Nasa crashes spacecraft into asteroid in planetary defence test

DART (Double Asteroid Redirection Test) was launched in November 2021 with plans to reach an asteroid known as Dimorphos which is not considered a threat to Earth.

Nasa wanted to find out whether intentionally crashing a spacecraft into an asteroid is an effective way to change its course, should an Earth-threatening asteroid be discovered in the future.

Nasa said that DART’s impact with Dimorphos demonstrated a viable mitigation technique for protecting the Earth.

“At its core, DART represents an unprecedented success for planetary defence, but it is also a mission of unity with a real benefit for all humanity,” said Nasa administrator Bill Nelson.

“As Nasa studies the cosmos and our home planet, we’re also working to protect that home and this international collaboration turned science fiction into science fact, demonstrating one way to protect Earth.”

Dimorphos is a small body just 160 metres in diameter. It orbits a larger, 780-metre asteroid called Didymos which also does not pose a threat to Earth.

The mission’s one-way trip confirmed that Nasa can successfully navigate a spacecraft to intentionally collide with an asteroid to deflect it, a technique known as kinetic impact.

The investigation team will now observe Dimorphos using ground-based telescopes to confirm that DART’s impact altered the asteroid’s orbit around Didymos. Researchers expect the impact to shorten Dimorphos’ orbit by about 1 per cent, or roughly 10 minutes. Precisely measuring how much the asteroid was deflected is one of the primary purposes of the full-scale test.

“Planetary Defence is a globally unifying effort that affects everyone living on Earth,” said Thomas Zurbuchen, associate administrator for the Science Mission Directorate at Nasa Headquarters in Washington.

“Now we know we can aim a spacecraft with the precision needed to impact even a small body in space. Just a small change in its speed is all we need to make a significant difference in the path an asteroid travels.”

The spacecraft’s sole instrument - the Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO) - together with a sophisticated guidance, navigation and control system enabled DART to identify and distinguish between the two asteroids, targeting the smaller body.

These systems guided the 570kg box-shaped spacecraft through the final 90,000km of space into Dimorphos, intentionally crashing into it at roughly 22,530km per hour to slightly slow the asteroid’s orbital speed.

DRACO’s final images, obtained by the spacecraft seconds before impact, revealed the surface of Dimorphos in close-up detail.

Lindley Johnson, Nasa’s planetary defense officer, said: “This demonstrates we are no longer powerless to prevent this type of natural disaster. Coupled with enhanced capabilities to accelerate finding the remaining hazardous asteroid population by our next Planetary Defence mission, the Near-Earth Object (NEO) Surveyor, a DART successor could provide what we need to save the day.”