Moon-Based Ground-Penetrating Radar Observation of the Latest Volcanic Activity at the Chang’E-4 Landing Site

The Moon-based ground-penetrating radar (GPR) onboard the Chang’E-4 (CE-4) Yutu-2 rover has deployed on the Moon’s far side, providing an unprecedented opportunity to study the shallow surface geological process and the history of the volcanic eruption of the Moon. The high-frequency radar observed a buried lens structure
$\sim $
27 m below the lunar surface, interpreted as paleoregolith by previous studies. In this study, we conducted a quantitative analysis of the dielectric properties of the buried lens structure observed during the CE-4 mission. Our results reveal that the relative permittivity and loss tangent of the structure is
$\sim $
10.5 and
$\sim $
0.037, respectively. Comparing our estimated dielectric properties with those of Apollo samples and radar-observed lava flows shows that the buried lens is neither regolith nor ejecta material but possibly basalt flow. In addition, we speculate that the buried basalt flow may represent the latest volcanic eruption on the Moon, possibly from the Eratosthenian-aged volcano that occurred approximately 2.5–2.2 billion years ago. Finally, we update the interpretation of the regolith stratigraphic structure observed by the Yutu-2 high-frequency radar at the CE-4 landing site.