Persistent but weak magnetic field at the Moon's midstage revealed by Chang'e-5 basalt.

The evolution of the lunar magnetic field can reveal the Moon's interior structure, thermal history, and surface environment. The mid-to-late-stage evolution of the lunar magnetic field is poorly constrained, and thus, the existence of a long-lived lunar dynamo remains controversial. The Chang'e-5 mission returned the heretofore youngest mare basalts from Oceanus Procellarum uniquely positioned at midlatitude. We recovered weak paleointensities of ~2 to 4 microtesla from the Chang'e-5 basalt clasts at 2 billion years ago, attesting to the longevity of the lunar dynamo until at least the Moon's midstage. This paleomagnetic result implies the existence of thermal convection in the lunar deep interior at the lunar midstage, which may have supplied mantle heat flux for young volcanism.