Why is it believed the backside of the moon has a thicker crust?
The correct answer and explanation is:
The belief that the far side of the Moon has a thicker crust is primarily based on observations and data gathered by space missions. When scientists first explored the Moon, especially after sending spacecraft to map its surface, they noticed differences between the near side (the side facing Earth) and the far side. The far side, which is often incorrectly called the “dark side,” is not always hidden from the Sun, but it does show marked geological distinctions compared to the near side.
One key factor contributing to the belief in a thicker crust on the far side is the Moon’s seismic activity and the behavior of its crust. Data from seismometers placed by the Apollo missions suggested that the crust is indeed thicker on the far side, particularly in certain areas. Furthermore, the far side has far fewer large maria, the dark, flat plains made by ancient volcanic activity, which are abundant on the near side. These maria were formed by volcanic eruptions, which likely occurred when the crust was thinner, allowing lava to rise more easily. The scarcity of maria on the far side implies a more rigid and thicker crust.
Another reason for this belief stems from the Moon’s formation and history. The far side of the Moon may have experienced a different thermal history, which could have contributed to a thicker crust. Some theories suggest that the impact history on the Moon was uneven. The near side of the Moon is more exposed to gravitational forces from Earth, which may have caused the crust on that side to be more stretched and thinner compared to the far side.
Additionally, satellite data from missions like NASA’s Gravity Recovery and Interior Laboratory (GRAIL) has provided detailed maps of the Moon’s gravitational field, further supporting the theory of a thicker crust on the far side, particularly in the highlands.