RESUMO
Scattering of light by a rough particulate surface like an asteroid causes a unique signature in the photopolarmetric measurements of the scattered light and yields useful information about the structure and optical properties of the surface. Calculations of scattered light from particles larger than a wavelength of light have been successfully done, using Fresnel's equation and the laws of geometrical optics. We extend these calculations to include Rayleigh and other small particle scattering processes. Small amounts of Rayleigh scattering mixed with Fresnel scattering cause significant changes in single and double events at the inversion angle of polarization plots, and affect their negative branches. The results of these calculations should be useful for remote measurements of the soils of asteroids and the outer planets.
RESUMO
Dust samples have been found to luminesce weakly under proton excitation, but not under ultraviolet. Damage, recovery, and heating effects have been investigated. Chips of breccia show luminescence, from white inclusions only, under ultraviolet and protons. Some rock chips show general luminescence, mainly from plagioclase. No natural or excited thermoluminescence has been found for dust or chips. The electron paramagnetic resonance spectrum shows the same broad Fe(3+) dipole resonance for dust and for some chips; other chips show no response. The polarization characteristics of dust are found to be identical to those of the Sea of Tranquillity, independently of proton damage. Chips show characteristics unlike any part of the lunar surface.
