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 than the near side is based on several observations, particularly from lunar missions and satellite data.
- Geological Evidence: The far side of the Moon is dominated by large, ancient, and heavily cratered highlands. These highlands are thought to have a thicker crust because they contain more of the heavier elements and minerals that form dense, rigid rock structures. The near side, in contrast, has a large “mare” region (the dark, flat plains formed by ancient volcanic activity), which indicates a thinner crust in comparison. The volcanic activity on the near side is believed to have created large basins where magma reached the surface more easily, thinning the crust in those areas.
- Seismic Data: Seismic waves measured during the Apollo missions suggest variations in the thickness of the crust between the two sides of the Moon. These waves travel differently depending on the thickness and composition of the material they pass through. The far side appears to have a crust that is about 10-15 kilometers thicker than the near side.
- Lack of Large Impact Basins on the Near Side: A key factor supporting the theory of a thicker far side crust is the Moon’s large impact basins. On the near side, there are fewer large basins compared to the far side, which likely indicates a thinner crust that is more prone to being impacted and reshaped. On the far side, the crust is thought to be thicker, providing more resistance to impact, thus resulting in the creation of larger basins.
- Magnetic Field Data: Some of the magnetic anomalies found on the far side further suggest differences in the crust’s composition and structure. The varying magnetic field strength could be due to the different thicknesses of the crust and the materials found beneath it.
In summary, these factors—geological evidence, seismic data, impact basins, and magnetic anomalies—point to the far side of the Moon having a thicker crust compared to the near side.