Direct N-body Simulations of Satellite Formation around Small Asteroids: Insights from DART’s Encounter with the Didymos System

作者：Harrison Agrusa, Yun Zhang, D. C. Richardson, Petr Pravec, Matija Ćuk, Patrick Michel, Ronald‐Louis Ballouz, Seth A. Jacobson, Daniel J. Scheeres, K. J. Walsh, O. S. Barnouin, R. T. Daly, E. E. Palmer, M. Pajola, Alice Lucchetti, Filippo Tusberti, Joseph DeMartini, Fabio Ferrari, Alex J. Meyer, Sabina D. Raducan, Paul Sánchez · 发表于：The Planetary Science Journal · 年份：2024 · DOI：10.3847/psj/ad206b · 被引用次数：30 · 研究领域：Astro and Planetary Science、Planetary Science and Exploration、Stellar, planetary, and galactic studies

Abstract We explore binary asteroid formation by spin-up and rotational disruption considering the NASA DART mission's encounter with the Didymos–Dimorphos binary, which was the first small binary visited by a spacecraft. Using a suite of N-body simulations, we follow the gravitational accumulation of a satellite from meter-sized particles following a mass-shedding event from a rapidly rotating primary. The satellite’s formation is chaotic, as it undergoes a series of collisions, mergers, and close gravitational encounters with other moonlets, leading to a wide range of outcomes in terms of the satellite's mass, shape, orbit, and rotation state. We find that a Dimorphos-like satellite can form rapidly, in a matter of days, following a realistic mass-shedding event in which only ∼2%–3% of the primary's mass is shed. Satellites can form in synchronous rotation due to their formation near the Roche limit. There is a strong preference for forming prolate (elongated) satellites, although some simulations result in oblate spheroids like Dimorphos. The distribution of simulated secondary shapes is broadly consistent with other binary systems measured through radar or lightcurves. Unless Dimorphos's shape is an outlier, and considering the observational bias against lightcurve-based determination of secondary elongations for oblate bodies, we suggest there could be a significant population of oblate secondaries. If these satellites initially form with elongated shapes, a yet-unidenti...