Quantifying Mercury's tidal response: A framework for understanding planetary interiors

Mercury's unique orbital dynamics, influenced by its proximity to the Sun and high eccentricity, lead to periodic variations in tidal forces and surface temperature patterns. The tidal Love numbers (TLNs), which characterize the planet's deformation and gravitational field changes, are highly sensitive to key internal parameters such as core size, mantle composition and rheology, and the presence of lateral and vertical heterogeneities e.g., [1-5]. Mercury's TLNs thus provide a quantitative framework for understanding how its internal structure responds to tidal forces. In this study, we systematically investigate how variations in these internal parameters affect Mercury's TLNs. We use numerical models to simulate the tidal response of the planet, taking into account a wide range of geophysical and thermodynamic conditions. In particular, we investigate the effects of core-mantle interactions, variations in mantle viscosity and temperature, and potential anisotropies within the lithosphere. Our results show that TLNs are particularly influenced by the size and state of the core, the thermal gradient across the mantle, and the degree of lateral heterogeneity within the inner layers. To validate and refine our models, we will integrate these results with observational constraints such as Mercury's mean density, moment of inertia, and surface deformation data e.g., [1, 6]. This study will provide important insights for interpreting future high-precision measurements from the BepiColombo mission [7]. By linking TLNs to Mercury's internal parameters, we aim to develop a robust framework for constraining the planet's internal structure, providing a deeper understanding of its geodynamic evolution and its significance in the broader context of the formation and evolution of terrestrial planets.

References:

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[4] Steinbrügge et al., 2018. Journal of Geophysical Research: Planets, 123(10), 2760-2772.

[5] Rivoldini et al., 2009. Icarus, 201(1), 12-30.

[6] Genova et al., (2019), Geophysical Research Letters, 46(7), 3625-3633.

[7] Hussmann and Stark, (2020), The European Physical Journal Special Topics, 229, 1379-1389.