Spectroscopic evidence for two achondrite parent bodies: asteroids 349 Dembowska and 4 Vesta |
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Authors: | Michael A Feierberg Harold P Larson Uwe Fink Howard A Smith |
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Institution: | Lunar and Planetary Laboratory, University cf Arizona, Tucson, AZ 85721, U.S.A. |
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Abstract: | A Fourier spectrometer was used to obtain IR spectra of asteroids 349 Dembowska and 4 Vesta (0.8–2.5μm; 25cm ?1 resolution). The spectrum of Dembowska shows olivine and pyroxene (Fs24 ± 8) with an olivine/pyroxene abundance ratio greater than 2, and possibly as high as 10. This is probably an unsampled achondritic composition, similar to the unique achondrite ALHA 77005. Similar olivine-rich compositions have also been proposed for the mantles of basaltic achondrite parent bodies. Dembowska's mineralogy therefore appears related in some way to the achondrites. but a direct link cannot as yet be made. Our IR observations of Vesta have more complete spectral coverage than those first obtained by Larson and Fink (1975b). Pyroxene (Fs50 ± 5) and plagioclase feldspar are both seen, with a pyroxene/feldspar abundance ratio between 1.5 and 2.0. Vesta's mineralogy is consistent with a mixture of eucrites and howardites on its surface. Time-resolved observations over one-half of the rotation period show no spectral variations at the 2% level, indicating compositional homogeneity. Both 349 Dembowska and 4 Vesta can be considered as candidates for the parent bodies of igneous meteorites. |
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