VIS-to-MIR reflectance and Raman spectroscopy of the CM2 NWA 12184 carbonaceous chondrite

Abstract

The spectral analysis of CM meteorites can help to constrain the mineralogical composition of their parent body, the C-type asteroids. The CM2 NWA 12184 was spectrally examined employing seven complementary techniques at different spatial resolutions, including VIS-to-MIR reflectance and Raman spectroscopy. Furthermore, the effects of space weathering on asteroids can be investigated by performing laboratory simulations on meteorites samples; thus, the meteorite was processed with He⁺ ions at 200 keV (maximum fluence of 1.0 × 10¹⁷ ions cm⁻²) to simulate the solar wind irradiation on C-type asteroids. We discriminated the mineralogical composition of the NWA 12184 at the millimeter scale and at the micrometer scale, investigating both matrix and chondrules. The ion experiment produced spectral darkening, reddening, shifting of the hydration band, and weakening of the absorption band ascribed to olivine in the VIS-NIR range, as well as the reduction in the olivine's peak in MIR range, clue of the sample's amorphization. The study identified the native mineralogy of the meteorite, the products of terrestrial weathering, and the aqueous and thermal alteration experienced by the parent body of the sample.