Terahertz time-domain spectroscopic investigation of proton-irradiation-induced dielectric evolution in ophicalcite

Ophicalcite, which is enriched in serpentine and carbonate phases that are pervasive across the Martian surface, serves as an optimal terrestrial analogue for investigating the evolution of hydrated minerals on Mars. In this study, the optical and electrical properties of ophicalcite were systematically investigated within the 0.2-1.0 THz range using Terahertz Time-Domain Spectroscopy (THz-TDS) under simulated Martian surface conditions involving proton irradiation and low-temperature environments. The optical parameters of ophicalcite exhibited significant variations following proton irradiation. By applying the Effective Medium Theory (EMT), the intrinsic complex permittivity of the samples was extracted to characterize their optical properties in the terahertz frequency range. Furthermore, within the temperature range of 80 K to 280 K, both the refractive index and the real part of the complex permittivity of ophicalcite exhibited a substantial increase after proton irradiation. By utilizing ophicalcite as a terrestrial analogue, this study demonstrates the distinct response characteristics of serpentine under simulated Martian conditions. Furthermore, the results demonstrate that Terahertz Time-Domain Spectroscopy (THz-TDS) can provide critical data support for future in situ exploration and remote sensing missions on Mars.