Thermal metamorphic history of Antarctic CV3 and CO3 chondrites inferred from the first- and second-order Raman peaks of polyaromatic organic carbon

Kaya

Meteorit & Planetary Scien

et al. 2020

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.

Section: Introductionmentioning

confidence: 99%

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

Kaya

Meteorit & Planetary Scien

et al. 2020

“…This is consistent with low petrologic type chondrites (such as types 1 and 2, which experienced thermal metamorphic temperatures of ≤ 150 °C 61 ), evident from the fact that the majority of previous studies showed the presence of carbonyls in those types of chondrites. However, we have shown the presence of abundant carbonyls in DOM 08006, a slightly more heated petrologic type 3.0 CO chondrite whose Raman carbon geothermometry calculation points to peak metamorphic temperatures of ~ 220–230 °C 44 . This suggests a pathway through which aldehyde and carboxylic acids can form and remain intact under such elevated temperatures.…”

Section: Discussionmentioning

confidence: 72%

“…Post-accretionary processes may also be responsible for the absence of carbonyls in QUE 93744. For instance, the peak metamorphic temperature of QUE 93744 was reported to be ~ 430–490 °C, twice as high as that for DOM 08006 44 . Such elevated temperatures might alternatively be responsible for the absence of carbonyls in QUE 93744.…”

Section: Resultsmentioning

confidence: 99%

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

Sava³

2021

Sci Rep

Self Cite

Meteorites contain organic matter that may have contributed to the origin of life on Earth. Carbonyl compounds such as aldehydes and carboxylic acids, which occur in meteorites, may be precursors of biologically necessary organic materials in the solar system. Therefore, such organic matter is of astrobiological importance and their detection and characterization can contribute to the understanding of the early solar system as well as the origin of life. Most organic matter is typically sub-micrometer in size, and organic nanoglobules are even smaller (50–300 nm). Novel analytical techniques with nanoscale spatial resolution are required to detect and characterize organic matter within extraterrestrial materials. Most techniques require powdered samples, consume the material, and lose petrographic context of organics. Here, we report the detection of nanoglobular aldehyde and carboxylic acids in a highly primitive carbonaceous chondrite (DOM 08006) with ~ 20 nm spatial resolution using nano-FTIR spectroscopy. Such organic matter is found within the matrix of DOM 08006 and is typically 50–300 nm in size. We also show petrographic context and nanoscale morphologic/topographic features of the organic matter. Our results indicate that prebiotic carbonyl nanoglobules can form in a less aqueous and relatively elevated temperature-environment (220–230 °C) in a carbonaceous parent body.

“…Estimated peak metamorphic temperatures are shown on top of (b). CV3 and CO3 data are from Yesiltas et al CM2 and CR2 data are from Busemann et al…”

Section: Resultsmentioning

confidence: 99%

“…We first removed artificial fluorescence background from the spectra by subtracting a polynomial with a shape size of 200 and a noise factor of 2. To derive Raman spectral parameters of the first order carbon bands, we fitted the background-removed spectra with a pair of Lorentzian functions (e.g., refs , , , and ).…”

Section: Methodsmentioning

confidence: 99%

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

Kaya

2021

ACS Earth Space Chem.

Self Cite

Carbonaceous chondrites are among the most primitive meteorites that escaped extreme temperatures and melting in their parent bodies and, as such, offer valuable records of the parent body origins, formation, and evolution. The presence of organic molecules and carbonaceous phases make CM chondrites invaluable as they may have contributed prebiotic material to early Earth. Fine-grained rims (FGRs) and organic-rich dark clasts are particularly interesting features, the origin, formation, and evolution of which are not fully understood. In this study, we aimed to characterize several FGRs and dark clasts in two CM2 chondrites, Aguas Zarcas and Jbilet Winselwan, using backscattered electron images, confocal micro-Raman spectroscopy, and nanoscale near-field infrared imaging and spectroscopy. The nano-FTIR spectra show that the dark clasts and FGRs are chemically heterogeneous at a submicron scale and those of Aguas Zarcas are composed of organics (such as aliphatics, aromatics, and carbonyls) as well as alteration phases (such as phyllosilicates, carbonates, and sulfates). The FGRs are compositionally almost identical and exhibit heterogeneous alteration as well as a lack of fragmentation. The thicknesses of FGRs positively correlate with the enclosed chondrule diameter regardless of the chondrule type. The samples appeared to have experienced minimal brecciation after the chondrules were surrounded by the FGRs. These observations suggest nebular origin for the FGRs. The presence of organics embedded within these FGRs may further indicate that they may have formed in the solar nebula as well. In comparison, Jbilet Winselwan contains relatively less organics and exhibits more thermally metamorphosed mineralogy and matrix textures. These features could be the result of short-duration heating, such as impact heating, which also likely caused shock and dehydration/decomposition of the hydrated phases.