The Moon is not a particularly large planet; why does it contain such a significant amount of these materials? This question has driven scientists to seek answers.
The Moon is the only natural satellite of Earth. It takes the Moon approximately 29.5 days to orbit Earth. The size of the Moon is about 27% that of Earth. The gravity on the Moon is only about 1/6 that of Earth’s gravity.
The Moon has accompanied Earth for over 4.5 billion years. Its existence has a profound impact on Earth. Without the presence of the Moon, Earth would undergo many significant changes.
The Moon is an essential natural satellite of Earth. (Photo: Baidu)
For instance, tidal patterns would be less pronounced, Earth’s axis would shift, the climate would undergo drastic changes, the night sky would be much darker, Earth would rotate faster, solar and lunar eclipses would not occur, and species that depend on lunar cycles would face extinction… All these factors illustrate how vital the Moon is to Earth.
As Earth’s satellite, humans have been observing this celestial body since ancient times. By the 1960s, many countries sought to explore the Moon. July 20, 1969, marked a historic moment for humanity when astronaut Neil Armstrong became the first person to set foot on the Moon. Following him, many other astronauts traveled to the Moon to explore and unveil the “mysteries” of this celestial body. Numerous strange discoveries have been made on the Moon.
Unveiling the “mystery” of the Moon
One significant discovery came from the Chang’e 4 lunar probe by the China National Space Administration. The Chang’e 4 spacecraft entered lunar orbit on December 12, 2018, and landed on January 3, 2019. The purpose of this mission was to determine the age and composition of an unexplored area of the Moon. Chang’e 4 is the first spacecraft to land on the far side of the Moon.
The landing site of Chang’e 4 is within a lunar crater named Von Kármán. Located in the southern hemisphere on the Moon’s far side, this area had not been explored by any human-made spacecraft prior. Specifically, this region lies in the portion of the Moon that only faces Earth, thus remaining perpetually hidden.
Von Kármán crater. (Photo: Baidu)
This crater has a diameter of approximately 180 km and is located within the South Pole-Aitken Basin, which has an enormous diameter of 2,500 km and a depth of 13 km. According to The Guardian, this is the oldest, largest, and deepest crater on the Moon’s surface.
Many studies have shown that the Aitken Basin was formed as a result of a massive celestial impact shortly after the Moon’s formation. Following this impact, a large amount of material from deep within the Moon was pushed up to the surface.
From a study published in the journal Geophysical Research Letters, Chinese scientists hope to uncover more “secrets” of the Moon through this exploration. According to the research, researcher Peter B. James and his team (from Baylor University) analyzed changes in gravitational forces around the Moon and discovered a mass of metal beneath its surface.
Close-up of a crater on the Moon. (Photo: Baidu)
The research team combined data comparing lunar topographic maps with data collected from NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission. According to the researchers, the anomaly in the Aitken Basin can be accurately explained by a large quantity of metal at depths of several hundred kilometers.
From this, they proposed two hypotheses: first, they developed mathematical models indicating that the remnants of an iron and nickel-rich asteroid may still exist beneath the Moon’s crust. The second hypothesis suggests that the Moon’s core in this area is densely packed with anomalous materials.
Researcher Peter B. James stated: “We believe that deep beneath the Aitken Basin lies a metal deposit five times larger than the island of Hawaii. Although this deposit is vast, it is difficult to observe from Earth because it is located in the Moon’s dark side. I also believe that one of the best laboratories for studying the Moon is the Von Kármán crater.”
The Chang’e 4 probe has found some astronomical information that we have not verified before. (Photo: Baidu)
Even more surprisingly, within this crater, the Chang’e 4 probe discovered some astronomical information that had not been previously verified. Below the Von Kármán crater lies a massive metal deposit at depths of up to 290 km, weighing around 22 million tons. The presence of metal within a celestial body is not uncommon; however, given that the Moon is not large, why does it have such a significant metal reserve?
The hidden metal deposit in the Aitken Basin is primarily composed of iron and nickel, the core components of most celestial bodies in the Solar System. In the primordial solar nebula, iron and nickel are two elements with relatively high masses. When iron and nickel become part of celestial bodies, they slowly sink to the central core due to their high density. Earth’s core is a massive iron-nickel alloy sphere, 3,400 km thick, with a mass equivalent to one-third of Earth’s total weight.
Investigating the origin of the metal deposit
Based on the mathematical models of Peter B. James and his research team, experts believe that the formation of this metal deposit actually stems from a colossal meteorite impact on Earth.
The planet that collided with Earth approximately 4.6 billion years ago is called Theia. Scientists theorize that the Moon was formed from this collision. This planet is thought to have been smaller than Earth at that time, with a size and mass similar to that of Mars. Its orbit was originally stable, but as Earth accumulated more surrounding material, Theia’s orbit became unstable. Eventually, it collided with Earth at a low and oblique angle.
4.6 billion years ago, Earth collided with the planet Theia. (Photo: Baidu)
The slow speed and shallow angle were insufficient to destroy Earth, but a significant portion of its crust was ejected. Heavy elements from Theia sank deep into Earth’s crust, while the remaining material and ejected debris coalesced into a single object over several weeks. Under its own gravity, perhaps within a year, it became a spherical object: the Moon. The impact is also believed to have shifted Earth’s axis, tilting it by 23.5°, causing the axial tilt that results in seasons on Earth. Additionally, it increased Earth’s rotation speed and initiated tectonic activities.
Erik Asphaug, a professor at the Lunar and Planetary Laboratory (LPL) at the University of Arizona, stated that the Moon formed from debris that was ejected into Earth’s orbit. However, two researchers, Alfred G. W. Cameron and William Ward, argue that the Moon was also formed by a tangential collision with a Mars-sized celestial body. However, the outer silicate layer of the colliding celestial bodies mostly evaporated, leaving behind a metallic core. Consequently, most of the material ejected into orbit would consist of silicates, causing the Moon to be deficient in iron upon solidification.
Evidence supporting this collision scenario has been gathered by a research team led by NASA from lunar rocks brought back by astronauts on the Apollo missions over 50 years ago.
Six locations were directly sampled from the manned Apollo Program landings from 1969 to 1972, returning 380.96 kg of lunar rocks and soil to Earth. Additionally, three Soviet Luna robotic spacecraft brought back another 326 grams from 1970 to 1976. The composition of the Moon they discovered has revealed characteristics of Theia.
The result of the impact was the formation of the Moon. (Photo: Baidu)
The CS Monitor reports that the Moon’s crust is composed of 43% oxygen, 20% silicon, 19% magnesium, 10% iron, 3% calcium, and 3% aluminum. The core of the Moon is believed to consist of iron, sulfur, and nickel, with the largest middle layer, or mantle, comprising olivine, clinopyroxene, and orthopyroxene.
The core of the Moon accounts for about 2% of the Moon’s total mass and is in a partially molten state. The surface layer of the Moon also contains small amounts of 0.42% chromium, 0.18% titanium, 0.12% manganese, potassium, uranium, thorium, hydrogen, and several other elements. All these elements form a coating known as regolith. Mafic plutonic rocks and basaltic maria are two types of rocks found in the regolith. Both are types of volcanic rocks formed from cooling lava.
Meanwhile, British scientists, in a report published in the Monthly Notices of the Royal Astronomical Society of the Royal Astronomical Society of Great Britain, announced that they have indeed found the composition of the Moon derived from debris generated by Earth’s collision with Theia. Among the debris from the collision, scientists discovered a mass of self-gravitating material, nearly the size of the Moon, containing nearly 1% iron similar to that of the Moon.
In the future, humanity will use the Moon as a site for resource extraction. (Photo: Baidu)
Thus, thanks to scientific tools, the history of Earth, the Moon, other celestial bodies, and their secrets are gradually being revealed. The Moon is not only a source of rare metals but also provides many other materials such as silicon, rare earth elements, titanium, aluminum, water, and helium-3 isotopes. In addition, the construction of lunar mines will also provide humanity with a base, stopover, or refueling point for spacecraft continuing to conquer other planets.
Currently, the Moon has become a coveted target for many major nations. Numerous billionaires and owners of private space companies have approached NASA to “claim” the Moon, including Amazon CEO Jeff Bezos and SpaceX founder Elon Musk. Moreover, the European Space Agency plans to start resource extraction on the Moon as early as 2025. Therefore, it is highly likely that in just a few years, we will be able to utilize many materials extracted from the Moon for production or refining.
