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A. S. Rivkin, D. E. Trilling, L. A. Lebofsky (University of Arizona)
The S-class asteroid 387 Aquitania was identified as anomalous by Burbine et al. [1] on the basis of 0.8--2.5 micrometer spectra taken by Bell et al. [2]. Burbine et al. noted 387~Aquitania has a very weak 2-micrometer pyroxene absorption, and features near 1.5 micrometers, which was interpreted as Al/Mg-spinel, possibly due to an enrichment in CAI abundances compared to common meteorites. Both igneous and primitive origins for 387 Aquitania (and a similar asteroid, 980 Anacostia) were offered, with neither preferred.
We obtained spectrophotometric data from 1.65--3.5 micrometer for 387~Aquitania using NSFCAM on the IRTF on Mauna Kea over three nights (3, 4, and 7 February 1998). These data all indicate that Aquitania has a 3-micrometer absorption feature, indicative of water of hydration. Data points obtained shortward of 2.5 micrometers agree well with previous data. On each of these nights, 3--5 other asteroids were observed and the large majority found to have no feature.
Our data support the finding of Burbine et al. that 387 Aquitania is an unusual member of the S class. We interpret the presence of the 3-micrometer feature as evidence for a more primitive surface for 387 Aquitania, and a mineralogy with affinities toward CV/CO chondrites.
[1] Burbine et al. (1992) Meteoritics v. 27 [2] Bell et al. (1988) LPSC v. 57