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27 May 2016 Tout le mois

Gabriel Tobie (University of Nantes) — Habitability of subsurface oceans on icy moons

Friday 27 May 2016 11:00-12:00 - Amphi

Abstract: 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. The composition of these oceans probably results from complex aqueous processes involving interactions between water, rock, organics and volatile compounds from which these bodies were built. Such aqueous processes were presumably vigorous during the early stage of interior differentiation when water and rock separated, but they could be still active in some icy bodies at present, as witnessed by the intense activity observed at Enceladus’ south pole by the Cassini spacecraft. The analysis of icy grains emitted from Enceladus indicates the presence of salt and organics mixed with ice, thus providing crucial constraints on the oceanic composition and indirect information on aqueous processes at its origin. The co-existence of water, organics and salts together with a strong heat source associated to tidal friction may potentially lead to the first bricks of life. Even if there is no direct evidence yet, similar ingredients might also be present within Europa, Titan and Pluto. Assessing the astrobiological potential of these oceanic environments require a better understanding of their present-day structure of the satellite interior as well as their possible evolution since their formation. In this seminar, I will give an overview of the current knowledge about the interior of icy moons, with a particular focus on Enceladus, Europa, Ganymede and Titan. I will discuss the possible occurrence of active aqueous processes on these bodies and the implications for the habitability of their subsurface oceans.

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