Valentin André

Poste : Doctorant

Courriel : valentin.andre2@univ-nantes.fr

Localisation : Nantes - 133

Domaine(s) de recherche : Planètes et lunes

I am a PhD student working on the deep interior dynamics of medium-sized moons of the Outer Solar System, mainly Io and Europa. I focus on determining their internal structure, bulk chemical composition and their silicate mantle thermal evolution by coupling geophysical, geochemical and petrological numerical models.

Planetary objects of interest: Io, Europa, Triton

Main research activities:

Internal structure and bulk composition of Io and Europa (2024-2026):

In this study, we modeled the internal structure and composition of the refractory interior of the innermost Jovian satellites and made several predictions for the upcoming Europa Clipper mission. The joint study of both Io and Europa allows to narrow the range of possible composition of the two moons. Thanks to a Monte-Carlo (MCMC) approach constrained on the mass, radius and Moment-of-Inertia factor (MoI) of the bodies, we showed that:

• a significant amount of a low-density component taken here as carbon (graphite) is required in the silicate interior of Io and Europa in order to have Fe/Si & Mg/Si ratios consistent with the solar composition. The graphite content varies between 3-8 wt% for Io and 1-22 wt% for Europa.
• the transformation of the accreted organic matter into graphite due to the thermal evolution of Europa can release enough water to entirely form its present-day hydrosphere. Europa could have accreted from dry silicates, insoluble organic matter and no ice in the circumjovian disk.
• in order to match the mass and MoI of Europa, the graphite content as well as the metallic core radius have to be anti-correlated with the hydrosphere thickness. Independant measurements of both the MoI and hydrosphere thickness by Europa Clipper will put strong constraints on the carbon content and differentiation state of Europa.

This work was realized in the framework of the ANR OSSO-BUCO (led by Bruno Reynard, LGL Lyon) and the ERC PROMISES (led by Christophe Sotin, LPG) and was published online in the Icarus journal, August 2026.

Thermal evolution of Europa’s silicate mantle (2025-):

This study aims to determine the thermal evolution of the mantle using the 3D numerical tool OEDIPUS developed by Gaël Choblet (LPG) that solves for thermal convection and that was later extended to include tidal dissipation (Marie Běhounková, Czech Department of Geophysics, Prague). In particular, we investigate the onset and location of partial melting in the mantle and how the different melt treatments and transports affect the dynamics of the convection and the tidal dissipation of Europa. 

Development of a new numerical model for silicate partial melting and application to the Earth and Europa (2026-):

Partial melting of rocks applied to planetary mantles in convection models are simplified in the way they ignore petrological and geological effects. For instance, a rock that experiences one or several episodes of melting becomes depleted in the most fusible minerals and elements (clinopyroxene, alkali, CaO, Al2O3…). Melting of the solid residue therefore requires a higher temperature at a given pressure compared to the unmelted rock. This affects the melt productivity as well as the composition of the melt and its physical properties (density and viscosity). I contribute to developping of  a new parameterized model for the partial melting of mafic rocks in the context of planetary mantles with the aim to integrate it to the OEDIPUS tool to complete the melting study of Europa.

Teaching activities: Mathematics, Petrology and Mineralogy, Geological Field Trips