Planetary defense test (DART) deflected an asteroid but unleashed a boulder swarm

Key takeaways

NASA’s DART mission crashed a spacecraft into the nearby asteroid Dimorphos to test a possible strategy for deflecting asteroids that are headed for Earth.

The test succeeded in knocking Dimorphos slightly off course but also dislodged from its surface 37 boulders that are now moving away from the asteroid.

The effort reveals an unintended consequence of technology to deflect asteroids on a collision course with Earth: Smaller rocks flying off into space could create their own problems.

In September 2022, NASA deliberately slammed a spacecraft into the asteroid Dimorphos to knock it slightly off course. NASA’s objective was to evaluate whether the strategy could be used to protect Earth in the event that an asteroid was headed toward our planet.

A new study led by UCLA astronomer David Jewitt found that the collision had an unintended consequence: It launched a cloud of boulders from its surface. And, as the paper notes, smaller rocks flying off into space could create their own problems.

“The boulder swarm is like a cloud of shrapnel expanding from a hand grenade,” said Jewitt, lead author of the study and a UCLA professor of earth and planetary sciences. “Because those big boulders basically share the speed of the targeted asteroid, they’re capable of doing their own damage.”

Jewitt said that given the high speed of a typical impact, a 15-foot boulder hitting Earth would deliver as much energy as the atomic bomb that was dropped on Hiroshima.

[link to newsroom.ucla.edu (secure)]