For a long time, it was the "dark side", although that part of the Moon is also illuminated by the Sun.
The "dark" refers rather to the fact that it is a face that can not be seen from the Earth.
And also, certainly, because it was not exploited no spaceship descended on its surface. So far.
Because this Friday, China launched the Chang-e-4 mission, which has a descent module and an exploration vehicle that is scheduled to land on the crater of Von Kármán, located on the dark side.
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The mission departed from the Xichang satellite launch center and the descent on the Moon is expected in early January.
The Von Kármán crater is a site of interest to scientists because it is within the oldest and largest impact zone on the lunar surface, the Aitken basin.
It is believed that it was probably formed by the impact of a giant asteroid billions of years ago.
Due to a phenomenon known as "synchronous rotation," we see only one face of the Moon because it takes the same time to spin on its own axis than to do it around the Earth.
The Chang & # 39; e-4 mission aims to open the way to send samples of rocks from that lunar region to Earth.
The exploration vehicle plans to research the geology of the region and the composition of its soil.
The dark side, or rather the moon's most remote hemisphere, looks quite different from the one we see on Earth.
Scientists explain that it has an older, thicker, cratered crust. There are also some of these "seas", those dark basalt plains created by the lava flow that are evident on the nearest side.
It is believed that the powerful impact produced by the Aitken basin may have crossed the crust until it reached the lunar mantle. The Chang-e-4's instruments could investigate if this is what happened and shed light on the early history of the only natural satellite on Earth.
The mission will also study the conditions for the transmission of radio waves on the other side of the Moon. The test is designed to lay the foundation for the future creation of radio telescopes in that region of the natural satellite, which is isolated from Earth's radio signals.
The descent module will carry with it a container of 3 kilograms of potato seeds and Arabidopsis, a genus of herbaceous plants, to perform a biological experiment.
This experiment in the "lunar minibiosphere" was designed jointly by 28 Chinese universities.
"We want to study seed respiration and photosynthesis on the moon," Liu Hanlong, director of the experiment and vice president of the University of Chongqing in central China, told Xinhua news agency a few months ago.
Xie Gengxin, the chief designer of the experiment, told Xinhua: "We have to keep the temperature in the miniosphere within a range of 1 to 30 degrees and properly control moisture and nutrition."
"Let's use a tube to direct natural light from the surface of the Moon to the container to make the plants grow."
When located on the far side of the natural satellite, the descent module will not be in the line of sight of the Earth. By him, to send the information to the control center must use the satellite Queqiao, orbited by China in May.
The probe project is based on that of its predecessor, the Chang-e-3, which landed in the Mare Imbrium region in 2013, although it has some important modifications.
China's lunar ambitions
The mission operating vehicle charges two cameras; a radiation experiment built in Germany called LND: and a spectrometer that will perform low-frequency radio astronomy records.
The vehicle carries a panoramic camera; a radar to explore below the lunar surface; an image spectrometer to identify minerals; and an experiment to examine the interaction between the solar wind (a stream of particles released from the sun) and the lunar surface.
Chang-e-4 is part of China's largest lunar exploration program. The first and second Chang & # 39; missions were designed to collect information from the orbit, while the third and fourth were built to perform operations on the surface of Earth's satellite.
The upcoming Chang & # 39; e-5 and Chang & # 39; e missions will aim to bring rocks and lunar soil samples to Earth.
Materials and energy for 10,000 years
In 2013, the BBC had the opportunity to interview Ouyang Ziyuan, a Chinese researcher in the department of lunar exploration and deep space, about sending the Chang & e3 mission.
Ziyuan said the scientific mission will serve to test new technologies and added that "China needs its own intellectual team to exploit the Moon and the Solar System."
The researcher outlined the program's goals: to reach the Moon, land safely, bring samples collected on the Moon to Earth, and eventually send manned missions there.
According to this scientist, the exploration of the Moon can be invaluable to mankind.
As there is no air there, solar panels could operate much more efficiently, and, as Ouyang says, a belt of these panels on our satellite could "sustain the whole world."
The Moon is also so rich in helium-3, a possible fuel for nuclear fusion, that "could solve the demand for human energy for at least 10,000 years"
"It is full of resources, especially rare minerals, titanium, uranium, which are very scarce on Earth, and these resources could be used without limitations."
"There are many possible developments, it is beautiful, so we hope we can use the Moon to support the sustainable development of humans and society," said the Chinese expert.