Early asymmetric growth of planetary stagnant lids

Convection within planetary bodies is often modelled using a temperature-dependent rheology which, when cooled from the surface, naturally leads to formation of so-called stagnant lid at cold outer surface. However, for sufficiently large planets phase diagram describing partially molten system may depend significantly on pressure in addition temperature, leading significant variations solid fraction. The aggregate therefore exhibit dependence both temperature and pressure, hence marked depth thermal structure due convection. Here, we consider growth stability lid. We first characterise effect pressure- evolution symmetric, This analysis further suggests that lead an instability growing importantly, asymmetric growth. find most unstable mode longest wavelengths, discuss implications stagnant-lid convection surfaces bodies. In particular, possibility this has crustal dichotomy found Moon.