PhD Defense : Tom Benest

PhD defence entitled “Study of the composition of the protosolar nebula and its role on the formation of giant planets and Galilean moons”. The defence will take place on Monday December 1st at 2 p.m in the LAM amphitheater, and will be in english. Please find the abstract and the jury composition below.

Members of the jury :

Nicolas ANDRÉ (SUPAERO, Toulouse) – Reviewer
Stéphanie CAZAUX (Delft University of Technology) – Riviewer
Tristan GUILLOT (LAGRANGE, Observatoire de la Côte d’Azur, Nice) – President
Valéry LAINEY (Laboratoire Temps Espace, Observatoire de Paris) – Examiner
Pierre VERNAZZA (LAM, AMU) – Examiner
Kevin BAILLIÉ (Laboratoire Temps Espace, Observatoire de Paris) – Invited member
Olivier MOUSIS (LAM, AMU) – Supervisor

Abstract :

This thesis explores the formation of the giant planets of the Solar System and their moons by studying the composition of the protosolar nebula (PSN). The potential of icy moons as environments favorable to life is another major motivation for this work. The building blocks that form the planets and moons reflect the region of the PSN where they formed. Therefore, comparing the measured composition of the planets and moons with the calculated composition of the PSN can constrain the conditions under which they formed. Complex organic molecules (COMs), which are considered essential ingredients for life, have been detected in comets and icy moons. Understanding their formation in the PSN and their presence in the Galilean moons is crucial. The D/H ratio is also an important tool for studying planet formation. This thesis uses a model that calculates the evolution of the PSN’s composition, coupled with a Lagrangian particle transport model, to constrain the formation conditions and composition of giant planets and moons.

This thesis explores the internal structure of Uranus, examining its D/H ratio and atmospheric composition. It considers the possibility of an internal composition not dominated by water ice and discusses avenues for compositions including other trace species or rocks. The results show that the interior of Uranus may have a more varied composition or a higher proportion of rocks.

Additionally, this thesis studies the formation of COMs in the PSN and their transport to Jupiter’s circumplanetary disk. One motivation for this thesis is their role in the composition of the Galilean moons.
The results show that the formation of such molecules in the PSN is likely and that they could be present in the Galilean moons. These results demonstrate that COM formation is linked to the origin of life in the universe. This topic is also part of the broader study of Jupiter’s Galilean moons. The future JUICE and Europa Clipper missions should provide new insights into the moons’ composition.