Objectives

Understanding the mechanisms and chemistry in play in the deep Earth without direct rock samples is a strong motivation to study the physical properties and phase relations of materials constituting our planetary interior. In addition to geochemical and cosmochemical constraints, Mineral Physics brings strong insights on the nature of the deep Earth, by comparing the physical properties of geomaterials (silicates and iron alloys) and their Pressure/Temperature phase diagrams to observations such as seismic travel times. Thanks to decades of experiments, we can now describe a model of the chemistry and mineralogical structure of the deep Earth anchored to data and observations. Beyond Earth, understanding the chemical and mineralogical evolution of silicates and iron alloys is also relevant to characterize the current state of other Solar planets, such as Venus, but also Earth-like exoplanets, including their surface habitability. Processes that formed the Earth structure as we see it today, Venus, and exoplanets, however, remain a challenge for the most advanced models. How to link pristine material as found in some meteorites to the present-day differentiated structure of our planet? Our project will provide mineral physics data to help at solving this question.

In this project, we will rely on a state-of-the-art combination of experiments and ab initio simulations that will allow us to characterize material properties at deep exoplanetary conditions and generate consistent datasets which can be used in planetary models.

Our project is divided into four complementary tasks:

Task 1

In task 1, we will investigate the phase diagram in the Fe-Si-Mg-O quaternary system (e.g. liquidus temperature and/or liquid/liquid immiscibility) to help deciding the effect of pressure, temperature, and chemistry on the planetary mantle to core ratio.

Task 2

In task 2, we will combine laser-shock study of liquid silicates, cold compression of glass proxy in the multi-megabar regime, and ab initio calculations, to evaluate the thermal expansion and compressibility of liquid silicates and help modeling the fate of the primordial magma ocean.

Task 3

Task 3 will study the mechanical properties of the solid portion of the mantle-based deformation experiments on model oxides and silicates in order to evaluate, in particular, the effect of differentiation and hence Fe-content on the planetary mantle mechanical properties.

Task 4

Finally, task 4 will combine these different results to model the time evolution of a magma ocean in the proto-Earth and young exoplanets.