The South Pole Aitken Basin has long been one of the Moon’s greatest enigmas — a colossal impact crater stretching across the far side of the lunar surface. Now, new research has revealed astonishing findings buried deep beneath this ancient scar, reshaping our understanding of how the Moon — and possibly our entire solar system — evolved.
A study led by Jeffrey C. Andrews-Hanna from the University of Arizona’s Lunar and Planetary Laboratory (LPL) shows that the South Pole–Aitken Basin was formed by a massive asteroid impact from the north, leaving behind a crater more than 1,200 miles wide and 250 miles deep.
What lies hidden within this impact zone could unlock secrets about the Moon’s internal structure, its mysterious asymmetry, and the geologic forces that shaped it billions of years ago.
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What Is the South Pole Aitken Basin?
Located on the Moon’s far side, the South Pole Aitken Basin is both the largest and oldest known impact structure on the Moon — and one of the largest in the entire solar system. Unlike the smooth plains of the near side, this region is rugged, heavily cratered, and permanently hidden from Earth’s direct view.
Formed over four billion years ago, the South Pole Aitken Basin represents a window into the Moon’s early history. Scientists believe that when the asteroid struck, it penetrated deep into the lunar crust, possibly even exposing material from the Moon’s mantle — a layer that remains otherwise inaccessible.
A Groundbreaking Discovery Beneath the Surface
Recent lunar mapping data combining topography, gravity gradients, and compositional scans has revealed that the South Pole Aitken Basin holds more than just impact scars. Researchers detected a massive concentration of thorium and KREEP materials — a chemical mix of potassium (K), rare earth elements (REE), and phosphorus (P) — in its southwestern region.
This discovery suggests that when the asteroid struck, it unearthed remnants of the Moon’s primordial magma ocean, leaving behind radioactive traces that have persisted for billions of years. Thorium, a heat-producing element, indicates that a thin layer of molten magma may have existed beneath the basin’s crust at the time of impact, extending the Moon’s volcanic lifespan far longer than scientists once believed.
The Chang’e 6 Mission Confirms the Pattern
Crucial confirmation has come from China’s Chang’e 6 mission, which successfully collected samples from the northeastern section of the South Pole Aitken Basin. Preliminary analysis revealed that these samples were low in thorium and KREEP, supporting the theory of a chemical divide across the basin.
This compositional contrast — rich thorium deposits to the southwest, poor deposits to the northeast — strongly supports the north-to-south impact trajectory proposed by Andrews-Hanna’s team. As he explains,
“These samples may reveal even more about the early evolution of the Moon than had been thought.”
The South Pole Aitken Basin, therefore, not only records a catastrophic impact event but also preserves a geochemical map of the Moon’s internal differentiation.
NASA’s Artemis Program Eyes the Basin’s South Pole
The new findings have intensified NASA’s interest in the South Pole Aitken Basin, particularly around its southern rim — a region where sunlight meets perpetual shadow. This unique environment, rich in volatile compounds and potential ice deposits, is considered ideal for the Artemis Program, which aims to return humans to the Moon.
Artemis astronauts will target the south polar highlands within the basin to collect rock and soil samples. By analyzing these materials, scientists hope to:
- Determine the depth of the impact excavation.
- Date the cooling and solidification of the lunar magma ocean.
- Understand the redistribution of radioactive elements across the Moon.
The South Pole Aitken Basin could also serve as a prime location for future lunar bases, offering both solar exposure for energy and shadowed craters that may hold frozen water — essential for sustaining long-term human presence.
Why the South Pole–Aitken Basin Matters
The South Pole Aitken Basin represents more than just a geological feature — it’s a cosmic archive. Every layer of debris, every chemical trace, tells a story about the Moon’s violent past and its slow evolution into the world we see today.
This discovery also sheds light on one of lunar science’s biggest puzzles: why the Moon’s near side is dark and volcanic while the far side is bright and mountainous. Scientists now believe that the South Pole Aitken impact redistributed heat-producing materials, driving volcanic activity on one hemisphere and leaving the other geologically quiet.
In short, the South Pole Aitken Basin may hold the key to understanding the Moon’s internal asymmetry, its thermal history, and the processes that shaped terrestrial planets across the solar system.
The Future of Lunar Science
Ongoing missions and future explorations promise to deepen our understanding of the South Pole Aitken Basin. Upcoming lunar orbiters, spectrometers, and sample-return missions are expected to map the basin’s subsurface structure, trace elemental distributions, and perhaps even detect new signs of volcanic remnants buried beneath the crust.
As humanity prepares to return to the Moon, the South Pole Aitken Basin stands as a natural laboratory — a place where ancient impact meets modern exploration, and where the story of the Moon’s birth may finally be told in full.
FAQs
What is the South Pole Aitken Basin?
The South Pole Aitken Basin is the Moon’s largest and oldest impact crater, spanning over 1,200 miles on its far side. It was created by a massive asteroid impact more than 4 billion years ago.
Why is the South Pole Aitken Basin important?
It provides a direct view into the Moon’s internal structure and records the distribution of radioactive materials like thorium and KREEP, crucial for understanding lunar evolution.
What has been discovered inside the South Pole Aitken Basin?
Researchers found evidence of thorium-rich ejecta, suggesting that remnants of the Moon’s ancient molten layer still existed beneath the basin at the time of impact.
How is NASA involved with the South Pole Aitken Basin?
NASA’s Artemis missions plan to explore this region, collect rock samples, and investigate its potential for future human colonization.
How does the South Pole Aitken Basin affect lunar asymmetry?
The impact likely redistributed heat-producing elements, explaining why the Moon’s near side is volcanic while the far side remains rugged and bright.
Conclusion: Unlocking the Moon’s Deepest Secrets
The South Pole Aitken Basin is far more than a crater — it’s a celestial record of impact, heat, and evolution. Each discovery within its depths adds a new chapter to the Moon’s story, guiding humanity closer to uncovering the truth of our cosmic origins.
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