Steinbrügge1, Gregor ; Dumberry, Mathieu ; Rivoldini, Attilio ; Schubert, Gerald ; Cao, Hao ; Schroeder, Dustin ; Soderlund, Krista Marie

Talk presented at AGU Fall Meeting 2021, New Orleans, online on 2021-12-14

Abstract: The present-day structure and dynamics of a planetary body represent a snapshot in its evolutionary history, with constraints on earlier epochs provided, for example, by remanent crustal magnetization and global contraction estimates [1]. We have constructed thermal evolution models for Mercury that are consistent with its present-day interior structure as inferred from geodetic measurements. The interior structure models follow the methodology presented in our earlier work [2] and are evolved backwards in time from a set of plausible present-day configurations using an imposed cooling rate. We assume an iron core with silicon and sulfur as its dominant light elements and use equations of state for Fe-S and Fe-Si derived from recent laboratory measurements [3]. We use adiabatic core temperatures below a thermally stratified upper layer and account for the presence of iron-rich snow layers [4]. As Mercury’s structure is evolved, we monitor the location and extent of the snow layers, the core-mantle boundary (CMB) temperature, and the evolution of planetary radius. When exploring the multiple evolutionary paths, the modeled global contraction is compared with measured values from Mercury’s geologic record [5,6]. The CMB temperature is used as a proxy for the generation of partial melt in the mantle and ultimately of Mercury’s volcanic history. We subsequently investigate how secular cooling affects the formation of iron-rich snow layers and the growth of a solid inner core, both of which are major buoyancy sources to drive Mercury’s core dynamo. In future work, we plan to implement these structural models in 3D numerical dynamo simulations to investigate the evolution of its magnetic field strength and morphology.

Keyword(s): Mercury, thermal evolution, core, Fe-S-Si
Funding: 3PRODPLANINT/3PRODPLANINT/3PRODPLANINT