Formation and Spectral Characteristics of Color Centers in NaCl Induced by Space Radiation

The surfaces of airless bodies are constantly exposed to high-energy particles and ionizing radiation, which interact with surficial materials, inducing crystal defects and modifying spectral characteristics. In this study, a series of irradiation experiments were performed to simulate different types of space radiation, including H⁺ ion irradiation, high-energy electron (HE) irradiation, X-ray irradiation and ultraviolet (UV) irradiation. Their visible and near-infrared (VNIR) reflectance spectra exhibit characteristic absorption features centered <1.0 μm, indicating the formation of various types of color centers in NaCl. In H⁺ ion irradiation and HE irradiation experiments, the irradiated NaCl samples showed a broad Raman envelope in the range of ∼50–300 cm⁻¹, indicating the formation of color centers. However, the Raman spectra of NaCl samples before and after X-ray irradiation seem identical. In addition, the UV irradiation experiment did not induce the formation of color centers. Currently, color centers have already been detected on airless bodies. Our results enhance their credibility by demonstrating that various types of space radiation can induce the formation of color centers in NaCl under simulated conditions. In future orbital and in situ missions, the colored NaCl can be identified via VNIR spectral and Raman spectral surveys, aiding in the analysis of radiation-induced processes on celestial bodies. Our experiments provide insights into the interaction mechanisms between space radiation and surface materials, helping to interpret spectral observations and evaluate the effects of space radiation.