The Dimorphos Boulder Swarm

The Astrophysical Journal. Letters

article

David Jewitt¹  Yoonyoung Kim²  Jing Li¹  Max Mutchler³ 

[1] Department of Earth, Planetary and Space Sciences, UCLA;Lunar and Planetary Laboratory, University of Arizona;Space Telescope Science Institute

DOI  :  10.3847/2041-8213/ace1ec

来源: IOP Publishing Limited

【 摘 要 】

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 comoving boulders, the largest of which is ∼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⁻¹, only slightly larger than the 0.24 m s⁻¹ gravitational escape velocity from the Didymos–Dimorphos binary system. The total boulder mass,M _b ∼ 5×10⁶ kg (density 2200 kg m⁻³ assumed), corresponds to about 0.1% of the mass of Dimorphos, and the boulders collectively carry about 3×10⁻⁵ 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% 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.

【 授权许可】

Unknown