ABSTRACT

Carbonaceous chondrites contain organic matter, but the majority consists of complex macromolecular organic matter collected after acid demineralization. The N contents in carbonaceous chondrites are much lower than C, limiting our understanding of N-bearing functional groups. However, such N-containing compounds could be precursors for life’s raw materials, making detailed chemical analysis essential. This study investigates N-containing organic matter such as N-heterocycles and amines, in various carbonaceous chondrites and xenolithic C-rich clasts using high-sensitivity N K-edge X-ray absorption near-edge structure (XANES) spectroscopy at SPring-8. We compared intact chondrites and insoluble organic matter (IOM) from Orgueil, Murchison, and Tagish Lake meteorites. Most chondrites exhibit three distinct N-XANES peaks: (A) pyridinic N (398.7 eV), (B) pyridinic N and/or nitriles (399.7 eV), and (C) pyrrolic N, amines, amides, and/or ammonium salts (400.8 eV). The Zag meteorite clast and ungrouped type 2 chondrites, such as Tagish Lake and Tarda, show an intense peak at 400.8 eV, indicating enrichment in non-conjugated N-compounds such as amines, amides, and/or ammonium salts. This suggests that their parent bodies contained more abundant ammonia and water. Comparing intact chondrites and IOM reveals significant differences in N-XANES features, suggesting acid-labile N-bearing moieties, like amides and ammonium salts, in addition to solvent extractable compounds such as amines and amino acids, are lost or altered during IOM extraction. This implies that extraterrestrial N compounds may be more diverse and abundant than previously recognized. These findings provide new insights into the N chemistry of meteorites and their potential contribution to the prebiotic inventory of early Earth.