Origin of the chaotic motion of the Saturnian satellite Atlas

TL;DR

This paper investigates the chaotic motion of Saturn's satellite Atlas, revealing that coupled resonances with Prometheus dominate its chaotic orbit, with analytical models confirming the resonance interactions as the primary cause.

Contribution

The study applies the CoraLin analytical model to analyze Atlas's chaotic orbit, demonstrating that coupled 54:53 resonances with Prometheus are the main drivers of chaos.

Findings

Chaotic zone covers most of Atlas's corotation sites.

Weak overlap of resonances with Pandora has minimal effect.

Simplified models with Prometheus and Saturn's oblateness capture key dynamics.

Abstract

We revisit the dynamics of Atlas. Using Cassini ISS astrometric observations spanning February 2004 to August 2013, Cooper et al. (2015) found evidence that Atlas is currently perturbed by both a 54:53 corotation eccentricity resonance (CER) and a 54:53 Lindblad eccentricity resonance (LER) with Prometheus. They demonstrated that the orbit of Atlas is chaotic, with a Lyapunov time of order 10 years, as a direct consequence of the coupled resonant interaction (CER/LER) with Prometheus. Here we investigate the interactions between the two resonances using the CoraLin analytical model (El Moutamid et al. 2014), showing that the chaotic zone fills almost all the corotation sites occupied by the satellite's orbit. Four 70:67 apse-type mean motion resonances with Pandora are also overlapping, but these resonances have a much weaker effect. Frequency analysis allows us to highlight the coupling between the 54:53 resonances, and confirms that a simplified system including the perturbations due to Prometheus and Saturn's oblateness only captures the essential features of the dynamics.