NASA's Plan to Deflect Would-Be Killer Asteroids
Astronomers are trying to deflect a near-Earth asteroid for the first time, to prepare for a future object on a collision course with the planet.

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(Inside Science) -- Science fiction books and films have frequently featured the threat of a giant asteroid colliding with our planet and making humans go the way of the dinosaurs. But smaller space rocks also pose threats, and they tend to be harder to spot in advance.

A massive asteroid on a collision course would sail through our atmosphere and explosively burst in the air or crater the ground. Its invasion would initiate blasts of fire and thermal radiation, and likely cause numerous casualties. Even asteroids falling into the ocean could drive tsunamis or earthquakes -- and even create undersea craters.

But if space scientists become aware of the threat of a hazardous asteroid early enough, they might be able to give it enough of a nudge to knock it off its disastrous course, long before it approached Earth. That’s the idea behind NASA’s Double Asteroid Redirection Test, known as DART. It's a spacecraft that’s set to launch in 2021, on course to deliberately smash into an asteroid in the fall of 2022.

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