Nasa says a mission to nudge a distant asteroid off course succeeded, showcasing a potential new method for saving Earth from dangerous space rocks that astronomers might identify in the future.

A Nasa spacecraft called Dart, which rammed the asteroid last month, was able to alter the trajectory of its moving target, officials at the space agency said on Tuesday.

“Nasa has proven that we are serious as a defender of the planet,” agency administrator Bill Nelson told reporters at a press conference.

The spacecraft, which is about the size of a refrigerator, slammed into an asteroid called Dimorphos at 22,500km/h on September 26. Dimorphos, roughly the size of a football stadium, orbits around a larger asteroid called Didymos. The momentum from the impact, combined with the recoil of the ejected particles the collision created, helped to substantially alter Dimorphos’ path through space.

Visit Daily Maverick’s home page for more news, analysis and investigations

Read more: Nasa craft rams distant asteroid in test of Earth defence 

Before the impact, Dimorphos orbited Didymos roughly once every 11 hours and 55 minutes. After the impact, Nasa said the orbit is now 11 hours and 23 minutes — a 32-minute change, based on astronomy observations. Dimorphos now orbits slightly closer to Didymos than it did before.

“For the first time ever, humanity has changed the orbit of a planetary body,” Lori Glaze, director of Nasa’s Science Mission Directorate, said during the press conference.

Nasa’s minimum requirement for Dart’s success would have been a trajectory change of 73 seconds, which the mission easily exceeded. The precision of the change has an error of plus or minus two minutes. A combination of four optical telescopes and planetary radar was used to determine the asteroid’s new orbit.

Dimorphos never posed a risk to Earth, but was merely a target asteroid to showcase this deflection technique. Asteroids similar in size to Dimorphos could cause regional devastation if they were to hit a populated area on the planet.

“I think that the Dart mission has demonstrated that we are capable of deflecting an asteroid, even a potentially hazardous asteroid of this size,” Glaze said. DM