Planetesimals and Satellitesimals: Formation of the Satellite Systems

TL;DR

This paper explores the formation of regular and irregular satellite systems around giant planets, emphasizing the physical processes in circumplanetary disks and the implications of planetesimal evolution for satellite origins.

Contribution

It presents a unified framework for understanding the origin of regular satellites of Jupiter and Saturn, linking planetesimal evolution to satellite formation in gaseous disks.

Findings

Regular satellites share common properties indicating an ordered formation process.

Mass ratios and compositions of satellites suggest specific accretion mechanisms.

Irregular satellites have distinct origins, reflecting different capture processes.

Abstract

The origin of the regular satellites ties directly to planetary formation in that the satellites form in gas and dust disks around the giant planets and may be viewed as mini-solar systems, involving a number of closely related underlying physical processes. The regular satellites of Jupiter and Saturn share a number of remarkable similarities that taken together make a compelling case for a deep-seated order and structure governing their origin. Furthermore, the similarities in the mass ratio of the largest satellites to their primaries, the specific angular momenta, and the bulk compositions of the two satellite systems are significant and in need of explanation. Yet, the differences are also striking. We advance a common framework for the origin of the regular satellites of Jupiter and Saturn and discuss the accretion of satellites in gaseous, circumplanetary disks. Following giant planet formation, planetesimals in the planet's feeding zone undergo a brief period of intense collisional grinding. Mass delivery to the circumplanetary disk via ablation of planetesimal fragments has implications for a host of satellite observations, tying the history of planetesimals to that of satellitesimals and ultimately that of the satellites themselves. By contrast, irregular satellites are objects captured during the final stages of planetary formation or the early evolution of the Solar System; their distinct origin is reflected in their physical properties, which has implications for the subsequent evolution of the satellites systems.