Recent research has unveiled intriguing differences between the Moon’s near and far sides, suggesting a significant temperature variation within its mantle. A Chinese research team recently published the first study of lunar rocks brought back by China’s Chang’e 6 sample return spacecraft in 2024. Their results indicate that the far hemisphere of the Moon may indeed be much colder than the near side. This discovery adds to the story that is still being told about the Moon’s geological history and formation.
The Moon likely formed from the debris left over after a huge, head-on collision between the Earth and a Mars-sized protoplanet. At first, the Earth was comprised largely of hot lava. Over the course of billions of years, it has been cooling down at the slowest possible rate since its birth. One of the primary goals of the research team was to gain a better understanding of the Moon’s internal dynamics. Their analysis included the mineral composition, using approximately 300g of lunar soil, with support from the Beijing Research Institute of Uranium Geology.
Distinct Characteristics of the Near and Far Sides
The Moon’s near side is the one that always faces Earth, and its far side has frequently been misnamed the Moon’s “dark side.” These two hemispheres display dramatic contrast in surface features and perhaps even their internal structure. The near side is covered in large, dark plains, known as maria. By contrast, the far side is characterized by heavily cratered, rugged highlands.
For decades, these unique traits have captivated scientists. This curiosity has inspired hypotheses of a massive temperature contrast between the mantles on either side. The new study provides stunning evidence for these expected differences. This was all done using data based on actual samples that will be returned by the Chang’e 6 mission.
“The near side and far side of the moon are very different at the surface and potentially in the interior. It is one of the great mysteries of the moon. We call it the two-faced moon. A dramatic difference in temperature between the near and far side of the mantle has long been hypothesized, but our study provides the first evidence using real samples.” – Professor Yang Li
This new study points to a much more extreme temperature difference—a whopping 100 degrees Celsius. This imbalance could persist for billions of years due to the Moon’s slow cooling history.
Analyzing Lunar Rocks for Clues
To calculate the resulting temperature variations inside the Moon, the scientists used two methods. To learn more, they analyzed the mineral compositions of existing lava flows and compared these findings with 3D computer simulations to infer thermal conditions. Next, they looked at the chemical composition of lunar materials to determine how hot their “parent rock” would have been.
His processing pipeline, created by UCL Earth Sciences Professor Pieter Vermeesch using state-of-the-art techniques, revolutionized this delicate analysis. In doing so, we developed a richer cosmological understanding of the geology of the moon. Scientists analyzed material from one of the largest craters on the moon’s far side. This means that we have an incredible opportunity to investigate areas that have previously been less studied.
“The sample collected by the Chang’e 6 mission is the first ever from the far side of the moon.” – Sheng He
The research was published in the journal Nature Geoscience. These discoveries are primed to shed new light on competing theories regarding the Moon’s temperature differences. Some scientists attribute these differences to past collisions with a now-lost smaller moon. Some researchers believe that gravitational tugs from Earth played a role too.
Implications for Lunar Exploration
These discoveries are more than just piquing our interest. Yet these worlds are not mere moments frozen in time. They reveal profound stories about the mechanics of planetary formation and evolution, influencing far more than the Moon. Learning how temperature variations form and remain will help guide future lunar missions and eventual human exploration of the Moon.
“These findings take us a step closer to understanding the two faces of the moon. They show us that the differences between the near and far side are not only at the surface but go deep into the interior.” – Mr. Xuelin Zhu
Lunar scientists are still hard at work untangling the mysteries of this fascinating field of lunar geology. Their findings set the stage for amazing new discovery and investigation of Earth’s nearest celestial companion.