Tracking low-velocity ejecta from the DART impact on Dimorphos

The DART impact on Dimorphos produced a large population of low-velocity ejecta, likely containing most of the excavated mass, whose early fate remains poorly constrained. We investigate the first 22 h evolution of ejecta launched at 1-9 cm/s with RAVEL, a custom-developed code that couples three dimensional orbital dynamics in the Didymos-Dimorphos system with post-impact surface transport, including re-impact, rebound, frictional sliding, and detachment. Re-accretion is rapid and asymmetric: more than 99% of the re-accreted mass returns to Dimorphos within 5 h. The slowest ejecta remain concentrated near the DART crater and dominate the primary ejecta blanket, whereas faster particles undergo orbital transport and preferentially populate antipodal and trailing regions. Surface motion strongly modifies the first-contact pattern, and the DART-derived rough terrain model produces ray-like deposits controlled by local topography and dominated by the slowest ejecta. These results provide testable predictions for ESA's Hera mission and link ejecta-blanket morphology to orbital dynamics and surface mechanical response.