DART-scale Impacts into a Complex Low-strength Target: Insights into Asteroid Dimorphos’s Interior from Simulations

Abstract Impact processes are fundamental in governing asteroid evolution. While recent space missions have provided ground-truth observations of the surface and orbital dynamics, interior features remain largely unexplored. NASA’s Double Asteroid Redirection Test (DART) mission recently achieved a successful kinetic impact on the near-Earth asteroid Dimorphos. The spacecraft imagery detected a boulder-strewn surface in the seconds before the impact, though its underlying structure remains uncertain. To examine the subsurface of Dimorphos, we modeled DART-scale impacts as a window into its interior. Impacts were simulated using the iSALE-2D shock physics code over extended time frames of up to 60 s, with half-spheroidal targets resolving surface curvature effects. Recent mechanical and material settings were incorporated based on the DART constraints. Among the scenarios tested, homogeneous cases with low cohesions (20–80 Pa) were found to match the reference β range reconstructed for the DART impact when the coefficient of internal friction was 0.5, if Dimorphos has the same bulk density as the binary system. This cohesion range represents one possible solution; alternatively, a lower cohesion (1 Pa) reproduced the reference β when the porosity was reduced to 20%. For heterogeneous scenarios, a double-layered interior featuring a loose layer surrounding a weak core, and a three-layered interior with multiple boulders clustered at the impact site produced β aligning with the reference β , implying the plausibility of diverse interiors for Dimorphos. The results provide insights into the interior morphology of Dimorphos, set to be probed by the European Space Agency Hera mission, with a rendezvous in late 2026.