Rock (geology)

Here’s how an asteroid impact would kill you

asteroid hitting Earth
DEATH FROM THE SKIES Computer simulations reveal that most of the lethality of an earthbound asteroid (illustrated) comes from gusting winds and shock waves.

It won’t be a tsunami. Nor an earthquake. Not even the crushing impact of the space rock. No, if an asteroid kills you, gusting winds and shock waves from falling and exploding space rocks will most likely be to blame. That’s one of the conclusions of a recent computer simulation effort that investigated the fatality risks of more than a million possible asteroid impacts.

In one extreme scenario, a simulated 200-meter-wide space rock whizzing 20 kilometers per second whacked London, killing more than 8.7 million people. Nearly three-quarters of that doomsday scenario’s lethality came from winds and shock waves, planetary scientist Clemens Rumpf and colleagues report online March 27 in Meteoritics & Planetary Science.

In a separate report, the researchers looked at 1.2 million potential impactors up to 400 meters across striking around the globe. Winds and shock waves caused about 60 percent of the total deaths from all the asteroids, the team’s simulations showed. Impact-generated tsunamis, which many previous studies suggested would be the top killer, accounted for only around one-fifth of the deaths, Rumpf and colleagues report online April 19 in Geophysical Research Letters.

“These asteroids aren’t an everyday concern, but the consequences can be severe,” says Rumpf, of the University of Southampton in England. Even asteroids that explode before reaching Earth’s surface can generate high-speed wind gusts, shock waves of pressure in the atmosphere and intense heat. Those rocks big enough to survive the descent pose even more hazards, spawning earthquakes, tsunamis, flying debris and, of course, gaping craters.

While previous studies typically considered each of these mechanisms individually, Rumpf and colleagues assembled the first assessment of the relative deadliness of the various effects of such impacts. The estimated hazard posed by each effect could one day help leaders make one of the hardest calls imaginable: whether to deflect an asteroid or let it hit, says Steve Chesley, a planetary scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., who was not involved with either study.

The 1.2 million simulated impactors each fell into one of 50,000 scenarios, which varied in location, speed and angle of strike. Each scenario was run with 24 different asteroid sizes,…