The rotation of Io predicted by the Poincar\'e-Hough model

TL;DR

This paper models Io's rotation using a 4-degree-of-freedom Poincaré-Hough model, predicting libration amplitudes and core stability, providing insights into its rotational dynamics.

Contribution

It introduces a detailed 2-layer rotational model for Io, predicting libration amplitudes and analyzing core stability, which advances understanding of its rotational behavior.

Findings

Longitudinal librations are about 30 arcseconds, regardless of core composition.

The core is predicted to be slowly unstable due to tidal effects.

The model offers new insights into Io's rotational dynamics.

Abstract

This note tackles the problem of the rotation of Io with the 4-degrees of freedom Poincar\'e-Hough model. Io is modeled as a 2-layer body, i.e. a triaxial fluid core and a rigid outer layer. We show that the longitudinal librations should have an amplitude of about 30 arcseconds, independent of the composition of the core. We also estimate the tidal instability of the core, and show that should be slowly unstable.