Optimized inversion of Chang’e-2 gamma-ray spectrum data into heat production rate for thermal evolution study: Imbrium Basin as an example

• The inversion method of Chang’e-2 gamma-ray spectrum data was optimized. • The heat production rate of the global lunar surface and Imbrium Basin was mapped. • The factors affecting the heat production rate in the Imbrium Basin were analyzed. • The Imbrium Basin structure was divided based on heat production rate. The lunar surface element distribution obtained from Chang’e-2 gamma-ray spectrometer has provided new insights into the thermal activity and element migration of the Moon. To further investigate lunar thermal evolution and geological activities, the heat production rate (HPR) distribution was selected as a breakthrough. An optimized inversion method for Chang’e-2 gamma-ray spectrum data, based on multivariate statistical analysis, was developed to effectively reduce the influence of time-varying factors by improving the background estimation and subtraction process. The results validated the utility of HPR for lunar research. The global HPR distribution maps not only provide a reference for assessing the thermal state of the lunar surface, demonstrating that radiogenic heat production can be reliably studied at a global scale, but also enable detailed investigations of regional geological processes. In the Imbrium Basin, HPR clearly reflects the effects of large-scale impact events and subsequent mare volcanic activity. High-HPR materials associated with impact ejecta can be distinguished from the lower-HPR mare basalts. Furthermore, by integrating HPR data with additional geological information, it is possible to assess and partially subdivide the structure of the Imbrium Basin, providing new quantitative insights into its evolution and compositional heterogeneity.