Seven ways for an asteroid to wipe out life on Earth

(PHOTO: MIRROR)

If you've ever spent an idle Friday afternoon pondering what would happen if an asteroid smashed into our planet, ponder no more.

Scientists have published a new study, outlining all the potential effects of an asteroid collision, and ranking them in order of the threat they pose to human life.

Perhaps surprisingly, wind blasts and pressure shock waves are likely to claim the most casualties, according to the study. In experimental scenarios, these two effects accounted for more than 60% of lives lost.

Shock waves arise from a spike in atmospheric pressure and can rupture internal organs, while wind blasts carry enough power to hurl human bodies and flatten forests.

Other potential effects include heat, flying debris, tsunamis, seismic shaking and cratering.

Land-based impacts were, on average, much more dangerous than asteroids that landed in oceans, according to the study.

Large, ocean-impacting asteroids could generate enough power to trigger a tsunami, but the wave's energy would likely dissipate as it travelled 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. Overall, tsunamis accounted for 20% of lives lost, according to the study.

The heat generated by an asteroid would account for nearly 30% of lives lost. Affected populations could likely avoid harm by hiding in basements and other underground structures, the study said.

Seismic shaking was of least concern, as it accounted for only 0.17% of casualties. Cratering and airborne debris were similarly less concerning, both garnering fewer than 1% of deaths.

The study was modelled on asteroids on ranging from 15 to 400 metres across - the diameter range of asteroids that most frequently strike the Earth.

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 inflict damage.

For example, the meteor involved in the 2013 impact in Chelyabinsk, Russia, was 17 to 20 metres across and caused more than 1,000 injuries, inflicting burns and temporary blindness on people nearby.

Only asteroids that span at least 18 metres in diameter are considered lethal.

Lead author Clemens Rumpf from the University of Southampton said the findings could help hazard mitigation groups better prepare for asteroid threats.

Small towns facing the impact of an asteroid 30 metres across may fare best by evacuating, but an asteroid 200 meters wide 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."

The findings will be presented at the 2017 International Academy of Astronautics Planetary Defense Conference in Tokyo, Japan, next month.

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