Séminaire de Max Rudolf

Résumé :

The icy ocean worlds orbiting the giant planets of the outer solar system display a rich variety of surface features, and many of these bodies have evidence of recent or ongoing eruptions of water. The processes that enable these eruptions are not entirely understood, but the upward transport of water from a subsurface ocean requires the existence of a pathway as well as excess pressure or volatile exsolution to overcome the excess density of water. On long timescales, planetary ice shells are expected to change thickness owing to changes in tidal dissipation, and these thickness changes give rise to thermal stresses and changes in ocean overpressure. Here, we consider the influence of changes in ice shell thickness on the thermal and mechanical evolution of ice shells and on the pressure within subsurface oceans. We apply models of cyclic thinning and thickening to understand the initiation of the ongoing eruption from Enceladus’ tiger stripe fissures, and present a multi-stage model for the formation of the tiger stripe fissures. We also consider the consequences of the emergence of a subsurface ocean on the stress state of an ice shell. The formation and growth of an ocean can lead to global tectonic compression, and we evaluate the implications for the geology of the mid-sized icy ocean worlds, including the physical libration of Mimas, the coronae of Miranda, and the occurrence of compressional features on Titania.