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Boundary layer dynamics in planetary mantles: the effect of realistic rheology

Academic lead
Dr Andrew Walker (School of Earth and Environment)
Dr Chris Davies (School of Earth and Environment), Dr Daniel Ruprecht (School of Mechanical Engineering)
Project themes
Geophysical flows, Particulate flows, sediments & rheology

Convection in rocky or icy planetary mantles controls the long-term evolution of the terrestrial planets and many of the moons in the solar system. The style of mantle convection is intimately linked to planetary habitability: it determines whether surface material participates in the global-scale dynamics (as on Earth) or remains isolated (as on Venus) and also determines the viability of magnetic field generation in the liquid core. At first sight the fluid dynamics of mantle convection  appears quite simple with the Prandtl number, Pr=1024, implying that fluid motion is almost inertia-free and the Reynolds number, Re≪1, implying that flow is not turbulent (although it may be chaotic). These parameters can easily be reached in numerical models. The rich and complex dynamics exhibited by the terrestrial planets arise since the physical properties that characterise mantle material, and in particular the rheology, are enormously sensitive to small changes in temperature, pressure and composition. The nonlinear feedbacks between transport properties and flow dynamics are most prevalent in the upper and lower boundary mantle layers and it is the rheology in these regions that is largely responsible for the diversity of planetary behaviour and evolution.