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Spectral and mineralogical diversity among the M-asteroids. P.S. Hardersen 1 , M.J. Gaffey 1 , P.A. Abell 2 , E.A. Cloutis 3 , V. Reddy 1 , S.K. Fieber-Beyer 1 1 University of North Dakota 2 NASA Johnson Space Center 3 University of Winnipeg. M-type Asteroids.
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Spectral and mineralogical diversity among the M-asteroids P.S. Hardersen1, M.J. Gaffey1, P.A. Abell2, E.A. Cloutis3, V. Reddy1, S.K. Fieber-Beyer1 1 University of North Dakota 2 NASA Johnson Space Center 3 University of Winnipeg
M-type Asteroids • Asteroids belonging to the taxonomic M-class have historically been identified based on relatively featureless spectra over visible wavelengths, and moderate albedos of ~20%. • Based on these spectral properties, M-type asteroids have been interpreted as having a metallic (Fe-Ni) or enstatite chondritic surface composition. • These asteroids have often been thought to be core fragments of once-larger differentiated parent bodies, exposed over time through collisional processes. • Extending the study of M-type asteroids into the near-IR will improve our understanding of the compositions of these objects.
IRTF: M-asteroid research Olivine feature. Low-Fe pyroxene feature. CV/CO-chondrite analogue?
IRTF: M-asteroid research • April 2005: Hardersen et al. (2005) show that six of eight M-asteroids have weak ~0.9-micron absorption features. • Primary interpretation: Features caused by surface low-Fe pyroxenes. • March 2006 (LPSC): Additional M-asteroids show spectral evidence of: • low-Fe pyroxene on additional asteroids. • weak olivine spectral features. • spectra similar to CO/CV-chondrites. • weak spinel-like features.
IRTF: M-asteroid research • Implications: The surface mineralogies of the Tholen M-asteroid group are spectrally and mineralogically diverse. Thus M-asteroids include objects with varying geological and thermal histories. • January 2007: Data have been obtained on 39 of the 47 Tholen M-asteroids with the IRTF/SpeX. Should obtain ~100% M-asteroid spectra by the conclusion of this program. • Application: M-asteroid spectra and interpretations are useful for understanding the thermal history of the main asteroid belt.