JUICE: ESA's Epic Voyage to Jupiter

The European Space Agency’s JUICE mission is embarking on a decade-long journey to Jupiter. It will create the most detailed picture ever of the gas giant’s chaotic atmosphere, powerful auroras, and mysterious depths, helping us understand giant planets across the universe.

Jupiter isn’t just a planet; it’s a miniature solar system, a churning ball of gas so massive it shaped the orbits of all its neighbors. For centuries, we’ve gazed at its stripes and its famous Great Red Spot, but we still have fundamental questions about how it works. The ESA’s JUICE mission is designed to answer them. Building on the discoveries of missions like Galileo and Juno, JUICE will conduct a long-term stakeout of the gas giant. While Juno flies in a tight, polar orbit for close-up snapshots, JUICE will observe from further out, allowing it to monitor the entire planet over weeks and months. This will enable scientists to track storms as they evolve, map the global circulation, and create a complete, four-dimensional ‘climate database’ for Jupiter. It’s a mission to understand the entire Jovian system—from its deep, churning interior to the top of its electrically charged atmosphere.

Read the original research paper: ‘Jupiter Science Enabled by ESA’s Jupiter Icy Moons Explorer’

JUICE will provide our best four-dimensional characterisation of this archetypal giant planet.
— Leigh N. Fletcher, JUICE Interdisciplinary Scientist

Jupiter’s atmosphere is a chaotic masterpiece. The distinct reddish belts and white zones are bands of rising and sinking gas, stretched around the planet by its incredibly fast 10-hour rotation. These bands are separated by powerful jet streams, some blowing faster than 500 km/h. Giant storms, like the centuries-old Great Red Spot, are vortices larger than Earth, swirling in the upper cloud decks. Unlike Earth’s weather, which is driven by the Sun, Jupiter’s meteorology is powered mostly by internal heat left over from its formation billions of years ago. JUICE will use its cameras and spectrometers to track cloud movements, measure temperatures, and identify the chemical makeup of different regions. By observing in different wavelengths of light, from ultraviolet to infrared, it can probe different depths of the atmosphere, essentially creating a vertical weather report for this giant world and figuring out what makes it tick.

The goal is to understand the mechanisms driving zonal jets and meteorological activity.
— Ricardo Hueso, Atmospheric Scientist

Like Earth, Jupiter has spectacular auroras, but they are thousands of times more powerful and they never stop. This is because Jupiter’s auroras have a dual power source. While some energy comes from the solar wind, most of it comes from Jupiter’s own system. Its volcanic moon, Io, spews tons of sulfur and oxygen into space every second. These particles get trapped by Jupiter’s immense magnetic field and funneled towards the poles, creating a constant, powerful light show. This process dumps a colossal amount of energy into Jupiter’s upper atmosphere, making it hundreds of degrees hotter than it should be—a mystery known as the ‘energy crisis’. JUICE will directly study this connection. Its UVS instrument will watch the auroras flicker and dance, while other instruments measure the temperature and wind changes below, revealing how this cosmic light show drives the climate of the entire upper planet.

To untangle Jupiter’s secrets, JUICE is equipped with a suite of ten powerful instruments that work together. It’s a true multi-disciplinary mission. The JANUS camera will take high-resolution visible-light images of storms and clouds, allowing scientists to track winds. The MAJIS spectrometer will analyze infrared light to map the chemical composition of the atmosphere and measure the temperature of the auroras. The UVS spectrograph will look at the ultraviolet light from the auroras to understand the energy of the particles crashing into the atmosphere. Meanwhile, the RPWI instrument will act like a radio receiver, listening for the ‘whistler’ signals produced by powerful lightning strikes deep within Jupiter’s clouds. By combining data from all these instruments, scientists can see how lightning in the deep cloud layers might be connected to waves that travel up and influence the auroras high above. This synergistic approach will give us the most complete view of Jupiter ever obtained.

Q: Why is it called the ‘Icy Moons Explorer’ if it also studies Jupiter?
A: Because the planet and its largest moons—Ganymede, Callisto, and Europa—are a deeply connected system. Material from the moons feeds Jupiter’s magnetosphere, which in turn powers the auroras. JUICE will study both the planet and its moons to understand how the whole system works together.

Q: How is the JUICE mission different from NASA’s Juno mission?
A: They are like teammates with different jobs! Juno flies in a close, polar orbit to study Jupiter’s deep interior and gravity field. JUICE will orbit further out, allowing it to stare at the planet for long periods to monitor weather and atmospheric changes, focusing on how the whole atmosphere is connected.

Q: Does Jupiter have auroras like the Northern Lights on Earth?
A: Yes, but they are much bigger, more powerful, and permanent! Unlike Earth’s auroras, which are mostly powered by the solar wind, Jupiter’s are mainly fueled by particles from its volcanic moon Io. This means Jupiter’s light show is always on.

Q: What is the ‘energy crisis’ on Jupiter?
A: It’s a long-standing mystery where Jupiter’s upper atmosphere is hundreds of degrees hotter than sunlight alone can explain. Scientists suspect the extra energy is dumped there by the powerful auroras or by atmospheric waves traveling up from deep inside the planet. JUICE’s instruments are designed to help solve this puzzle.