DPS 35th Meeting, 1-6 September 2003
Session 34. Asteroid Physical Studies III
Poster, Highlighted on, Friday, September 5, 2003, 3:30-6:00pm, Sierra Ballroom I-II

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[34.08] Orbit and Size Dependent Taxonomic Trends within the NEA Population

R.A. Fevig, U. Fink (LPL, University of Arizona)

We report the results of our visible to near-infrared spectrophotometric observations of near-Earth asteroids (NEAs) from 0.55 to 1.00 microns. All of our observations were made with the University of Arizona Steward Observatory Catalina Site 154 cm telescope using our CCD spectrograph. These 40 moderate-resolution spectra, along with 14 previously published spectra from this survey [1], show that there are a number of NEAs with spectral signatures consistent with the most common type of meteorite fall, the ordinary chondrites (OCs), with a slight trend toward increasing numbers of such objects with diminishing size in our sample. We also see evidence for orbit dependent trends in our data. The majority of objects with OC-like spectra are in highly eccentric orbits which encounter asteroids (meteoroids) in the main belt and cross the orbits of multiple terrestrial planets. S-type NEAs reside primarily in orbits which cross only Mars and either never encounter main-belt objects or do so at relatively low energies due to low eccentricity orbits.

Additionally, we have performed a statistical analysis of size and orbit dependent taxonomic trends within the NEA population using a larger set of taxonomically classified NEAs. We have folded the taxonomic classifications of others ([2],[3],[4],[5],[6],[7]) in with our own and will report on the correlation between NEA taxonomic classes and size, source region, and impact probability.

[1] M. Hicks et al. (1998) Icarus 133, 69-78. [2] S. Bus and R. Binzel (2002) Icarus 158, 106-145. [3] R. Whiteley (2001) Ph.D. dissertation, University of Hawaii. [4] R. Binzel et al. (2001) Icarus 151, 139-149. [5] S. Xu et al. (1995) Icarus 115, 1-35. [6] E. Howell (1995) Ph.D. dissertation, University of Arizona. [7] L. McFadden et al. (1989) In Asteroids II , 442-467. University of Arizona Press.

This research has been funded in part by NASA Planetary Astronomy Grant NAG 53937 and NASA Training Grant NGT 550243.

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Bulletin of the American Astronomical Society, 35 #4
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