Phase Separation in Giant Planets: Inhomogeneous Evolution of Saturn

Astrophysics, abstract
astro-ph/0305031

From: Jonathan J. Fortney [view email]

Date: Thu, 1 May 2003 23:20:34 GMT   (270kb)

Authors:
Jonathan J. Fortney,
William B. Hubbard (Lunar and Planetary Laboratory, University of Arizona)

Comments: 33 pages, Accepted to Icarus

We present the first models of Jupiter and Saturn to couple their evolution
to both a radiative-atmosphere grid and to high-pressure phase diagrams of
hydrogen with helium and other admixtures. We find that prior calculated phase
diagrams in which Saturn’s interior reaches a region of predicted helium
immiscibility do not allow enough energy release to prolong Saturn’s cooling to
its known age and effective temperature. We explore modifications to published
phase diagrams that would lead to greater energy release, and propose a
modified H-He phase diagram that is physically reasonable, leads to the correct
extension of Saturn’s cooling, and predicts an atmospheric helium mass fraction
Y_atmos = 0.185, in agreement with recent estimates. We also explore the
possibility of internal separation of elements heavier than helium, and find
that, alternatively, such separation could prolong Saturn’s cooling to its
known age and effective temperature under a realistic phase diagram and heavy
element abundance (in which case Saturn’s Y_atmos would be solar but heavier
elements would be depleted). In none of these scenarios does Jupiter’s interior
evolve to any region of helium or heavy-element immiscibility: Jupiter evolves
homogeneously to the present day. We discuss the implications of our
calculations for Saturn’s primordial core mass.

References and citations for this submission:

SLAC-SPIRES HEP (refers to ,
cited by, arXiv reformatted);

CiteBase (autonomous citation navigation and analysis)