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 confirmed to have altered the orbit of the entire binary asteroid system around the Sun. Dimorphos orbits the larger asteroid Didymos, and the two together revolve around the Sun. Post-impact observations revealed that the system's 770-day solar orbit was shortened by approximately 0.15 seconds.

The DART spacecraft's collision with Dimorphos not only shortened its orbit around Didymos by 33 minutes but also ejected a significant amount of debris. This debris carried additional momentum, effectively doubling the force imparted by the spacecraft alone. As a result, the binary system's trajectory around the Sun was slightly adjusted.

Thomas Statler, lead scientist for solar system small bodies at NASA Headquarters, stated,

"This is a tiny change to the orbit, but given enough time, even a tiny change can grow to a significant deflection."

To measure the impact's effect on Didymos' solar orbit, researchers combined radar data with observations of stellar occultations—events where the asteroid passes in front of a star, temporarily blocking its light. Between October 2022 and March 2025, 22 such occultations were recorded by volunteer astronomers worldwide. These precise measurements confirmed the slight alteration in the binary system's solar orbit.

The success of the DART mission demonstrates the viability of kinetic impactors as a method for planetary defense. While the Didymos-Dimorphos system poses no threat to Earth, the mission provides valuable insights into how similar techniques could be employed to deflect potentially hazardous asteroids in the future.