The recent findings from China's Chang’e 6 mission have shaken up our knowledge of lunar geology, particularly concerning the Moon's farside, which had long been shrouded in mystery. This exciting research highlights active volcanic processes and sheds light on the lunar history we thought we understood.
While many of our earlier missions, including Apollo and Soviet Luna missions, focused on the Moon's nearside, which is visible from Earth, the Chang’e 6’s sample return has provided unprecedented insights from the more enigmatic farside. The mission successfully transported 4.27 pounds (1.935 kilograms) of lunar material back to Earth, marking the first time samples were gathered from this remote region. The analysis, published recently in the prestigious journal Nature, indicates long-term volcanic activity on the Moon.
The team, led by researcher Q. W. L. Zhang, examined 108 distinct basalt fragments collected from two small samples taken by the mission on June 2, 2024. Through isotopic decay analysis of these fragments, they determined most were approximately 2.8 billion years old, but one notable basalt fragment dates back around 4.2 billion years, making it the oldest known sample of KREEP basalt collected so far.
Unlike the nearside, largely composed of maria—vast basalt plains characterized by their dark color—the farside’s surface is predominantly covered by highlands and deep craters. The newfound samples indicate the presence of ancient volcanic activity, prompting experts to revisit previous theories about the Moon's geological evolution.
Planetary geologist and professor emeritus at Brown University, James Head, emphasized the significance of the Chang’e 6 findings, stating, “The enigmatic lunar farside is so different from the lunar nearside in so many ways, and returned samples will allow us to make major strides in solving these problems.”
The Chang’e 6 mission's selection of the southern basalt mare patch within the Apollo Basin was strategic, as this area lies deep within the South Pole-Aitken Basin, showcasing some of the Moon's lowest elevations. This positioning likely permitted ancient volcanic materials to breach the otherwise thicker crust of the farside, yielding samples previously difficult to attain.
The discovery of KREEP basalts on the Moon’s farside challenges earlier assertions and theories. Previously, KREEP basalts had only been detected on the nearside, leading scientists to speculate about the origins of the Moon’s geological features. An interesting hypothesis proposed was the existence of a second smaller Moon created from debris during the formation of our own Moon around 4.5 billion years ago. The material from this supposed pancake moon may have added mass to the thicker crust of the farside, preventing lighter elements like KREEP from being evenly distributed.
With the evidence of KREEP basalts discovered during the Chang’e 6 mission, there is increasing pressure to reevaluate how we understand the Moon's formation and evolution, moving away from the notion established by the so-called "big splat" hypothesis.
The analysis also unearthed how volcanism varies between the two sides of the Moon. While volcanic activity has been confirmed on the nearside as far back as 4 billion years ago, the volcanic history of the farside was significantly nuanced.
Scientists believe there’s significance in the age of the basalts returned by the Chang’e 6 mission, as it indicates more comprehensive volcanic activity on the Moon than previously thought. The KREEP-poor samples, occurring about 1.4 billion years after the KREEP-rich eruptions, suggest there might have been significant shifts within the Moon’s geological processes, emphasizing the importance of both the past and present aspects of lunar research.
To drive future explorations, NASA is also advancing with its Commercial Lunar Payload Services program, which is set to deliver additional science instruments to the Moon, with planned missions focusing on the farside. This collaboration opens the door to more rigorous data collection and exploration to answer the Moon's mysteries yet to be solved.
Meanwhile, the Mare Orientale impact basin on the Moon presents another layer of intrigue to lunar geological studies. A new geological map developed aims to identify the original impact melt structures beneath layers of lava flows. If successful, this could help ascertain the age of the Mare Orientale, giving researchers valuable insights related to impact history on both the Moon and Earth.
A key aspect of the development of this geological map was to distinguish regions likely containing original melt from younger geological features, analogous to separating layers of sediment to study Earth’s geological history. Runyon and his team draw parallels between lunar impacts and those on Earth, asserting the Moon’s preserved record offers invaluable perspectives on our planet’s tumultuous early days.
By knowing the timelines of these lunar impacts, researchers could gain insights concerning Earth’s atmospheric conditions during its formative years, particularly considering interactions with volcanic materials. Some hypotheses suggest extensive bombardment could have influenced Earth's capacity to support life by either stifling evolutionary possibilities or enriching the conditions suitable for life.
These intriguing findings inspire renewed enthusiasm and motivate scientists to continue exploring the Moon. The breadth of knowledge gained from the Chang’e 6 mission and the increasing mapping of Mare Orientale speak volumes about advances we are making as a global community dedicated to lunar research.
Though this knowledge has spilled forth, there's much more to come. Each mission provides yet another piece to the puzzle of the Moon's history and its impact on Earth itself. Stretched over eons and centuries, these ancient celestial mechanics help us reshape our perspectives on the history of life as we know it.
Extraterrestrial exploration stands at the forefront of human curiosity and scientific pursuit, paving new pathways to answering fundamental questions rooted deep within our shared history.
