Effects of space weathering on diagnostic spectral features: Results from He+ irradiation experiments

► Minerals show different sensitivity under the same conditions of ion irradiation. ► Ion irradiation induces band strength decrease but negligible band center shift. ► He+ Irradiated olivine spectrum matches spectra of olivine-dominated asteroids. ► Irradiated ilmenite exhibits higher reflectance and stronger absorption features. We performed ion irradiation of mineral samples with 50keV He+, aimed to investigate ion irradiation effects on diagnostic spectral features. Reflectance spectra of samples in 0.375–2.5μm are measured before and after ion irradiation. Silicates, including Luobusha olivine, plagioclase and basaltic glass, have shown reddening and darkening of reflectance spectra at the VIS–NIR range. Olivine is more sensitive to ion irradiation than plagioclase and basaltic glass. Irradiated Panzhihua ilmenite exhibits higher reflectance and stronger absorption features, which is totally different from lunar soil and analog silicate materials in other experiments. Using continuum removal and MGM fit, we extracted and compared absorption features of olivine spectra before and after irradiation. Ion irradiation can induce band strength decrease of olivine but negligible band centers shift. We estimate band centers shift caused by ion irradiation are quite limited, even less than variations due to chemical composition in silicates. It provides one possible explanation for no systematic shift in band positions in lunar soil. Irradiated Luobusha olivine spectrum matches spectra of olivine-dominated asteroids. Our results suggest space weathering should be new clues to explain the subtle difference between A-type asteroid spectra and laboratory spectra of olivine.