Don’t look up, these asteroids might be too difficult to destroy. It’s not all bad news though

Batting away an asteroid as demonstrated by NASA last year might be the best solution to preventing rogue space rocks hitting Earth.

Defending earth from rogue space rocks roared back into the public consciousness in 2022 with the film Don’t Look Up and NASA’s successful Double Asteroid Redirection Test (DART) last year, but now Australian researchers at Curtin University have produced research supporting the use of kinetic impacts to alter the course of ‘rubble pile’ asteroids.

Although asteroids might conjure up pictures of gargantuan, solid rocks floating in space, rubble piles are the result of tiny rocks and dust particles coalescing under very weak, gravitational attraction.

“If you want to create your own rubble pile [asteroid], just go into your backyard, take a rock, [hit with] a sledgehammer and smack the rock to oblivion,” says lead researcher Professor Fred Jourdan.

“There’s going to be small pebbles, there’s going to be dust, and a lot of area between, and that’s exactly what a rubble pile is: the difference on Earth is that it just collapses in its own way, in space it’s bound by its own gravity.

“Everything, all those rocks, are attracted by each other.”

But even though this weak gravity might bring all these rocks together in a loose coalition, separating them appears to be decidedly difficult.

Studying dust samples from the Sydney Harbour Bridge sized Itokawa asteroid, Jourdan and his colleagues found these rubble piles can take a beating.

Itokawa probably formed after a massive space impact around 4.2 billion years ago causing its parent asteroid to fragment. That means the asteroid is almost as old as our solar system.

During that time, it’s had countless collisions with other space rocks and remained intact throughout.

That means it’s probably not going to shatter if an object was to be deliberately smashed into it, as NASA did with the asteroid Dimorphos last year.

“What we found is that a rubble pile, despite the constant bombardment, can take a beating, and it has for more than 4.2 billion years,” Jourdan says.

“DART didn’t try to destroy the asteroid, it just tried to push it out of the way, and that’s exactly what we say.

“Because it’s so resistant, you can bombard it with other stuff  more aggressive that’s going to be able to push the asteroid out of the way, without completely destroying it.

“We don’t want to destroy these asteroids, if you did, you might get plenty of fragments and this might be, in some cases, even worse than one single fragment.”

Jourdan’s team also suggested going for the nuclear option might be a viable option if kinetic impact was ruled out.

But rather than launching a high-powered warhead into the asteroid to vaporise it, the detonation of such a weapon in close proximity to the asteroid would provide a suitable shockwave to steer the rubble pile out of the way.

The Curtin team will next take samples from the larger asteroid Bennu which was probed by NASA’s OSIRIS-REx mission for study later this year, and will also take receipt of samples from the Martian moon Phobos at the end of the decade.