DPS 34th Meeting, October 2002
Session 22. Titan
Oral, Chair(s): M.E. Brown and A. Coustenis, Wednesday, October 9, 2002, 10:10-10:30am and 11:00am-12:30pm, Ballroom

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[22.08] South polar clouds on Titan imaged with adaptive optics on the Gemini and Keck telescopes

H.G. Roe, I. de Pater (U.C.~Berkeley), B.A. Macintosh (IGPP/LLNL), C.P. McKay (NASA/ARC)

We report high spatial resolution narrowband imaging of Titan taken in December 2001 with adaptive optics on the Gemini North 8-meter and W.M.~Keck II 10-meter telescopes. The narrowband filters were chosen to selectively probe Titan's surface, troposphere, and stratosphere. The data we present have been processed minimally using only standard near-infrared reduction techniques (sky subtraction, flat-fielding, and bad-pixel masking). Images in the tropospheric-probing filters show a general brightening south of ~0\fdgS as well as discrete cloud features at far southern latitudes varying on the time scales of hours to days. In particular, over the period 18-21 December 2001 UT we observed the evolution of several features, including three discrete southern features (61\fdgS, 76\fdgS, and 85\fdgS) that vary in intensity over just 3 hours on 21 December 2001 UT. In our tropospheric probing filter the flux from the discrete cloud features represents 0.1-1.% of Titan's total flux and the derived area for each cloud is in the range of 104-105 km2, referenced to Titan's surface, making these cloud features apparently similar to those reported by Griffith (2000). Although Titan's global weather pattern almost certainly evolves on the timescale of years, our observations strongly suggest that the cloud features reported by Griffith \textit{et al.}\ (1998) and (2000) were in the southern polar region. We expect the current weather pattern to persist long enough that the Cassini mission should focus its initial Titan cloud observation plans on the southern polar region; due to the changing seasons on Titan, Cassini should look for clouds in the northern polar region later in its nominal mission.

HGR was funded by a NASA Ames Research Center GSRP fellowship.

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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.