Nasa’s Dart mission changed path of asteroid: ‘A defender of the planet’

Nasa confirmed that its Dart planetary defence mission successful changed the course of an asteroid it slammed into two weeks ago.

The Double Asteroid Redirection Test – Dart – mission was a proof-of-concept intended to test whether or not Nasa could effectively move an Earth-threatening asteroid before it reached the planet. The agency slammed a refrigerator-sized spacecraft into the asteroid Dimorphos on 22 September.

The impact changed the asteroid's orbit around its parent asteroid, Didymos, shortening its orbit by approximately 32 minutes. Nasa administrator Bill Nelson said in a press release on Tuesday that the agency would have considered an orbit change of 10 minutes a success, suggesting the test exceeded expectations.

Dr Nancy Chabot, from the Johns Hopkins University Applied Physics Laboratory, which led the mission for Nasa, said: “This is a 4% change in the orbital period of Dimorphos around Didymos. Dart just gave it a small nudge. But if you wanted to do this in the future, you’d want to do it years in advance.

“Warning time is really key here in order to enable this sort of asteroid deflection to be used in the future as part of a much larger planetary defence strategy.”

Mr Nelson confirmed that if an asteroid was on a collision course with Earth, that – given enough advanced warning – the agency could use the tactic to change its direction.

“I believe that Nasa has proven that we are serious as a defender of the planet,” he said.

The Nasa administrator said the Dart mission was launched just before Thanksgiving last year and the spacecraft travelled for 10 months and 7 million miles (11.3 million kilometres) to hit the asteroid.

Nasa officials celebrated on 22 September as the spacecraft's final photos showed it closing distance between it and the asteroid's surface. When the spacecraft stopped sending back photos moments after showing an extreme close-up of the asteroid's surface, agency officials realised it had successfully struck the rock.

Since the impact, astronomers have confirmed the asteroid's orbit has changed. Images released by Nasa showed ejecta cast off of the asteroid in a long tail, indicating something had struck it and blown apart rocks on its surface.

Director of Nasa’s planetary science division Dr Lori Glaze said during the press conference that the agency will continue its focus on planetary defence. Those efforts will focus on developing the capability for long-range scouting missions to examine asteroids that pose potential threats and for developing early warning systems.

“Time is the single most important factor in being able to implement any technique for defence,” she said.

Nasa worked with the Italian Space Agency on the Dart mission project and Dr Glaze said that international cooperation is a key factor in planetary defence, as it was “not just an American” concern.

According to Dr Glaze, one of the agency’s upcoming missions is establishing a near-Earth orbital surveyor to scan the space around the planet for objects of interest or potential threats.