Ocean worlds in the Solar system and beyond

The exploration of Jupiter’s and Saturn’s system respectively by Galileo (1996-2003) and Cassini-Huygens (2004-2017), has revealed that several moons around Jupiter (Europa, Ganymede, Callisto) and around Saturn (Titan, Enceladus, Mimas) harbor a subsurface salty ocean underneath their cold icy surface. By flying through the icy-vapor plume erupting from Enceladus' south pole, Cassini proceeded for the first time to the analysis of fresh materials coming from an extraterrestrial ocean. These analyses revealed that Enceladus possess all the ingredients for the emergence of life. Even if there is no direct evidence yet, similar ingredients might also be present within Europa, Ganymede and Titan, which will be characterized by future exploration missions currently under development at ESA (JUICE) and NASA (Europa Clipper, Dragonfly). Although the astrobiological potential of these ocean worlds are very promising, at the exception of Enceladus, their oceanic environments are still poorly known. In this seminar, after giving an overview of the current knowledge on these ocean moons, I will present how future exploration and laboratory works will allow us to better determine the physico-chemical conditions of their subsurface oceans. In particular, I will discuss the possible occurrence of active aqueous processes on these bodies and the implications for the habitability of their subsurface oceans. Finally, I will discuss how the numerical models and experiments developed for ocean moons can be used to characterize the physico-chemical evolution of water-rich exoplanets that we are just starting to unveil.