5:33 PM - 5:36 PM
[PPS22-P07] Characterization of aqueous alteration of the C-complex asteroids by reflectance spectra of carbonaceous chondrites
3-min talk in an oral session
There is a weak correlation between the 3μm-band absorption position and subtype of the meteorites that expresses the alteration degrees (Rubin et al. 2007). Samples with the absorption position at shorter wavelengths are more altered, while those with the absorption position at longer wavelengths are less altered. This trend is consistent with previous studies (Beck et al. 2010, Takir et al. 2013). However, samples with the absorption position at middle wavelengths show a wide range of alteration degrees. Therefore, it is the case that the absorption position at shortest or longest wavelengths corresponds to greatest or least alteration, respectively. In addition, Fe/Mg ratios of matrix phyllosilicates and the 3μm-band absorption position show a weak correlation. The absorption position shifts from long to short wavelengths with decreasing Fe contents.
On the other hand, 0.7μm-band depth shows no correlation to subtype and thus the 0.7μm-band properties seem to have no relation to the degrees of aqueous alteration. The 0.7μm-band depth also shows no correlation to Fe/Mg ratio of matrix phyllosilicates. Since the 0.7μm band is attributed to Fe3+ and Fe2+ charge transfer in phyllosilicates, the lack of the correlation suggests no clear relation between the alteration degrees and Fe3+/Fe2+ ratios of matrix phyllosilicates
In this study, we investigated relationships between 3μm and 0.7μm band properties and the mineralogy of CM carbonaceous chondrites, and we show that it is possible to characterize to some extent the degrees of aqueous alteration of C-complex asteroids using reflectance spectroscopy.