The Moon’s most ancient and mysterious scar—a colossal basin at its south pole—may soon reveal secrets of its violent past, thanks to the upcoming Artemis II mission. New scientific models suggest that astronauts could uncover traces of a massive, “severed” asteroid impact that carved out the South Pole–Aitken Basin (SPA), a crater so vast it stretches over 2,500 kilometers across the lunar far side. If Artemis II lands in this region, as currently planned, the crew may collect samples from depths never before explored, offering unprecedented insights into the Moon’s internal composition and the early solar system.
The SPA is not just the largest known impact basin on the Moon; it is also one of the oldest, dating back to the Moon’s early history. Unlike most craters, which are roughly circular, SPA has an unusual tapered shape, tapering from north to south. This asymmetry has long puzzled scientists, but recent high-resolution 3D simulations led by planetary scientist Shigeru Wakita at Purdue University suggest a dramatic explanation: the basin was formed by a differentiated asteroid—one with a dense iron core and a rocky outer layer—that struck the Moon at a shallow angle from the north.
According to the simulations, this asteroid, estimated at about 260 kilometers in diameter, approached the Moon from the north at roughly 13 kilometers per second, striking at a low angle of approximately 30 degrees. The force of the impact was so intense that the upper layers of the asteroid were stripped away upon contact, while the dense iron core plunged deeper into the lunar surface, shaping the basin’s distinctive form. The collision also ejected material from depths exceeding 90 kilometers, scattering debris across the lunar south pole. This means that future astronauts landing in this area could potentially find fragments of the Moon’s deep interior, including rocks and minerals that have remained untouched for billions of years.
A Window into the Moon’s Deep Past
The South Pole–Aitken Basin is a treasure trove for planetary scientists. Its size and age make it a critical site for understanding the Moon’s formation and the frequency of large impacts during the solar system’s early days. The basin’s far-side location also means it has been shielded from many of the smaller impacts that have pockmarked the near side, preserving its original structure and the materials excavated during the impact event.
Wakita’s team used advanced computational models to reconstruct the impact scenario, revealing that the asteroid’s shallow trajectory was key to the basin’s unique shape. As the asteroid’s core penetrated the lunar crust, it created a deep, elongated depression, while the outer layers disintegrated upon impact. This process not only explains the basin’s morphology but also suggests that the ejected material could contain clues about the Moon’s mantle and even the primordial magma ocean that once covered its surface.
Why the South Pole?
The lunar south pole is a prime target for Artemis II and future missions for several reasons. Permanently shadowed craters in the region are thought to harbor water ice, a critical resource for sustainable human exploration. The area’s geological diversity—including the SPA—offers a rare opportunity to study the Moon’s deep structure. NASA’s updated mission timeline now places the first crewed landing in the Artemis program no earlier than 2028, but Artemis II, set to launch in 2026, will conduct a lunar flyby, testing the Orion spacecraft’s systems for future landings.
What Artemis II Could Uncover
While Artemis II itself will not land on the Moon, its success will pave the way for Artemis III and subsequent missions to collect samples from the SPA. If astronauts do eventually land in this region, they could retrieve materials ejected from depths never before accessed. These samples could provide direct evidence of the Moon’s internal composition, the nature of the ancient impactor, and even the conditions of the early solar system.
For now, the findings from Wakita’s simulations and other recent studies highlight the scientific potential of the SPA. The basin’s formation story is a testament to the violent and dynamic history of our nearest celestial neighbor, and the Artemis missions promise to rewrite our understanding of the Moon’s origins.
The Road Ahead
NASA’s Artemis program remains on track, with Artemis II’s crewed lunar flyby scheduled for April 2026. The mission will carry four astronauts—Reid Wiseman, Victor Glover, Christina Koch, and Jeremy Hansen—around the Moon, marking the first crewed lunar mission in over half a century. While the first crewed landing is now targeted for no earlier than 2028, the insights gained from Artemis II will be crucial for planning future expeditions to the south pole, and beyond.
As the Artemis program progresses, the scientific community eagerly anticipates the day when astronauts can step onto the lunar surface and begin unraveling the mysteries of the South Pole–Aitken Basin. Until then, the findings from simulations and remote sensing continue to shape our expectations of what lies beneath the Moon’s dusty surface.
For the latest updates on the Artemis missions, visit NASA’s Artemis page. Share your thoughts on how lunar exploration could reshape our understanding of the solar system in the comments below.
