ESA’s Jupiter Icy Moons Explorer, Juice, is set to embark on an eight-year cruise to Jupiter starting April 2023. The mission will investigate the emergence of habitable worlds around gas giants and the Jupiter system as an archetype for the numerous giant planets now known to orbit other stars.

This animation depicts Juice’s journey to Jupiter and highlights from its foreseen tour of the giant planet and its large ocean-bearing moons. It depicts Juice’s journey from leaving Earth’s surface in a launch window 5–25 April 2023 and performing multiple gravity assist flybys in the inner Solar System, to arrival at Jupiter (July 2031), flybys of the Jovian moons Europa, Callisto and Ganymede, orbital insertion at Ganymede (December 2034), and eventual impact on this moon’s surface (late 2035).

An Ariane 5 will lift Juice into space from Europe’s Spaceport in Kourou. A series of gravity assist flybys of Earth, the Earth-Moon system and Venus will set the spacecraft on course for its July 2031 arrival at Jupiter. These flybys are shown here in order – Earth-Moon (August 2024), Venus (August 2025), Earth (September 2026, January 2029) – interspersed by Juice’s continuing orbits around the Sun. Juice’s flyby of the Earth-Moon system, known as a Lunar-Earth gravity assist (LEGA), is a world first: by performing this manoeuvre – a gravity assist flyby of the Moon followed just 1.5 days later by one of Earth – Juice will be able to save a significant amount of propellant on its journey.

Juice will start its science mission about six months prior to entering orbit around Jupiter, making observations as it approaches its destination. Once in the Jovian system, a gravity assist flyby of Jupiter’s largest moon Ganymede – also the largest moon in the Solar System – will help Juice enter orbit around the gas giant. While in Jupiter orbit, the spacecraft will spend four years making detailed observations of Jupiter and three of its largest moons: Ganymede, Callisto and Europa.

During the tour, Juice will make two flybys of Europa (in July 2032), which has strong evidence for an ocean of liquid water under its icy shell. Juice will look at the moon’s active zones, its surface composition and geology, search for pockets of liquid water under the surface, and study the plasma environment around Europa, also exploring the moon’s tiny atmosphere and hunting for plumes of water vapour (as have been previously detected erupting to space).

A sequence of Callisto flybys will not only be used to study this ancient, cratered world that may too harbour a subsurface ocean, but will also change the angle of Juice’s orbit with respect to Jupiter’s equator, making it possible to investigate the polar regions and environment of Jupiter at higher latitudes (2032–2034).

A sequence of Ganymede and Callisto flybys will adjust Juice’s orbit – properly orienting it while minimising the amount of propellant expended – so that it can enter orbit around Ganymede in December 2034, making it the first spacecraft to orbit another planet’s moon. Juice’s initial elliptical orbit will be followed by a 5000 km-altitude circular orbit, and later a 500 km-altitude circular orbit.

Ganymede is unique in the Solar System in that it is the only moon to have a magnetosphere. Juice will investigate this phenomenon and the moon’s internal magnetic field, and explore how its plasma environment interacts with that of Jupiter. Juice will also study Ganymede’s atmosphere, surface, subsurface, interior and internal ocean, investigating the moon as not only a planetary object but also a possible habitat.

Over time, Juice’s orbit around Ganymede will naturally decay – eventually there will not be enough propellant to maintain it – and it will make a grazing impact onto the surface (late 2035). The animation concludes with an example of what the approach to impact could look like.

The Juice launch itself will be a historical milestone for more reasons than one. It will be the final launch for Ariane 5, ending the launcher’s nearly three-decade run as one of the world’s most successful heavy-lift rockets. Its duties are being taken over by Ariane 6.

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