Internal, thermal & magnetic states of Super-Earths
Updated: Mar 11, 2019
New study paints a new picture for the internal states of extrasolar terrestrial-like planets and their habitability.
Ascertaining planetary structure, evolution and habitability require better understanding of key internal geophysical and geochemical processes, which drive the planetary geochemical differentiation, internal composition, core sizes and heat budgets. All of which depend on the behavior of planetary constituent materials, particularly silicates and Iron, at extreme conditions. New advances in laboratory high-pressure experiments on iron’s and silicates’ compressible, melting and transport properties are providing new constraints that demand a reassessment of super-Earths’ thermal and magnetic evolution models.
Any complete picture of planetary internal composition, evolution and formation scenarios require better understanding of the behavior of their constituent materials at extreme conditions.
We reveal that for planets more massive than 3 ME, a thick layer of deep magma oceans surrounding a solid iron cores will develop. We then carefully assess the power requirements required to maintain the convective state of these cores, and show that the drastic rise in the conductive losses along the CMB will dominate the heat flux in the more massive planets, driving their cores into a subadiabatic and non-convective state. Absence substantial intrinsic heat sources, the cessation of convection that will consequently shut down the dynamo action in their cores. Our results lend support to the recently proposed concept of “super habitability”, employed to describe terrestrial-like planets with enhanced characteristics amenable to their habitability (Heller & Armstrong 2014). We have shown that it most likely extends only up to ~ 4 ME. Beyond which, a new paradigm that describes the suitability of carbon-based life forms on more massive rocky planets might be needed. We believe our work will make a very valuable contribution to ApJ wide audience.