“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 US$325 million 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.”

Nasa Administrator Bill Nelson reminded people earlier in the day 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: a 160-metre (525-foot) asteroid named Dimorphos. It is 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 aeons without threatening Earth, making them ideal save-the-world test candidates.

Launched last November, the vending machine-size Dart – short for Double Asteroid Redirection Test – 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.

With an image beaming back to Earth every second, Adams and other ground controllers in Laurel, Maryland, 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.

Flight controllers cheered, hugged one another and exchanged high fives. Their mission complete, the Dart team went straight into celebration mode. There was little sorrow over the spacecraft’s demise.

“Normally, losing signal from a spacecraft is a very bad thing. But in this case, it was the ideal outcome,” said Nasa programme scientist Tom Statler.

Johns Hopkins scientist Carolyn Ernst said the spacecraft was definitely “kaput”, with remnants possibly in the fresh crater or cascading into space with the asteroid’s ejected material.

Scientists insisted Dart would not shatter Dimorphos. The spacecraft packed a scant 570kg (1,260 pounds), compared with the asteroid’s 5 billion kg (11 billion pounds). But that should be plenty to shrink its 11-hour, 55-minute orbit around Didymos.

01:46

China to send rocket on collision course with asteroid to knock it into safer orbit

China to send rocket on collision course with asteroid to knock it into safer orbit

The impact should pare 10 minutes off that, but telescopes will need anywhere from a few days to nearly a month to verify the new orbit. The anticipated orbital shift of 1 per cent might not sound like much, scientists noted. But they stressed it would amount to a significant change over years.

“Now is when the science starts,” said Nasa’s Lori Glaze, planetary science division director. “Now we’re going to see for real how effective we were.”

Planetary defence experts prefer nudging a threatening asteroid or comet out of the way, given enough lead time, rather than blowing it up and creating multiple pieces that could rain down on Earth.

Multiple impactors might be needed for big space rocks or a combination of impactors and so-called gravity tractors, not-yet-invented devices that would use their own gravity to pull an asteroid into a safer orbit.

“The dinosaurs didn’t have a space programme to help them know what was coming, but we do,” Nasa’s senior climate adviser Katherine Calvin said, referring to the mass extinction 66 million years ago believed to have been caused by a major asteroid impact, volcanic eruptions or both.

The non-profit B612 Foundation, dedicated to protecting Earth from asteroid strikes, has been pushing for impact tests like Dart since its founding by astronauts and physicists 20 years ago.

Monday’s feat aside, the world must do a better job of identifying the countless space rocks lurking out there, warned the foundation’s executive director, Ed Lu, a former astronaut.

Significantly less than half of the estimated 25,000 near-Earth objects in the deadly 140-metre range have been discovered, according to Nasa. And fewer than 1 per cent of the millions of smaller asteroids, capable of widespread injuries, are known.

The Vera Rubin Observatory, nearing completion in Chile by the National Science Foundation and US Energy Department, promises to revolutionise the field of asteroid discovery, Lu noted.

Finding and tracking asteroids, “That’s still the name of the game here. That’s the thing that has to happen in order to protect the Earth,” he said.