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The famous lunar view that humans see when they look up at night reveals a face with dark "seas" and bright craters. The mysterious far side, which was not revealed until humans began sending probes, then people in the 1960s, is much more crowded with craters and has few dark plains on the near side.
But what made the two sides so different? It is a subject of debate.
Researchers led by Meng-Hua Zhu, of the University of Science and Technology of Macau, now claim that a dwarf planet hitting the moon shortly after its initial training could have caused the unbalanced world we see today. 39; hui. They published their research on May 20 in the Journal of Geophysical Research: Planets.
A series of collisions at the scale of a planet
The usual story of Moon formation is that at one point in Earth's history, a planet-sized body hit our planet, throwing materials high up into space, where they finally merged to meet today. But even this dramatic story can not explain all the quirks of the Earth's moon, like the difference between the near and far sides of the moon.
An index came in 2012, when NASA's GRAIL mission showed that the lunar side crust is thinner than the opposite side.
Thus, over the years, while both sides suffered many asteroid strikes, the close side cracked open. Basins filled with lava filled with water and hardened in the dark maria, or plains, that we see today. But the hidden side has a thicker crust, so there are a lot of craters. But it is more difficult to explain why the two hemispheres have different thicknesses.
One way to solve the problem is to create a small world – the size of the dwarf planet Ceres, which resides in the asteroid belt – would have touched the near face of the Moon after its formation and solidification. The impact would have projected materials and, when these were relocated, they could have fallen mainly on the other side of the moon, burying it within 3 to 6 miles of lunar regolith. Zhu and his colleagues performed a series of computer simulations to test this scenario and discovered that an object plunging the first Moon at a speed of between 14,000 and 15,000 miles at the time would recreate the Moon as we see it today. It may seem fast, but it's only about a quarter of the speed of most small meteors that hit the Earth.
The impact could also help clarify some of the long-standing issues surrounding the materials that make up the Moon. They are very similar to Earth in some respects – a sign that the Moon is actually formed from terrestrial debris – and dissimilar in other respects, indicating additions from an outside world.
This would make our moon a composite of three different big bodies – a different type of three-body problem.
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