1,721,081 research outputs found
Space weathering on minor bodies induced by ion irradiation: some experimental results", Mem. S.A.It. Suppl. 6, 45-50 (2005).
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Modelling asteroid surfaces from observations and irradiation experiments: the case of 832 Karin
Full text linkWe define a new approach to model asteroidal space weathering. We started from recent results of ion irradiation experiments (60–400 keV) of meteorites and silicates to give an accurate description of space weathering, and we included its effects in the Shkuratov model. We found that the reddening and darkening process (in the range 0.3–2.5 μm) does not significantly affect the position or relative intensities of the mafic silicate absorption features and it mainly affects the continuum of reflectance spectra. This continuum is parameterized by a CS coefficient, which is strongly related with the number of displacements per unit area (damage parameter); we consequently obtained an exposure time curve, and corresponding astrophysical timescales. We applied this new description of space weathering to model observed spectra of Asteroid 832 Karin, in the 0.4–2.4 μm spectral region. The obtained exposure time is slightly lower than the age of the impact and collisional breakup which originated the Karin asteroidal family, i.e., about 5.75×106 years
Optical constants of particulate minerals from reflectance measurements: the case of calcite
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Spectral Alteration of Meteorite Epinal Induced by Ion Irradiation: a Simulation of Space Weathering Effects on Near Earth Asteroids
No full textWe present results obtained for Epinal (H5), an ordinary chondrite meteorite, irradiated with 60 keV Ar++ ions, simulating solar wind
heavy particle irradiation. Bidirectional reflectance spectra (0.3–2.67 μm) measured after irradiating Epinal samples with different ion fluencies exhibit a progressive reddening that is similar to the spread of spectra observed for S-type near-Earth asteroids. The timescales for inducing the same effects in space as those obtained in laboratory are estimated to be 104–106 yr. These results suggest irradiation by heavy ions may be a very efficient weathering process in near-Earth space
Space Weathering Of Silicates Simulated By Nanosecond Pulse Uv Excimer Laser, Below And Above The Ablation Threshold
No full textLaser irradiation experiments have been performed on powdered silicates (othopyroxene, clinopyroxene, and olivine) using a nanosecond pulse UV excimer laser (193 and 248 nm) to simulate the effects of space weathering induced on minor bodies of the Solar System by micrometeorite bombardment. We have used different fluences (from 0.05 to 2 J/cm2) to weather the samples, experimenting below and above the ablation threshold. All the irradiated materials have shown reddening and darkening of their UV–vis-NIR reflectance spectra. In addition we have found that: (1) below ablation threshold, weathering effects increase with increasing number of laser pulses, and with increasing fluence, confirming that
a thermal process is active; (2) above ablation threshold, weathering is much stronger and efficient than in the previous case, and is independent on the number of pulses.We show that astrophysical time-scales, i.e. times necessary to obtain similar effects on planetary objects, are of about 108 yr for both olivine and pyroxene in the case of ablation. The time grows up to 1010 yr in the case of thermal effects. We infer that micrometeorite bombardment can be rightly simulated by laser irradiation only considering congruent laser ablation
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