NASA's DART Mission Alters Asteroid System's Solar Orbit

NASA's Double Asteroid Redirection Test (DART) mission, which intentionally impacted the asteroid moonlet Dimorphos in September 2022, has been found to not only alter Dimorphos' orbit around its larger companion, Didymos, but also to subtly shift the entire binary system's trajectory around the Sun.

The DART spacecraft's collision with Dimorphos ejected a significant amount of debris into space, effectively doubling the momentum transfer from the impact. This resulted in a measurable change in the binary system's solar orbit, marking the first time a human-made object has altered the path of a celestial body around the Sun.

To confirm DART's influence on the binary system, researchers conducted precise measurements of Didymos' orbit around the Sun. They utilized radar and ground-based observations, as well as tracking stellar occultations—events where the asteroid passes in front of a star, causing a brief dimming. These observations were made possible by volunteer astronomers worldwide, who recorded 22 stellar occultations between October 2022 and March 2025.

The study also provided insights into the densities of both asteroids. Dimorphos was found to be slightly less dense than previously thought, supporting the theory that it formed from debris shed by a rapidly spinning Didymos. This material eventually coalesced into Dimorphos, classifying it as a 'rubble pile' asteroid.

These findings demonstrate that targeting the secondary asteroid in binary systems is a viable strategy for kinetic impact deflection, enhancing planetary defense capabilities. The European Space Agency's Hera mission, launched in 2024, is set to visit the Didymos system later this year to further assess the impact's effects, including measuring the crater, the asteroid's mass and structure, and the efficiency of the deflection.