The two sides of the Moon differ in surface color and composition, roughness, and other features. In a new study, scientists have suggested that the reason for this could be that the depths of the two hemispheres have different temperatures.
Two sides of the Moon
As any large celestial body, the Moon has a shape close to spherical, and any division of it into hemispheres is to some extent artificial. However, in the case of our moon, at least one separation is very justified. One of its hemispheres is always turned toward us and the other away from us.
Moreover, when people saw the latter for the first time in 1959, they were very surprised at how different it was from the near side of us. Recently, NASA experts working with the GRAIL mission published a study suggesting that the causes may lie deep within the two hemispheres.
In general, the hemisphere near us is darker. This is due to the huge eruptions of basaltic lava that once solidified on its surface and formed what we know as seas. At the same time, the hemisphere far from us is brighter, but its topography is more irregular.
Temperature at depth and crustal plasticity
In general, the fact that the near side of the Moon is more volcanically active means that the crust there has more plasticity. According to scientists’ estimates, the difference is not so great. It is 2-3%, but it is enough to explain the difference in relief.
However, the increased plasticity should also have its own explanation. According to the authors of the study, its source should be the uneven heating of the Moon’s depths in different hemispheres. And it should be quite significant – about 170°C.
This is hard to imagine for the Earth, because inside it is a molten ball in which temperature and pressure increase uniformly from the surface to the center. However, the Moon is considered a geologically dead body, meaning its interior is generally cold.
And this is what makes it possible for the described temperature difference to exist. In this pattern, there could be pockets of liquid lava inside our moon, which is heated by the decay of radioactive elements such as thorium. They’re responsible for the different appearance of the hemispheres.
According to phys.org
