Earth Planets Space, Vol. 60 (No. 1), pp. 49-59, 2008
S. M. Lederer1, D. L. Domingue2, J. E. Thomas-Osip3, F. Vilas4, D. J. Osip5, S. L. Leeds6, and K. S. Jarvis7
1Dept. of Physics, CSUSB, 5500 University Parkway, San Bernardino, CA 92407
2Johns Hopkins University/Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD 20723
3The Observatories of the Carnegie Institute of Washington, Las Campanas Observatory, Colina El Pino, Casilla 601, La Serena, Chile
4Planetary Astronomy Group, Astromaterials Research and Exploration Science, NASA Johnson Space Center/KR, Houston, TX 77058
5The Observatories of the Carnegie Institute of Washington, Las Campanas Observatory, Colina El Pino, Casilla 601, La Serena, Chile
6Dept. of Physics, CSUSB, 5500 University Parkway, San Bernardino, CA 92407
7ESC Group/ Hamilton Sundstrand, Houston, TX 77058
(Received December 8, 2006; Revised August 22, 2007; Accepted August 28, 2007; Online published February 12, 2008)
We present an analysis of Hapke photometric modeling applied to uniform ground-based UBVRIJHK broadband data of asteroid 25143 Itokawa collected over a wide range of solar phase angles (4°-130°) during the 2004 apparition (Thomas-Osip et al., this issue, hereafter Paper I). Our photometric analyses indicate that Itokawa has a blocky surface with properties different from other, albeit larger, S-class asteroids studied using similar Hapke modeling analyses. Images from the Hayabusa spacecraft affirm the Hapke modeling results, demonstrating the ability of Hapke photometric modeling to predict a rocky asteroid surface correctly; this is the first time that a predicted rocky surface has been observed by a spacecraft. The single particle scattering functions are dominantly forward scattering, suggesting the surface material is composed primarily of clear particles whose scattering is dictated by the particle's surface as opposed to internal scatterers (more typical of S-class asteroids), while the opposition parameters indicate that the regolith may be more compact than most of the limited number of asteroids visited by spacecraft to date. The roughness properties, single particle scattering properties, and opposition surge characteristics are all indicative of a surface where multiple scattering does not play a major role in defining the photometric properties of the regolith.
Key words: Surfaces, asteroids, photometry, regoliths, composition.