China's Chang'e-6 samples reshape understanding of lunar impact history

China's Chang'e-6 mission returned 28 tiny impact‑melt fragments from the Moon’s far side on June 25 2024. By measuring argon isotopes in these rocks, researchers dated their formation and found a steady, long‑term record of impacts rather than a brief, intense spike about 3.9 billion years ago, challenging the long‑standing Late Heavy Bombardment theory.

The study notes that earlier samples from the near side—collected by Apollo and Luna missions—were biased toward debris from the large Imbrium impact, giving a misleading impression of a cataclysmic event. "The lunar farside bombardment was not dominated by a cataclysmic spike," said Wanfeng Zhang of the Guangzhou Institute of Geochemistry. Additional analysis of noble gases showed that Earth’s magnetosphere slows solar‑wind particles on the near side, while the far side receives the wind at full speed.

These findings suggest a more gradual accumulation of impacts during the early solar system and may prompt a revision of models for planetary evolution and the conditions that shaped early Earth.