DART did not test stopping an actual threatening asteroid; it demonstrated a method that requires early detection and detailed knowledge of the target’s physical characteristics and trajectory for effectiveness.

The DART mission proves that kinetic impact can alter the orbit of a small asteroid moonlet, marking a practical milestone for planetary defense while noting uncertainties Hera will resolve before broader application.

Dimorphos’ orbital period around Didymos was shortened by roughly 32 to 33 minutes, far exceeding NASA’s minimum success threshold, thanks to both momentum transfer and plume ejecta amplifying the effect (beta around 3.6).

Changes depend on Dimorphos’s composition and structure, with beta estimates spanning about 2.2 to 4.9 due to uncertainties about mass and surface properties.

Hera, the European Space Agency’s follow-up mission, launched in late 2024, is set to arrive at the Didymos system in late 2026 to precisely measure Dimorphos’s mass, study crater formation, and calibrate DART results for a better physical understanding.

DART targeted Dimorphos, a roughly 150-meter moonlet of Didymos, on September 26, 2022, from about 11 million kilometers away, marking the first deliberate attempt to alter another world’s orbit for defense feasibility.

The mission showed ejecta recoil can substantially amplify momentum, making the encounter more effective than a simple impact would predict.