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O. Forni (IAS-CNRS), C. Federico (Univ. Perugia), P. Cerroni (IAS-CNR)
The study of the Martian interior has recently drawn attention on the possible existence of the high pressure Spinel to Perovskite phase transition inside the planet. This transition is endothermic and tends to inhibit the convection especially in Mars where gravity and mantle thickness are smaller than in the Earth. Moreover the upper and lower mantle are characterised by different rheological properties and this may influence the thermal state of Mars.
We describe the results of convective models that incorporate visco\-sity contrasts between the upper and lower mantle taking into account the strong dependence of viscosity with temperature in both parts of the Martian mantle. We use a finite element method to solve convection models in a cylindrical geometry in presence of phase transitions. Knowing that in the Earth the lower mantle is more viscous than the upper mantle, we study in the case of Mars, viscosity ratios ranging from 1 to 100 in order to obtain informations on the convective plan-form as well as on the heat transport efficiency.