Bracing for Impact

At a weeklong conference, scientists imagined what would happen after learning an asteroid is hurtling toward Earth.

An asteroid hurtling toward Manhattan at night.
Photo illustration by Slate. Photos by Damien VERRIER/iStock/Getty Images Plus and Trifonov_Evgeniy/iStock/Getty Images Plus.

Imagine this: Scientists have just detected an asteroid hurtling toward Earth. According to their calculations, the damage would be catastrophic, and we don’t have long to prepare. Experts determine that the best plan of action would be to launch armed spacecraft, perhaps with nukes, to rendezvous with the asteroid.

Though this sounds suspiciously like the plot of Armageddon, it’s also the plot of the sixth International Academy of Astronautics Planetary Defense Conference. Representatives from NASA, the Federal Emergency Management Agency, the European Space Agency, the U.N., and other international space experts have gathered in College Park, Maryland, this week to do a cosmic fire drill. The premise of this role-play universe begins with an imaginary asteroid called 2019 PDC, which has a 1 in 100 chance of striking Earth in 2027. According to NASA, those odds were selected for this drill because experts worldwide generally agree that that’s the threshold for when we should take collective action.

Sure, it seems far-fetched, but it’s only a matter of time until we’re faced with a serious asteroid threat. This year has already seen three close asteroid flybys, between 73,500 and 274,000 miles away from us, but none close enough to sound the alarm. (For reference, the distance between Earth and the moon is 238,900 miles.) Small asteroids pass within 4 million miles of Earth all the time. Earth has definitely seen some giant impacts before, but it seems in our best interest to be ready next time around. (As this amazing shirt from the European Space Agency says: Dinosaurs didn’t have a space agency.) So, the logic goes, practice makes perfect.

The conference looked like any other—experts giving presentations in a nondescript meeting hall—but instead of covering new advances in the field, the talks gave a broad outline of the hypothetical impact scenario and discussed the questions and decisions that would stem from it. The scenario is wrapped around an excellent and compelling storyline. Though every tweet from organizers and attendees, as well as the PowerPoint slides, included the word EXERCISE in bold letters, I found myself getting drawn into the role-play as I watched the conference livestream from home (and, apparently, so did some momentarily alarmed folks on Twitter, prompting one astronomy account to remind followers that the scenario was not real). Like a good sci-fi storyline, each day of the exercise advanced the story forward. While Day 1 took place in real time, Day 2 took place three months later, in July 2019, and then we jumped forward to Dec. 30, 2021, on Day 3, to 2024 in Day 4, and to 10 days before impact on Day 5.

At first, efforts focused on quantifying the problem: Where might the asteroid strike, and with how much force? By Day 3, experts had calculated that 2019 PDC would land in the middle of Denver, completely incinerating the immediate area (one scientist used the phrase “molten buildings” to describe the damage) and casting shock waves hundreds of miles out. “Windows are breaking from Pueblo to Laramie,” said physicist Mark Boslough to set the scene at his end-of-day briefing about the asteroid’s physical effects.

A great deal of discussion has focused on how best to deflect the asteroid’s path. Some suggested deploying kinetic impactors, launched to collide with the asteroid and knock it into a different path, as well as launching nuclear weapons. The problem is that scientists aren’t yet sure exactly how each method would move the asteroid because they’re not sure of the asteroid’s mass, which, as you may guess, matters a lot when it comes to physics. The logistics of this exercise assume that humankind will send a probe up to study the asteroid more closely, but given the lag in how long it takes for spacecraft to reach the asteroid, scientists will need to make a decision about their deflection method before the probe sends back additional data.

In imaginary 2024, the experts decide to send up a series of kinetic impactors, which successfully move the asteroid out of Earth’s path, but the force of the impacts also causes a chunk of the asteroid to break off—and the simulation has it hitting Earth in April 2029. Luckily, the fake piece is small, by celestial standards: It’s estimated at 60 meters. While it will likely become smaller or even vaporize while entering our atmosphere, it still has the power to inflict damage; for instance, the Tunguska meteor in 1908 was thought to be around the same size, and while it didn’t leave a crater, it flattened hundreds of miles of Arctic forest. On Day 5, it was revealed that 2019 PDC would hit Manhattan in 10 days, an incident “worse than Tunguska.” Experts drew up models of the damage and began planning for evacuations.

Unsurprisingly, much of the drill focused on decision-making and mission logistics. How do we learn as much as we can about this asteroid, and what do we do to minimize its damage? But a full-scale rehearsal like this also brings more practical considerations to the forefront, and attendees’ questions and experts’ analyses highlight the very real concerns people might have should a scenario like this arise in real life.

At the end of Day 3, for instance, one attendee seemed pretty hand-wavy about potentially destroying a huge swath of the western U.S., even for a thought exercise, saying, “I might be biased since we’re all on the East Coast here, but … ” This person went on to ask: Had we considered possibly sending spacecraft up just to nudge the asteroid slightly away from any major population center, instead of nudging it out of Earth’s orbit? The speaker, NASA’s Brent Barbee, politely shot him down. “I would characterize that as a last resort. Our primary goal would be to move the asteroid off of Earth,” he said. The moderator of the Q&A also jumped in to add that the impactors’ targeting wouldn’t be precise enough to ensure the exact amount the asteroid would be moved. But still, this questioner is probably not alone. The people who would be tasked with huge decisions like this are more likely to live in certain cities, and, as well-intentioned as they may be, that could color decisions.

But it’s also not clear who, ultimately, will get to make those calls. Attendees brought up questions about the possibilities of different countries “getting in each other’s way” when it comes to launching spacecraft meant to work together, like if three different space agencies each contributed kinetic impactors to a global mission. “With a mission of this scope, you’d need strong coordination,” said discussion moderator Paul Chodas, of NASA’s Jet Propulsion Laboratory. “With procedures and protocols, we could achieve the coordination necessary, but it would be essential to coordinate very closely.”

In theory, there would be an international team that coordinates important intergalactic decisions, like how to launch defense against the asteroid or, if nuclear weapons are used, who actually initiates the detonation. (Hopefully, this coordination is better than that of the crew in Armageddon, when Bruce Willis pushes young Ben Affleck out of the way at the last moment.) “We don’t have those procedures in place right now, but we’re developing them,” Chodas said.

Figuring that out appears to be outside the purview of this conference, but it seems like a piece of the puzzle law and politics experts should figure out long before we’re faced with an actual asteroid threat. And one hopes that any team meant to represent the interests of all humans on Earth includes delegates from countries that don’t have their own space programs but can contribute in other ways, like drawing up policies and offering technical expertise. Currently, the International Asteroid Warning Network is the go-to group for finding and monitoring near-Earth objects and coordinating international resources, and while there are a good number of institutions from space-faring countries represented, it’s definitely biased toward wealthier powers.

This thought experiment also demonstrates how important it will be to bring in experts outside of physics and astronomy. In several summaries, experts have mentioned the consequences of a huge asteroid event on plane or train travel and internet access, as well as the possible destabilization of the economy as property values in potential strike areas plummet. Others have pointed out that areas outside the immediate strike zones will likely be ravaged by wildfires caused by the impact. There are real costs to culture, as well. One researcher noted that when 2019 PDC incinerates Manhattan, museums like the Met would need to move their collections elsewhere as quickly as possible.

My favorite question came from an attendee who has clearly seen his share of action movies: “How big would [the asteroid] need to be to pop the cork on Yellowstone?” The scientists onstage didn’t seem to immediately understand his question, so the attendee went on to explain that an impact could destabilize the Wyoming supervolcano. “We have not considered volcanic impacts,” replied one of the scientists. “Well,” the attendee said, “maybe it’s something to take a look at.”

Future Tense is a partnership of Slate, New America, and Arizona State University that examines emerging technologies, public policy, and society.