Elastic collisions in ion irradiation experiments: A mechanism for space weathering of silicates |
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Authors: | Rosario Brunetto Giovanni Strazzulla |
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Affiliation: | a Dipartimento di Fisica, Università di Lecce, via Arnesano, I-73100 Lecce, Italy b INAF-Osservatorio Astrofisico di Catania, via S. Sofia 78, I-95123 Catania, Italy |
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Abstract: | Ion irradiation experiments have been performed on silicates (bulk samples) rich of olivine, pyroxene, and serpentine to simulate the effects of space weathering induced on asteroids by solar wind ions. We have used different ions (H+, He+, Ar+, Ar2+) having different energies (from 60 to 400 keV) to weather the samples, probed by Raman spectroscopy and UV-vis-NIR reflectance spectroscopy. All the irradiated materials have shown reddening and darkening of reflectance spectra in the 0.25-2.7 μm spectral range. We have found that the increase of the spectral slope of the continuum across the 1-μm band is strongly related with the number of displacements caused by colliding ions because of elastic collisions with the target nuclei. The spectral slopes have been compared, at increasing ion fluence, with those from irradiated Epinal meteorite. We show that formation of nuclear displacements by solar wind ion irradiation is a physical mechanism that reddens the asteroidal surfaces on a time-scale lower than 106 years. |
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Keywords: | Spectroscopy Experimental techniques Radiation chemistry Meteorites Asteroid surfaces |
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