The probe is aimed at the Jupiter system, and humans are relentlessly pursuing distant mysteries

Recently, the European Space Agency's Jupiter Icy Moon Probe was launched, which will focus on observing Jupiter and its three icy moons many years later. This mission will use new technologies and new plans to focus on multiple key targets such as extraterrestrial life, which can be regarded as another example of deep space satisfying human curiosity. In the future, humans are expected to develop more powerful space vehicles and better detection methods.

Ariane-5 large rocket launches Jupiter Icy Moon Probe (Source: ESA)

In fact, deep space exploration has always been an important direction of aerospace research, especially the exploration of Jupiter, the largest planet in the solar system, which has a mass more than twice that of all other planets in the solar system combined. Jupiter is the first gas giant planet discovered by humans, mainly composed of liquid and gaseous hydrogen, with no solid surface.

However, deep space exploration is limited by rocket launch capabilities, and it is difficult to directly give the probe a sufficient initial speed. After humans master the technology of planetary gravity assist, the flyby probe can continue to accelerate and eventually reach a speed that can theoretically escape the solar system, making it possible to visit Jupiter.

In the 1970s, several American probes flew past Jupiter, initially unveiling the mysterious "veil" of Jupiter, especially the close observation of the Great Red Spot in Jupiter's atmosphere. Later, many deep space probes used Jupiter as an important "transit station" on their long journeys.

The first systematic study of Jupiter by humans was conducted by the Galileo probe. Although the high-gain antenna failed, causing a significant drop in its ability to communicate with the Earth, the Galileo probe still achieved the feat of orbiting Jupiter 34 times between 1995 and 2003, and conducted in-depth research on the structure, magnetic field, and atmosphere of Jupiter and its satellite system. Through the continuous movement of the magnetic poles, it initially formed the conclusion that "there is a huge ocean under the ice layer on the surface of Jupiter's satellites", which is the so-called "Ice Moon", and further promoted the Jupiter Ice Moon exploration plan.

The prerequisite for detecting Jupiter's satellites is to have a full understanding of Jupiter. To this end, the US Juno probe "took the lead" in 2011 and entered orbit around Jupiter in 2016 to study Jupiter from all angles, focusing on determining the proportion of various gases in Jupiter, mass, gravitational field and magnetic field and other details.

The Jupiter Icy Moon Probe and the Europa Clipper, which the United States plans to launch in 2024, will both study Jupiter's icy moons. ESA's main target is Ganymede, the moon of Jupiter. The probe will also repeatedly fly over Europa and Callisto to look for traces of organic molecules. NASA will focus on exploring Europa, the moon of Jupiter.

Both missions are closely related to the hypothesis of "life on Jupiter" that concerns scientists.

Europa is widely known for science fiction. Although it is smaller than the moon, there may be a huge ocean up to 150 kilometers deep under the 15-25 kilometers thick ice layer, and the water content is expected to be much higher than that of the earth. The strange reddish-brown cracks and spots on the surface of Europa are believed to be sulfides and mineral salts. Previously, the Galileo and Juno probes confirmed that there is geological activity inside Europa, which is constantly heating the ocean and ice.

Schematic diagram of Jupiter Icy Moon Probe (Source: ESA)

What do these findings mean? As we all know, the three prerequisites for the development of life on Earth are liquid water, elements that can form organic matter, and energy. These conditions may be met on Jupiter's icy moon, so it is not ruled out that microorganisms that can adapt to extreme environments can be bred.

So why did ESA decide to focus on Ganymede? On the one hand, Ganymede's water content is likely to be far greater than Europa's. On the other hand, Ganymede is indeed very special.

Ganymede is the largest satellite in the solar system and the only satellite known to have a magnetosphere, a thin oxygen-containing atmosphere, and a suspected ionosphere. Its internal structure is quite complex: there may be a flowing core containing iron, an excited magnetic field, and a large amount of ice and ocean covering the globe. Scientists can't resist this mysterious temptation anyway.

Therefore, the exploration mission of Jupiter's icy moon has put forward new demands and promoted research and development work. The core scientific research payloads are designed around Ganymede: penetrating radar can penetrate the ice layer several kilometers thick to explore the ice structure and traces of water; laser altimeter can detect tidal deformation and topography, revealing the internal activities of Ganymede; a variety of instruments will study Ganymede's gravity field, magnetic field and ionosphere in detail, and systematically establish an "archive".

However, energy supply is a big problem for distant planetary exploration missions. Near Jupiter, the energy density of the sun drops sharply to about 4% of that near Earth. Inheriting the valuable experience of its predecessors, the Jupiter Icy Moon Probe will challenge itself to use weak solar energy to maintain the operation of scientific instruments, and has the opportunity to become the spacecraft with the longest operating distance using solar energy.

Visiting the Jovian system also faces a huge challenge, that is, distance. The distance between the Earth and Jupiter is nearly 600 million kilometers at its closest. Limited by the performance of the rocket, the Jupiter Icy Moon Probe must repeatedly rely on the gravity of Venus and the Earth for boosts, which takes up to 7 years. It is expected to arrive near Jupiter around 2030, so there will only be 3 years to actually carry out the research mission. The "Europa Clipper" was originally planned to be launched by the SLS heavy rocket, without the help of gravity boost, and reach Jupiter's orbit within 1 to 2 years. However, due to cost and scheduling issues, the "Europa Clipper" switched to a combination of the Falcon Heavy rocket and planetary boost.

It is not difficult to see that for more distant planetary exploration missions, rocket carrying capacity is still a bottleneck. Looking to the future, human curiosity and demanding mission requirements will stimulate the further improvement of rocket carrying capacity, helping humans to move further towards the stars and the sea. (Author: Mao Xinyuan)