Explaining JUICE: Mission to Jupiter and its moons

Jupiter Icy Moons Explorer is the European Space Agency’s $1.7bn exploration programme for the Jovian orbit.

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The Jupiter Icy Moons Explorer (JUICE) has lifted off from French Guiana to begin its eight-year journey to Jupiter and its icy moons, which scientists think could support living organisms.

The mission was initially scheduled to take off on Thursday but was delayed because of lightning risk. It took off at 2:14pm (12:14 GMT) from the Kourou spaceport, on the northeast coast of South America.

Led by the European Space Agency (ESA), JUICE will explore three possible ocean-bearing moons – Europa, Ganymede and Callisto. Under their icy surfaces are thought to be huge oceans of water – a crucial ingredient for life as we know it.

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Nicolas Altobelli, a JUICE project scientist at ESA, said it would be “the first time that we explore habitats beyond the frost line” between Mars and Jupiter.

Beyond that line, temperatures plummet and “liquid water can no longer exist on the surface”, Altobelli told AFP news agency earlier this year.

The orbiter will be launched by the Arianne 5 rocket, which was previously used to launch the James Webb Space Telescope.

This is the first mission by the ESA to a Jovian orbit system and the first mission to a moon other than Earth’s.

Why is a mission to Jupiter important?

Jupiter is about 318 times the size of Earth and has 80 to 95 moons orbiting it, according to NASA.

JUICE will investigate Jupiter’s gaseous complex surface in depth and its relationships with the oxygen and icy sub-surface saltwater ocean moons.

The orbiter will have 10 state-of-the-art instruments on board that are some of the most powerful ever sent into the solar system. Nine of the instruments are led by European partners and one by NASA.

By July 2031, the spacecraft will have entered Jupiter’s orbit, from which it will probe Ganymede, Europa and Callisto.

There have been seven missions to Jupiter so far. NASA’s Juno is still ongoing and its Clipper is set to launch later this year.

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Jupiter’s moons vs Earth

JUICE will explore three of Jupiter’s largest moons – Ganymede, Callisto and Europa.

There is hope Jupiter’s icy moons will have some kind of living organisms, said Carole Larigauderie, JUICE project head at French space agency CNES.

“On Earth, we still find life forms at the bottom of the abyss. Tiny microbes such as bacteria and archaea have been found to be able to survive on Earth without sunlight, raising hopes that life elsewhere will be able to do the same. As well as water and energy, life needs nutrients,” she said.


Ganymede is the largest moon in the solar system, according to NASA, and Earth is about 2.4 times bigger than it. It is larger than the planet Mercury. It is the only moon in the solar system that possesses its own magnetic field, like Earth.

JUICE is expected to reach Ganymede’s orbit by 2034, where it will fly by the planetary mass 12 times.

The mission’s main goals for Ganymede are to explore its magnetic field and hidden ice ocean and study its habitability.


Callisto is believed to have the oldest surface in the solar system. Earth is about 2.6 times the heavily cratered object, according to NASA.

JUICE is expected to fly by the Callisto 21 times and get as close as 200km (124 miles) to it. Once there, it will study the environment around early Jupiter.


According to NASA, Earth is about 4.1 times the size of Europa and is believed to have a young and active surface that may vent water vapour to space via plumes and geysers.

JUICE will make two flybys around Europa to search for any pockets of water, explore the surface, and look for any signs of activity.

If one or more of Jupiter’s moons tick all the boxes to host life, the “logical next step” would be to send a mission to land on the surface, said Cyril Cavel, JUICE project manager at manufacturer Airbus.

Although there are no plans for such a mission, which could definitively prove the existence of life beyond Earth, “that’s part of the dream”, he said.

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Source: Al Jazeera and news agencies