E-type asteroid spectroscopy and compositional modeling

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We present near-infrared spectroscopic observations (0.8-2.5 μm) of E-type asteroids. We combine these observations with visible wavelength spectra obtained by other researchers and perform Hapke theory mixing model simulations of E-type asteroid spectra in order to constrain possible compositions. Aubrites were originally suggested as the meteorite analog for the E-type asteroids because of their similar visible wavelength colors and high albedos. The designation "E" was originally linked with the mineral enstatite, common in aubrite meteorites. More recently, the sulfides troilite and oldhamite have been suggested as possible components of E-type asteroids. We tested the suggested compositional interpretations of aubrite meteorites and/or aubrites enhanced with sulfides. We also tested compositions of aubrites mixed with low-iron silicate minerals. We find that E types can be separated into three groups on the basis of inferred composition: "Nysa-like" E types are consistent with silicate mineralogy higher in iron than the mineral enstatite; "Angelina-like" asteroids are consistent with silicate mineralogy, including a sulfide such as oldhamite; and "Hungaria-like" E types are not inconsistent with aubrites. Our results indicate that some E-type asteroids may be composed of materials that are not sampled by meteorites. Copyright 2004 by the American Geophysical Union.

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Journal of Geophysical Research E: Planets

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