ESA sent a glass of "juice" to Jupiter, or will it reveal the mystery of the "ice moon" there?

Jupiter is the largest planet in the solar system. Its mass accounts for more than 70 percent of the total mass of all celestial bodies in the solar system except the Sun. It is 2.5 times the mass of all planets except itself and 318 times the mass of the Earth. Jupiter is also a large planet with many satellites, with as many as 95 discovered so far.

Jupiter is like a small sun in the solar system, revolving around the sun with its many descendants. Studying Jupiter and its family is of great significance to understanding the solar system and the future direction of mankind.

On April 14, ESA launched a probe to Jupiter, called Jupiter Icy Moons Explorer, which literally means "Jupiter Icy Moon Explorer". Its abbreviation JUICE means juice, so people also call this probe "juice". It is a glass of "juice" that ESA sent to Jupiter after traveling billions of kilometers.

The main mission of this "juice" to visit Jupiter is to explore several icy satellites of Jupiter, also known as "ice moons". This is because the surface temperature of these satellites is between -150 and -170 degrees Celsius, so the surface is frozen and covered with thick ice; and the moon is the natural satellite of the earth, and people extend this name to the satellites of other planets, so these frozen satellites of Jupiter are called "ice moons".

"Juice" is going to Jupiter with full sincerity to visit the poor and inquire about the suffering. It will travel alone in space for nearly eight years and arrive at Jupiter in 2031. It will mainly visit several "ice moons" such as Europa, Ganymede, and Callisto at close range, and will eventually become an artificial satellite of Ganymede. This will be the first time that humans have flown a probe around the natural satellite of another planet.

Why are scientists so interested in the "Ice Moon"? Because beneath the mysterious veil of the ice cap, there are many unknown secrets.

In fact, humans have begun observing and exploring the planet Jupiter since the last century. NASA has sent several unmanned spacecraft to Jupiter for exploration, including Pioneer 10, 11, Voyager 1, 2, Galileo, Juno, New Horizons, etc., and have gained a preliminary understanding of Jupiter including some of its satellites.

But it is not easy to find out the details because the sky is high and the emperor is far away. The mission of "Juice" is to conduct more professional and specialized observations and understanding of Jupiter's icy satellites based on previous exploration and discovery, and strive to uncover the mysteries under the veil of ice to see if there are any possible signs of life there.

The project planning and research of this mission took eleven years and cost US$1.7 billion. It embodies the research and development essence of scientific teams from European countries such as France, Germany, Italy, and the United States, Japan and other countries.

"JUICE" carries many advanced scientific instruments, including but not limited to: a laser altimeter, which can study the tidal deformation and topography of icy satellites; an icy satellite exploration radar, which has the ability to detect deep into the ice layer and can study the structure nine kilometers below the surface of icy satellites; a 3GM radio set, which will be used to study the gravity field of icy satellites, the extent of internal oceans, the neutral atmosphere and ionosphere structure of Jupiter and its satellites, etc.

According to the plan, "JUICE" will make 21 flybys of Callisto between 2031 and 2034, with the closest distance to the surface being only 200 kilometers. During this period, starting from July 2032, "JUICE" will fly over Europa twice, with the closest distance being only 400 kilometers. The main purpose is to measure the thickness of its ice layer and search for organic molecules and signs of life.

After that, the probe will start its main engine and enter orbit around Ganymede, operating at an altitude of 500 kilometers for at least 9 months to get a clear view of the largest satellite in the solar system. When the fuel it carries runs out, in order to ensure that it does not contaminate other satellites of Jupiter, JUICE will die by impacting Ganymede, and the debris will remain on Ganymede forever.

Juice's mission ended on Ganymede, so what's so special about Ganymede? Let's take a look at it now.

Ganymede is not only the largest of Jupiter's many satellites, but also the largest of all known satellites in the solar system. Ganymede has a diameter of about 5,262 kilometers and a mass of about 1.5 trillion tons. From this volume, it can be seen that its volume has exceeded Mercury, one of the eight planets, but due to its lower density, its mass is much smaller than Mercury.

Calculated from the nearest to the farthest distance from Jupiter, Ganymede is the seventh satellite orbiting Jupiter, with an average orbit radius of about 1.07 million kilometers and a revolution and rotation period of about seven days. In other words, like our moon and many of Jupiter's satellites, Ganymede is also a satellite that is tidally locked by the planet's gravity, always facing the host star with one side and facing away from the host star with the other side.

Ganymede is the only satellite in the solar system known to have a magnetosphere. Scientists have inferred that Ganymede probably has a flowing core composed of rich iron, and the magnetic field is generated by the movement of this flowing core. Ganymede has a thin atmosphere on its surface, which contains atomic oxygen, oxygen and ozone, but it is not yet certain whether it has an ionosphere.

Ganymede is mainly composed of silicate rocks and ice bodies, and the entire star is clearly layered. Current detections show that Ganymede is composed of almost equal amounts of rock and water, and the water mainly exists in the form of ice bodies, so the mass of the ice bodies accounts for about 46% to 50% of the total mass of the star.

Scientists speculate that two hundred kilometers below the surface of Jupiter, there may be a saltwater ocean sandwiched between two layers of ice, and this ocean is four hundred kilometers deep; other scientists believe, based on various observational data, that the ocean of Ganymede may be far more than that, and there may be multiple layers of oceans sandwiched between the ice bodies, these oceans are superimposed on each other, and the depth is more than one thousand kilometers.

Therefore, Ganymede is the largest reservoir in the solar system. The total amount of water it contains is the largest among all the planets in the solar system, and the total water storage capacity is 30 times that of the Earth!

The structure of Ganymede is roughly divided into three layers. In a star with a radius of about 2,631 kilometers, the inner core radius is approximately between 500 and 900 kilometers, the outer layer of ice mantle is approximately between 800 and 1,000 kilometers thick, and the middle part is a silicate mantle.

Many of the studies on Jupiter's icy satellites are still scientific speculations that have not been confirmed, and there are still more questions to be observed and discovered. The mission of "JUICE" is to gain a deeper and more detailed understanding of Jupiter and its icy satellites based on some of the past explorations.

In past explorations, Europa has become one of the planets in the solar system most likely to have life, because it has many conditions for the existence of life, such as geothermal energy and subglacial oceans. More importantly, it is closer to Jupiter and is more devastated by Jupiter's gravity, so the entire planet will be more dynamic, and the core energy required for life lies in movement.

Therefore, searching for signs of life will be the main mission of "JUICE" on Europa.

Ganymede is nearly twice as far from Jupiter as Europa, so the tidal activity caused by Jupiter's gravity is much smaller. Scientists are convinced that the possibility of life existing there is extremely small. This is why the "juice" was finally splashed on Ganymede after completing its mission, to avoid falling onto Europa and contaminating the subglacial ocean where there may be life.

However, some accidents cannot be ruled out, and perhaps signs of life may be discovered unexpectedly, which would change the final impact plan. Juice will orbit Ganymede for at least nine months, and possibly even more than a few years. Its main tasks are: first, to understand the only satellite in the solar system with a magnetic field, what this magnetic field is, and what impact it has on its evolution and the surrounding area; second, whether there is an under-ice ocean here, and how big the maximum water storage capacity of this solar system is; third, as the largest satellite in the solar system, is it possible to become a habitable place for humans in the future.

Of course, all the explorations and discoveries of Jupiter and its icy satellites have positive guiding significance for the study of the formation and future evolution of the solar system, as well as the study of exoplanets.

Therefore, the successful launch of "Juice" is considered the most important space science event of the year. However, the successful launch is only the first step in a long journey, and there is still a long way to go to achieve the real success of the mission.

Because the journey of Juice to Jupiter is not as simple as most people imagine: once launched, it will go straight to Jupiter. In fact, after launch, Juice has to make a long detour around the Earth, the Moon, and Venus and other celestial bodies, relying on the gravitational slingshot effect of these celestial bodies to reach the kinetic energy to fly to Jupiter.

It's a bit like throwing a discus. "Juice" will make many circles around the Earth-Moon system and Venus. The circle will get bigger and bigger, and the speed of "juice" will get faster and faster. In 2029, "juice" will be thrown out with great force like a discus and enter the transfer orbit from Earth to Jupiter. After a two-year journey, it will reach Jupiter in 2031.

The entire journey of "Juice" is billions of kilometers, and it is full of unknown risks. If there is any mistake, it may disappear and the mission will fail. I sincerely hope and expect that "Juice" can overcome all difficulties and dangers, reach its destination, and complete the mission entrusted by mankind. What do you think? Welcome to discuss.

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