NASA says that each year, an asteroid the size of a car pummels into Earth’s atmosphere, blazes into a fireball, and burns up before it can crash into the surface. We got a taste of this terrifying phenomenon this January, when a space rock burned over Detroit, leaving just six fragmented meteorites scattered in its wake. But sometimes the situation can be considerably larger — and much more dangerous. Case in point: the Chelyabinsk asteroid that blasted over Russia five years ago, glowing 30 times brighter than the sun.
According to an analysis published in Nature in 2013, the 20-meter-wide asteroid struck Earth’s atmosphere at 40,000 miles per hour, vaporized into a meteor, and broke apart into smaller pieces about 18 to 27 miles above the planet’s surface. The energy of the blast was equivalent to 500 kilotons of blown-up TNT, and the resulting shockwave left a field of damage 55 miles on either side of its trajectory. This was the largest impact on Earth by an asteroid recorded in modern times since 1908, when an asteroid some 50 to 100 meters wide burned up over Siberia.
The 2013 shockwave left considerable damage in its wake: As it hurled over Russia’s Chelyabinsk region, the shockwave knocked people off their feet, shattered more than 3,600 apartment windows, and forced the collapse of a factory roof. These damages resulted in the injury of at least 950 people, including 204 children.
As the asteroid burned in the atmosphere, traveling at 12 miles per second, it began to fall apart. An estimated four to six tons — just 0.05 percent of the asteroid — made it to the ground as meteorites. The largest chunk, weighing 1,250 pounds, was found eight months later at the bottom of Lake Chebarkul. An examination of the other meteorites showed that some pieces were formed sometime within the first 4 million years of the solar system’s existence.
The Chelyabinsk asteroid came in with a blast stronger than a nuclear explosion, but its effects were still relatively tame in comparison to what massive asteroids can do — and have done — to the planet. Just as NASA predicts that an asteroid will hit Earth’s atmosphere every year, it also says that every 2,000 years, a space rock the size of a football field pummels Earth, causing “significant damage to the area.” Things get even dicier when we consider longer timescales. Every few million years, the ultimate galactic bad boys — like the asteroid that killed the dinosaurs — are predicted to make their fiery way through the atmosphere.
Because NASA knows this, the scientists there are also thinking of ways to protect civilization from the inevitable. As of now, we have three major strategies to prevent a Armageddon-type situation: A gravity tractor, a kinetic impactor, and nuclear detonation.