Optical spectroscopic characterizations of laser irradiated olivine grains

Abstract

Context. Visible and near-infrared spectra of asteroids are known to be susceptible to nanophase irons produced by space weathering processes, thus making mineral identifications difficult. Mid-infrared spectroscopy may retain more mineral features owing to its lattice vibrational nature. Aims. We investigate the structure and reflectance spectral feature changes of olivine grains before and after simulated space weathering. Methods. We irradiate olivine grains by using pulsed laser to simulate varying degrees of micrometeorite bombardments. Reflectance measurements from 0.5 to 25 µm and radiative transfer calculations were carried out in order to compare them with each other. Results. Both the experimental simulations and modeling results indicate that the mid-infrared spectral features of olivine grains can survive the intense irradiations. Although the Christansen Feature is slightly shifted to longer wavelength, major vibrational bands remain essentially unchanged, because the lattice structure is quite immune to even the strongest irradiations, as revealed by both the X-ray diffraction and Raman scattering measurements. Conclusions. Mid-infrared spectroscopy is much more immune to productions of nanophase irons and amorphous materials and thus may be used more reliably in remote detections of minerals on asteroid surfaces.

Comparison of space weathering spectral changes induced by solar wind and micrometeoroid impacts using ion- and femtosecond-laser-irradiated olivine and pyroxene

“…If we compare the spectral changes of our laser irradiation experiments with those in the literature, we find alterations of a similar level, even though these were done mostly using nanosecond laser pulses that induce different post-irradiation processes in the sample. The olivine albedo changes are comparable for instance to those in the work of Yang et al (2017), who used the same olivine material, and the pyroxene changes are similar to the work of Sasaki et al (2002).…”

“…Samples obtained from it are denoted OPX (OrthoPyroXene). We also used olivine pebbles from Hebei Province, China, as in Yang et al (2017). Samples from the olivine pebbles are denoted OL.…”

Optical spectroscopic characterizations of laser irradiated olivine grains (Corrigendum)

“…This is a corrigendum to Yang et al (2017). There is a typo in the Fo (Mg-number) of the olivine sample.…”

Phase-angle dependence of colour ratios and potential implications for lunar remote sensing

“…To answer this question, we used OLV and OPX samples irradiated by a pulse laser to simulate the micrometeorite bombardment weathering process (Yang et al 2017;Jiang et al 2019). Figure 14 shows the ratio R905/R750 for the samples mentioned above as a function of the albedo (represented by R750).…”

“…Figure 14 shows the ratio R905/R750 for the samples mentioned above as a function of the albedo (represented by R750). Except for the four minerals measured in this study, the data of samples with different levels of laser irradiations from Yang et al (2017) (OLV-Y) and Jiang et al (2019) (OPX-J, LRS) are also plotted. The unirradiated OLV-Y and OPX-J samples have the same bulk composition as the OLV and OPX used in this study.…”