HIGH-ALBEDO C-COMPLEX ASTEROIDS IN THE OUTER MAIN BELT: THE NEAR-INFRARED SPECTRA
- Public Relations Center, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara 252-5210 (Japan)
- Astronomical Institute, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai 980-8578 (Japan)
- Okayama Astrophysical Observatory, National Astronomical Observatory of Japan, 3037-5 Honjo, Kamogata, Asakuchi, Okayama 719-0232 (Japan)
Primitive, outer-belt asteroids are generally of low albedo, reflecting carbonaceous compositions like those of CI and CM meteorites. However, a few outer-belt asteroids having high albedos are known, suggesting the presence of unusually reflective surface minerals or, conceivably, even exposed water ice. Here, we present near-infrared (1.1-2.5 {mu}m) spectra of four outer-belt C-complex asteroids with albedos {>=}0.1. We find no absorption features characteristic of water ice (near 1.5 and 2.0 {mu}m) in the objects. Intimate mixture models set limits to the water ice by weight {<=}2%. Asteroids (723) Hammonia and (936) Kunigunde are featureless and have (60%-95%) amorphous Mg pyroxenes that might explain the high albedos. Asteroid (1276) Ucclia also shows a featureless reflection spectrum with (50%-60%) amorphous Mg pyroxenes. Asteroid (1576) Fabiola shows a possible weak, broad absorption band (1.5-2.1 {mu}m). The feature can be reproduced by (80%) amorphous Mg pyroxenes or orthopyroxene (crystalline silicate), either of which is likely to cause its high albedo. We discuss the origin of high-albedo components in primitive asteroids.
- OSTI ID:
- 22118781
- Journal Information:
- Astronomical Journal (New York, N.Y. Online), Vol. 146, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
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