The Moon with its back to the Earth forever

As the Earth's only natural satellite, the Moon is the Earth's most faithful partner, for billions of years around the Earth, under the Earth's gravity, the Moon is gradually locked by the Earth's tides, with only one side facing the Earth, the other side is forever hidden in the darkness.

Therefore, since ancient times, people's fantasies about the back of the moon have never been interrupted, and there is no shortage of people who believe that the back of the moon is an alien base, until the late 1950s when human aviation technology gained further development and the Soviet Union launched the Moon 3 probe, which took the world's first photo of the back of the moon.

China launched the Change 4 lunar probe at the end of 2018 and achieved the first human soft landing on the back of the Moon, and Tutu 2 continued to research on the back of the Moon, followed by the return of Change 5 with a sample, providing first-hand information for humans to gain a deeper understanding of the surface morphology of the back of the Moon and the development and evolution of the Moon.

Now we know that there is no rumored alien base on the back of the Moon, but the public photos show that the shape of the back of the Moon seems to be a bit different from the front: the back of the Moon is more cratered, with craters caused by meteorite impacts as far as the eye can see

But in fact, the solar system is very vast, planets in the solar system are like a walnut in the theater, it is still very difficult to hit this walnut accurately, and the moon is just a small planet with a diameter of only 3400 km, even the eight planets are not considered, why would it suffer so many meteorite impacts, leaving tens of thousands of craters large and small?

By analyzing samples of lunar soil, scientists found that most of the craters on the Moon were formed in this period 3.8-4.1 billion years ago, which means that within these 300 million years, the Moon suffered from intensive meteorite impacts. , and

At the beginning of the formation of the solar system, space is indeed not very stable, meteorite impact is a common thing, but the moon suffered from the impact of this period, the sun formed 500-800 million years, and the entire solar system tends to be stable, these impacts of meteorites from where?

When Pluto was discovered early last century, astronomers speculated that there were many asteroids outside the orbit of Neptune, and Pluto was only one of them. The Dutch astronomer Herald Koppel believed that there was an orbital region of icy matter orbiting at the edge of the solar system.

This idea was later revised and studied by astronomers, who eventually confirmed the existence of a dense region of asteroids outside the orbit of Neptune, which is somewhat similar to the inner solar system's asteroid belt, a convergence of small bodies in the solar system.

The Kipper Belt is a circular disk of material beyond the known planets in the solar system, all remnants of the early formation of the solar system, extending from Neptune's orbit to about 50 astronomical units from the Sun, although, unlike the asteroid belt, the objects orbiting here are mainly frozen low-boiling mixtures, such as water, ammonia, and methane, from which most comets in the solar system originate. So why would the stably orbiting Kipper Belt suddenly rush out of control in swarms into the solar system?

The planets in our solar system did not form at the same time; for example, Neptune and Uranus were formed relatively late. When they were formed, the strong gravitational force disturbed the surrounding materials, such as the Kipper Belt, where the objects were disturbed by the gravitational force, they deviated from their original orbits and rushed towards the solar system, thus causing a bombing meteorite impact in the solar system.

Not only did the Moon suffer, but other planets in the solar system were not spared either

For example, Mars, Venus, and Earth, as well as Mercury, all suffered violent impacts, and we can see that the other planets also have many large and small craters, while the craters are not visible on Earth because the Earth's active geological movements have gradually covered them up.

The core of the Moon cooled completely 3.5 billion years ago, and there was no geological movement like the Earth's, and those craters stayed on the surface forever, but why are the craters on the back of the Moon more numerous and deeper than those on the front of the Moon?

Morphological, the back of the Moon is more impacted than the front, with craters of varying sizes densely packed, and even some craters with craters within craters, suggesting that the same place was impacted twice.

The terrain is also extremely treacherous, with many peaks as high as about 2000 meters, while the front of the Moon seems to be gentler, not only is there no great contrast between the undulations, but the number of craters is also significantly less after analysis scientists were surprised to find that the back of the Moon not only gullies, even the longest and shortest axis of the Moon are extended to the back of the Moon. And as far as the thickness of the moon's surface is concerned, the back of the moon is also a full 25 kilometers higher than the front.

Scientists believe that at the beginning of the formation of the Earth, a huge planet and the Earth collided, the main part and the Earth melted into one, and the rest went into space with the fragments of the Earth, and under the action of gravity aggregated together to form the Moon, at this time the surface temperature of the Moon is a completely molten state, the surface temperature is basically above 2000 ℃.

The Earth is basically in the same state, and because the Earth's core is more active, and the atmosphere is protected, the Earth's cooling rate is much slower.

When the Moon is gradually tidally locked by the Earth

The side facing the Earth will continue to be affected by high temperatures, and the molten rock is difficult to cool, so meteorite impacts do not leave much of a trace.

The back side of the moon is subject to less heat radiation from the Earth and cools and condenses much faster, leaving a dense crater and treacherous terrain, so it is not surprising that the difference between the back and front sides of the moon.