P218 The viscosity of Super-Earths and implications for their magnetic field generation Vlada...

P218The viscosity of Super-Earths and

implications for their magnetic field generation

Vlada Stamenković, Doris Breuer and Tilman SpohnJoint 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!

( , ) exp effE P VP T

RT

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!

*

( , ) exp effE P VP T

RT

THEREFORE:We include pressure dependence!

& Implications for mantle convection and dynamos!

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RESULTS 1: Viscosity

• NOW WE GET:– Large mantle viscosities and increasing with depth (adiabate)

Old

New

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RESULTS 2: NO convection

• Due to the large viscosity we get:– Super-Earths are not fully convecting planets!

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NO CONVECTION

RESULTS 2: NO convection

• Due to the large viscosity we get: – Super-Earths are not fully convecting planets!

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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!

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0(8 10 )Gyrs

Earth Super-Earth

0

B

• Contact:Vlada Stamenkovic,

Vlada.Stamenkovic@dlr.de

P218

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