ANR OASIS : Organics and Aqueous Systems in Icy Satellites

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 the aqueous processes within their interior.

The goal of the OASIS project is to understand how these aqueous processes have controlled the chemical evolution of these icy worlds and what consequences they have on the habitability of their subsurface oceans. For that purpose, we will quantify the efficiency and potential duration of water-rock interactions during the evolution of icy worlds, the consequences of aqueous alteration on the organic inventory, the conditions under which such aqueous processes may remain active until present. These objectives will be achieved by combining laboratory experiments of aqueous alteration of minerals and organic compounds by NH3-rich (and CO2-rich) aqueous solutions representative of icy world context to modeling of water-rock interactions and evolution of fluid composition from the accretion stage to present. The work will be mostly focused on Enceladus and Titan, in support to the interpretation of the data collected by the Cassini- Huygens mission. Some aspects of the investigations, notably the compositional signatures of alteration products will also be used for the preparation of the future exploration of Jupiter’s moons, Europa and Ganymede (ESA Jupiter ICy moon Explorer (JUICE) and NASA Europa Multiple Flyby mission). More generally, the project will provide experimental and theoretical constraints on aqueous processes in icy bodies, which could be used for a variety of volatile-rich objects, including Pluto and the other large Kuiper Belt Objects (KBOs).


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The research program of the OASIS project will be structured around two complementary investigations, each of them divided in three main tasks. The OASIS objectives will be achieved by associating researchers with complementary skills in alteration experiments, thermodynamic modeling and internal dynamics modeling, from LPG (Nantes), Georessources (Nancy) and CRPG (Nancy), and by actively interacting with international collaborators. To fulfill the objectives, the project requires equipment funding for the acquisition of experimental apparatus for the alteration experiments as well as for completing the existing computing facilities for the modeling part of the project. Requested funds also include operation costs for the experiments, travel expenses, and salary for two PhD students and one post-doc. The first PhD student and the post-doc will work on the experimental investigation of the project, while the second PhD student will work on the modeling aspects, in the framework of a co-tutelle thesis with Charles University in Prague.

> Les publications :

- Běhounková, M., Tobie, G., Choblet, G., Kervazo, M., Daswani, M. M., Dumoulin, C., & Vance, S. D. (2020). Tidally‐induced magmatic pulses on the oceanic floor of Jupiter's moon Europa. Geophysical Research Letters, e2020GL090077.

- Choblet, G., Tobie, G., Sotin, C., Běhounková, M., Čadek, O., Postberg, F., & Souček, O. (2017). Powering prolonged hydrothermal activity inside Enceladus. Nature Astronomy, 1(12), 841-847.


The project coordinator is Gabriel Tobie, CNRS Researcher.


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