GRAIN SIZE CONTROLLING PROCESSES WITHIN EUROPA’S ICE SHELL G. Tobie, P. Duval and C. Sotin
نویسندگان
چکیده
Introduction: Magnetic data gathered by the Galileo spacecraft [1] as well as images of the tectonically active surface [2,3] provide circumstantial evidence that a soft, probably liquid, layer may exist few kilometers to few tens beneath the cold icy surface of Europa. However, the thickness and the thermal state of the icy crust still remain poorly constrained. Uncertainties mainly results from our misunderstanding of ice rheology at low stresses relevant for both convective and tidal deformations [4]. Several laboratory studies and field data analysis indicate that the flow law for deviatoric stresses lower than 0.1 MPa is associated with a stress exponent of 2 and is grain-size sensitive [5,6]. These results can be questioned because of the long time needed to obtain reliable data. However, a clear indication of the decrease of the stress exponent (n<2) below 0.1 MPa is also found from the analysis of Earth's polar ice sheet field data [7].
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Coupled convection and tidal dissipation in Europa’s ice shell using non-Newtonian grain-size-sensitive (GSS) creep rheology
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