37th DPS Meeting, 4-9 September 2005
Session 15 Asteroid Physical Studies
Poster, Monday, September 5, 2005, 6:00-7:15pm, Music Recital Room

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[15.24] Albedo Distributions of Near-Earth and Intermediate Source Region Asteroids

E.F. Tedesco (UNH), W.F. Bottke (SwRI), S.J. Bus, E. Volquardsen (IfA, UH), A. Cellino, M. Delbo (INAF-OAT), D.R. Davis (PSI), A. Morbidelli (Obs. de la Cote d'Azur), J.L. Hora (CfA), J.D. Adams (Cornell Univ.), M. Kassis (Keck)

We discuss the implications of recent radiometric observations of Near-Earth Asteroids (NEAs) and main belt asteroids near NEA Intermediate Source Regions (ISRAs) and their implications. The derived sizes and albedos are vital for developing reliable NEA population models.

From a sample of ~100 ISRAs, we find: 1) only ~20% of the ISRAs are "dark", in agreement with the model of Morbidelli et al., 2002 (Icarus 158, 329), and 2) the existence of a strong trend of increasing albedo with decreasing size for ISRAs, consistent with this effect found by Delbo et al., 2003 (Icarus 166, 116) for a sample of 11 small S-class NEAs.

The present results are not due to selection effects since the population from which this sample is drawn is essentially complete. Furthermore, the dearth of small asteroids with low albedos and the trend of increasing albedo with decreasing size, is independent of the thermal model used.

Whether the observed predominance of high-albedo objects is real and indicative, for example, of peculiar surface characteristics associated with small asteroids in general (possibly related to short exposure times to space weathering), or is simply the result of systematic errors in the thermal models, is a matter for further analysis.

This work is supported by NASA Grant NNG04GK46G and is based in part upon work supported by NASA under Cooperative Agreement no. NCC 5-538 issued through the Office of Space Science, Planetary Astronomy Program.

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