Dynamics and thermal evolution of icy moons' interiors: experimental and numerical approaches

Basic data for this project

Description

The icy moons of giant planets (e.g. Titan, Enceladus, Callisto, Ganymede, Europa) are remarkable in their diversity and distinct evolutionary paths. Their unique signatures of past and present activity, including plausible active tectonic surfaces and habitable subsurface oceans, challenge our understanding of planetary formation and evolution. Despite close-up monitoring by past planetary missions, a number of key questions around the internal structure and thermal state of icy moons remain unanswered: How can a global liquid layer survive beneath the icy crust? What is the effect of anti-freeze impurities in the crystallization of primordial oceans and the dynamics of ice layers? What radial models explain best the available geophysical observation? The ability of current geodynamic models to resolve the information encoded in the spacecraft data is however largely limited by the lack of data on the properties of icy materials at relevant conditions. The project NEVIS is thus designed to overcome these limitations and to address the above key science questions through an interdisciplinary approach combining experimental and theoretical studies of icy materials and numerical modelling of thermal convection. NEVIS will be conducted in the frame of two PhD projects, one experimental and one numerical, and its success relies on the expertise of mineral physicists and geodynamicists in Germany and Taiwan. First, we will employ unique spectroscopic techniques, only available at the host institutions (Raman/Brillouin/Time-domain Thermo-reflectivity TDTR), and ab initio simulations to determine the thermodynamic (e.g. phase diagram, density, liquidus curve) and transport (thermal conductivity) properties of icy phases in the ternary H2O-NH3-NaCl system, which is a proxy for the chemistry of primordial oceans. We will then conduct series of numerical simulations of thermo-chemical convection in the stagnant lid regime to study the evolution of a basal layer of differentiated material at the bottom of a water ice shell using StagYY, a state-of-the-art code of convection. Further, we will combine results from the numerical simulations with the new data on icy materials in classical parameterized convection methods to determine the radial structure and thermal history of large icy moons, and the dynamics of their outer ice layers. A major outcome here will be radial models with unprecedented ability to interpret the geophysical observations. The expected results are thus critical to the (re)interpretation of data from past, current and upcoming space missions and to define future exploration strategies.