At this time of national celebration, do not forget that on the back side of the moon, which is invisible on the earth, there are also China's Chang'e-4 and Yutu-2 operating there. Originally designed to work on the far side of the moon for only 3 months, Yutu-2 has now been in service for 1,000 days, with a total driving range of 839 meters.
Before Chang'e-4, no probe or human had ever been to the far side of the moon. Coupled with the fact that the far side of the moon is always away from the Earth, it seems more and more mysterious. Chang'e-4 landed in the Aitken Basin, an extremely old giant crater at the south pole on the far side of the moon. Here, scientists have discovered foreign bodies weighing up to 22 billion kilograms (2200 trillion tons). So, where did these things come from? How mysterious is the far side of the moon?
Some argue that we can't see the far side of the moon because the moon doesn't rotate, or that it's a rare coincidence. But this is not the case, if the moon does not rotate, when the moon is orbiting the earth, we can observe the moon from different angles, so that we can see all the sides of the moon, so there will be no concept of the front and back of the moon.
In addition, this is not a very coincidental phenomenon, but an ordinary phenomenon. The intensity of the Earth's gravitational action on different parts of the Moon varies, resulting in tidal force. The closer to the Earth, the stronger the force, causing the Moon to stretch, causing tidal uplifts to form on either side of the Moon that is close to and away from the Earth.
In the distant past, the moon's rotation speed is relatively fast, and the earth's gravitational pull on the moon's tidal uplift will hinder the moon's rotation, so the moon's rotation angle momentum is constantly consumed, making the moon's rotation speed more and more slow. Until one day, the Moon's rotational angular velocity drops to coincide with the angular velocity of its orbit around the Earth, reaching a tidal locked state.
As a result, for every degree the Moon rotates in its orbit, the Moon rotates the same number of degrees around its axis of rotation, causing the Far side of the Moon to hide from the Earth all the time. This phenomenon is common in the solar system, such as jupiter's four largest moons and Saturn's locked Titan. Pluto and Charon are even more special, as they are tidally locked into each other.
It wasn't until humans launched lunar probes and flew to the far side of the moon that the mysteries there began to be lifted. The view on the far side of the moon is shocking, and unlike the front that is covered with black moon seas, the far end of the moon is covered with a large number of craters, which are the "scars" left by the moon to block meteorites for the earth.
Due to the obstruction of the Moon itself, it is impossible to emit radio waves on the far side of the Moon to communicate directly with the Earth. Before Chang'e-4, China first launched the Queqiao satellite, which operates in a special orbit and can relay the Earth-Moon communication.
With the help of Queqiao, Chang'e-4 and Yutu-2 can communicate with Earth. The Aitken Basin, where Chang'e-4 is located, is unique, and it is thought to have formed 4 billion years ago, when the moon was just 500 million years old and was suffering a massive impact from an asteroid, thus forming the oldest crater on the moon.
Not only that, but this crater is also very large, with a diameter of about 2500 kilometers, and the radius of the moon is only 1737.4 kilometers, and the circumference is 10911 kilometers. Deep underground 290 kilometers below the surface of the Aitken Basin, scientists have detected dense blocks of metal that are 380 million times more massive than the Great Pyramid of Giza.
The analysis shows that the metal block is mainly composed of iron and nickel, which is similar to the composition of the Earth's core. Scientists don't know exactly how this huge metal is trapped deep under the moon, and there are two main explanations.
One explanation is that the meteorite that hit the basin had a core rich in iron and nickel, and after it hit the lunar surface, it brought a large amount of metal, which slowly sank to the ground over time. Another explanation is that there were large amounts of iron-nickel minerals on the lunar surface that year, and when the asteroid hit these minerals, the huge heat caused the minerals to melt and then sink into the ground. In addition, there is a bolder conjecture that this may be the ancient giant starship crashed here.
The exact cause behind this may only be cracked by the Yutu II, which is running there. Previously, Yutu-2 found a strange "stone stele" on the far side of the moon, which is believed to be debris from the impact of an asteroid.
In addition, in a small crater that had recently formed, Yutu-2 also found a strange gelatinous substance. This unknown material is distinctly different from the surrounding lunar soils and lunar rocks, and their color appears to be dark green, which has attracted the attention of scientists.
In short, there are still many mysteries hidden on the far side of the moon that need to be solved. As the only lunar rover currently operating on the far side of the moon, Yutu-2 has high hopes from astronomers, hoping that it will also bring us more new surprise discoveries.