Rivoldini, A. ; Morard, G. ; Antonageli, D. ; Van Hoolst, T. ; Le Maistre, S. ; Dehant, V.

Invited talk presented at JpGU Meeting 2021, Okayama, online on 2021-06-03

Abstract: Nutations are periodic changes in the orientation of the planet mainly due to the gravitational interaction with the Sun. The amplitude of the nutations dependents on a well known forcing and on the interior structure of Mars and in particular on the liquid core. One of the prime objectives of the RISE experiment on the ongoing InSight mission is to measure precisely the nutations of Mars and from the data infer the radius of its core and constrain its chemical composition. Sulfur is commonly considered to be the main light element in the core of Mars, but the amount required to match the core density inferred from geodesy data is in excess of 25wt%. This is significantly larger than what is expected from geochemical modeling. Another candidate light element that can dissolve appreciably in liquid iron-sulfur at Mars core conditions is oxygen. In this study, we build a new thermodynamic model of liquid iron-oxygen-sulfur to describe the thermoelastic properties of the core and investigate how the thermal structure of the core and its thermoelastic properties affect nutations.

Keyword(s): Mars, nutation, RISE, core, rotation
Funding: 3PRODPLANINT/3PRODPLANINT/3PRODPLANINT