An asteroid named 2015 PDC has just been discovered, the teams learn. Its course will bring it swinging unnervingly close to the Earth on September 3, 2022. By April 4, 2016, they know that the chance of an impact is 43 percent. In December that year, the forecasted "risk corridor" stretches from the Western Pacific across the Philippines, Southeast Asia, India, Iran and to Turkey. Impact is now certain.
Fortunately, this scenario is entirely hypothetical, and the 2015 PDC isn’t real. The asteroid is a challenge posed to teams at The Planetary Defense Conference, currently taking place in Italy. Chris Mills reports on the "asteroid war games" for Gizmodo:
Over the course of five days, the conference attendees play out an asteroid scenario that, in real-world terms, would last about seven years. People like me, stuck on a different continent, can follow along online. The exercise kicked off with the sighting of our hypothetical world-wrecker, asteroid 2015 PDC.
Each day of the conference corresponds to passing time and more information in the hypothetical asteroid scenario. 2015 PDC starts out as a chunk of space rock measuring 1,200 feet long, which Mills reports would release energy equivalent to 2,250 million tons of TNT on impact. On land it would destroy everything within 20 miles. In the ocean it would trigger a 20-foot-high tsunami.
So the teams in Italy try to deflect the course of impeding doom. Matt Holman, director of the Minor Planet Center at Smithsonian, told Gizmodo:
You don’t really try to change its direction. Imagine it like an intersection — there’s going to be a point in time where the asteroid and the Earth are in the same place. You can’t change the roads that they’re on, but you can speed it up or slow it down, so that they avoid one another.
The effort to deflect involves sending six Kinetic Impactor spaceships launced in August 2019. A mock press release on the launch writes:
The six interceptor missions should be more than enough to deflect the asteroid away from its collision course, but the precise size of the deflection cannot be predicted because it depends very much on the uncertain size and mass of the asteroid.
Of the six spacecraft, only four manage to make any difference. One fails to launch its missiles; another misses the asteroid. But the succesful four knock a huge chunk of the asteroid on an Earth-missing trajectory. Unfortunately, a small fragment remains on collision course. That’s the first update for day five of the conference.
Exercises like this aren’t just for kicks. They help researchers anticipate what might be needed in during a real-world impact case. Mills writes:
One interesting — and highly realistic — aspect of the asteroid scenario are the media relations and geopolitics playing out every day. Conference attendees have colour-coded lanyards: red for world leaders, green for media, with others for scientists and members of the public.
In addition to working out the physics to defeat the asteroid, the teams have to work out the delicate geopolitics (that list of at-risk nations isn’t exactly the most stable), and work out the best media plan to inform the public, without boosting the membership of doomsday cults too much.
By the day of the impact in 2022 (later on during day five), the teams have determined that the fragment will enter the Earth’s atmosphere over Dhaka, Bangladesh, but it should break up and burn during entry. So this year, the disaster was averted. Let’s hope we can keep up that track record.