The upcoming Artemis missions are set to explore the Moon’s largest crater, the South Pole-Aitken basin, which spans approximately 1,930 km in length and 1,600 km in width. This significant geological feature, formed around 4.3 billion years ago following an impact from a large asteroid, has now become a focal point for understanding the Moon’s formation and evolution.
Recent research from the University of Arizona, led by Jeffrey Andrews-Hanna, has revealed critical insights about the crater’s characteristics. Through detailed analysis, the study indicates that the impact that created the South Pole-Aitken basin likely originated from the north, contrary to previous beliefs that suggested a southern impact angle. This new understanding of the crater’s formation has substantial implications for the upcoming missions aimed at landing on its southern rim.
Understanding the Geological Impact
The South Pole-Aitken basin is not just a colossal crater; it is a geological treasure trove. The new findings suggest that impact craters do not distribute material uniformly, with the area at the down-range end typically receiving a thicker layer of ejecta from the impact. The revised understanding of the impact’s direction indicates that astronauts landing near the basin will have the opportunity to collect samples from the Moon’s deep interior, providing crucial insights without the need for extensive drilling.
This region is particularly valuable because it may contain remnants of the Moon’s primordial magma ocean. As this molten layer cooled, heavier minerals sank to form the mantle, while lighter minerals rose to create the crust. Some elements, including potassium, rare earth elements, and phosphorus—collectively known as KREEP—were left behind in the last stages of crystallization. These elements are concentrated on the near side of the Moon, leading to significant volcanic activity and the formation of the dark basaltic plains that are visible from Earth.
New Insights into Lunar Asymmetry
One of the fascinating aspects of the research is the explanation for the lunar asymmetry observed between the near and far sides of the Moon. According to the findings, the crust on the far side is likely thicker, which may have influenced the distribution of the remaining magma ocean. The impact that formed the South Pole-Aitken basin provided a unique opportunity to study this asymmetry, as the basin’s western flank shows high concentrations of radioactive thorium, a marker for KREEP-rich material, while the eastern side does not.
This stark contrast suggests that the impact penetrated the lunar crust at a boundary where KREEP-enriched magma still existed beneath parts of the far side. As a result, the collision opened a window into the transition zone between the two hemispheres, allowing researchers to explore how these regions evolved differently.
The implications for the Artemis missions are significant. By collecting samples from this radioactive region, astronauts will provide scientists with valuable data to test existing models of lunar formation and evolution. The results could reveal how the Moon transformed from a molten body into the geologically diverse satellite we observe today, offering insights into its two very different hemispheres.
This groundbreaking research was published in Nature and highlights the importance of the upcoming Artemis missions in expanding our understanding of the Moon. As astronauts prepare to land near the South Pole-Aitken basin, the potential to uncover the secrets of the Moon’s geological past is a tantalizing prospect for scientists and space enthusiasts alike.
