Why an Asteroid Strike Would Turn Humans Into Nightwalkers

Flattened cities, blankets of debris, earthquakes, tsunamis, wildfires, and shockwaves are just some of the ways a large asteroid impact could devastate life on Earth.

Now add depleting the ozone layer to that list.

A new model of asteroid smashes shows how a space rock plunging into the deep ocean would drastically alter atmospheric chemistry, leading to severe ozone depletion worse than anything in recorded history.


—Image courtesy Don Davis, NASA

Ozone is the name for the molecule made of three oxygen atoms, which can exist throughout Earth’s atmosphere. Ground-level ozone is an air pollutant, and breathing it can cause serious respiratory issues.

But high-level, or stratospheric, ozone is the stuff that shields Earth from the most damaging types of the sun’s ultraviolet light.

Holes in the ozone layer mean more of this harmful UV reaches the surface, and that can spell disaster for life—skin diseases, cataracts, and DNA mutations, for starters. Not to mention the damage “bad” UV can do to plant growth and thus the global food supply.

(Related: “Rocket Launches Damage Ozone Layer, Study Says.”)

In the worst case seen in the new model, the amount of damaging UV hitting humans “would produce major sunburn” in just a few minutes, study leader Elisabetta Pierazzo, of the Planetary Science Institute in Arizona, said in a press release.

“We could stay inside to protect ourselves, but if you go outside during daylight hours you would burn. You would have to go outside at night, after sunset, to avoid major damage.”

In a first-of-its-kind simulation, Pierazzo modeled what would happen to Earth’s atmosphere if either a 1,640-foot-wide (500-meter-wide) asteroid or a 0.62-mile-wide (1-kilometer-wide) asteroid slammed into a 2.5-mile-deep (4-kilometer-deep) ocean.

Both impacts would send huge amounts of vaporized water high into the air. Seawater contains chloride and bromide, compounds that can break apart ozone by stealing away its oxygen atoms.

According to the models, the one-kilometer impact “can produce significant global perturbation of upper atmospheric chemistry, including multiyear global ozone depletion comparable to record ozone holes recorded in the mid-1990s,” Pierazzo said.


A model, based on satellite data, of the 2008 ozone hole over Antarctica.

—Image courtesy NASA

Getting rid of so much ozone for so long would create spikes in the UV index, the scale used to indicate the intensity of UV light hitting Earth’s surface.

So far, the highest UVI recorded on Earth was 20, Pierazzo said.

The 500-meter asteroid strike could cause the UVI to jump above 20 for several months in the northern subtropics. The one-kilometer impact would see the global UVI rise to an unprecedented 56.

According to Pierazzo, we still face technological limitations when it comes to diverting an asteroid headed for Earth.

(Related: “Bombing Earth-bound Asteroids a Viable Option, Experts Say.”)

So her solution is simply to prepare for the worst, a la 1950s fallout shelters.

If warned of an impending asteroid, farmers could plant crops with higher UV tolerance, she said, while some food could be stored to tide us over during a few years of reduced productivity.

Oh, and we humans had better get used to artificial lighting.

Human Journey