When NASA crashed into an asteroid, it did way more than ‘nudge’ it

It was an unprecedented, successful test — proving humanity could alter the path of a menacing asteroid, should one ever be headed our way. Now, the space agency revealed that the DART mission didn’t simply vastly exceed expectations for moving the asteroid Dimorphos, but the impact changed the rubbly space rock’s shape.

The impact cut Dimorphos’ loop around its parent asteroid (they journey around the sun as a pair, or binary system) by a whopping 33 minutes and 15 seconds — when the original goal was to change it by at least 73 seconds. “And the entire shape of the asteroid has changed, from a relatively symmetrical object to a ‘triaxial ellipsoid’ – something more like an oblong watermelon,” Shantanu Naidu, an engineer at NASA’s Jet Propulsion Laboratory, said in a statement.

Naidu led the new research from the DART mission, short for Double Asteroid Redirection Test, which was recently published in The Planetary Science Journal.

To grasp Dimorphos‘ new shape, scientists used telescopes on Earth to observe how light reflected off the two asteroids, as well as watching when the asteroids would cast a shadow on each other. The graphic below shows the change in the 525-foot-wide (160-meter) space rock, which is no longer largely symmetrical.

The modeled shape of the asteroid Dimorphos, before and after impact.
Credit: NASA / JPL-Caltech

The asteroid Dimorphos just two seconds before impact from the DART spacecraft.
Credit: NASA / Johns Hopkins APL

Astronomers, and the public, will soon have much closer views of post-impact Dimorphos. The European Space Agency’s Hera mission will rendezvous with and survey the asteroid pair in 2026. “Now that NASA’s DART mission has impacted the moonlet, Hera will turn the grand-scale experiment into a well-understood and repeatable planetary defense technique,” the agency explained.

It’s important, if not critical, for humanity to find potentially threatening asteroids and have the technological ability to deflect them. But, fortunately, sizeable impacts are rare:

– Every single day about 100 tons of dust and sand-sized particles fall through Earth’s atmosphere and promptly burn up.

– Every year, on average, an “automobile-sized asteroid” plummets through our sky and explodes, explains NASA.

– Impacts by objects around 460 feet in diameter (big enough to cause significant regional destruction) occur every 10,000 to 20,000 years.

– A “dinosaur-killing” impact from a rock perhaps a half-mile across or larger happens on 100-million-year timescales. There’s no known threat from these colossal asteroids for the next century, and the likelihood of an impact in the next thousand years is exceedingly low.