NASA’s attempt to thwap an asteroid by crashing a spacecraft into it has succeeded spectacularly, changing the rock’s motion through space significantly and offering promise that this still-experimental technique could someday be applied as a practical form of planetary defense, agency officials said Tuesday.

The Double Asteroid Redirection Test was just that — a test. The targeted asteroid, named Dimorphos, posed no threat. It won’t come within 4 million miles of Earth at any point in the foreseeable future. Dimorphos orbits a larger asteroid named Didymos. Both were circling the sun about 7 million miles from Earth when the DART spacecraft took aim on the evening of Sept. 26.

DART is NASA’s first “planetary defense” mission. The goal was to test whether this technique, called a kinetic impactor, would deliver enough of a punch to a speeding space rock to knock it significantly off course.

NASA crashes spacecraft into asteroid, passing planetary defense test

It did. Before DART’s arrival, Dimorphos orbited Didymos in 11 hours and 55 minutes. Then: Blam! The newly calculated orbit: 11 hours and 23 minutes.

That 32-minute change in the orbital period was at the high end of a range of estimated outcomes, NASA’s head of planetary science, Lori Glaze, said. DART surpassed the agency’s minimum benchmark for a successful mission by more than 25 times.

“We showed the world NASA is serious as a defender of this planet,” said NASA Administrator Bill Nelson.

The mission “felt like a movie plot,” he said. “But this was not Hollywood.”

How it works: NASA hopes to hit an asteroid now in case we really need to knock one away later

Despite the enthusiasm emanating from NASA officials, there is not a fully developed system for intercepting asteroids. The key to planetary defense is finding potentially hazardous asteroids long before they cross Earth’s path. Astronomers can calculate whether they are on a trajectory to strike the planet.

“You gotta know they’re coming,” Glaze said.

The idea of a kinetic impactor is to give a hazardous asteroid a nudge many years before its anticipated impact with Earth. This is not a last-minute technique for saving the world.

“We really need to have that warning time for a technique like this to be effective,” said Nancy Chabot, DART coordination lead at the Johns Hopkins University Applied Physics Laboratory, which handled the mission under a NASA contract.


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