Temporally transitional mantle convection: Implications for Mars

摘要

The thermal evolution of terrestrial planets such as Earth, Mars, and Venus is strongly dominated by the convective processes in the planet's silicate mantle. The actual style of convection controls the efficiency of heat transport and thus the cooling behavior of the whole planet. In the present study we investigate the heat transport properties of variable viscosity convection, focusing on the temporally transitional behavior discovered recently. While the difference of the newly found convective regime to the already known stagnant lid and episodic behavior has been elaborated in our previous study, the present work investigates the applicability of the observed intermittent behavior to the thermal evolution of terrestrial planets. A 3-D numerical mantle convection code is applied and calculations are carried out in the parameter range for which the temporally transitional behavior has been found. Using the described approach, it is possible to investigate the transition from a (temporarily) mobilized to a stagnant surface in a fluid dynamically consistent manner. While such a scenario has been suggested for Mars' early history, it has so far been investigated only by means of parameterized convection models. We show that the sporadic surface mobilization events may indeed occur on time scales relevant for Mars. In order to assess their influence on the subsequent thermal evolution of planetary bodies, an internal heating of the mantle and a secular cooling of the core are additionally taken into account. The obtained results are compared to the findings of thermal evolution studies employing parameterized convection models. We show that the thermal consequences of a temporal transition from a mobile to a stagnant surface are indeed correctly described by parameterized models as done in previous studies.