P218 The viscosity of Super-Earths and implications for their magnetic field generation Vlada Stamenković, Doris Breuer and Tilman Spohn Joint Planetary Interior Physics Research Group of The University of Münster and the IPR DLR Berlin

PROBLEM: We want to model the thermal evolution of Super-Earths! –Processes: Plate tectonics, Magnetic fields, etc But have only thermal properties, especially viscosity, for small pressures. Viscosity controls the thermal evolution of planets and depends on temperature T and pressure P! PRESSURE IS EXTREMELY IMPORTANT FOR SUPER-EARTHS AND HAS BEEN IGNORED SO FAR! P218

PROBLEM: We want to model the thermal evolution of Super-Earths! –Processes: Plate tectonics, Magnetic fields, etc But have only thermal properties, especially viscosity, for small pressures. Viscosity controls the thermal evolution of planets and depends on temperature T and pressure P! PRESSURE IS EXTREMELY IMPORTANT FOR SUPER-EARTHS AND HAS BEEN IGNORED SO FAR! THEREFORE: We include pressure dependence! & Implications for mantle convection and dynamos ! P218

RESULTS 1: Viscosity NOW WE GET: –Large mantle viscosities and increasing with depth (adiabate) Old New P218

RESULTS 2: NO convection Due to the large viscosity we get: –Super-Earths are not fully convecting planets! P218 NO CONVECTION

RESULTS 2: NO convection Due to the large viscosity we get: –Super-Earths are not fully convecting planets! P218 NO CONVECTION CONTRARY TO ALL OLDER MODELS, WHERE FULL CONVECTION ASSUMED !

RESULTS 3: NO magnetic fields? High viscosity and Low-lid thermally insulate the core There is not enough power Φ to drive the magnetic dynamo! P218 Earth Super-Earth B

Contact: Vlada Stamenkovic, P218 For detailed answers come to: