NASA has confirmed that its Double Asteroid Redirection Test spacecraft successfully altered the orbital motion of an asteroid system, marking a significant milestone in planetary defense research. Scientists reported that the 2022 kinetic impact not only changed the orbit of the small asteroid moonlet Dimorphos around its companion Didymos, but also slightly shifted the motion of the entire binary system around the Sun.
The findings come from a study published in the journal Science Advances examining data collected after the spacecraft deliberately collided with Dimorphos in September 2022. The mission aimed to test whether a high speed spacecraft could deflect an asteroid through kinetic impact, a strategy considered for preventing potential future collisions with Earth, according to the study.
Dimorphos and its larger companion form a binary asteroid system that orbits the Sun as a single unit. Following the impact, researchers observed that Dimorphos’ orbit around Didymos shortened by approximately 33 minutes from its original 12 hour orbital period. The new analysis shows that the collision also produced a subtle change in the binary system’s overall orbital motion around the Sun.
Scientists measured a small variation in the system’s orbital speed equivalent to roughly 0.15 seconds. Although minimal, researchers note that small orbital adjustments can accumulate over extended periods, potentially producing large changes in an asteroid’s trajectory. Such gradual shifts are central to planetary defense strategies that rely on early detection and long lead times before potential impact events.
To confirm the orbital changes, astronomers used a technique known as stellar occultation, which occurs when an asteroid passes in front of a distant star and briefly blocks its light. By precisely timing when the starlight dims and reappears, scientists can calculate an asteroid’s position, velocity, and orbital characteristics with high accuracy.
Observations were conducted by professional and volunteer astronomers worldwide between October 2022 and March 2025. During this period, researchers recorded 22 stellar occultation events involving the Didymos Dimorphos system. The combined data enabled scientists to refine measurements of the system’s motion and confirm that the spacecraft’s impact produced detectable orbital changes.
Another key finding involves the momentum enhancement factor generated by debris ejected during the collision. When the spacecraft struck Dimorphos, large quantities of surface material were expelled into space. This debris created an additional reactive force that increased the overall momentum transferred to the asteroid.
Researchers calculated a momentum enhancement factor of approximately two, meaning that ejecta from the impact effectively doubled the deflection force beyond the spacecraft’s direct kinetic energy. This effect provides important insights for designing future asteroid deflection missions, as it demonstrates that surface material properties and ejecta dynamics significantly influence impact outcomes.
Scientists estimate the change in orbital velocity of the binary system at roughly 11.7 microns per second. While extremely small, this variation demonstrates that human made spacecraft can measurably influence the motion of celestial bodies. Over years or decades, similarly small velocity changes could accumulate enough to divert a hazardous asteroid away from Earth.
The mission represents the first confirmed instance of a spacecraft altering the orbit of a natural object in space through direct impact. Researchers say the results validate kinetic impact as a practical planetary defense method if potentially dangerous asteroids are identified early.
Future planetary defense efforts are expected to build on the mission’s findings by improving impact modeling, refining asteroid composition studies, and developing rapid response strategies for potential threats.