NASA just redirected an asteroid by smashing a spacecraft into it

An artist's depiction of the DART spacecraft approaching Dimorphos, with the larger Didymos in the background.

(Image credit: NASA/Johns Hopkins University Applied Physics Laboratory)

NASA has intentionally slammed a spacecraft into an asteroid in the first ever test of Earth’s planetary defense system.

NASA’s Double Asteroid Redirection Test (DART) spacecraft smashed into the asteroid Dimorphos at 7:14 p.m. ET on Monday (Sept. 26) in humanity’s first attempt to alter an asteroid’s trajectory. NASA believes the impact will be a vital demonstration of how humans could one day nudge a dangerous asteroid away from a catastrophic collision course with our planet.

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The probe's goal was to slow the orbit of Dimorphos around its larger partner — the 1,280-feet-wide (390 m) asteroid Didymos. NASA will deem the mission a success if Dimorphos’s 12-hour orbit slows by 73 seconds, but the real change could be by as much as 10 minutes. Neither asteroid poses a threat to Earth. Data that will pour in for weeks to come will tell us how successful that mission was, said Nancy Chabot, Coordination Lead for the DART mission, in a live webcast of the event.

DART’s final moments were captured by its onboard Didymos Reconnaissance and Asteroid Camera for Optical Navigation (DRACO), which automatically steered the spacecraft into its collision course with the distant asteroid. NASA scientists said that Dimorphos wasn’t even visible to DART’s DRACO camera system until it was within one hour of impact, after which it became just one pixel in the camera’s field of view. Three minutes prior to impact, the asteroid grew to just 42 pixels in size. As the craft approached Dimorphos, the rough terrain and shadowy boulders became bigger and bigger before the image blanked out.

Scientists will get a better picture of the impact’s immediate aftermath by turning to the Italian space agency's LICIACube — a smaller "cubesat" spacecraft that split from DART on Sept. 11. Orbiting the aftermath of the collision at a distance of 34 miles (55 km), LICIACube will beam photos back to Earth of the trajectory-altering impact and the plume of material thrown out by the crash. And now, telescopes on all seven continents will be trained on the asteroid, measuring brightening of the rock that's thrown off from the collision to determine the extent of orbital changes that occurred.

Ben Turner is a U.K. based writer and editor at Live Science. He covers physics and astronomy, tech and climate change. He graduated from University College London with a degree in particle physics before training as a journalist. When he's not writing, Ben enjoys reading literature, playing the guitar and embarrassing himself with chess.