Rotational bulge and one plume convection pattern: Influence on Martian true polar wander |
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| Authors: | Hlne Rouby Marianne Greff-Lefftz Jean Besse |
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| Institution: | aInstitut de Physique du Globe de Paris, Laboratoire de Géomagnétisme et Paléomagnétisme, Boîte 89 - 4 place Jussieu - 75252 Paris Cedex 05, France |
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| Abstract: | Motion of the entire solid planet with respect to its spin axis have been proposed on Mars. This movement is known as True Polar Wander (TPW). According to the conservation of angular momentum with no external torque, on geological time scales the axis of maximum inertia of a planet is aligned with the rotation axis. Then rearrangement of masses within the mantle disturbs the planet's inertia and induces TPW. The convection pattern on Mars is possibly controlled by a sequence of single plumes originating from the core-mantle boundary. Using a homogeneous model of the martian mantle and modelling the plume as a sphere, we calculate the inertial tensor perturbations caused by the plume mass anomaly. We investigate the stabilizing influence of the remnant rotational bulge due to the lithosphere elasticity on these perturbations. It appears that, during early martian history, the elastic lithosphere was thin enough to allow its fractures under the inertia perturbations induced by a hot plume. Consequently, the lithosphere's behaviour became effectively viscoelastic and the plume could induce large TPW. We conclude that one plume convection pattern should have greatly influenced the rotation pole behaviour during early Mars history: around 4 Gyr ago, Mars already could have experienced two TPW events lasting possibly only a few million years each. We then compare our scenario with others already published in the literature. |
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| Keywords: | Mars TPW Dichotomy Tharsis Rotation Inertial interchange Rotational bulge |
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