J.R. Neeley^a,b, B.E. Clark^a, M.E. Ockert-Bell^a, M.K. Shepard^c, J. Conklin^d, E.A. Cloutis^e, S. Fornasier^f and S.J. Bus^g

^aDepartment of Physics, Ithaca College, Ithaca, NY 14850
^bDepartment of Physics, Iowa State University, Ames, IA 50011
^cDepartment of Geography and Geosciences, Bloomsburg University, Bloomsburg, PA 17815
^dDepartment of Mathematics, Ithaca College, Ithaca, NY 14850
^eDepartment of Geography, University of Winnipeg, Winnipeg, MB, R3B 2E9
^fLESIA, Observatoire de Paris, 5 Place Jules Janssen, F-92195 Meudon Principal Cedex, France
^gInstitute for Astronomy, 2680 Woodlawn Dr., Honolulu, HI 96822

This work updates and expands on results of our long-term radar-driven observational campaign of main-belt asteroids (MBAs) focused on Bus-DeMeo Xc- and Xk-type objects (Tholen X and M class asteroids) using the Arecibo radar and NASA Infrared Telescope Facilities (Ockert-Bell et al., 2008, Ockert-Bell et al., 2010,Shepard et al., 2008a, Shepard et al., 2008b and Shepard et al., 2010). Eighteen of our targets were near-simultaneously observed with radar and those observations are described in Shepard et al. (2010). We combine our near-infrared data with available visible wavelength data for a more complete compositional analysis of our targets. Compositional evidence is derived from our target asteroid spectra using two different methods, a χ² search for spectral matches in the RELAB database and parametric comparisons with meteorites. We present four new methods of parametric comparison, including discriminant analysis. Discriminant analysis identifies meteorite type with 85% accuracy. This paper synthesizes the results of these two analog search algorithms and reconciles those results with analogs suggested from radar data (Shepard et al. 2010). We have observed 29 asteroids, 18 in conjunction with radar observations. For eighteen out of twenty-nine objects observed (62%) our compositional predictions are consistent over two or more methods applied. We find that for our Xc and Xk targets the best fit is an iron meteorite for 34% of the samples. Enstatite Chondrites were best fits for 6 of our targets (21%). Stony-iron meteorites were best fits for 2 of our targets (7%). A discriminant analysis suggests that asteroids with no absorption band can be compared to iron meteorites and asteroids with both a 0.9 and 1.9 μm absorption band can be compared to stony-iron meteorites.

Reference
Neeley JR, Clark BE, Ockert-Bell ME, Shepard MK, Conklin J, Cloutis EA, Fornasier S and Bus SJ  (in press) The composition of M-type asteroids II: Synthesis of spectroscopic and radar observations. Icarus
[doi:10.1016/j.icarus.2014.05.008]
Copyright Elsevier

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