NASA announced plans to redirect the course of a small asteroid approaching Earth. The space agency will attempt to do this by using the Double Asteroid Redirection Test (DART), the first ever mission to demonstrate an asteroid deflection technique for planetary defense.
"DART would be NASA's first mission to demonstrate what's known as the kinetic impactor technique -- striking the asteroid to shift its orbit -- to defend against a potential future asteroid impact," said Lindley Johnson, NASA's planetary defense officer.
DART would be tested on an asteroid system called Didymos (Greek for "twin"), a binary asteroid system made up of two asteroids: Didymos A, and a smaller one, Didymos B, which orbits its larger neighbor. DART would impact only the smaller of the two bodies, Didymos B.
As Didymos approaches Earth in October 2022, NASA will launch a spacecraft towards Didymos B. The refrigerator-sized craft would strike the smaller body at a speed approximately six kilometers per second, which is about nine times faster than a bullet. The impact will change the asteroid's speed by a small fraction of its total velocity.
That small nudge will add up over time to a big shift of the asteroid's path away from Earth. "With DART, we can show how to protect Earth from an asteroid strike with a kinetic impactor by knocking the hazardous object into a different flight path that would not threaten the planet," said DART investigation co-lead Andy Cheng.
NASA unveiled the plan coinciding with International Asteroid Day which commemorated the 1908 meteorite strike in Russia's Podkamennaya Tunguska River. It was considered the largest recorded asteroid impact in Earth's history that it leveled trees and knocked over people in a town 40 miles away.
DART is one of the two techniques explored by NASA to prevent an asteroid impact on Earth. The other method being looked into is the gravity tractor which is to tug an asteroid by keeping a large mass near it. Shooting down an asteroid is out of the question as there is no existing weapon that could keep up with the rock's velocity of 12 miles per second.