PHASE CURVES OF METEORITES AND TERRESTRIAL ROCKS - LABORATORY MEASUREMENTS AND APPLICATIONS TO ASTEROIDS

The measurement of the radiation reflected by a particulate surface as a function of the phase angle can be a powerful method for deriving information about the physical and chemical properties of the materials composing the surface layers of atmosphereless bodies of the Solar System. Several theoretical descriptions of the light scattering by a particulate surface have been developed to explain the observations of the phase functions for a number of Solar System bodies (asteroids, satellites of Jupiter, Moon, and Mercury). However, laboratory measurements on naturally occuring materials, both terrestrial and extraterrestrial, are needed to improve the understanding of the physics of the processes involved. The authors report the results of laboratory measurements carried out at the Teramo Observatory to study the reflectance of powdered meteorites and terrestrial rocks at various phase angles. We analyzed the reflectance of 17 meteorites: 14 chondrites (3 C-type, 5 L-type, 4 H-type, 2 LL-type), and 3 achondrites. In addition, a study of the effects on the phase curve of varying the size fraction and the compaction degree has been carried out on terrestrial rocks (peridotite, diabase, quartz-rich sand). © 1990.