A Single Ejection Model of the DART/Dimorphos Debris Trail

Abstract

The collision of the NASA DART spacecraft with asteroid Dimorphos resulted in the formation of a distinctive and long-lived debris trail, formed by the action of solar radiation pressure on ejected particles. This trail briefly displayed a double appearance, which has been interpreted as the result of a double ejection. We present a model that can produce a transient double trail without the need to assume a double ejection. Our model explains the appearance of the double trail as a projection of the cone walls when viewed from a large angle to the cone axis and avoids the problem of producing dust in two epochs from a single, instantaneous impact. The particles follow a broken power-law size distribution, with differential indices q = 2.7 ± 0.2 (1 μm ≤ a ≤ 2 mm), 3.9 ± 0.1 (2 mm < a ≤ 1 cm), and 4.2 ± 0.2 (1 cm < a ≤ 20 cm). We find that the total trail mass in particles from 1 μm to 20 cm in size (for an assumed density 3500 kg m−3) is ∼1.7 × 107 kg, rising to 2.2 × 107 kg, when extended to boulders up to 3.5 m in radius. This corresponds to 0.4%–0.6% of the mass of Dimorphos.

BYORP and Dissipation in Binary Asteroids: Lessons from DART

“…Because the impact made the binary tighter, DART actually net-drained energy from the Didymos system (as the fast ejecta escaped rapidly). Slow ejecta was estimated by Ofek et al (2024) to amount to about 10 6 kg moving at 10 m s −1 , while Kim & Jewitt (2023) estimate a mass of >10 7 kg but moving at speeds <1 m s −1 . While the slow ejecta may have contributed significantly to the momentum change of Dimorphos, it carried a negligible fraction of the impact's energy.…”