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Project Progress

Deputy PI Jonathan Lunine in conjunction with colleague Julie Castillo-Rogez last year demonstrated that the moment of inertia of Titan could be explained with a hydrated silicate core. This model became even more promising with indications that to-be published gravity data on Titan suggests an internal compressibility possibly larger than what an internal ammonia-water ocean under a thin crust could provide. This motivated Lunine to further investigate, again in conjunction with Castillo-Rogez, how such a hydrated silicate model could work, in particular, how to slow the onset of the dehydrate by leaching radioactive elements from the core into the ocean early on. The results, presented at the 2011 DPS meeting (joint with EPSC) in France in October, included a plausible mechanism for leaching, solubility studies, and an inventory of the decay products showing that the outgassed argon-40 is larger than but consistent with that observed to be present in Titan’s atmosphere. The work also provides a mechanism for reinitiating geologic activity on Titan during the last ½-1 billion years of its history, consistent with impact crater counting and recent isotopic studies from Cassini (reported at the same DPS meeting). Indeed, the mechanism of renewed geologic activity involves warm water destabilizing methane clathrate to release methane, and possibly delaminate ethane clathrate from the base of the crust to sequester it in the deep interior.