Callisto's Nonresonant Orbit as an Outcome of Circum-Jovian Disk Substructure
Yap, Teng Ee & Batygin, Konstantin (2026)
- Published
- Jan 1, 2026
- Journal
- arXiv e-prints
At a GlanceAI
Shows that a circum-Jovian disk pressure bump can trap Callisto and prevent its capture into the Laplace resonance without requiring late accretion.
SummaryAI
The paper demonstrates that a pressure bump in the circum-Jovian disk can act as a migration trap that isolates Callisto and prevents its capture into the Io–Europa–Ganymede Laplace resonance, removing the necessity of late or slow accretion for Callisto. By exploring bump parameters, the authors identify a 'Goldilocks' range of bump aspect ratios that reproduce the observed architecture and discuss consequences for Callisto's formation timing and interior interpretation.
Method SnapshotAI
They run N-body simulations that self-consistently include satellite-disk interactions with a parameterized pressure bump to study migration and resonance capture.
Background
Familiarity with satellite migration, circumplanetary disk physics, and mean-motion resonance dynamics is needed to follow the paper.
AI Abstract
The Galilean moons of Io, Europa, and Ganymede exhibit a 4:2:1 commensurability in their mean motions, a configuration known as the Laplace resonance. The prevailing view for the origin of this three-body resonance involves the convergent migration of the moons, resulting from gas-driven torques in the circum-Jovian disk wherein they accreted. To account for Callisto's exclusion from the resonant chain, a late and/or slow accretion of the fourth and outermost Galilean moon is typically invoked, stalling its migration. Here, we consider an alternative scenario in which Callisto's nonresonant orbit is a consequence of disk substructure. Using a suite of N-body simulations that self-consistently account for satellite-disk interactions, we show that a pressure bump can function as a migration trap, isolating Callisto and alleviating constraints on its timing of accretion. Our simulations position the bump interior to the birthplaces of all four moons. In exploring the impact of bump structure on simulation outcomes, we find that it cannot be too sharp nor flat to yield the observed orbital architecture. In particular, a "Goldilocks" zone is mapped in parameter space, corresponding to a well-defined range in bump aspect ratio. Within this range, Io, Europa, and Ganymede are sequentially trapped at the bump, and ushered across it through resonant lockstep migration with their neighboring, exterior moon. The implications of our work are discussed in the context of uncertainties regarding Callisto's interior structure, arising from the possibility of non-hydrostatic contributions to its shape and gravity field, unresolved by the Galileo spacecraft.