NASA's DART spacecraft changes asteroid moonlet's orbit

NASA's Double Asteroid Redirection Test spacecraft struck the asteroid moonlet Dimorphos on 26 September 2022. The intentional collision was the first full-scale demonstration of kinetic impact as a technique for changing the motion of a celestial object.

Dimorphos orbits the larger asteroid Didymos and posed no threat to Earth. Mission planners selected the binary system because telescopes could measure a change in the moonlet's orbital period from variations in brightness. The test changed the orbit around Didymos, not the pair's path into a dangerous trajectory toward Earth.

Images streamed from DART until impact, and the companion LICIACube observed the debris. Ground and space telescopes later measured that the orbital period shortened by more than the minimum mission requirement. The confirmed orbital change was announced after analysis; impact and measurement are related but not identical moments.

Kinetic impact is only one possible planetary-defence method. Its effectiveness depends on warning time, object size, material properties and impact geometry. The debris plume amplified momentum transfer in this case, but results from one moonlet cannot be applied mechanically to every asteroid.

NASA mission data establish the collision and later measured outcome. This record uses the impact date while explaining the evidence that validated deflection. It does not imply that Earth had narrowly escaped a real threat or that a complete defence system now exists without detection, planning and international decision-making.