Dynamical origin of Dimorphos from fast spinning Didymos

Abstract

Didymos is a binary near-Earth asteroid. It is the target of the DART and HERA space missions. The primary body, Didymos, rotates close to the spin at which it is expected to shed mass. The secondary body, Dimorphos, is a 140 meters moon that orbits the primary body in about 12 hours. Here we investigate the possible origin of Dimorphos. Using 1D models of ring/satellite interactions, we study the evolution of material lost from Didymos' surface and deposited as a ring at its equator. We find that due to viscous spreading, the ring spreads outside the Didymos' Roche limit forming moonlets. A fraction of the mass will form Dimorphos and a set of objects near the Roche limit, while most of the ring's mass falls back on Didymos. To match the properties of today's Dimorphos, the total mass that must be deposited in the ring is about 25% of Didymos' mass. It is possible that a fraction of the material travelled several times between the ring and the surface of Didymos. The models produce an orbit similar to that observed for a Didymos tidal parameter k2/Q<1e-5. If the ring deposition timescale is long (>100 yr) (so the material flux is small) Dimorphos could be irregularly shaped as it forms from the collision of similar-sized satellitesimals. However, the top-shape of Didymos is expected to be achieved due to a fast spin-up of the asteroid, which would result in a short deposition timescale (<yr). In that case, the satellite would form from progressively accreting material at the Roche Limit, resulting in an ellipsoidal Dimorphos constructed of small pieces with sizes of the order of meters, which is apparently in agreement with the recent images of Dimorphos obtained by DART mission.

Accepted in ICARUS in 05/01/2023 (YICAR_115428)

References in corpus (15)

• Formation of asteroid pairs by rotational fission
• Formation of Regular Satellites from Ancient Massive Rings in the Solar System
• Numerical simulations of impacts involving porous bodies: I. Implementing sub-resolution porosity in a 3D SPH Hydrocode
• Landslides and Mass Shedding on Spinning Spheroidal Asteroids
• Long-term & large-scale viscous evolution of dense planetary rings
• Constraints on the Physical Properties of Main Belt Comet P/2013 R3 from its Breakup Event
• Compositions and origins of outer planet systems: Insights from the Roche critical density
• Formation of Multiple-Satellite Systems From Low-Mass Circumplanetary Particle Disks
• SPH Simulations for Shape Deformation of Rubble-Pile Asteroids Through Spinup: The Challenge for Making Top-Shaped Asteroids Ryugu and Bennu
• Constraints on the perturbed mutual motion in Didymos due to impact-induced deformation of its primary after the DART impact
• Dynamical Evolution of the Didymos-Dimorphos Binary Asteroid as Rubble Piles following the DART Impact
• Formation of moons and equatorial ridge around top-shaped asteroids after surface landslide
• Dynamics around Non-Spherical Symmetric Bodies: I. The case of a spherical body with mass anomaly
• Effects of immersed moonlets in the ring arc particles of Saturn
• Exploring the recycling model of Phobos formation: rubble-pile satellites

Cited by in corpus (3)

• Direct $N$-body simulations of satellite formation around small asteroids: insights from DART's encounter with the Didymos system
• The Dynamical State of the Didymos System Before and After the DART Impact
• Rapid formation of binary asteroid systems post rotational failure: a recipe for making atypically shaped satellites