High-albedo asteroid 434 Hungaria: Spectrum, composition and genetic connections

Abstract

New data in the wavelength region of approximately 0.4-2.5 μm have been obtained for asteroid 434 Hungaria. This is the most complete visible to near-infrared spectrum to date for this object. The near-infrared portion of the spectrum (about 0.8-2.5 μm) is smooth, featureless, and agrees well in the overlap region with new visible region data. However, visible region (about 0.45-0.9 μm) data appear to exhibit weak, broad spectral absorption features near 0.5, 0.6-0.7, and 1 μm. If real, the presence of such features would strongly constrain the compositional determination of Hungaria since it has a relatively high albedo of 46%. Most minerals that exhibit similar absorption features, and are commonly found in meteorites, have a much lower albedo. Asteroid 434 Hungaria has been observed more than six times in these overlapping spectral regions, and it is now possible to assess its mineral composition with some confidence. The dominant phase on this asteroid is an iron-free mineral, probably enstatite. Hungaria may contain secondary phases causing subtle, visible-region absorption features. Alternatively, the surface layer(s) of the asteroid may be contaminated by an absorbing species from an external source.