Abstract
Plate tectonics is largely responsible for material and heat circulation in Earth, but for unknown reasons it does not exist on Venus. The strength of planetary materials is a key control on plate tectonics because physical properties, such as temperature, pressure, stress, and chemical composition, result in strong rheological layering and convection in planetary interiors. Our deformation experiments show that crustal plagioclase is much weaker than mantle olivine at conditions corresponding to the Moho in Venus. Consequently, this strength contrast may produce a mechanical decoupling between the Venusian crust and interior mantle convection. One-dimensional numerical modeling using our experimental data confirms that this large strength contrast at the Moho impedes the surface motion of the Venusian crust and, as such, is an important factor in explaining the absence of plate tectonics on Venus.
Highlights
Plate tectonics is largely responsible for material and heat circulation in Earth, but for unknown reasons it does not exist on Venus
We carried out laboratory deformation experiments to constrain the nature of rheological layering across the Moho, and we discuss how this may explain the absence of plate tectonics on Venus
Rheological structure can be inferred from flow laws that represent the strength of solids, which are dependent on strain rate, temperature, and chemical composition[10,11]
Summary
Plate tectonics is largely responsible for material and heat circulation in Earth, but for unknown reasons it does not exist on Venus. This strength contrast may produce a mechanical decoupling between the Venusian crust and interior mantle convection. The large viscosity contrast between a planetary surface and mantle interior is a key factor for stagnant-lid convection, as when the planetary surface is stiff and sluggish as compared with the planetary interior, mantle convection can only occur beneath the lithosphere[5] In these modeling studies, rheological structure has been shown to play an important role in the evolution of Venus. Mackwell et al.[8] determined the flow law for diabase using rock deformation experiments These results, when applied to rheological structures in Venus, suggest that a large strength contrast exists between its crust and mantle. In the Peierls mechanism, the strain rate is exponentially proportional to applied stress as follows: e_~As2 exp
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