Infrared diffuse reflectance spectra of weathered and unweathered CR2 chondrites: Comparison with asteroids

摘要

The presence and intensity of absorption band near 3μm in the reflectance spectra are due to the presence and abundance of hydrates and/or hydroxylions. Previously, we have shown that Renazzo (CR2 chondrite) is an excellent spectral match to 2 Pallas (B-type asteroid) in the wavelength region near 3μm. In this paper, we have measured infrared diffuse reflectance spectra of eight Antarctic CR2 chondrites and have compared reflectance spectra of CR2 chondrites with those of eight asteroids which belong to the C, G, B and F taxonomic classes. The spectral absorption near 3μm of Antarctic CR2 chondrites are deepened and rounded compared to that of Renazzo (fell 1824). This difference implies the presence of corrosion products probably due to terrestrial weathering of the Antarctic CR2 chondrites. This is the reason why no asteroids has been found that has an Antarctic CR2 meteorite counterpart. In addition to the close similarity between Pallas and Renazzo, the overall spectral profile of 511 Davida also exhibit similarity to the Renazzo spectrum.