JUICE spacecraft launched to investigate the habitability of Jupiter’s icy moons

The European Space Agency (ESA) successfully launched its JUICE spacecraft to study Jupiter’s icy moons on Friday, April 14th. The Jupiter Icy Moons Explorer mission will visit three of Jupiter’s largest moons — Europa, Ganymede, and Callisto — to investigate whether they could be potentially habitable, a question that has been igniting debate among astronomers since the first evidence of subsurface oceans on these moons was seen by the Galileo mission in the 1990s. 

JUICE launched at 8:14AM ET from Europe’s Spaceport in French Guiana, carried by an Ariane 5 rocket. The launch had been delayed from its original launch date of April 13th due to weather conditions, but the skies today were clear for liftoff. 

The spacecraft separated from the rocket shortly after liftoff, making signal contact with Earth at 9:04AM. It then deployed its large solar arrays, which unfurled to their full size of 27 meters across, with full deployment confirmed at 9:33AM. With that, the spacecraft begins its eight-year journey to the Jupiter system. 

The launch had to occur within a tiny window of just one second in order to work with the spacecraft’s complex trajectory. The spacecraft will begin its journey around the orbit of Earth, making a flyby of Earth and the Moon in August 2024. This will be the first time that a spacecraft will perform a maneuver called a Lunar-Earth gravity assist (LEGA), which involves flying first past the Moon and then past Earth just a day and a half later. This will give the spacecraft a boost, but it requires launching at an exact time.

“We have to launch on the second in order to have the right trajectory towards the first orbit around the Sun that will allow us to come back to Earth,” ESA payload system engineer Alessandro Atzei explained in a prelaunch briefing. 

The spacecraft will continue by circling toward the inner solar system, making a flyby of Venus in 2025 before traveling back out to Earth’s orbit for two more flybys in 2026 and 2029. Then, it will be able to power out toward Jupiter, arriving at the Jupiter system in 2031.

This journey is designed to conserve as much fuel as possible, as the spacecraft will need its fuel reserves to perform maneuvers at Jupiter. Once JUICE arrives at Jupiter, it will perform a total of 35 flybys of Europa, Ganymede, and Callisto, the three icy moons.

At this point, the spacecraft will be so far from the Sun that its huge solar panels, which are 85 square meters in area, will produce just a few hundred watts of power, or about enough to run a microwave. Its instruments have to be designed to operate while using power very sparingly as well as dealing with the harsh radiation environment of Jupiter. 

The 10 instruments on board include remote sensing instruments like a camera and spectrograph for observing targets that are far away as well as in situ instruments like a magnetometer and radio and plasma wave instrument for measuring the immediate environment around the spacecraft. A further experiment on board, called the Planetary Radio Interferometry and Doppler Experiment, or PRIDE, will test whether it is possible to use radio telescopes on Earth to determine the spacecraft’s precise position.

These instruments will be used to investigate Jupiter’s moons, with a particular focus on Ganymede. Ganymede is unusual in that it is the largest moon in the solar system and the only moon known to produce its own magnetic field. That magnetic field sits within the powerful magnetic field of Jupiter, and the two interact producing strong auroras around the moon. Ganymede’s surface is also of interest as it varies in age, with both smooth younger terrain and areas of much older pockmarked terrain, which can help scientists understand how the Jupiter system evolved over billions of years.

The most intriguing feature of Ganymede, though, is that, like Europa and Callisto, it is thought to have a liquid water ocean beneath a crust of ice several miles thick. Evidence for this comes from the Galileo mission, which found perturbations of Jupiter’s magnetic field near Europa that suggested a subsurface ocean, plumes of water bursting through the surface detected by Hubble, and the detection of water vapor in Europa’s atmosphere made using ground-based telescopes. 

Given the necessity of liquid water for almost all forms of life, that has made these moons some of the best locations in the solar system to search for potentially habitable environments. The JUICE spacecraft will not look for evidence of life directly but will look for indications that the moons could potentially host life by looking for biosignatures such as the presence of biologically essential elements like carbon and oxygen. 

To assess whether these environments really are habitable, scientists need to look at the bigger picture of the Jupiter system as a whole. “To understand this question of habitability we need to explore the Jupiter system globally — so to study Jupiter, its atmosphere, its weather, its strong rotating magnetic field, the volcanic moon Io, the other moons in the system, and how all these bodies are connected to each other,” JUICE project scientist Olivier Witasse explained in the science briefing. “So Jupiter is really a miniaturized solar system.”

Studying this system can help us learn about the entire solar system as well as investigate whether these distant worlds could potentially host life. “Today, we have sent a suite of ground-breaking science instruments on a journey to Jupiter’s moons that will give us an exquisite close-up view that would have been unimaginable to previous generations,” said Carole Mundell, ESA’s director of science, in a statement. 

“The treasure trove of data that ESA Juice will provide will enable the science community worldwide to dig in and uncover the mysteries of the jovian system, explore the nature and habitability of oceans on other worlds and answer questions yet unasked by future generations of scientists.”