Ranking hazardous asteroid effects from least to most destructive
Large, ocean-impacting asteroids could generate enough power to trigger a tsunami, but the wave’s energy would likely dissipate as it traveled and eventually break when it met a continental shelf. Even if a tsunami were to reach coastal communities, far fewer people would die than if the same asteroid struck land, Rumpf said. Overall, tsunamis accounted for 20 percent of lives lost, according to the study.
The heat generated by an asteroid accounted for nearly 30 percent of lives lost, according to the study. Affected populations could likely avoid harm by hiding in basements and other underground structures, Rumpf said.
Seismic shaking was of least concern, as it accounted for only 0.17 percent of casualties, according to the study. Cratering and airborne debris were similarly less concerning, both garnering fewer than 1 percent of deaths.
Only asteroids that spanned at least 18 meters (nearly 60 feet) in diameter were lethal. Many asteroids on the lower end of this spectrum disintegrate in Earth’s atmosphere before reaching the planet’s surface, but they strike more frequently than larger asteroids and generate enough heat and explosive energy to deal damage. For example, the meteor involved in the 2013 impact in Chelyabinsk, Russia, was 17 to 20 meters (roughly 55 to 65 feet) across and caused more than 1,000 injuries, inflicting burns and temporary blindness on people nearby.
Understanding risk
“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.
Melosh, who wasn’t involved in the study, added that the findings “lead one to appreciate the role of air blasts in asteroid impacts as we saw in Chelyabinsk.” The majority of the injuries in the Chelyabinsk impact were caused by broken glass sent flying into the faces of unknowing locals peering through their windows after the meteor’s bright flash, he noted.
The study’s findings could help mitigate loss of human life, according to Rumpf. Small towns facing the impact of an asteroid 30 meters across (about 98 feet) may fare best by evacuating. However, an asteroid 200 meters wide (more than 650 feet) headed for a densely-populated city poses a greater risk and could warrant a more involved response, he said.
“If only 10 people are affected, then maybe it’s better to evacuate the area,” Rumpf said. “But if 1,000,000 people are affected, it may be worthwhile to mount a deflection mission and push the asteroid out of the way.”
— Read more in Clemens M. Rumpf et al., “Asteroid impact effects and their immediate hazards for human populations,” Geophysical Research Letters (19 April 2017) (DOI: 10.1002/2017GL073191)
