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Silicates
Silicates are a major component in the Solar System. Consequently, obtaining optical constants (real and imaginary part of the refraction index) in the laboratory has a main relevance to interpret spectral observations and remote sensing data of planetary, asteroid, TNOs' (trans-neptunian objects) surfaces, and comets.
Silicates show strong reddening and darkening of their visible-NIR reflectance spectra, when exposed in the laboratory to ion irradiation or laser ablation, the former simulating solar wind and cosmic ion irradiation, the latter simulating micrometeorite bombardment.
We performed an optical characterization of UV laser ablated silicates (olivine, pyroxene), starting from their reflectance spectra in the 0.3-2.5 micron spectral range (experiments performed at room temperature). The goal was to provide useful tools to model space weathering effects on surfaces of asteroids and TNOs.
UV laser ablation affects the upper layers of the target, because silicates strongly absorb at these wavelengths. Thus, in a reflectance spectrum, both the contributions of the altered and underlying unaltered layers are present; of course the relative amount depends on the optical properties and on the wavelength.
Applying the inversion of the Hapke scattering model to spectra of altered samples allows to estimate effective optical constants; these represent an easy and useful tool to characterize a weathered surface in the Solar System, and to check if that surface is compatible with the presence of altered silicates.
The following datafiles include effective optical constants of San Carlos olivine and Bamble orthopyroxene, before and after laser ablation, in the 0.3-2.5 micron range (room temperature).
Data are from: Brunetto et al., 2007. Optical characterization of laser ablated silicates, Icarus, Vol. 191, pp. 381-393. More details can be found in the paper.
Please make reference to Brunetto et al. 2007, Icarus 191, 381, when using these optical constants.
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gle@oact.inaf.it