCE: Someone devises this scenario, and they spend part of their conference - part of the week - kind of working through it. It's like a choose-your-own-adventure kind of thing, or like a Dungeons & Dragons kind of game. But this is completely serious roleplaying. What they're working through this time is a pretend asteroid that they're saying was discovered recently. It's 300 to a thousand feet across - so pretty big. It's been detected about 35 million miles away and has a 1 percent chance of striking the Earth eight years from now.
GREENFIELDBOYCE: So remember; this is all fake. It's all made-up. But a rock this size could totally take out a city. And so over the course of this week, as this pretend asteroid gets closer, every day they're going to be making decisions and getting new information and kind of playing out the whole thing.
So I talked to the guy who devised this. His name is Paul Chodas, and he's director of the Center for Near-Earth Object Studies at NASA's Jet Propulsion Laboratory. And he says he deliberately designed this to sort of stress the whole system.
PAUL CHODAS: The asteroid is not in a convenient orbit at all. It's not like one of these asteroids that we go to with our science missions where, you know, you get to pick a nice asteroid that's easy to get to. In planetary defense, the asteroid picks you.
GREENFIELDBOYCE: He says he planned this so that there's eight years' advance notice. And that sounds like a lot of time, but really it's not because they would want to plan multiple missions to go see this space rock and get more information and, you know, ultimately try to shift its trajectory.
CHANG: So how likely is it that something like this would actually happen?
GREENFIELDBOYCE: So for asteroids in the size that's being played out in this scenario - so, like, 300 to a thousand feet - it is tens of thousands of years between impacts. So you know, it's not very likely to happen anytime soon.
CHANG: That's mildly reassuring.
GREENFIELDBOYCE: But the thing is it could happen. I mean, the vast majority of asteroids in this size range have yet to be spotted by NASA.
CHANG: OK, so just remind everyone, this is still a hypothetical scenario. Seriously, though, if an asteroid were to be barreling towards the Earth, what are the options? I mean, how do you actually avoid a collision?
GREENFIELDBOYCE: Well, you would try to knock it off course. I mean, basically you would send spacecraft to either, like, push it - like, literally sort of knock it away. Or in some cases, they do talk about nuclear weapons. I mean, that's a real possibility.
CHANG: So this conference wraps Friday. You are absolutely going to have to come back and tell us what happens.
GREENFIELDBOYCE: I will. But remember; this is all just a fake drill. It's nothing real. They are not working off a real scenario.
CHANG: That's NPR science correspondent Nell Greenfieldboyce. Thanks, Nell.
GREENFIELDBOYCE: Thank you.
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