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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[53.08] Episodic outgassing as the origin of atmospheric methane on Titan

G. Tobie (U. Nantes, France), J. I. Lunine (U. Arizona), C. Sotin (U. Nantes, France)

Titan is the only moon of the solar system with a massive atmosphere mainly composed of nitrogen (~96 (~3 solar-ultraviolet-driven chemistry leads to a complex suite of organic molecules. Moreover, it would remove the present-day atmospheric inventory in a time span of a few tens of millions of years, if no reservoir resupplies it in a continuous fashion over geologic time. The first Cassini-Huygens observations militate against the presence of extensive exposures of liquid reservoirs, raising anew the issue of the source –if any- of geologically persistent atmospheric methane. However, these observations also suggest widespread outgassing and “cryo” (water-ammonia-based) volcanism. Here we demonstrate that methane stored in form of clathrate hydrate within the interior could have outgassed episodically over Titan’s history. We expect past intensive resurfacing and recent outgassing induced by thermal plumes in the outer icy layer to resupply methane against photodestruction, and thus to maintain the atmospheric abundance at or above a few percent. We will discuss how recent Cassini-Huygens observations can be understood in the framework of our model.

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