Tethys: Lithospheric thickness and heat flux from flexurally supported topography at Ithaca Chasma

We have identified flexural uplift along the flanks of Tethys' Ithaca Chasma using Cassini stereo- derived topography. Modeling the topography as a broken elastic plate yields an effective elastic lithospheric thickness in the range of 5 - 7 km and, combined with the strength envelope of the lithosphere, a mechanical lithospheric thickness of 16 - 20 km. Surface heat fluxes are 18 - 30 mW/m(2) for adopted strain rates of 10(-17) - 10(-14) s(-1). These heat fluxes are more than 4 times higher than those calculated from thermal history models of Tethys and indicate a strongly enhanced local heat flux associated with the formation of Ithaca Chasma. We use crater- size frequency counts and a lunar- like impact chronology to fix the time of formation of Ithaca Chasma at 4 Ga from present- day. Ithaca Chasma predates the Odysseus basin and thus could not have been formed by this impact feature.