Space & Innovation

What Happens If an Asteroid Takes Aim at Los Angeles?

Say if there's an asteroid barreling toward the US West Coast and there's no way of stopping it, what would we do? Well, NASA and FEMA have a plan.


The solar system is filled with errant space rocks buzzing through interplanetary space and a few hundred of them are known to have orbits that bring them close enough to Earth to cause concern. Though none are thought to stray too close to Earth to be an impact risk in the next century, those are the asteroids we know of, there's thought to be a lot more out there. And some of them are likely pretty big. So let's have fun with this question: what if one takes aim at Earth and a major US city, say Los Angeles, is about to take one for the team?

Though the City of Angels is no stranger to Hollywood doomsdays - notably being on the front lines of an alien invasion in "Battle: Los Angeles" and being torn a new one in the hilarious disaster flick "2012" - the region is the focus of regular earthquake alerts and seems to be constantly fighting wildfires. In short, disaster always feels as if it's just around the corner in this city.

Now, as if Los Angeles doesn't have enough to contend with, NASA and FEMA carried out a joint emergency planning meeting last month that ran a simulation to model a large asteroid strike in the region to see how we might plan for and react to such an event.

"It is critical to exercise these kinds of low-probability but high-consequence disaster scenarios," said FEMA Administrator Craig Fugate in a statement. "By working through our emergency response plans now, we will be better prepared if and when we need to respond to such an event."

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The simulation assumed that a (fictitious!) asteroid has been discovered and that astronomers realize there's a 2 percent probability that it will hit Earth on Sept. 20 2020. Two percent might not sound like much, but if we consider its estimated size of between 300 and 800 feet (100 to 250 meters), we quickly realize that if it does impact it will cause significant regional destruction. Naturally, this discovery would motivate intense observations of the space rock in the hope of refining its impact risk and work out where it will hit should the worst happen.

Let's call this marauding space rock "Asteroid 2016 OMG."

Usually, we like to run simulations of asteroids that are approaching Earth but have enough time to jump into action and deflect them off course. Though there are many bona fide ideas as to how we might deflect an asteroid from hitting Earth - including using space lasers to vaporize water on the asteroid to thrust it off course, using "gravity tractor" spacecraft and even impactors (nukes not necessarily required) - in this NASA/FEMA simulation we don't have the luxury of time. It would take years to develop a spacecraft and send it to the asteroid and then who knows how long to physically deflect the thing. Forget blowing it to smithereens with a nuclear warhead, that's way too Hollywood for this reality. No, it's pretty much as bad as it can get; Earth is going to get punched.

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In the simulation, by the end of 2017 astronomers have refined OMG's orbit so well that we know it's going to impact within a thin probability ellipse stretching across SoCal and into the Pacific Ocean. Now we know the time and the place, it's up to the emergency response agencies to formulate how best to respond.

First things first: Don't panic.

This might not sound like much of a strategy, but at least there's time to move people away from the impact zone and resources into the area to quickly deal with the aftermath.

"The high degree of initial uncertainty coupled with the relatively long impact warning time made this scenario unique and especially challenging for emergency managers," said Leviticus A. Lewis, FEMA's National Response Coordination Branch Chief. "It's quite different from preparing for an event with a much shorter timeline, such as a hurricane."

During the simulation, attendees formulated plans for how to disseminate information about the future impact, while combating misinformation in the public arena. Then of course we'd need to consider the effects of Los Angeles taking a direct hit and the different outcomes if 2016 OMG lands in the desert versus slamming into the ocean. Though a landmass impact would cause widespread devastation, a water impact would trigger a moderate tsunami that could flood huge regions of coastline. Also of huge concern would be the energy stemming from the air burst as the asteroid plows through the atmosphere. As was dramatically illustrated by the comparatively small Russian meteor that exploded over the city of Chelyabinsk in 2013, we cannot underestimate the damage that would be inflicted on a populated area by the resulting shock wave.

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Though there's no word on how well everyone performed, it's good to know the scenario is being considered. Looking back over the geological history of Earth, where asteroid impacts are commonplace, it's only a matter of time before we get hit by a large chunk of rock from outer space.

"These exercises are invaluable for those of us in the asteroid science community responsible for engaging with FEMA on this natural hazard," said Lindley Johnson, NASA's Planetary Defense Officer. "We receive valuable feedback from emergency managers at these exercises about what information is critical for their decision making, and we take that into account when we exercise how we would provide information to FEMA about a predicted impact."

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