Saturn's Rings: Atmsopheric Effects of Ring Shadow, Ring Shine, and Thermal Emission
Abstract
Cassini explored for nearly a half Saturnian year. During this epoch, in addition to seasonal solar inclination changes, the ring shadow moved from the northern hemisphere to covering a large region of the southern hemisphere. The intensity of both ultraviolet and visible sunlight penetrating through the rings varied depending on Saturn's axial tilt relative to the Sun and the optical thickness of each ring system, i.e. the rings act like semi-transparent venetian blinds. This effect magnifies the seasonal effect of axial tilt alone acting to reduce or even turn off photochemistry and haze generation, an effect exhibited by the presence of a bluish northern atmosphere in 2004 and color change to blue in the southern hemisphere after equinox. We report on the impact of the oscillating ring shadow, seasonal axial tilt, and solar cycle, on photochemistry of hydrocarbons, ammonia, and phosphine in Saturn's stratosphere and upper troposphere. The impact on the abundance of long-lived photochemical products leading to haze formation and on disequilibrium species is explored. Data from Cassini's CIRS, UVIS, and VIMS datasets that provide constraints for hazes and molecular abundances.
In addition to visible light reflected from the rings, UV photons have also been shown to reflect from the rings. This acts to enhance photolysis on the sunlit hemisphere. We examine the impact of ultraviolet ring-shine on the photochemistry of the upper atmosphere. Lastly, we examine the impact of thermal ring photons on the heating of the hemisphere upon which they shine. The research described in this paper was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Copyright 2019 California Institute of Technology. Government sponsorship is acknowledged.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.P13B3511E
- Keywords:
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- 5704 Atmospheres;
- PLANETARY SCIENCES: FLUID PLANETS;
- 5729 Ionospheres;
- PLANETARY SCIENCES: FLUID PLANETS;
- 6255 Neptune;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS;
- 6293 Uranus;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS