Presentation Information
[PPS01-P17]Coupling mineral assemblage modelling and thermal evolution of the deep interiors of Uranus’ icy satellites
*Artem Lebedev1,2,3, Giuseppe Mitri2,3, Camilla Cioria2,3, Anastasia Consorzi2,3 (1.Department of Physics, University of Trento, 2.Department of Engineering and Geology, D'Annunzio University, 3.International Research School of Planetary Sciences)
Keywords:
Uranus,Icy satellites,Thermal evolution,Mineral assemblage,Thermal modeling
The four largest Uranus's icy satellites are predicted to have a well-defined outer icy shell and a rocky interior. Considering different internal differentiation scenarios, the rock interior can be subdivided into dehydrated and hydrated mineral layers (Castillo-Rogez et al., 2023). In our study, we focused on the dehydration process of deep interior. The present-day interior structure is derived from the coupling of the thermal evolution model to the mineral evolution of the satellites, accounting for both a hydrated and dehydrated scenario.
We solve the radial heat diffusion equation in a one-dimensional model. For the rocky layers, we assume local thermodynamic equilibrium at the evolving pressure-temperature conditions and compute mineral assemblages and physical properties with PerpleX (Connolly, 1990), following Cioria and Mitri (2022). We use Orgueil (CI) chondrite as the precursor composition to generate hydrated and dehydrated assemblages.
The model's thermal evolution begins at the satellites' formation time and accounts for radiogenic and tidal heating, with the latter estimated from the tidal Love number k2 computed using the ALMA3 code (Melini et al., 2022). To accurately estimate ocean evolution, we also accounted for changes in ammonia content caused by ocean freezing.
Figure 1 summarizes the results for Titania. Panel A shows the time evolution of the temperature profile, and Panel B the corresponding density structure. The white line marks the boundaries between the ice shell, the liquid ocean, and the rocky interior. The ocean reaches a maximum thickness of ~70 km and later partly freezes; even for an initial ammonia content of 1% by hydrosphere mass, a residual ocean of ~12 km persists at present. As the deep interior warms to a peak temperature T ≦ 1000 K at ~1.8 Gyr, dehydration is maximized. This produces a density discontinuity at ~310 km radius and progressively reduces water content in the overlying hydrated silicates.
Additionally, we used the Monte Carlo approach to assess the influence of not strictly defined model parameters on the deep interior structure predictions. We found similar results for deep interior dehydration in Oberon and Titania, and evidence of only partial dehydration in Ariel and Umbriel.
Acknowledgements
A.L., G.M., C.C. and A.C. acknowledge support from the Italian Space Agency (2024-5-HH.0). This abstract was produced while A.L. (CUP E66E24000200005) was attending the PhD program in PhD in Space Science and Technology at the University of Trento, Cycle XL, with the support of a scholarship financed by the Ministerial Decree no. 629 of 24th April 2024, based on the NRRP - funded by the European Union - NextGenerationEU - Mission 4 "Education and Research", Component 1 "Enhancement of the offer of educational services: from nurseries to universities" - Investment 4.1 "Extension of the number of research doctorates and innovative doctorates for public administration and cultural heritage"
We solve the radial heat diffusion equation in a one-dimensional model. For the rocky layers, we assume local thermodynamic equilibrium at the evolving pressure-temperature conditions and compute mineral assemblages and physical properties with PerpleX (Connolly, 1990), following Cioria and Mitri (2022). We use Orgueil (CI) chondrite as the precursor composition to generate hydrated and dehydrated assemblages.
The model's thermal evolution begins at the satellites' formation time and accounts for radiogenic and tidal heating, with the latter estimated from the tidal Love number k2 computed using the ALMA3 code (Melini et al., 2022). To accurately estimate ocean evolution, we also accounted for changes in ammonia content caused by ocean freezing.
Figure 1 summarizes the results for Titania. Panel A shows the time evolution of the temperature profile, and Panel B the corresponding density structure. The white line marks the boundaries between the ice shell, the liquid ocean, and the rocky interior. The ocean reaches a maximum thickness of ~70 km and later partly freezes; even for an initial ammonia content of 1% by hydrosphere mass, a residual ocean of ~12 km persists at present. As the deep interior warms to a peak temperature T ≦ 1000 K at ~1.8 Gyr, dehydration is maximized. This produces a density discontinuity at ~310 km radius and progressively reduces water content in the overlying hydrated silicates.
Additionally, we used the Monte Carlo approach to assess the influence of not strictly defined model parameters on the deep interior structure predictions. We found similar results for deep interior dehydration in Oberon and Titania, and evidence of only partial dehydration in Ariel and Umbriel.
Acknowledgements
A.L., G.M., C.C. and A.C. acknowledge support from the Italian Space Agency (2024-5-HH.0). This abstract was produced while A.L. (CUP E66E24000200005) was attending the PhD program in PhD in Space Science and Technology at the University of Trento, Cycle XL, with the support of a scholarship financed by the Ministerial Decree no. 629 of 24th April 2024, based on the NRRP - funded by the European Union - NextGenerationEU - Mission 4 "Education and Research", Component 1 "Enhancement of the offer of educational services: from nurseries to universities" - Investment 4.1 "Extension of the number of research doctorates and innovative doctorates for public administration and cultural heritage"