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E.L. Schaller, M.E. Brown, H.G. Roe (Caltech), A.H. Bouchez (Keck Observatory), C.A. Trujillo (Gemini Observatory)
Tropospheric clouds were consistently observed near Titan’s south pole from November 2001 through December 2004. Of 68 images taken on separate nights before December 2004 with our Keck, Gemini and Palomar adaptive optics observing programs, 66 had a cloud or clouds near the south pole. However, since December 2004, cloud activity has dropped off dramatically. Of the 28 images taken from December 2004 through March 2005, only one image showed even a small cloud near the pole. Our 14-inch telescope Titan monitoring campaign also shows no significant deviations from Titan’s nominal lightcurve from December 2004 to May 2005. These observations are also consistent with Cassini flyby images that show very limited to nonexistent south polar cloud activity in the TB through T5 flybys.
We suggest that seasonal change may be responsible for the observed breakup of the south polar cloud system. Titan southern summer solstice was in October 2002. The south pole ceased to be the area of maximum solar insolation in July 2005. Several authors (e.g. Brown et al. 2002, Tokano 2005) have predicted that convective cloud activity should move north as Titan moves away from southern summer solstice. The drop off we see in south polar cloud activity may be indicative of this seasonal variation.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.