NASA Asteroid Impact Mission Triggers Surprise Avalanche of Space Boulders

In September 2022, NASA slammed a spacecraft into the asteroid Dimorphos. Hubble’s latest observations show a giant swarm of boulders shaken loose by the impact, scattered like stars in the asteroid’s wake.

The new images will help an upcoming mission to the asteroid study the results of the Double Asteroid Redirection Test, to help refine and better plan for such impacts in the future.

“We see a cloud of boulders carrying mass and energy away from the impact target. The numbers, sizes, and shapes of the boulders are consistent with them having been knocked off the surface of Dimorphos by the impact.”

“This tells us for the first time what happens when you hit an asteroid and see material coming out up to the largest sizes. The boulders are some of the faintest things ever imaged inside our Solar System.”

The aim was to try to knock Dimorphos slightly off its current orbit around larger asteroid Didymos, to test how capable we are of doing so in the possible event of a hazardous asteroid headed in Earth’s direction.

We still don’t know a lot about the ongoing effects of the impact so scientists are continuing to monitor the binary asteroid, using telescopes such as Hubble to detect the faint changes that might be missed by other instruments.

Although the DART spacecraft smacked into Dimorphos at a speed of around 22,500 kilometers per hour, the rubble probably isn’t broken-off asteroid chunks.

Prior to the impact, images from DART show loose boulders on the asteroid’s surface; the impact likely knocked them loose, although precisely how is not yet known.

A spacecraft called Hera, launching in 2024, will be visiting the asteroid to study the results of the impact test.

Continued Hubble check-ins will help scientists calculate the boulders’ trajectories away from the asteroid so we can figure out exactly where they launched from – which, in turn, could help us figure out how they launched in the first place.