NASA’s DART Mission: The Day Humanity Changed an Asteroid’s Orbit
On September 26, 2022, NASA deliberately crashed the DART spacecraft into Dimorphos. The impact tested whether a spacecraft could change an asteroid’s motion.
On September 26, 2022, NASA’s DART spacecraft deliberately flew into Dimorphos, a small asteroid orbiting a larger asteroid called Didymos. The collision was the first test of a planetary defense technique known as kinetic impact: striking an asteroid with a spacecraft to change its motion.
Why hit an asteroid?
Dimorphos was not on a collision course with Earth. NASA chose it as a test target because astronomers could measure how long it took to orbit Didymos before and after the impact. The question was whether a small change made deliberately, with enough warning, could become a useful tool for planetary defense.
The spacecraft’s final seconds
As DART closed in, its onboard camera sent images of Dimorphos back to Earth. The asteroid grew larger in each frame. The last complete image was captured about two seconds before the spacecraft struck its surface.
Did the test work?
Yes. Before the impact, Dimorphos took about 11 hours and 55 minutes to orbit Didymos. Measurements after the collision put its orbital period at about 11 hours and 23 minutes: roughly 32 minutes shorter. The result showed that a spacecraft impact can measurably alter an asteroid’s motion.
Why September 26 matters
DART did not stop an asteroid that was heading for Earth. It tested a method that could help protect Earth if a hazardous asteroid were discovered far enough in advance. On September 26, 2022, that idea moved from planning to a successful experiment in space.