Is Titan's shape caused by its meteorology and carbon cycle?

Abstract

Titan's shape is characterized by a difference between the long equatorial radius and the polar radius that is several hundred meters larger than that predicted by the flattening due to its spin rate. The North polar region is covered by large mare filled with hydrocarbons, including ethane. Moreover global circulation models predict ethane precipitation on the polar areas. This study shows that the shape of Titan can be explained by the subsidence associated with the substitution of methane with ethane-rich liquids percolating into the crust which, as suggested by evolution models, may be composed of methane clathrate hydrates. Such substitutions have been observed in laboratory experiments. This process would provide an additional methane source as required for sustaining the presence of this constituent in Titan's atmosphere through its history. A 270m subsidence of the polar caps is explained by the circulation of 1.5 to 6 × 10 18 kg of ethane in the top three kilometers of an initially methane-clathrate crust. This process would have operated during the last 300-1200 Myr at the present ethane production rate. Copyright 2012 by the American Geophysical Union.