DART proves humanity can nudge an asteroid's orbit

NASA’s DART deliberately struck Dimorphos, a small moonlet of Didymos, at about 6 km/s and shortened its orbital period around Didymos by roughly 33 minutes—a result well beyond the required 73 seconds for success—largely due to ejecta momentum (beta ~3.6). This confirmed that a kinetic-impact deflection can alter an asteroid’s trajectory if done years in advance, though the exact effectiveness depends on the target’s composition; ESA’s Hera mission, launched in 2024, will measure Dimorphos’s mass and crater to turn the result into a calibrated figure ahead of any future planetary-defense decisions.