Researchers studying samples brought back from the Moon by the Chang’e-5 mission report that the basalt at the landing site is approximately two billion years old. The result shows that the Moon was volcanically active later than expected. Determining the precise age of this young lava flow on the Moon also provides calibration of the crater-counting technique used to date lunar (and other planetary) surfaces. 

The Chang’e-5 mission – the first lunar sample return since the 1970s – landed in Oceanus Procellarum, an area of solidified lava from an ancient volcanic eruption. The mission collected samples from the surface and returned them to Earth for laboratory analysis. Xiaochao Che et al. analyzed two basalt fragments from the Chang’e-5 sample using lead isotope dating and elemental abundance measurements. 

They find that the rocks formed from magma that erupted about 2 billion years ago, later than other known volcanic lunar samples. There must have been a heat source in the region to explain this late volcanic activity, the authors say. They find no evidence for high concentrations of heat-producing radioactive elements in the deep mantle of the Moon, which had previously been suggested as the cause of these lavas, so alternate explanations (like tidal heating) are required. 

The ages of the samples will help calibrate the crater-counting technique used for dating planetary surfaces, which was previously not well constrained between 1 and 3 billion years ago.