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Multi-wavelength observations of Asteroid 2100 Ra-Shalom

2007; Elsevier BV; Volume: 193; Issue: 1 Linguagem: Inglês

10.1016/j.icarus.2007.09.006

1090-2643

Michael K. Shepard, B. E. Clark, M. C. Nolan, L. A. M. Benner, S. J. Ostro, Jon D. Giorgini, F. Vilas, K. S. Jarvis, Susan M. Lederer, L. F. Lim, Tim McConnochie, J. F. Bell, Jean‐Luc Margot, A. S. Rivkin, C. Magri, Daniel J. Scheeres, Petr Pravec,

Geology and Paleoclimatology Research

Abstract We observed near-Earth asteroid (NEA) 2100 Ra-Shalom over a six-year period, obtaining rotationally resolved spectra in the visible, near-infrared, thermal-infrared, and radar wavelengths. We find that Ra-Shalom has an effective diameter of D eff = 2.3 ± 0.2 km , rotation period P = 19.793 ± 0.001 h , visual albedo p v = 0.13 ± 0.03 , radar albedo σ ˆ OC = 0.36 ± 0.10 , and polarization ratio μ c = 0.25 ± 0.04 . We used our radar observations to generate a three-dimensional shape model which shows several structural features of interest. Based on our thermal observations, Ra-Shalom has a high thermal inertia of ∼103 J m−2 s−0.5 K−1, consistent with a coarse or rocky surface and the inferences of others [Harris, A.W., Davies, J.K., Green, S.F., 1998. Icarus 135, 441–450; Delbo, M., Harris, A.W., Binzel, R.P., Pravec, P., Davies, J.K., 2003. Icarus 166, 116–130]. Our spectral data indicate that Ra-Shalom is a K-class asteroid and we find excellent agreement between our spectra and laboratory spectra of the CV3 meteorite Grosnaja. Our spectra show rotation-dependent variations consistent with global variations in grain size. Our radar observations show rotation-dependent variations in radar albedo consistent with global variations in the thickness of a relatively thin regolith.