A chemical sequence of macromolecular organic matter in the CM chondrites

Abstract

Abstract-A new organic parameter is proposed to show a chemical sequence of organic matter in carbonaceous chondrites, using carbon, hydrogen, and nitrogen concentrations of solvent-insoluble and high-molecular weight organic matter (macromolecules) and the molecular abundance of solvent-extractable organic compounds. The H/C atomic ratio of the macromolecule purified from nine CM chondrites including the Murchison, Sayama, and seven Antarctic meteorites varies widely from 0.11 to 0.72. During the H/C change of ~0.7 to ~0.3, the N/C atomic ratio remains at ~0.04, followed by a sharp decline from ~0.040 to ~0.017 between H/C ratios from ~0.3 to ~0

Gradual and stepwise pyrolyses of insoluble organic matter from the Murchison meteorite revealing chemical structure and isotopic distribution

“…This quantity was considerably larger than that observed for other volatile elements (e.g., hydrogen, sulfur, and oxygen). These results are consistent with Naraoka et al (2004) in which the N/ C atomic ratios of IOM samples from carbonaceous chondrites hardly decreased compared to the H/C atomic ratios when heating to 800°C. This feature of nitrogen can probably be attributed to its possession of three valence electrons.…”

Scanning electron microscopical and cross sectional analysis of extraterrestrial carbonaceous nanoglobules

“…Similar shrinkage was also noted in the TEM and is accompanied by minor changes in the shape of the C K edge measured using electron energy-loss spectroscopy (Garvie and Buseck 2004). We speculate that this shrinkage is associated with H loss, as meteoritic organic matter is H-rich (Naraoka et al 2004).…”

Compositional diversity in insoluble organic matter in type 1, 2 and 3 chondrites as detected by infrared spectroscopy

“…Such dehydration has been interpreted to be the result of short duration heating events (Nakato et al, 2008). Short term heating converts primitive IOM into a condensed aromatic structure (Kitajima et al, 2002;Yabuta et al, 2005), with lower H and N contents (Naraoka et al, 2004). The heated CM Y-86720 analyzed in this study has been studied extensively, and the current interpretation is that this meteorite was subjected to a relatively high temperature event (700-750°C) (Akai, 1992).…”

“…2). Aliphatic C-H stretching intensity has been shown to be sensitive to heating -in primitive chondrites, laboratory heating decreases C-H stretching intensity very rapidly (Kebukawa et al, 2010a), and the H/C ratio tends to decrease with increased thermal processing (Naraoka et al, 2004;Alexander et al, 2007Alexander et al, , 2010. Therefore, the intensity of aliphatic C-H stretching vibrations in spectral group A IOM is consistent with type 1 and 2 (that are known to have experienced extensive aqueous alteration) CR, CI and CM chondrites never having experienced sustained temperatures in excess of 150°C (Zolensky et al, 1993).…”