The Opposition Effect and Negative Polarization of Structural Analogs for Planetary Regoliths

✍ Scribed by Yu. Shkuratov; A. Ovcharenko; E. Zubko; O. Miloslavskaya; K. Muinonen; J. Piironen; R. Nelson; W. Smythe; V. Rosenbush; P. Helfenstein

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 404 KB
• Volume: 159
• Category: Article
• ISSN: 0019-1035
• DOI: 10.1006/icar.2002.6923

✦ Synopsis

To better understand the negative polarization and brightness opposition effects observed on airless celestial bodies, we carried out simultaneous photometric and polarimetric measurements of laboratory samples that simulate the structure of planetary regoliths. Computer modeling of shadow-hiding and coherent backscatter in regolith-like media are also presented. The laboratory investigations were carried out with a photometer/polarimeter at phase angles covering 0.2 • -4 • and wavelengths of 0.63 and 0.45 µm. We studied samples that characterize a variety of microscopic structures and albedos. A particle-size dependence of the negative branch of polarization for powdered dielectric surfaces was found. Colored samples such as a powder Fe 2 O 3 exhibit a very prominent wavelength dependence of the photometric and polarimetric opposition phenomena. Metallic powders usually exhibit a wide branch of the negative polarization independent of the size of particles. For fine dielectric powders, both opposition phenomena become more promi-1 This paper was presented at the conference "Asteroids 2001