When an asteroid strikes Earth, which of its effects –scorching heat, flying debris, towering tsunamis — would claim the most lives?
A new study says violent winds and shock waves are the most dangerous in such calamity. The study explored seven effects associated with asteroid impacts–heat, pressure shock waves, flying debris, tsunamis, wind blasts, seismic shaking and cratering–and estimated their lethal effects in varying sizes.
The researchers ranked the effects from most to least deadly with wind blasts and shock waves on top, causing more than 60% of lives lost. Shock waves from atmospheric pressure can rupture internal organs, while wind blasts carry enough power to hurl human bodies and flatten forest trees.
“This is the first study that looks at all seven impact effects,” said Clemens Rumpf at the University of Southampton in the United Kingdom, and lead author of the new study published in Geophysical Research Letters, a journal of the American Geophysical Union.
Rumpf said his findings, to be presented at the 2017 International Academy of Astronautics Planetary Defense Conference in Tokyo, Japan, could help hazard mitigation groups better prepare for asteroid threats.
Though deadly asteroid impacts are still rare, Rumpf said Earth is struck by an asteroid 60 meters (more than 190 feet) wide approximately once in every 1500 years, whereas an asteroid 400 meters (more than 1,300 feet) across is likely to strike the planet every 100,000 years. “The likelihood of an asteroid impact is really low, but the consequences can be unimaginable,” he said.
Rumpf and his colleagues used models to pepper the globe with 50,000 artificial asteroids ranging from 15 to 400 meters (49 to 1312 feet) and then estimated how many lives would be lost. Land-based impacts were more dangerous than asteroids that landed in oceans, they said.
The heat by an asteroid accounts for nearly 30% of lives lost, according to the study. This can be averted by hiding in basements and other underground structures, Rumpf said.
Ocean-impacting asteroids could trigger a tsunami, but the wave’s energy would likely dissipate at a continental shelf. Even if a tsunami were to reach coastal communities, far fewer people would die, Rumpf said. Overall, tsunamis accounted for 20% of lives lost, according to the study.
Seismic shaking was of least concern, as it accounted for only 0.17% of casualties, followed by less effective cratering and airborne debris at 1% of deaths.
“This report is a reasonable step forward in trying to understand and come to grips with the hazards posed by asteroids and comet impactors,” said geophysicist Jay Melosh, a distinguished professor in the Department of Earth, Atmospheric and Planetary Sciences at Purdue University in Lafayette, Indiana.
If 1 million people are affected, it may be worthwhile to mount a deflection mission and push the asteroid out of the way, he noted.