Saturn

Temporal Evolution Of Water Abundance In Saturn’s Hot Vortex Of 2011-2013

By Keith Cowing

Status Report

astro-ph.EP

May 8, 2025

Filed under astro-ph.EP], atmosphere, Enceladus, Enceladus plumes, Saturn, Saturn's Great Storm of 2010, Spectroscopy, Water

Temporal Evolution Of Water Abundance In Saturn’s Hot Vortex Of 2011-2013 — Water line area maps expressed in units of µmˆ% of continuum. The four observation time windows are July 2011 at 67.09 µm, February 2012 at 66.44 and 67.09 µm, July-August 2012 at 66.44 and 67.09 µm, and January-February 2013 at 66.44 and 67.09 µm. Saturn’s 1-bar level is represented by the black ellipse, with the north pole facing upwards. A selection of iso-latitudes are plotted with grey lines. The rotation axis corresponds to the thin dashed black line. The beam spatial extent is illustrated by the circle in a dashed blue line. The black dots correspond to the central position of the spatial pixels. The position and extension of the beacon (see Table 3) at mid-observation time is represented with the thick dashed black lines. A cubic interpolation was applied to the data. — astro-ph.EP

Water vapour is delivered to Saturn’s stratosphere by Enceladus’ plumes and subsequent diffusion in the planet system. It is expected to condense into a haze in the middle stratosphere.

The hot stratospheric vortex (the `beacon’) that formed as an aftermath of Saturn’s Great Storm of 2010 significantly altered the temperature, composition, and circulation in Saturn’s northern stratosphere. Previous photochemical models suggested haze sublimation and vertical winds as processes likely to increase the water vapour column density in the beacon.

We aim to quantify the temporal evolution of stratospheric water vapour in the beacon during the storm. We mapped Saturn at 66.44 and 67.09 μm on seven occasions from July 2011 to February 2013 with the PACS instrument of the Herschel Space Observatory. The observations probe the millibar levels, at which the water condensation region was altered by the warmer temperatures in the beacon. Using radiative transfer modelling, we tested several empirical and physically based models to constrain the cause of the enhanced water emission found in the beacon.

The observations show an increased emission in the beacon that cannot be reproduced only accounting for the warmer temperatures. An additional source of water vapour is thus needed. We find a factor (7.5±1.6) increase in the water column in the beacon compared to pre-storm conditions using empirical models. Combining our results with a cloud formation model for July 2011, we evaluate the sublimation contribution to 45-85% of the extra column derived from the water emission increase in the beacon.

The observations confirm that the storm conditions enhanced the water abundance at the millibar levels because of haze sublimation and vertical winds in the beacon. Future work on the haze temporal evolution during the storm will help to better constrain the sublimation contribution over time.

Observations of the Temporal Evolution of Saturn’s stratosphere following the Great Storm of 2010-2011 I. Temporal evolution of the water abundance in Saturn’s hot vortex of 2011-2013

Camille Lefour, Thibault Cavalié, Helmut Feuchtgruber, Raphael Moreno, Leigh Fletcher, Thierry Fouchet, Emmanuel Lellouch, Erika Barth, Paul Hartogh

Comments: 26 pages, 16 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2505.02595 [astro-ph.EP] (or arXiv:2505.02595v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2505.02595
Focus to learn more
Submission history
From: Camille Lefour
[v1] Mon, 5 May 2025 12:00:45 UTC (42,385 KB)
https://arxiv.org/abs/2505.02595
Astrobiology,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

Follow on Twitter