An Earth Encounter As the Cause of Chaotic Dynamics in Binary Asteroid (35107) 1991VH

TL;DR

This paper proposes that a close Earth encounter caused the chaotic rotation observed in binary asteroid (35107) 1991VH by perturbing its secondary component from a stable spin-orbit resonance, with implications for its internal dissipation properties.

Contribution

It introduces a hypothesis linking Earth encounters to chaotic dynamics in binary asteroids and constrains the secondary's tidal dissipation parameters based on orbital history.

Findings

Earth encounter could have triggered the secondary's chaotic rotation.

The secondary was likely in a 1:1 spin-orbit resonance before perturbation.

Persistent excited state depends on internal energy dissipation efficiency.

Abstract

Among binary asteroids, (35107) 1991VH stands out as unique given the likely chaotic rotation within its secondary component. The source of this excited dynamical state is unknown. In this work we demonstrate that a past close encounter with Earth could have provided the necessary perturbation to allow the natural internal dynamics, characterized by spin-orbit coupling, to evolve the system into its current dynamical state. In this hypothesis, the secondary of 1991VH was previously in a classical 1:1 spin-orbit resonance with an orbit period likely between 28-35 hours before being perturbed by an Earth encounter within $\sim80,000$ km. We find if the energy dissipation within the secondary is relatively inefficient, this excited dynamical state could persist to today and produce the observed ground-based measurements. Coupled with the orbital history of 1991VH, we can then place a constraint on the tidal dissipation parameters of the secondary.