New lunar samples from Chang'e-6 challenge the Late Heavy Bombardment

Analyses of Chang'e-6 samples show material tied to the South‑Pole Aitken Basin dates to about 4.25 billion years and prompt a recalibration of some crater ages by roughly 340 million years, leading authors to describe a gradual decline in impact frequency rather than a clear spike at 3.9 billion years.

Scientists are publishing results from samples returned by China's Chang'e-6 mission to the Moon's far side. These are the first direct rock samples collected from that hemisphere, and they provide new data on lunar geology and impact history. Prior sample collections came only from the near side, so far-side chronology was previously unconstrained. A recent paper in Science Advances reports several implications for crater dating and the early impact environment. Key findings: - Chang'e-6 returned both basalt and norite from the Apollo Basin on the far side; norite is interpreted as material connected to the South‑Pole Aitken (SPA) Basin impact. - Lead–lead dating of the norite yields an age of about 4.25 billion years for material associated with the SPA Basin. - Crater-age estimates on the far side and near side appear broadly similar, supporting comparable impact rates across both hemispheres. - Incorporating the far-side samples shifts some calibration points in the lunar Chronology Function by roughly 340 million years for certain regions. - The distribution of crater ages is consistent with a gradual decline in impact frequency, and the concentration of 3.9‑billion‑year dates on the near side may reflect ejecta from the Imbrium event rather than a solar-system-wide spike. Summary: The Chang'e-6 sample analyses place SPA-related material at about 4.25 billion years and prompt modest recalibration of crater-count dating in some areas. The authors present a picture of a slowly declining impact rate instead of a distinct Late Heavy Bombardment spike at 3.9 billion years, while noting that large single events like Imbrium can dominate local age distributions. Further analyses and related publications are anticipated as researchers continue to study the returned materials.