New research shows that Nasa's Dart spacecraft, which crashed into the asteroid moonlet Dimorphos in 2022, has changed the orbit of the binary asteroid system around the sun. This marks the first time a human-made object has measurably altered a celestial body's path in this way. The findings highlight potential methods for planetary defense against hazardous space objects.
In 2022, Nasa's Double Asteroid Redirection Test (Dart) mission successfully collided a spacecraft with Dimorphos, the smaller moonlet in the binary asteroid system consisting of Didymos and Dimorphos. The impact was intended to test kinetic deflection as a strategy for protecting Earth from potentially dangerous asteroids. Initial assessments confirmed that the collision shortened Dimorphos' orbit around its parent asteroid, Didymos, by altering its path.
A follow-up study published in 2024 by a team at Nasa's Jet Propulsion Laboratory (Jpl) detailed that Dimorphos' orbital period around Didymos was reduced by about 33 minutes, with its trajectory nudged roughly 120 feet closer to the larger asteroid. Dimorphos, approximately 560 feet wide, posed no threat to Earth, making it an ideal target for the experiment.
The latest research, announced in a Jpl press release, reveals that the impact affected not only Dimorphos but the entire binary system's orbit around the sun. Didymos and Dimorphos share a 770-day orbital period around the sun, which has now been altered by about 11.7 microns per second, equivalent to 1.7 inches per hour. Lead author Rahil Makadia noted, “Over time, such a small change in an asteroid’s motion can make the difference between a hazardous object hitting or missing our planet.”
This achievement represents the first instance where a human-made object has measurably changed the solar orbit of a celestial body. Scientists view it as a promising step in developing feasible defenses against near-Earth objects, though further studies will assess long-term effects and refine deflection techniques.