Core Viewpoint - Chinese scientists have made a significant breakthrough by determining that the South Pole-Aitken (SPA) basin, the oldest and largest impact structure on the Moon, was formed 4.25 billion years ago, providing a crucial anchor point for understanding the early impact history of the solar system [4]. Summary by Sections - The Moon, as Earth's only natural satellite, is marked by numerous impact craters, which serve as historical records of solar system impacts. The SPA basin, with a diameter of approximately 2,500 kilometers, is the oldest impact scar on the Moon, marking a key point in lunar evolution and the beginning of impact history [3]. - The formation of the SPA basin occurred about 320 million years after the formation of the solar system, establishing an initial anchor point for the statistical dating of lunar impact craters. The calculated model age of the SPA basin aligns with isotopic dating results, indicating that the impact flux on the Moon's front and back sides was roughly equivalent during its early history [3]. - The research confirms that the global thermal event occurring 4.35 to 4.33 billion years ago is unrelated to the large impact that formed the SPA basin, providing a reference point and scientific basis for reconstructing the early evolutionary sequence of the Moon [3].