37th DPS Meeting, 4-9 September 2005
Session 45 Titan's Atmosphere
Poster, Wednesday, September 7, 2005, 6:00-7:15pm, Music Recital Room

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[45.25] Geographic control of Titan's mid-latitude clouds

H.G. Roe, M.E. Brown, E.L. Schaller, A.H. Bouchez (Caltech), C.A. Trujillo (Gemini Observatory)

Observations of tropospheric clouds (1-6) and the recent Huygens images of channels show that Titan has an active methane hydrological cycle. Titan's south polar clouds are now well known (3-5) and thought to be driven by small seasonal variations in surface temperature (3). The recent discovery (6) and continued observations (7) of significant cloud activity at 40\circS latitude led to the suggestion that these mid-latitude clouds are the result of either seasonally evolving global circulation or surface geography (6). We report here further observations of Titan that clearly link the formation of the mid-latitude clouds to a region of Titan's surface centered at ~350\circW longitude, ~40\circS latitude. Analysis of the complete dataset does not support the earlier suggestion (6) that these clouds are a new phenomenon related to seasonal change. The strong link between geographic location and cloud formation along with the lack of evidence for seasonal change in the mid-latitude clouds leads to the conclusion that a geological mechanism is responsible for the formation of these clouds. We propose that geysers or cryovolcanism are sporadically active near ~350\circW longitude, ~40\circS latitude. The implied rate of volatile release would easily supply enough methane to balance the loss to photolytic chemistry in the upper atmosphere.

1.~Griffith, C.A., Owen, T., Miller, G.A., Geballe, T., Nature 395, 575-578 (1998). 2.~Griffith, C.A., Hall, J.L., Geballe, T.R., Science 290, 509-513 (2000). 3.~Brown, M.E., Bouchez, A.H., Griffith, C.A., Nature 420, 795-797 (2002). 4.~Roe, H.G., de Pater, I., Macintosh, B.A., McKay, C.P., ApJ 581, 1399-1406 (2002). 5.~Bouchez, A.H., Brown, M.E., ApJ 618, L53-L56 (2005). 6.~Roe, H.G., Bouchez, A.H., Trujillo, C.A., Schaller, E.L., Brown, M.E., ApJ 618, L49-L52 (2005). 7.~Porco, C.C., et al., Nature 434, 159-168 (2005).

HGR is supported by an NSF Astronomy & Astrophysics Postdoctoral Fellowship (NSF AST-0401559). ELS is supported by an NSF Graduate Research Fellowship. Additional support was provided by an NSF grant to MEB (NSF AST-0307929).

The author(s) of this abstract have provided an email address for comments about the abstract: hroe@gps.caltech.edu

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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.