11:30 AM - 11:45 AM
[PPS03-09] Space Weathering Simulation of Small Bodies with UV Irradiation
- Rapid Changes of Visible Reflectance
Keywords:Space weathering, Ultraviolet irradiation, Reflectance decrease, S-type asteroids
Space weathering is the process to change the optical properties of surface materials of airless rocky bodies. The three typical changes are reddening (increase in spectral slope), darkening (overall darkening), and attenuation of the absorption band in the reflectance spectrum. These changes are thought to be caused by formation of nanophase iron particles in amorphous rim of surface mineral grains. Responsible processes are micrometeorite impacts, solar wind and cosmic ray irradiation, and ultraviolet light from the sun.
So far various experiments of pulse laser irradiation simulating high velocity dust impacts and ion irradiation simulating solar wind irradiation are carried out, only a preliminary work has been done for ultraviolet light irradiation. We conducted a space weathering simulation experiment by irradiation of ultraviolet light on olivine and pyroxene (enstatite) pellet samples. Visible reflectance of olivine and enstatite decreases by 40% and 20%, respectively. Such spectral decrease may be saturated, without altering spectra of longer infrared wavelength. Pulsed laser irradiation should overprint the change by UV irradiation: more darkening from visible and NIR range. Our results suggest that on space weathering of asteroids solar UV is the main cause for the first 1-10 yr, then solar wind irradiation until 1 Myr, and space weathering by micrometeorite impacts afterwards on the surface.
Figure Photograph of olivine and enstatite pellet samples before and after UV irradiation (0.095 h). The number of irradiations increases toward the right.
So far various experiments of pulse laser irradiation simulating high velocity dust impacts and ion irradiation simulating solar wind irradiation are carried out, only a preliminary work has been done for ultraviolet light irradiation. We conducted a space weathering simulation experiment by irradiation of ultraviolet light on olivine and pyroxene (enstatite) pellet samples. Visible reflectance of olivine and enstatite decreases by 40% and 20%, respectively. Such spectral decrease may be saturated, without altering spectra of longer infrared wavelength. Pulsed laser irradiation should overprint the change by UV irradiation: more darkening from visible and NIR range. Our results suggest that on space weathering of asteroids solar UV is the main cause for the first 1-10 yr, then solar wind irradiation until 1 Myr, and space weathering by micrometeorite impacts afterwards on the surface.
Figure Photograph of olivine and enstatite pellet samples before and after UV irradiation (0.095 h). The number of irradiations increases toward the right.