What to do if an asteroid comes our way
If an asteroid strikes, don’t head for the hills, or the windows: Head for the basement.
A study aimed at sorting out the effects of a catastrophic asteroid impact found that violent winds and pressure shock waves would be the biggest killers, accounting for more than 60 percent of the lives lost in simulated scenarios.
“This is the first study that looks at all seven impact effects generated by hazardous asteroids and estimates which are, in terms of human loss, most severe,” Clemens Rumpf, a senior research assistant at the University of Southampton in Britain, said today in a news release from the American Geophysical Union.
Rumpf is the lead author of the study, which is published in Geophysical Research Letters, an AGU journal.
The seven effects on Rumpf’s list are wind blasts, shock waves, heat, flying debris, tsunami waves, cratering and seismic shaking. The researchers lumped wind blasts and shock waves together because those phenomena would tend to occur together in the wake of an asteroid strike.
The winds whipped up by an impact would carry enough power to hurl human bodies and flatten forests, while the spike in atmospheric pressure would set off shock waves strong enough to rupture internal organs.
To gauge the damage, the researchers ran 50,000 simulated scenarios with artificial asteroids ranging from 15 to 400 meters (49 to 1,312 feet) across. They found that land-based impacts would be roughly 10 times as dangerous as ocean impacts.
Large asteroids hitting the ocean could generate huge tsunami waves; however, the waves’ energy would tend to dissipate as it traveled. Tsunamis accounted for more than 70 percent of the deaths associated with an ocean impact, but only about 20 percent of the lives lost across all scenarios.
Heat effects were implicated in nearly 30 percent of the deaths in the land-based simulations, and here’s where Rumpf offered his advice. He said affected populations were likely to avoid harm by hiding in basements and other underground structures.
Cratering and airborne debris each accounted for less than 1 percent of the deaths. Seismic shaking was of the least concern, causing only 0.17 percent of the casualties in the simulated scenarios.
Rumpf emphasized that the risk of an asteroid strike is low, ranging from once every 1,500 years for a 190-foot-wide space rock to once every 100,000 years for a 1,300-foot-wide monster.
The scenarios suggest that most asteroids on the lower end of the spectrum burn up in the atmosphere. An asteroid would have to be wider than 60 feet across to be lethal. That’s roughly the width of the asteroid involved in the 2013 Chelyabinsk meteor blast, which injured hundreds of people in the vicinity of the Siberian city but caused no known deaths.
Most of the injuries in Chelyabinsk occurred when the shock wave from the blast sent broken window glass flying into the faces of spectators.
Purdue geophysicist Jay Melosh, who wasn’t involved in the study, said the report represents “a reasonable step forward in trying to understand and come to grips with the hazards posed by asteroids and comet impactors.”
Rumpf said the findings could help Earthlings plan for future asteroid strikes.
“If only 10 people are affected, then maybe it’s better to evacuate the area,” he said. “But if a million people are affected, it may be worthwhile to mount a deflection mission and push the asteroid out of the way.”
Rumpf plans to present his findings at the 2017 International Academy of Astronautics Planetary Defense Conference, set for next month in Tokyo.