The Gas Giant Evolutions of Jupiter and Saturn During the Cassini Era

Date

2014-12

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Abstract

There have been many significant shifts in the dynamics on Jupiter and Saturn during the Cassini era. This study explores observations from the Imaging Science Subsystem (ISS) on Cassini. This work conducted a global survey of Saturn’s vortices, which shows that there are significant variations in vortex activities across the globe. ISS images at different wavelengths also suggest complicated vertical structures for Saturn’s vortices. The study also addresses the comparative analysis between vortex activities on Jupiter and Saturn.

The long-term Cassini imaging also captured the eruption of a giant storm in Saturn’s NH in December 2010. With the unprecedented observational resources from the ground-based telescopes coupled with the Cassini spacecraft, some important characteristics of the dynamical and thermal structures of the giant storm have been previously studied. This study attempts to quantify any precursors to this storm and analyzes the ripple across Saturn’s dynamic atmosphere.

Primary results show a change in northern hemispheric vortex count on Saturn from the years 2008, 2010, 2011, 2012, to 2013 from 11±2, to 7±1, to 5±1, to 14±1 and 18±1, respectively. The giant storm mainly developed in the first half of 2011, and dissipated in August 2011 (Sayanagi et al., 2012; Sanchez-Lavega et al., 2012) even though its remnants had a lingering influence that lasted long after the storm subsided. Our analyses indicate there are correlations between the development of the 2010 giant storm and Saturn’s vortices. However, we cannot rule out the roles of Saturn’s seasonal cycle in the temporal variation of Saturn’s vortices during this time frame.

Jupiter’s two hemispheres have roughly the same number of vortices, which is different from Saturn where the SH has many more vortices than in the NH from 2004 – 2010. Variations are due to the different obliquities and hence different seasonal cycles between the two planets. The comparison also reveals that a correlation exists between the highest number of vortices and the easterly zonal velocity minima between Jupiter and Saturn. This suggests that atmospheric instabilities play a critical role in generating vortices on both planets.

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Keywords

Saturn, Atmopshere

Citation

Portions of this document appear in: Trammell, Harold Justin, Liming Li, Xun Jiang, Mark Smith, Sarah Hörst, and Ashwin Vasavada. "The global vortex analysis of Jupiter and Saturn based on Cassini Imaging Science Subsystem." Icarus 242 (2014): 122-129.