JUpiter ICy Moon Explorer (JUICE) mission

The JUpiter ICy Moon Explorer (JUICE) is a planned European Space Agency (ESA) spacecraft to visit the Jovian system, focused in particular on studying three of Jupiter's moons; Ganymede, Callisto, and Europa. It will characterise these worlds, all thought to have significant bodies of liquid water beneath their surfaces, as potentially habitable environments. Selection of the mission for the L1 launch slot of ESA's Cosmic Vision science programme was announced on May 2, 2012
The Jupiter Icy Moon Explorer (JUICE) would perform detailed investigations on Ganymede( largest moon of jupiter ) as a planetary body and evaluate its potential to support life. Investigations of Europa and Callisto would complete a comparative picture of these Galilean moons. The three moons are believed to harbour internal liquid water oceans, and so are central to understanding the habitability of icy worlds.
The main science objectives for Ganymede, and to a lesser extent for Callisto, are:
Characterisation of the ocean layers and detection of putative subsurface water reservoirs;
Topographical, geological and compositional mapping of the surface;
Study of the physical properties of the icy crusts;
Characterisation of the internal mass distribution, dynamics and evolution of the interiors;
Investigation of the exosphere;
Study of Ganymede's intrinsic magnetic field and its interactions with the Jovian magnetosphere.
For Europa, the focus is on the chemistry essential to life, including organic molecules, and on understanding the formation of surface features and the composition of the non water-ice material. Furthermore, JUICE will provide the first subsurface sounding of the moon, including the first determination of the minimal thickness of the icy crust over the most recently active regions.