These planetary-mass moons are planned to be studied because they are thought to have significant bodies of liquid water beneath their frozen surfaces, which would make them potentially habitable for extraterrestrial life.

[12][13] In July 2015, Airbus Defence and Space was selected as the prime contractor to design and build the probe, to be assembled in Toulouse, France.

[15] The main spacecraft design drivers are related to the large distance to the Sun, the use of solar power, and Jupiter's harsh radiation environment.

The Juice science payload has a mass of 280 kilograms (620 lb) and includes the JANUS camera system, the MAJIS visible and infrared imaging spectrometer, the UVS ultraviolet imaging spectrograph, RIME radar sounder, GALA laser altimeter, SWI submillimetre wave instrument, J-MAG magnetometer, PEP particle and plasma package, RPWI radio and plasma wave investigation, 3GM radio science package, the PRIDE radio science instrument, and the RADEM radiation monitor.

This scenario assumed an early June 2022 launch, however, the delta-V requirements are representative due to the rather short, repetitive orbital configurations of Europa, Ganymede and Callisto.

[26] The three moons are thought 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:[26] 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 volcanically-active regions.

More distant spatially resolved observations will also be carried out for several minor irregular satellites and the volcanically active moon Io.