Low-energy ring particle accretion as the origin of Pan's equatorial ridge
Abstract
Pan is a small Saturnian satellite embedded within the planet's A ring, characterized by a polygonal equatorial ridge whose formation mechanism remains debated. A proposed explanation is ring particle accretion, yet previous simplified models could not address the ridge's complex multi-lobed morphology without ad hoc assumptions, and the cause of its latitudinal spread remains unclear. This work studies the complex low-energy dynamics around Pan to verify whether the ring particle accretion paths are consistent with the observed ridge morphology. We model particle motion using a CR3BP with spherical harmonic perturbations. Accretion paths are analyzed via grid-search simulations of trajectories transiting the L1 and L2 necks, using backward propagation from Pan's surface to determine the impacting material's original orbital characteristics. Asymmetric accreting particle populations, with inner-ring particles located closer to Pan and contributing more significantly to the impact flux, produce impact distributions that correlate with the ridge structure, especially for the Saturn-facing hemisphere. The ridge latitudinal spread is recovered only when the out-of-plane position and velocity of the accreting particles are strictly limited, consistent with accretion from a thin disk such as Saturn's rings. Furthermore, analysis of the particles' impact conditions revises the previously estimated minimum accretion duration downward by an order of magnitude, to 104 yr, while accreting material is shown to originate from ring particles that once populated the Encke Gap. By systematically sampling admissible low-energy trajectories near Pan, our grid-search approach resolves the complex accretion dynamics that previous simplified narrow-stream models do not capture, revealing that the ridge's main morphological features emerge naturally from the local low-energy dynamical environment.
Related
- A Dark-matter Origin of Little Red Dots: Early Seeding and Super-Bondi Accretion
- Cosmogenic neutrinos from FRII galaxies as potential origin of the ultra-high-energy KM3-230213A event
- Cosmic Ray Diffusion and the Origin of Very High Energy Gamma-Ray Emission in Young Massive Stellar Clusters
- The Influence of the Inclination of the Accretion Disk in Black Hole X-Ray Binaries on the Energy Spectrum Characteristics
- Radiative Efficiency Enhancement by Electromagnetic Energy Dissipation in Strongly Magnetized Supercritical Accretion Flows around Kerr Black Holes
BibTeX
@misc{baj2026lowenergy,
title = {{Low-energy ring particle accretion as the origin of Pan's equatorial ridge}},
author = {Marco Baj and Iosto Fodde and Lucia Francesca Civati and Fabio Ferrari},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.03060},
eprint = {2609.03060},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.03060},
}
RIS
TY - UNPB
TI - Low-energy ring particle accretion as the origin of Pan's equatorial ridge
AU - Marco Baj
AU - Iosto Fodde
AU - Lucia Francesca Civati
AU - Fabio Ferrari
PY - 2026
DA - 2026/09/02
PB - arXiv
DO - 10.48550/arxiv.2609.03060
UR - https://arxiv.org/abs/2609.03060
AB - Pan is a small Saturnian satellite embedded within the planet's A ring, characterized by a polygonal equatorial ridge whose formation mechanism remains debated. A proposed explanation is ring particle accretion, yet previous simplified models could not address the ridge's complex multi-lobed morphology without ad hoc assumptions, and the cause of its latitudinal spread remains unclear. This work studies the complex low-energy dynamics around Pan to verify whether the ring particle accretion paths are consistent with the observed ridge morphology. We model particle motion using a CR3BP with spherical harmonic perturbations. Accretion paths are analyzed via grid-search simulations of trajectories transiting the L_1 and L_2 necks, using backward propagation from Pan's surface to determine the impacting material's original orbital characteristics. Asymmetric accreting particle populations, with inner-ring particles located closer to Pan and contributing more significantly to the impact flux, produce impact distributions that correlate with the ridge structure, especially for the Saturn-facing hemisphere. The ridge latitudinal spread is recovered only when the out-of-plane position and velocity of the accreting particles are strictly limited, consistent with accretion from a thin disk such as Saturn's rings. Furthermore, analysis of the particles' impact conditions revises the previously estimated minimum accretion duration downward by an order of magnitude, to 10^4 yr, while accreting material is shown to originate from ring particles that once populated the Encke Gap. By systematically sampling admissible low-energy trajectories near Pan, our grid-search approach resolves the complex accretion dynamics that previous simplified narrow-stream models do not capture, revealing that the ridge's main morphological features emerge naturally from the local low-energy dynamical environment.
ER -