Saturn's internal structure and carbon enrichment

¹ Observatoire de Besançon, CNRS – UMR 6091, BP 1615, 25010 Besançon Cedex, France e-mail: Olivier.Mousis@obs-besancon.fr
² Physikalisches Institut, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland

Received: 19 September 2005
Accepted: 17 November 2005

Abstract

We use the clathrate hydrate trapping theory to calculate the enrichments in O, N, S, Xe, Ar and Kr compared to solar in Saturn's atmosphere. For this, we calibrate our calculations using two different carbon abundance determinations that cover the domain of measurements published in recent decades: one derived from the NASA Kuiper Airborne Observatory measurements and the other obtained from the Cassini spacecraft observations. We show that these two carbon abundances imply a different minimum heavy element content for Saturn. Using the Kuiper Airborne Observatory measurement for calibration, the amount of ices accreted by Saturn is found to be consistent with current interior models of this planet. On the other hand, using the Cassini measurement for calibration leads to an ice content in the planet's envelope that is higher than the one derived from the interior models. In this case, reconciling the interior models with the amount of C measured by the Cassini spacecraft requires that significant differential sedimentation of water and volatile species has taken place in Saturn's interior during its lifetime.