Physics
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agufm.p23c..02b&link_type=abstract
American Geophysical Union, Fall Meeting 2007, abstract #P23C-02
Physics
5700 Planetary Sciences: Fluid Planets, 5704 Atmospheres (0343, 1060), 5739 Meteorology (3346), 5754 Polar Regions, 6275 Saturn
Scientific paper
We present new imagery and quantitative results for wind and cloud structures in the south polar region of Saturn, obtained by Cassini/VIMS. A hurricane-like vortex feature is well observed in images obtained on October 11, 2006 and May 11, 2007, with a deep "eye" of cloud-free skies extending about 1 bar deeper than the surrounding ring of clouds. Winds measured in both reflected sunlight and in thermal radiation show comparable speeds throughout the region, suggesting little vertical wind shear over the 0.5-3-bar altitude range. Discrete clouds at 88 degrees S. planetographic latitude observed near the 0.5-2-bar level whip around the pole at speeds approaching 200 m/s. At greater latitudes, near the "eye" of the system, winds are much slower: about 45 m/s at 89.5 degrees S. latitude. From 88 degrees to 76 degrees S. latitude, the zonal wind structure as a function of radius/latitude is close to that expected for flows which maintain constant angular momentum. The picture that emerges is that this system is a giant polar vortex, spanning more than 15,000 km in diameter and at least 40 km in depth. Two distinct types of reflective, discrete clouds are observed interspersed throughout the region: bright clouds at continuum wavelengths from 0.6 to 2.7 microns characterized in our preliminary modeling as having imaginary indices of refraction near 0.002 at 0.7 micron, and spectrally dark clouds with twice that value. This suggests that two types of discrete clouds, colored by two distinct chemical compositions, reside in the south polar region. This is perhaps indicative of upwellings of materials from two distinct altitude regions in the depths of the south pole.
Atreya Sushil K.
Baines Kevin Hays
Brown Harvey R.
Buratti Bonnie Jean
Clark Roger Nelson
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