ESA JUICE RED BOOK — PART 5

Voyager and Galileo data indicate that Europa possesses important prerequisites for habitability. Galileo’s detection of induced magnetic fields (Kivelson, 2000; 2002) combined with imaged surface characteristics (Pappalardo, 1999) and thermal modelling of the moons’ evolution (Spohn and Schubert, 2003), indicate the presence of a liquid water ocean below the icy crust. However, the depth and composition of the ocean, as well as the dynamics and exchange processes between the ocean and the deep interior or the upper ice shell, remain unclear. Furthermore, it is unknown whether liquid water reservoirs or compositional boundaries exist in the shallow subsurface ice and how the dynamics of the outermost ice shell is related to geologic features and surface composition.

On Europa, recent modelling relates chaotic terrains with shallow lenses of liquid water (Schmidt et al., 2011)

One of the objectives of JUICE is to explore for the first time the subsurface in the most recent active regions to understand the exchange processes from the subsurface to the surface and also to constrain the minimal thickness of the ice shell in the most active regions

At closest approach, JUICE will probe the Europan crust possibly down to the ice-ocean interface, if the ice shell is only a few km thick as expected in some models (Greenberg and Geissler, 2002). JUICE will help to solve the controversy concerning the depth of the ocean over liquid water reservoirs with the ice shell, and will determine whether or not liquid water can ascend through the ice shell from a subsurface ocean to the surface (e.g. Pappalardo et al., 1999)