Variations in planetary convection via the effect of climate on damage

The generation of plate tectonics on Earth and its absence on the other terrestrial planets (especially Venus) remains a significant conundrum in geophysics. We propose a model for the generation of plate tectonics that suggests an important interaction between a planet's climate and its lithospheric damage behavior; and thus provides a simple explanation for the tectonic difference between Earth and Venus. We propose that high surface temperatures will lead to higher healing rates (e.g. grain growth) in the lithosphere that will act to suppress localization, plate boundary formation, and subduction. This leads to episodic or stagnant lid convection on Venus because of its hotter climate. In contrast, Earth's cooler climate promotes damage and plate boundary formation. The damage rheology presented in this paper attempts to describe the evolution of grain size by allowing for grain reduction via deformational work input and grain growth via surface tension- driven coarsening. We present results from convection simulations and a simple "drip-instability" model to test our hypothesis. The results suggest the feasibility of our proposed hypothesis that the influence of climate on damage may control the mode of tectonics on a planet.