Every full moon night, when we look up at the full moon, we always find that the "silver disk" is not pure in color, with large areas of dark spots in some regions. People once imagined that it was a vast "ocean", and astronomers called it the "Mare Orientale". It was not until high-performance astronomical telescopes were used to re-examine that large area of dark gray land that it was found that it was actually just a vast desert-like plain with no obvious elevations, similar to the oceans on Earth. The total area of the Mare Orientale accounts for about 25% of the entire lunar surface, and there are 22 identified Mare Orientales, of which 19 face the Earth, including the Mare Imbrium, Mare Tranquillitatis, Mare Serenitatis, Mare Fecunditatis, Mare Nubium, etc. There is also an area on the backside of the moon called "Mare Moscovense", which was discovered in photos of the backside of the moon sent back by the unmanned probe "Luna 3" launched by the Soviet Union. The largest Mare Orientale is Mare Imbrium, with an area of about 5 million square kilometers, which is even larger than half of China. In addition to the "Mare Orientale", there are also some plains on the surface of the moon called "Mare Lacus", "Mare Palus", and "Mare Sinus". In essence, they are no different from the "Mare Orientale".
How were these Mare Orientale formed? Originally, the moon was often hit by small celestial bodies such as comets and asteroids. If the impacting small celestial bodies were not large, they would only leave pits and uneven surfaces on the surface of the moon; if there were larger celestial bodies impacting, it would cause a large eruption of magma in the moon, and these magmas would cover the concave areas left after the impact. After the lava cooled, it formed large areas of "Mare Orientale" on the surface of the moon.
The Mare Orientale on the moon is a huge titanium-iron ore storage base. With the development of technology, humans should be able to rationally utilize these abundant mineral resources on the moon.