A bizarre 'decapitated' asteroid likely made the moon's largest impact crater. NASA's Artemis astronauts may land near the proof

A new study suggests that the moon’s largest impact basin, the South Pole–Aitken (SPA) basin, was formed by a differentiated asteroid—a large space rock that had separated into a dense iron core and a rocky outer layer. Measuring over 1,200 miles wide, the SPA basin’s distinctive elongated shape is best explained by a 160-mile-wide asteroid striking the moon’s far side at a shallow 30-degree angle, traveling north to south at approximately eight miles per second. This unique impact caused the asteroid’s outer layers to shear off while its dense core continued forward, creating the basin’s tapered elliptical shape. The research, based on high-resolution 3D simulations, also indicates that the impact would have ejected material from deep within the moon’s mantle toward the lunar south pole. This is significant because NASA’s Artemis program plans to send astronauts to the south polar region, where they may encounter deposits of mantle material excavated from depths exceeding 56 miles. Such samples could provide valuable insights into the moon’s internal composition and its geological history, potentially revealing details about the moon’s formation more than four billion years ago. Understanding the SPA basin’s formation has long been a challenge for scientists, with debates surrounding the size, speed, and trajectory of the impactor. The new findings help clarify these uncertainties and emphasize the importance of the basin as a scientific target. While NASA’s Artemis III mission was initially slated to land near the south pole, the first crewed moon landing is now planned for Artemis IV no earlier than 2028. Nevertheless, the study underscores the potential for future lunar missions to collect critical samples that could deepen our understanding of the moon’s evolution and the early solar system. Published in the journal Science Advances, this research not only sheds light on one of the moon’s most prominent features but also highlights the synergy between advanced simulations and upcoming exploration efforts. The SPA basin remains a key focus for lunar science, promising to unlock secrets about planetary formation and impact processes.