Evaluation of Recent Measurements of Mercury’s Moments of Inertia and Tides Using a Comprehensive Markov Chain Monte Carlo Method

Recent estimates of Mercury’s rotational state yield different obliquity values, resulting in normalized polar moment of inertia values of either 0.333 or 0.346. In addition, recent measurements of Mercury’s tidal response, as expressed by its Love number k2, are higher than previously reported. These different measurements have implications for our understanding of Mercury’s interior structure. We perform a comprehensive analysis of models of Mercury’s interior structure using a Markov Chain Monte Carlo approach, where we explore models that satisfy the various measurements of moments of inertia and mean density. In addition, we explore models that either have Mercury’s tidal response as a measurement or predict its tidal response. We find that models that match the lower polar moment value also fit or predict the recent, higher Love number. Models that match the higher polar moments predict Love numbers even higher than current estimates. For the resulting interior structure models, we find a wide range of viscosities at the core–mantle boundary, including low values that could be consistent with the presence of partial melt, with higher viscosities also equally allowed in our models. Despite the possibility of low viscosities, our results do not show a preference for particularly high temperatures at the core– mantle boundary. Our results include predicted values for the pressure and temperature of Mercury’s core, and the displacement Love numbers