Herschel Temporal Monitoring Observations Of H2O In Saturn's Hot Stratospheric Vortex Between 2011 And 2012
Résumé
The planetary-scale storm that perturbed Saturn's seasonal cycle in its northern hemisphere in 2010-2011 has left a hot stratospheric vortex at 40∘N. This large vortex is still observable as of mid-2012. Cassini and ground-based observations have shown that the temperature and the chemistry of hydrocarbons have been perturbed in the vortex. We have observed Saturn when the vortex was visible with the Herschel Space Observatory in July 2011, February and July 2012 to map H2O at 66 and 67 microns and CH4 at 120 microns with the PACS instrument and CH4 at 159 microns with the HIFI instrument. We use the CH4 maps as a temperature probe and the H2O maps to check if the chemistry of oxygen compounds has also been perturbed by the vortex. In this paper, we will present the observations and their analysis to illustrate the temporal evolution of the abundance of H2O in the vortex. For instance, we inferred an increase by a factor of 30-100 of the H2O column in the vortex with Herschel/PACS in July 2011 in a preliminary analysis. T. Cavalié is supported by funding from CNES.