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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[15.11] Expanding the Spectral Compositional Information of Asteroid 349 Dembowska

K. S. Jarvis (Jacobs Sverdrup/ESCG), P. A. Abell, F. Vilas (JSC/NASA), A. Cochran (Univ. of Texas at Austin), M. S. Gaffey (Univ. of North Dakota)

Dembowska is an unusually bright asteroid (geometric albedo=0.38+/-.02, Tedesco et al., 1992), with a taxonomic classification of R. Various interpretations of previous datasets have suggested a pyroxene-olivine mixture (e.g. Feireberg et al. 1980, Gaffey et al. 1993) that range from differentiated to partial melts. Data acquired at IRTF at various sub-earth-latitudes and rotational phases have been interpreted to suggest a heterogeneous surface composed of low calcium pyroxene and olivine with a localized zone of brightened albedo north of -25 latitude is seen(Abell, 2003). UV-Vis spectra (0.39 -0.56 microns) were acquired of asteroid 349 Dembowska in 1997 and 2001 at McDonald Observatory, TX using the 2.7-m and 2.1-m telescopes, respectively. We are in the process of analyzing previous datasets and hope to correlate and augment compositional and evolutionary interpretations with our spectral data. Many small absorption features are seen in our data and are repeatable from spectrum to spectrum. Most if not all of these bands are attributable to spin-forbidden crystal field transitions in Fe2+ (Cloutis, 2002). Fe2+ is not an unexpected component of mafic silicates and is often seen in low calcium pyroxenes. No bands were seen that could be attributed to other mineralogical components (for example, C3+, Mn3+, etc.). A broader, shallow feature is seen in some of the spectra, centered around 0.5 microns, and is being investigated. If the source of this feature is interpreted to be a sulfide related absorption feature, it would support a partial differentiation thermal history for the asteroid.

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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.