37th DPS Meeting, 4-9 September 2005
Session 53 Titan III
Oral, Thursday, September 8, 2005, 4:20-6:00pm, Music Concert Hall

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[53.07] Titan's Methane Monsoon : Evidence of Catastrophic Hydrology from Cassini RADAR

R. D. Lorenz (LPL, U. Arizona), Cassini RADAR Team

Radar imagery from the October 2004 TA encounter (1) indicated a number of bright, narrow, sinuous features that might be cracks or canyons - two of these appeared to connect to the apices of triangular radar-bright striated features that may be alluvial fans rendered radar-bright by wavelength-scale (>2cm) cobbles or boulders. The findings of the Huygens probe seem to support the idea of pluvial and fluvial activity on Titan. The February 2005 T3 encounter provided radar imagery of another region with two areas of dendritic networks of bright sinuous features, one being a remarkable collection of apparently braided channels draining into a radar-bright plain. We present analysis of the topological properties (branching ratios, tortuosity etc.) of these networks and channels, supporting an origin via erosion by heavy rainfall on a relatively uncohesive terrain, and present some terrestrial analogs.

We consider these observations in the context of a paradigm for Titan (2,3,4) reminiscent of the hydrology of the US desert southwest, where long droughts are punctuated by catastrophic downpours. Even though the annual average rainfall is modest (energetically limited to ~1cm/yr (3)) pluvial/fluvial erosion is a major agent of geomorphological change. Although perhaps climatologically inaccurate, the term ``Methane Monsoon" coined by Arthur C. Clarke (5) is an evocative name for the paradigm.

References (1) C. Elachi et al., Science, 308, 970-974, 2005. (2) R. D. Lorenz, Science, 290, 467-468, 2000. (3) R. D. Lorenz and J. Mitton, Lifting Titan's Veil, Cambridge University Press, 2002. (4) R. D. Lorenz et al., Geophysical Review Letters, 32, L01201, 2005 (5). A. C. Clarke, Imperial Earth, , Victor Gollancz, London, 1975

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