戴夏飛 Frédéric Deschamps

Exploring Rocky Planets Interiors

My research activities address the dynamics, evolution, and structure of rocky planets and icy moons interiors, with a particular focus on the Earth's mantle. A central task of this work is to perform simulations of convection to understand the role played by key parameters, such as viscosity, on the flow pattern and on the heat and mass transfers through planetary mantles and ice shells. In the past few years, I used seismic attenuation data to show that the large anomalies in seismic shear-wave velocity observed by seismic tomography strong in the deep mantle are caused by both compositional and thermal changes. Still using seismic attenuation, I developed a method to constrain the temperature at the boundary between the Earth’s core and mantle (CMB). I modelled the topography at the CMB, and showed that it can be used as a test to decide the nature, purely thermal or thermo-chemical, of seismic anomalies observed in this region. I explored the impact of variations in thermal conductivity on mantle convection, a key result being that at the CMB heat may locally flow from the mantle to the core. This finding has considerable implications to understand the evolution of the Earth’s magnetic field. I built a thermal evolution model for Europa, a satellite of Jupiter, taking into account tidal dissipation within this body and showing that its outer ice shell thickness is in the range 15-45 km. This result reconciles estimates made from surface geology observations and numerical modeling. Still for Europa, I showed that pockets of molten ice can be generated close to the surface as long as the ice layer remains thinner than 40 km. Altogether these researches brought new insights on deep Earth and icy moons structures and evolutions. They further triggered or were used for new research works.