ACCESSORY PHASES IN AUBRITES - SPECTRAL PROPERTIES AND IMPLICATIONS FOR ASTEROID 44-NYSA

The reflectance spectra of meteoritic metal, meteoritic troilite and the CR carbonaceous chondrite EET8770 have been measured in order to investigate the causes of the spectral differences between the surface of the E-class asteroid 44 Nysa and the opaque free fraction of the Happy Canyon aubrite meteorite. The data indicate that the spectral differences require the presence on Nysa's surface of a small amount of a spectrally red sloped material, of which metal and troilite are the most reasonable candidates, and a material possessing absorption bands near 0.9 mum and 1.8 mum. A material similar to the carbonaceous chondrite inclusions found in some aubrites can provide a match to the 0.9 mum feature and perhaps the 1.8 mum feature. The required abundances of these components depends on whether they are areally distributed or intimately mixed with an enstatite rich material. Based on the petrologic associations seen in aubrites and a series of simulated mineral mixtures, an intimate mixture of 69-92% enstatite and 1-11% metal + troilite and an areal component of 7-20% carbonaceous chondrite type material can provide a reasonable match to the 0.3-2.6 mum spectrum of Nysa.