The Dimorphos Boulder Swarm

Abstract

We present deep Hubble Space Telescope images taken to examine the ejecta from the DART spacecraft impact into asteroid Dimorphos. The images reveal an extensive population of co-moving boulders, the largest of which is about 7 m in diameter (geometric albedo 0.15 assumed). Measurements of 37 boulders show a mean sky-plane velocity dispersion of 0.30+/-0.03 m/s, only slightly larger than the 0.24 m/s gravitational escape velocity from the Didymos/Dimorphos binary system. The total boulder mass, 5e6 kg (density 2200 kg/m3 assumed), corresponds to about 0.1 percent of the mass of Dimorphos and the boulders collectively carry about 3e-5 of the kinetic energy delivered by the DART spacecraft impact. The sky-plane distribution of the boulders is asymmetric, consistent with impact into an inhomogeneous, likely rubble-pile, body. Surface boulder counts on Didymos show that the observed boulder swarm could be ejected from as little as 2 percent of the surface of Dimorphos (for example a circular crater at the impact point about 50 m in diameter). The large, slow-moving boulders are potential targets to be investigated in-situ by the upcoming ESA HERA mission.

arXiv comment22 pages, 9 figures

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Cited by in corpus (7)

• The Dynamical State of the Didymos System Before and After the DART Impact
• Dimorphos orbit determination from mutual events photometry
• Lessons learned from NASA's DART impact about disrupting rubble-pile asteroids
• High-Speed Boulders and the Debris Field in DART Ejecta
• Evaluating Short-Warning Mitigation via Intentional Robust Disruption of a Hypothetical Impact of Asteroid 2023 NT1
• Chondrule Formation During Low-Speed Collisions of Planetesimals: A Hybrid Splash-Flyby Framework
• Secondary impact debris in the Didymos system: what could be observed by Hera?