The Origin and Evolution of Saturn, with Exoplanet Perspective

TL;DR

This paper reviews the origin and evolution of Saturn, emphasizing core accretion, and compares it with exoplanet data to understand planetary formation processes.

Contribution

It provides a comprehensive synthesis of observational and theoretical insights into Saturn's formation, including exoplanet perspectives and volatile enrichment mechanisms.

Findings

Core accretion is favored for Saturn's formation.

Saturn's C/H ratio is super-solar, twice that of Jupiter.

Volatile delivery mechanisms are key to heavy element enrichment.

Abstract

Saturn formed beyond the snow line in the primordial solar nebula that made it possible for it to accrete a large mass. Disk instability and core accretion models have been proposed for Saturn's formation, but core accretion is favored on the basis of its volatile abundances, internal structure, hydrodynamic models, chemical characteristics of protoplanetary disk, etc. The observed frequency, properties and models of exoplanets provide additional supporting evidence for core accretion. The heavy elements with mass greater than 4He make up the core of Saturn, but are presently poorly constrained, except for carbon. The C/H ratio is super-solar, and twice that in Jupiter. The enrichment of carbon and other heavy elements in Saturn and Jupiter requires special delivery mechanisms for volatiles to these planets. In this chapter we will review our current understanding of the origin and evolution of Saturn and its atmosphere, using a multi-faceted approach that combines diverse sets of observations on volatile composition and abundances, relevant properties of the moons and rings, comparison with the other gas giant planet, Jupiter, analogies to the extrasolar giant planets, as well as pertinent theoretical models.