September 16, 2019



Science Objectives

The JUpiter ICy moons Explorer (JUICE) mission will perform detailed investigations of Jupiter and its system in all their inter-relations and complexity, with particular emphasis on Ganymede as a planetary body and potential habitat. Investigations of Europa and Callisto would complete a comparative picture of the Galilean moons.

Jupiter is the archetype for the giant planets of the Solar System and for the numerous giant planets now known to orbit other stars. Moreover, Jupiter's diverse Galilean satellites, three of which are believed to harbour internal oceans, are central to understanding the habitability of icy worlds.

Understanding the Jovian system and unravelling its history, from its origin to the possible emergence of habitable environments, will give us a better insight into how gas giant planets and their satellites form and evolve. In addition, new light is expected to be shed on the potential for the emergence of life in Jupiter-like exoplanetary systems.

The JUICE mission will address two themes of ESA's Cosmic Vision programme:

  • What are the conditions for planet formation and emergence of life?
  • How does the Solar System work?

A road of exploration: from discovery of the Jovian moons
by Galileo to the characterization of their potential internal oceans by JUICE. Credit: ESA

Internal oceans - habitable worlds?

The focus of JUICE is to characterize the conditions that may have led to the emergence of habitable environments among the Jovian icy satellites, with special emphasis on the three ocean-bearing worlds, Ganymede, Europa and Callisto. Ganymede has been singled out for detailed investigation since it provides a natural laboratory for analysis of the nature, evolution and potential habitability of icy worlds in general, but also because of the role it plays within the system of Galilean satellites, and its unique magnetic and plasma interactions with the surrounding Jovian environment.

The main science objectives for Ganymede, and to a lesser extent for Callisto, are:

  • characterization of potential oceans and detection of putative subsurface water in the crust
  • topographical, geological and compositional mapping of the surface
  • study of the physical properties of the icy crusts
  • characterization of the internal mass distribution, dynamics and evolution of the internal layers
  • investigation of the exosphere
  • study of intrinsic magnetic fields (Ganymede only), and induced magnetic fields and their interactions with the Jovian magnetosphere

For Europa, JUICE will perform only two flybys above interesting areas for exobiology, chemistry and geology. On those zones, JUICE will provide the first subsurface sounding, to seek water reservoirs and determine the minimal thickness of the icy crust over the most recently active regions.

 M. Carroll
Artist's impression of the JUICE spacecraft in the Jovian system and in orbit around Ganymede.
The illustration shows Jupiter and its large moons: Ganymede,
Europa, Io and Callisto. Credit: ESA; Artist: M. Carroll

Jupiter system as an archetype for gas giants

The mission will also focus on characterizing the diversity of processes in the Jupiter system that may be required to provide a stable environment at Ganymede, Europa and Callisto on geologic time scales.

Studies of the Jovian atmosphere will be focused on investigating its structure, dynamics and composition. The circulation, meteorology, chemistry and structure of Jupiter will be studied from the cloud tops to the thermosphere. These observations will be attained over a sufficiently long temporal baseline with broad latitudinal coverage to investigate evolving weather systems and the mechanisms driving transport of energy, momentum and matter between the different layers.

JUICE science objectives in the Jovian atmosphere. Credit: ESA

The focus in the Jovian magnetosphere will include an investigation of the three-dimensional properties of the magnetodisc and in-depth study of the coupling processes within the magnetosphere, ionosphere and thermosphere. Aurora and radio emissions and their response to the solar wind will be elucidated.

Within Jupiter's satellite system, JUICE will also study the moons' interactions with the magnetosphere, gravitational coupling and long-term tidal evolution of the Galilean satellites.

Complex interactions within the Jovian system will be a focus of the JUICE investigations. Credit: ESA


JUICE launches in June 2022 on an Ariane 5 using a ballistic trajectory with Venus and Earth gravity assists, and arrives at Jupiter in January 2030. Jupiter Orbit Insertion (JOI) begins a 2.5 years phase of Jovian system study (Jupiter, its magnetosphere, Europa and Callisto), followed by an 8 month phase in orbit around Ganymede (Ganymede Orbit Insertion: GOI). Elliptic and circular orbits are planned around Ganymede for scientific observations in order to achieve all the mission's objectives. Highlights of the science phases include:

  • Cruise/ Interplanetary transfer (7.6 years).
  • Jupiter equatorial phase #1/Transfer to Callisto (11 months): Jovian atmosphere structure, composition, and dynamics. Jovian magnetosphere as a fast magnetic rotator and giant accelerator. Remote observations of the inner Jovian system.
  • Europa flybys (36 days): Composition of selected targets with emphasis on non-ice components. Geology and subsurface of the most active areas. Local plasma environment.
  • Reduction of Vinf / Jupiter high latitude phase with Callisto (260 days): Jupiter atmosphere at high latitudes. Plasma and fields outside the equatorial plane. Callisto internal structure, surface and exosphere. Remote observations of Ganymede, Europa, Io and small moons.
  • Jupiter equatorial phase #2/ Transfer to Ganymede (11 months): Interactions of the Ganymede magnetic field with that of Jupiter. Jovian atmosphere and magnetosphere as in phase #1.
  • Elliptic orbit around Ganymede #1 (30 days): Global geological mapping. Search for past and present activity. Global compositional mapping. Local plasma environment and its interactions with Jovian magnetosphere.
  • High-altitude (5,000 km) circular orbit around Ganymede (90 days).
  • Elliptic orbit around Ganymede #2 (30 days).
  • Medium altitude (500 km) circular orbit around Ganymede (102 days): Extent of the ocean and its relation to the deep interior. Ice shell structure including distribution of subsurface water. Geology, composition and evolution of selected targets at very high resolution. Global topography. Local plasma environment. Sinks and sources of the ionosphere and exosphere. Deep interior.
  • Low altitude (200 km) circular orbit around Ganymede (30 days).
  • Nominal end of the mission after 11 years.