Hit on asteroid Dimorphos sent rocks rolling

When a NASA spacecraft successfully knocked an ­asteroid off course last year it sent dozens of boulders skittering into space.

This image taken on December 1 shows the asteroid Dimorphos nearly four months after it was hit by NASA’s DART mission.

When a NASA spacecraft successfully knocked an ­asteroid off course last year it sent dozens of boulders skittering into space, images from the Hubble telescope show.

NASA’s fridge-sized DART probe smashed into the pyramid-sized, rugby-ball-shaped ­asteroid Dimorphos about 11 million kilometres from Earth last September.

The spacecraft knocked the asteroid significantly off course in the first such test of Earth’s planetary defences.

New images taken by the Hubble Space Telescope show that the collision also sent 37 boulders – ranging from 1m to 7m across – floating into the cosmos.

They represent around 2 per cent of the boulders that were ­ already scattered across the surface of the loosely-held-together asteroid, scientists estimated in a new study.

The finding suggests that possible future missions to divert life-threatening asteroids heading towards Earth could also spray off boulders in our direction.

But these particular rocks do not pose any threat to Earth ­because they have barely gone anywhere.

They are drifting away from Dimorphos at about a kilometre per hour – roughly the speed a giant tortoise walks, Hubble shows.

The boulders are moving so slowly that the European Space Agency’s Hera mission – which is due to arrive at the ­asteroid in late 2026 to inspect the damage – will even be able to take a look at them.

“The boulder cloud will still be dispersing when Hera ­arrives,” said David Jewitt, a planetary scientist at the University of California at Los Angeles and lead author of the new study.

“It’s like a very slowly ­expanding swarm of bees.”

The “spectacular observation” by Hubble “tells us for the first time what happens when you hit an asteroid and see ­material coming out.

“The boulders are some of the faintest things ever imaged inside our solar system,” Professor Jewitt said.

The dispersal of the boulders indicates that DART left a crater about 50m wide on Dimorphos, according to Professor Jewitt. The whole asteroid is 170m across.

The scientists plan to continue following the boulders to work out their trajectory and ­determine how exactly they launched off the surface.

The study was published in the Astrophysical Journal Letters.

AFP