  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.
