Biconical reflectance, micro‐Raman, and nano‐FTIR spectroscopy of the Didim (H3‐5) meteorite: Chemical content and molecular variations

Abstract

The Didim meteorite contains multiple lithologies and clasts of different petrologic types in a single stone. A mixture of H5 clasts in an unequilibrated H3 host was previously observed in Didim, according to the initial characterization reported in the Meteoritical Bulletin Database, providing an opportunity to investigate molecular composition that contains varying degree of equilibrium with varying mineralogy. We have taken a "from large scale to small scale" approach to spectroscopically investigate the chemical content of Didim. Centimeter-scale biconical reflectance spectra show that Didim contains abundant olivine, pyroxene, and other optically active minerals, evident from a strong Band I near 0.93 µm and a weak Band II near 1.75 µm. Micrometer-scale Raman spectroscopic investigations reveal the presence of carbonaceous material in addition to forsteritic olivine, pyroxene (augite and enstatite), feldspars, and opaque phases such as chromite and hematite. 3-D Raman tomographic imaging shows that the carbonaceous material near chondrules extends underneath a large olivine grain, going further down toward the interior, indicating that the observed carbonaceous matter is likely indigenous. Nano-scale infrared measurements reveal that the observed chemical materials in Didim contain spectral, and therefore, molecular, variations at the~20 nm spatial scale. These chemical variations are normally not accessible via conventional infrared techniques, and indicate the presence of different cations in the molecular composition of observed minerals. By taking the "large scale to small scale" approach, we show that these compositional variations can be captured and investigated nondestructively in meteorites to understand formation/evolution of chemical components in the parent body.

Nano‐FTIR Investigation of the CM Chondrite Allan Hills 83100

“…Figure 10 shows a comparison of the amplitude and phase spectra of positions A, D, and B, as well as nano‐FTIR amplitude and phase spectra of single crystal enstatite (this study), forsterite (Dominguez et al., 2014), and olivine chondrule spectra from Yesiltas et al. (2020). The phase spectra of points A and D have prominent features around 925, 960, and 985 cm −1 , suggesting that the material these spectra represent are compositionally similar.…”

Nano-FTIR spectroscopic identification of prebiotic carbonyl compounds in Dominion Range 08006 carbonaceous chondrite

“…The mineralogies of a carbonaceous chondrite and a cometary dust grain have been investigated at ~ 20 nm spatial resolution using nano-FTIR, although within a limited (1100–800 cm −1 ) spectral range 33 . Recently, molecular variations at the ~ 20 nm spatial scale were shown for meteoritic minerals within 1600–850 cm −1 34 . Kebukawa et al 35 reported nano-FTIR analyses of organics and minerals in two carbonaceous chondrites with ~ 30 nm spatial resolution using photothermal nano-FTIR spectroscopy.…”

Nanoscale Infrared Characterization of Dark Clasts and Fine-Grained Rims in CM2 Chondrites: Aguas Zarcas and Jbilet Winselwan

“…Dark clasts are present in many different types of meteorites including chondrites and achondrites. − Dark clasts are usually carbon- and organic-rich and are often foreign to the host meteorite (i.e., xenolithic clasts in ordinary chondrites ,, and howardites. , On the contrary, the organic matter in CM chondrites is usually present in their matrices and that the dark clasts in CM chondrites may host more carbon, thus organic matter, compared to the matrix.…”