It will be the last journey for the Ariane 5 rocket. For years it was Europe’s gateway to space, bringing dozens of satellites there and most recently the James Webb Space Telescope. At around 2.15 p.m. Central European Time, it will now take off for the last time from the European spaceport in French Guiana. On board will be the European Space Agency ESA’s Jupiter Icy Moons Explorer, or Juice for short.

Juice has a long journey ahead: the space probe is to fly to the giant among the planets, Jupiter. If the flight is successful, it will arrive at its place of deployment eight years later, in July 2031. There she should not only explore the gas giant more closely, but also its three moons Callisto, Europa and Ganymede. Researchers suspect that oceans of liquid water could be hidden under their kilometer-thick ice sheets, in which life could have originated. Juice would be the first spacecraft to orbit a moon other than Earth’s.

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Is life possible on Jupiter?

ESA mission engineer Angela Dietz knows that certain elements that can serve as building blocks for molecules are needed for life to arise. “There are opportunities on Europa and Ganymede,” she says. Europe in particular could harbor life in its oceans. Among the three icy moons, it is closest to Jupiter, which is why it has more warmth and energy. “We can only examine whether the basics are there,” says Dietz. A direct proof of living beings is not possible.

To explore Jupiter and its moons, Juice has ten scientific instruments on board. Nine from European partners and one from the US space agency Nasa. For example, the spacecraft has a magnetometer that allows it to study Jupiter’s magnetic environment. The gas giant has the strongest and largest magnetic field of any planet in the solar system.

Radar echo sounder to illuminate layers of ice

Juice will also carry out radar and laser measurements. The radar can also collect data under the ice layer. According to Dietz, you can go up to 19 kilometers through the ice. No such radar was on board on previous NASA missions to Jupiter. With the laser altimeter “Gala” (Ganymede Laser Altimeter), the surface of Ganymede is to be measured. This is important in order to understand the development of the moon, says Hauke ​​Hussmann, who is responsible for the “Gala” experiment. “The second important aspect to be added to the Jovian system is tidal deformation.” The moons would deform as they orbited the planet.

“The extent of this change over time can give us information about whether there is liquid water inside, i.e. whether there is a global ocean on ‘Ganymed’, as model calculations predict,” says Hussmann. With the data and images from the “Janus” camera, in which the German Aerospace Center played a major role, a digital 3D model of the moon, which is completely covered with ice, can later be created.

Several flybys to Jupiter

But how is it possible that liquid water should exist hundreds of millions of kilometers away from the sun? “Jupiter, with its enormous mass, has huge tidal forces that it exerts,” says Hussmann. This leads to friction inside the moons and heat is generated as a result. “This is the energy source that plays a significant role in the moons.”

Juice will fly past the icy moons several times and collect data. A total of 35 flybys are planned. Getting the spacecraft anywhere near Jupiter and its moons is a challenge. After all, the planet is hundreds of millions of kilometers from Earth. After its launch, the probe must first fly past the moon and the earth, then it flies past Venus, then back to the earth, and only then does it finally reach its destination.

“If we had a bigger rocket, we could fly straight to Jupiter,” says Andrea Accomazzo, director of flight operations for the Juice mission. But that’s not possible with the Ariane 5 rocket. It takes the flybys of Earth and Venus to build up speed. “During these flybys, we kind of steal the energy from the orbits of the planets, which is then transferred to the probe,” he explains. This accelerates Juice so that it arrives at Jupiter at the right speed.

Use under extreme conditions

However, the first 99 minutes after the start will still be important – when the solar panels unfold. They are 85 square meters in size and supply the spacecraft with power. “They absolutely have to develop,” says Accomazzo. Since the sunlight around Jupiter is 25 times weaker than on Earth, the solar panels are essential for propelling the spacecraft.

Accomazzo sees another challenge, probably the most critical of the entire mission: arriving at Jupiter. Appropriate braking maneuvers must be carried out on site within a certain period of time. “If that doesn’t work, we’ll fly past Jupiter,” he explains. “And then the mission is over.”

The high levels of radiation and extreme temperatures can also jeopardize the safety of the mission. Jupiter possesses one of the most intense radiation environments in the solar system, which can damage sensitive electronics. The space probe is therefore equipped with special protective shields. A layer of innovative multi-layer insulation protects Juice from the extreme temperatures – 250 degrees Celsius when flying past Venus, minus 230 degrees Celsius when flying past Jupiter. Its purpose is to ensure that the internal temperature of the probe remains stable.

Juice mission ends on Ganymede

Even if all goes well, there is still one obstacle waiting for Juice after the 35 flybys. More precisely, it is waiting for the mission controllers in the European Space Operations Center ESOC in Darmstadt. You must use Jupiter’s gravity to steer the spacecraft into orbit around Ganymede, the largest moon in the solar system. Juice would be the first spacecraft to change orbit from another planet to one of its moons.

Ganymede is the last station of Juice. It is planned that the probe will probably crash there in September 2035. Hopefully by then she will have collected enough data for researchers to understand how the solar system works and what conditions must be met for life and other planets to form.

with material from the dpa

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