'We have impact!' NASA slams spacecraft into asteroid in unprecedented test

A NASA spacecraft slammed into an asteroid at blistering speed Monday in an unprecedented dress rehearsal for the day a killer rock menaces Earth.

The galactic grand slam happened 11.3 million kilometres away, with the spacecraft — the Double Asteroid Redirection Test (DART) — plowing into the rock at 22,500 km/h. Scientists expected the impact to carve out a crater, hurl streams of rocks and dirt into space and, most importantly, alter the asteroid's orbit.

"We have impact!" Mission Control's Elena Adams announced, jumping up and down and thrusting her arms skyward.

Telescopes around the world and in space aimed at the same point in the sky to capture the spectacle. Though the impact was immediately obvious — DART's radio signal abruptly ceased — it will be days or even weeks to determine how much the asteroid's path was changed.

The $325-million US mission was the first attempt to shift the position of an asteroid or any other natural object in space.

"As far as we can tell, our first planetary defence test was a success," Adams later told a news conference, the room filling with applause. "I think Earthlings should sleep better. Definitely, I will."

WATCH | DART's impact with asteroid:

Earlier in the day, NASA Administrator Bill Nelson reminded people via Twitter that, "No, this is not a movie plot." He added in a prerecorded video: "We've all seen it on movies like Armageddon, but the real-life stakes are high."

Monday's target was a 160-metre asteroid named Dimorphos. It's actually a moonlet of Didymos (Greek for "twin"), a fast-spinning asteroid five times bigger that flung off the material that formed the junior partner.

The pair have been orbiting the sun for eons without threatening Earth, making them ideal save-the-world test candidates.

Launched last November, the vending machine-size DART navigated to its target using new technology developed by Johns Hopkins University's Applied Physics Laboratory, the spacecraft builder and mission manager.

DART's on-board camera, a key part of this smart navigation system, caught sight of Dimorphos barely an hour before impact.

"Woo hoo," exclaimed Adams at the time. "We're seeing Dimorphos, so wonderful, wonderful."

With an image beaming back to Earth every second, Adams and other ground controllers in Laurel, Md., watched with growing excitement as Dimorphos loomed larger and larger in the field of view alongside its bigger companion. Within minutes, Dimorphos was alone in the pictures; it looked like a giant grey lemon, but with boulders and rubble on the surface. The last image froze on the screen as the radio transmission ended.