Pyroxene mineralogies of near‐Earth vestoids |
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| Authors: | Thomas H Burbine Paul C Buchanan Tenzin Dolkar Richard P Binzel |
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| Institution: | 1. Departments of Geology and Physics & Astronomy, Bates College, Lewiston, Maine 04240‐6028, USA;2. Kilgore College, Kilgore, Texas 75662, USA and Museum für Naturkunde, Humboldt‐Universit?t zu Berlin, Invalidenstrasse 43, D‐10115 Berlin, Germany;3. Mount Holyoke College, South Hadley, Massachusetts 01075, USA;4. Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA |
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| Abstract: | Abstract— We have calculated pyroxene mineralogies of seven near‐Earth asteroids (NEAs) with reflectance spectra similar to HEDs (howardites, eucrites, and diogenites). Two different sets of formulas (Gaffey et al. 2002; Burbine et al. 2007) are used to calculate the pyroxene mineralogies of the NEAs from their Band I and II centers. The band centers have been adjusted to compensate for the low temperatures on the asteroid surfaces. All of the derived mineralogies from the Gaffey et al. (2002) formulas and the Burbine et al. (2007) formulas overlap. The derived wollastonite (Wo) contents are very similar with differences being only approximately 1 mol%. The derived ferrosilite (Fs) contents differ by only 3 to 8 mol%. The determined pyroxene mineralogies for all seven near‐Earth vestoids are consistent with eucrites or howardites. None of the objects have pyroxene mineralogies consistent with diogenites. The absence of near‐Earth vestoids with pyroxene mineralogies similar to diogenites may indicate that it is difficult to produce sizeable (km‐sized or larger) bodies that are predominantly composed of diogenitic material, suggesting these objects are rubble piles of mixed ejecta. |
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