2024-08-26 09:00:28
The two hemispheres of the Moon, the closest natural satellite to Earth, differ significantly: the near side (which always faces Earth) and the far side (which is never seen from our planet). Let’s look at the reasons behind these topographical differences.
Topographic Differences: An Overview
On the near side of the Moon there are huge basalt plains, called “seas” or “maria”, which are quite smooth and dark. On the other hand, the far side is mainly covered by rugged terrain and craters, and much less of these basaltic plains. This asymmetry has raised questions for scientists for many years.
Theories and Scientific Evidence
Meteorite Impact and Basalt Formation:
- Near Face: Basalt seas on the near side of the Moon formed from ancient lava flows that filled large impact basins. These flows occurred during a period of intense volcanic activity around 3 to 4 billion years ago. The presence of these bulges suggests that this region was impacted by large meteorites, causing the release of magma from the lunar interior.
- Far Ahead: Although the far side has also had an impact, it does not have as many large basins. This may be due to lower concentrations of heat-generating radioactive elements in the underlying mantle, resulting in less volcanic activity and therefore fewer lava flows filling the basins hit
- Thickness of the Lunar Crust:
- The lunar crust is much thicker on the far side than on the near side. According to data collected by missions such as the Lunar Reconnaissance Orbiter (LRO), the crust has an average thickness of about 30-40 km on the near side, and on the far side it can reach 50-60 km. This difference in crustal thickness affects the ability of magma to reach the surface. Thicker crust laterally prevented large volumes of magma from emerging, limiting the formation of basalt seas.
- Gravitational Influence of the Earth:
- The Earth and the Moon are in a tidally coupled configuration, meaning that the Moon always shows the same face to the Earth. The proximity of the Earth influenced the distribution of masses on the Moon. The Earth’s gravitational force has caused the Moon’s mantle to deform slightly, facilitating the release of magma on the near side.
- Differences in Composition and Distribution of Elements:
- Differences in the composition of radioactive elements between the two sides of the Moon also play an important role. Isotopic studies have shown a higher concentration of heat-generating elements, such as uranium and thorium, on the near face. These elements provided the heat to keep the magma in a liquid state for a longer time, which favored volcanism on the nearby face.
(Photo: NASA)
Implications for Planetary Science
The topographical differences between the near sides of the Moon not only help us better understand our satellite, but also provide valuable information about processes that can occur on other celestial bodies. By studying the Moon, scientists can extrapolate their findings to other planets and moons in the solar system, furthering our knowledge of planetary formation and evolution.
Future Explorations
Future missions to the Moon, both manned and unmanned, will continue to deepen the topographical and geological differences between the two sides. Projects like NASA’s Artemis program aim to establish a sustainable presence on the Moon, allowing for more detailed and longer investigation of its surface and internal structure.
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