Saturn's Atmosphere and rings: A Recent Assessment Using Infrared Imaging
Abstract
For the past several years, a program devoted to understanding the Saturn system prior to the arrival of the Cassini spacecraft has used thermal infrared imaging to define the variability of temperature, cloud properties, and minor constituents in the atmosphere, together with thermal properties of the ring system. This resarch, sponsored by NASA programs at the Infared Telescope Facility and the W. M. Keck Observatory on Mauna Kea, Hawaii, has used images at wavelengths between 5.2 and 24.3 μ m. Thermal features have been noted which change with time, particularly in Saturn's south polar region. Upper stratospheric temperatures are distincly higher at latitudes poleward of 83oS; this is also true of the lower stratosphere/upper troposphere where the region within 1o of the pole is paricularly warm. A series of alternating warm and cool axisymmetric bands characterizes the morphology of the tropospheric temperature field at ``midlatitudes'' from approximately 45o to 83oS. Zonal wave features are present in Saturn's upper troposphere, achieving particular prominence in a moderately warm band between approximately 35o and 45o S and in the warmest band between 25o and 25oS, planetocentric. The equatorial region (15oN to 15oS) is much cooler than the rest of the planet in both the troposphere and the stratosphere, with a slightly warmer band detectable in the upper stratosphere within 1--2o latitude of the equator. Besides the prominent zonal wave structure in Saturn's troposphere, the most prominent zonal features are those which are observable at 5.2 μ m, showing the optical thickness of clouds at the NH3 condensation level. Distinct brightening of the ring system is apparent as a function of placement in orbit, with the coolest portion of the rings being those in shadow behind the planet. Ring brightess as a function of distance from the planet generally follows the same qualitative trend of optical thickness as in the visible.
- Publication:
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AGU Spring Meeting Abstracts
- Pub Date:
- May 2004
- Bibcode:
- 2004AGUSM.P22A..05O
- Keywords:
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- 6265 Planetary rings;
- 6275 Saturn