EPSC Abstracts Vol. 13, EPSC-DPS2019-488-4, 2019 EPSC-DPS Joint Meeting 2019 c Author(s) 2019. CC Attribution 4.0 license. Rigid nutations of Mars Rose-Marie Baland, Marie Yseboodt, Sébastien Le Maistre, Attilio Rivoldini, Marie-Julie Péters, Tim Van Hoolst and Véronique Dehant Royal Observatory of Belgium, Ringlaan 3, B-1180 Brussels, Belgium (
[email protected]). Abstract 2. Comparison between existing rigid nutation models The presence of a liquid core can amplify the nuta- tions of Mars. We compute accurate series for the nu- Reasenberg and King (1979) [9] computed the Solar tation of a rigid Mars, which are required to avoid in- torque on Mars as evolving on a unperturbed precess- troducing bias in the determination of Mars core char- ing elliptic orbit. They obtained the main nutation acteristics from the future nutation measurements with terms for the motion of the axis of figure in space. the RISE (Rotation and Interior Structure Experiment, These series are currently used to define the rotation onboard InSight) and LaRa (Lander Radioscience, on- model of Mars and to analyse radio-science data (e.g. board ExoMars2020) radioscience experiments. [12, 13]), but are wrongly taken as equivalent to the angular momentum axis series. As the difference in orientation between the figure and angular momentum 1. Context axes is a few mas, following this approach could lead to large bias in the core characteristics determination. The RISE and LaRa radioscience experiments will de- termine the rotation (length-of-day variations, polar 0.6 5 0.4 motion, and precession/nutation) of Mars [1, 2].