“That’s a full 33 minutes shorter than its original orbital period, a finding that implied that a substantial amount of ejecta was produced.”
The DART team predicted a head-on hit would shave just under 10 minutes off Dimorphos’s 11 hour 55 minute orbit. It took 33. At least a million kilograms of rock blew off the moonlet and acted as extra thrust. The navigation camera saw the target as two pixels an hour before impact, and a half-ton spacecraft still moved an asteroid three times further than planned.