Chemical changes in terrestrial lunar simulants exposed to gamma radiation simulating lunar ionizing radiation environment

Recent research has focused on using in-situ lunar materials for infrastructural construction to develop sustainable lunar infrastructure for human habitats. The development of any infrastructural material for construction typically involves some chemical reactions. For lunar infrastructural construction research, terrestrially derived lunar simulants (which match the chemical compositions and particle size of actual lunar samples from the Apollo and Luna missions) are typically utilized for these feasibility studies. However, there are differences between these lunar simulants and the actual lunar regolith, since the simulants are not subjected to ionizing radiations from galactic cosmic radiation (GCR) and solar energetic particles (SEP) prevalent on the moon. In this study, the simulant materials were subjected to gamma radiation to simulate similar ionizing conditions on Earth. It is demonstrated in this manuscript that gamma irradiation results in the formation of entrapped radicals, which significantly changes the chemical signatures of the terrestrially derived lunar simulants (characterized using Terahertz and Electron Paramagnetic resonance spectroscopy), raising questions and describing the need for further detailed material investigations for the terrestrial methodologies being developed for in-situ resource utilization (ISRU) for lunar construction.