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

Abstract

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/m² 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.