It’ll be Tough to Stop an Asteroid at the Last Minute, but not Impossible

Artist's impression of the DART mission impacting the moonlet Dimorphos. Credit: ESA

On September 26th, 2022, NASA’s Double-Asteroid Redirect Test (DART) made history when it rendezvoused with the asteroid Didymos and impacted with its moonlet, Dimorphos. The purpose was to test the “Kinetic Impact” method, a means of defense against potentially-hazardous asteroids (PHAs) where a spacecraft collides with them to alter their trajectory. Based on follow-up observations, the test succeeded since DART managed to shorten Dimorphos’ orbit by 22 minutes. The impact also caused the moonlet to grow a visible tail!

However, as Hollywood loves to remind us, there are scenarios where a planet-killing asteroid gets very close to Earth before we could do anything to stop it. And there is no shortage of Near Earth Asteroids (NEAs) that could become potential threats someday. Hence why space agencies worldwide make it a habit of monitoring them and how close they pass to Earth. According to a new study by a group of satellite experts, it would be possible to build a rapid-response kinetic impactor mission that could rendezvous and deflect a PHA shortly before it collided with Earth.

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The First Telescope Images of DART's Impact are Starting to Arrive

Artist's impression of the DART mission impacting the moonlet Dimorphos. Credit: ESA

On September 26th, at 23:14 UTC (07:14 PM EST; 04:14 PM PST), NASA’s Double Asteroid Redirect Test (DART) spacecraft successfully struck the 160-meter (525 ft) moonlet Dimorphos that orbits the larger Didymos asteroid. The event was live-streamed all around the world and showed footage from DART’s Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO) as it rapidly approached Dimorphos. In the last few seconds, DART was close enough that individual boulders could be seen on the moonlet’s surface.

About 38 seconds after impact, the time it took the signal to reach Earth, the live stream ended, signaling that DART had successfully impacted Dimorphos and was destroyed in the process. Meanwhile, teams of astronomers stretching from the Indian Ocean to the Arabian Peninsula watched the impact with their telescopes. One, in particular – the Les Makes Observatory on the island of Le Reunion in the Indian Ocean – captured multiple images of the impact. These were used to create a real-time video and show the asteroid brightening as it was pushed away, followed by material ejected from the surface.

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