With its high bulk density, large liquid core, active magnetic field and heterogeneous surface, Mercury is an endmember planet in the Solar System with unique and still unexplained characteristics. The NASA mission MESSENGER, which orbited Mercury from 2011 until 2015, revolutionized our understanding of the innermost planet. Yet, it left a number of key questions unanswered, including how to disclose the link between the planet’s volcanic surface, the evolution of the deep interior and its present-day structure. The ESA-JAXA mission BepiColombo launched in 2018 will orbit Mercury from the late 2025 with the main scientific objectives of understanding “the internal structure and physical characteristics and the surface composition and evolution” of Mercury.
Thermal models of Mercury’s evolution have been successful at explaining important global constraints such as the net amount of radial contraction, thickness of the crust, and history of magnetic field generation. Critically, all such state-of-the-art models do this whilst assuming a homogeneous mantle composition. However, spectral measurements of the MESSENGER spacecraft provide abundant evidence of compositional heterogeneity in Mercury’s igneous surface and crust. These data, when combined with melting experiments at conditions of Mercury’s interior, indicate that the mantle is significantly more structured than geophysical models currently consider, possibly preserving traces of its formation from a crystallizing magma ocean.
In this project, we intend to develop petrological and geodynamic models linking Mercury’s surface and deep interior. By combining experiments, thermodynamic and geophysical modeling, we will develop a new paradigm for Mercury’s interior evolution, the first that is faithful to each of the geophysical, petrological, and geochemical constraints we have for the planet. This new paradigm will be central to interpreting the wealth of data that will come from the BepiColombo mission.