When NASA’s DART spacecraft deliberately collided with the asteroid moonlet Dimorphos at nearly 14,000 miles per hour in September 2022, initial headlines celebrated humanity’s having redirected a celestial body.
Yet the full implications of that kinetic impact—carefully reconstructed over years through ground-based observations, radar tracking, and precise orbital modeling—emerged only recently.
NASA confirmed this week that the DART spacecraft collision didn’t just alter the orbit of the small asteroid named “Dimorphos.” It also nudged the orbit of the entire asteroid system – including its larger companion, Didymos – around the Sun. It’s the first time in human history that a manmade object has measurably changed the path of a celestial body around our bright star.
DART: The Test That Proved We Could Move an Asteroid
The DART mission — short for Double Asteroid Redirection Test — launched in November 2021 to prove that we could physically redirect an asteroid if one were ever found on a collision course with Earth.
The spacecraft spent nearly a year in transit before its planned impact in late September 2022.
At the time, early results were promising. Scientists confirmed that the goals for redirecting Dimorphos’ (and Didymos’) orbital path actually far exceeded the mission’s “success threshold.” Planetary defense researchers celebrated.
However, answering the bigger questions took years. Had the impact actually moved the entire asteroid system through space in the way researchers wanted? Was it a successful example of defending Earth against potentially dangerous asteroids in the long run?
A Tiny Shift, Years in the Making
The orbital period of Didymos around the Sun runs 770 days, and the shift DART created amounted to just 0.15 seconds. Detecting a change that small required years of observation.
NASA researchers, along with volunteer astronomers around the world, tracked 22 “stellar occultations” – rare moments when the asteroid passed directly in front of a distant star, causing the star’s light to briefly blink out or flicker. Those measurements, combined with radar data and ground-based observations collected between October 2022 and March 2025, gave scientists the precise answers they needed.
“This work is highly weather dependent and often requires travel to remote regions with no guarantee of success. This result would not have been possible without the dedication of dozens of volunteer occultation observers around the world,” said Steve Chesley, a senior research scientist at NASA’s Jet Propulsion Laboratory.
“Over time, such a small change in an asteroid’s motion can make the difference between a hazardous object hitting or missing our planet,” Rahil Makadia added, the study’s lead author at the University of Illinois Urbana-Champaign.
DART: Proof of Concept for Planetary Defense
Neither Didymos nor Dimorphos posed any threat to Earth – NASA was clear on that face throughout the mission. The exercise was always about preparation.
NASA is currently building the Near-Earth Object Surveyor, a next-generation space telescope designed specifically for planetary defense. Its focus will be on the hardest-to-spot threats: dark asteroids and comets that reflect very little light and could otherwise go undetected until it’s too late.
The DART mission was a proof of concept.
