Work

Dynamical evolution and surface accretion of DART impact ejecta in the (65803) Didymos system

Year: 2026

Type: article

Abstract: The DART spacecraft impacted Dimorphos, the small moonlet of the Didymos binary system, on 26 September 2022. The impact ejected dust, fragments, and boulders into the near-binary environment. In November 2026, ESA's Hera mission is expected to arrive at the binary system to characterise both asteroids and investigate the post-impact consequences in detail. We investigated the dynamical evolution of DART-generated impact ejecta and quantified their surface accretion patterns within the Didymos binary system. We constructed high-fidelity ejecta dynamics, including polyhedron asteroid gravity and solar radiation pressure with combined occultations. The initial conditions of the ejecta were generated from the observation-constrained velocity--size distribution and ejecta-cone geometry. In total, 20 million trajectories were integrated to characterise the ejecta evolution and surface accretion. More than 93.5% of DART-generated ejecta particles escape from the system within two years, while only approximately 0.002% remain in the near-binary environment. The deposited layer on Dimorphos reaches the order of 1.5 mm at mid-to-low latitudes. On Didymos, the accreted layer is mostly thinner than 0.3 mm, but it may reach 3--11.5 mm in a localised high-density region. Most DART-generated ejecta are removed from the binary system, while a small but dynamically meaningful subset remains near the system or accretes onto the asteroid surfaces. The surface accretion distribution is strongly controlled by the initial ejecta-cone geometry, especially the cone-axis direction.

Source: Astronomy and Astrophysics

DOI: 10.1051/0004-6361/202662228