Variations Of Organic Functional Chemistry In Carbonaceous Matter From The Asteroid 162173 Ryugu
Primordial carbon delivered to the early earth by asteroids and meteorites provided a diverse source of extraterrestrial organics from pre-existing simple organic compounds, complex solar-irradiated macromolecules, and macromolecules from extended hydrothermal processing.
Surface regolith collected by the Hayabusa2 spacecraft from the carbon-rich asteroid 162173 Ryugu present a unique opportunity to untangle the sources and processing history of carbonaceous matter.
Here we show carbonaceous grains in Ryugu can be classified into three main populations defined by spectral shape: Highly aromatic (HA), Alkyl-Aromatic (AA), and IOM-like (IL). These carbon populations may be related to primordial chemistry, since C and N isotopic compositions vary between the three groups. Diffuse carbon is occasionally dominated by molecular carbonate preferentially associated with coarse-grained phyllosilicate minerals.
Compared to related carbonaceous meteorites, the greater diversity of organic functional chemistry in Ryugu indicate the pristine condition of these asteroid samples.
Scanning transmission x-ray microscoy (STXM) and scanning transmission electron microscopy (STEM) imaging and x-ray absorption near-edge structure (XANES) spectroscopy of Ryugu insoluble organic matter (IOM). Each set of images in A–C are a correlated STXM image at 290 eV, a false-color map of organic functional chemistry (magenta = aromatic C=C at 285 eV; green = ketone C=O at 286.7 eV; blue = carboxyl COOH at 288.5 eV), and a high-angle annular dark field (HAADF) STEM image. A IOM from Chamber A sample A0106. B, C IOM from Chamber C sample C0107. D Hierarchical clustering dendrogram of fitted XANES spectra from Ryugu IOM samples A0106 and C0107. The length of horizontal lines indicates the distance between spectral locations in a 21-dimensional space determined by Gaussian peak fitting. Samples labeled with IOM denote average spectra of surrounding IOM in the vicinity of the discrete grains (excluding other discrete grains). E XANES spectra from individual discrete grains and nanoglobules in A–C, compared to bulk, fluffy-textured IOM from A0106 and C0107, as well as IOM from the Orgueil (CI) and Murchison (CM) carbonaceous chondrites. via PubMed
Variations of organic functional chemistry in carbonaceous matter from the asteroid 162173 Ryugu, Nat Commun. 2024; 15: 7488. Published online 2024 Aug 29. doi: 10.1038/s41467-024-51731-w via PubMed (open access)
Astrobiology, Astrochemistry,
