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arXiv · 2610.34081

Planetesimal Delivery to Giant Planet Circumplanetary Disks: Bulk Ice Enrichment and an Ice-rich Iapetus

Ignacio Mosqueira
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Abstract

The regular satellites of Jupiter and Saturn are substantially enriched in ice relative to the rock-rich solids of the outer Solar System. In addition, the satellites interior to Titan and distant Iapetus are icier than Titan itself. Collisional processes and subsequent migration can readily alter compositions deep in the planetary potential well, but producing a distant, ice-rich satellite with Iapetus's radius of about 700 km is a challenge \citep{mosqueira2026a}. We show that differential ablation and capture of icy and rocky fragments from differentiated outer Solar System bodies can explain the bulk Jovian and Kronian satellite ice enrichment and supply the substantial ice-rich inventory needed for Iapetus. For 1\,m--1\,km fragments with the canonical size-distribution index \(p=3.5\) and a source containing 30\% ice by mass, the fixed radial distance Saturn calculation deposits material with ice fractions of 0.66 (delivery of vapor-only rock) or 0.50 (with retained rock melt) at 20 Saturn radii and nearly pure ice at 60 Saturn radii. Following three-dimensional trajectories over repeated passages through the pressure-supported gas gives ice fractions of about 0.4 near 20 Saturn radii and 0.9 near 60 Saturn radii. The matching Jupiter calculation yields a similar bulk ice enrichment, with a corresponding compositional gradient across the Galilean satellite region. These delivery profiles supply ice-enriched material for satellite formation. Yet satellitesimal inward migration subsequently modifies the material incorporated into satellites and thus alters their bulk compositions. We briefly discuss the implications for the PDS~70 planetary system.

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Ignacio Mosqueira. 2026-10-25. Planetesimal Delivery to Giant Planet Circumplanetary Disks: Bulk Ice Enrichment and an Ice-rich Iapetus. https://arxiv.org/abs/2610.34081

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