Mars interior structure models from tidal measurements

Besides the mean planetary density, obtained from the planet's mass and size, the polar moment of inertia (MOI) gives important constraints on the interior structure of a planet. Nevertheless, these constraints are not sufficient for precisely determining the state and size of the planet's core, nor do they provide strong constraints on mantle composition and temperature. On the other hand, the additional use of the latest estimates of mean crustal density and thickness and an assumed bulk Fe/Si ratio for Mars (e.g. chondritic with Fe/Si=1.7) can strongly reduce the set of interior models, which are parameterized in terms of core composition and size, and of mantle composition and temperature. Unfortunately, the origin of Mars and the value of the Martian Fe/Si bulk ratio are not well known. We therefore propose to complement the MOI and the mean density with the latest estimate of the tidal Love number k2 in order to better constrain the interior structure and composition. We consider spherically symmetric models of Mars, consisting of a crust parameterized by mean density and thickness, a mantle with different mineralogical compositions and temperature profiles, and a core parameterized by size, composition (Fe, Ni and FeS), and state (liquid, solid or both). For the presently known values, with their associated uncertainties, of the mean density, the MOI and the Love umber k2, we calculate sets of possible interior models in terms of the above arameterization and compute the bulk Fe/Si ratios.