Space Weathering of the 3-micron Phyllosilicate Feature induced by Pulsed Laser IrradiationOPEN ACCESS
B.S Prince, M.J. Loeffler
Icarus, available online 11 October 2021
• The effects of laser irradiation on CI and CM simulant samples have been studied using in situ spectroscopy of the 3-μm absorption region.
• Laser irradiation causes both samples to increase in spectral slope.
• Laser irradiation causes both samples to darken initially but subsequent irradiation causes them to brighten slightly.
• Laser irradiation causes the band depth on the 3-μm absorption band to increase by as much as 30%.
• The band shape does not change and the position of the band minima of the 2.72 μm shifts less than 0.001 μm as a result of laser irradiation.
• Our results suggest that this spectral region could be very useful to determine the asteroid composition on surfaces on hydrated asteroids that have undergone extensive aqueous alteration.”
“Here we present results from pulsed laser irradiation of CI and CM simulant samples in an effort to simulate space weathering on airless bodies via micrometeorite impacts. For this study, we focused on determining what type of alteration occurs in the 3-micron absorption region, as this region will be critical to ascertain compositional information of the surface regolith of hydrated asteroids. Generally, using entirely in situ spectral analysis, we find that the laser produces similar effects in both samples. Specifically, irradiation causes the blue spectral slope to decrease until it is relatively flat and that the sample darkens initially with laser irradiation but brightens back to about half of its original level by the end of the irradiation. Furthermore, we also find that laser irradiation causes the band depth on the 3-micron absorption band to increase by as much as 30%, yet the shape of the entire absorption band does not change and the band minima of the 2.72 micron shifts less than 0.001 micron after laser irradiation. The constancy of the latter two parameters, which will be most critical to compositional analysis, suggests that this spectral region could be very useful to determine the asteroid composition on surfaces on hydrated asteroids that have undergone extensive aqueous alteration even if the surface had been subject to a significant amount of space weathering. Whether the same conclusion will be generally applicable to other surfaces containing minerals with a wide range of aqueous alteration is currently unclear but will be tested in future studies. “