Rivoldini, Attilio ; Tosi, Nicola ; Lécaille, Manon ; Van Hoolst, Tim ; Trinh, Anthony ; Baland, Rose-Marie ; Yseboodt, Marie ; Xiao, Haifeng

Talk presented at 46th COSPAR Scientific Assembly 2026, Florence, Italy on 2026-08-04

Abstract: Interior structure inferences of Mercury based on geodesy data can be strongly affected by prior assumptions about the detailed thermal structure of the core. In particular, the presence of a conductive, upper core thermally stratified layer (CTSL) is often neglected, although it directly affects the temperature profile of the core and, as a result, core composition and inner core radius inferences. The upper CTSL is a key ingredient in numerical dynamo simulations that are able to explain important features of Mercury’s magnetic field. Additional support for a CTSL layer also follows from thermal evolution studies using constraints on dynamo action in the core. In this study, we assess how core composition assumptions, the present-day thermal state, and theCTSLaffectMercury’sannuallibrationamplitude,long-periodlibration,obliquity,andtidal Love numbers. To determine the present-day thermal state, we use results from whole-planet thermal evolution simulations that are consistent with assumptions on core composition and are constrained by crustal thickness and past and present dynamo activity. We also investigate the effects of internal couplings and dynamical shape of the libration and obliquity.

Funding: 3PRODPLANINT/3PRODPLANINT/3PRODPLANINT