The transition from soluble to insoluble organic matter in interstellar ice analogs and meteorites

Abstract

Context. Carbonaceous chondrites are sources of information on the origin of the Solar System. Their organic content is conventionally classified as soluble (SOM) and insoluble organic matter (IOM), where the latter represents the majority. Aims. In this work, our objectives are to identify possible relations between soluble and insoluble organic matter generated in laboratory experiments and to extrapolate the laboratory analog findings to soluble and insoluble organic matter of meteorites to test their connection. Methods. Using laboratory experiments, processes possibly linking IOM analog (IOMA) to SOM analog (SOMA) precursors are investigated by assuming that dense molecular ices are one of the sources of organic matter in the Solar System. Each organic fraction is analyzed by laser desorption coupled to a Fourier transform ion cyclotron resonance mass spectrometer on a comprehensive basis. Results. SOMA and IOMA significantly differ in their chemical fingerprints, and particularly in their aromaticity, O/C, and N/C elemental ratios. Using an innovative molecular network, the SOMA-IOMA transition was tested, revealing connection between both classes. This new network suggests that IOMA is formed in two steps: a first generation IOMA based on precursors from SOMA, while a second IOMA generation is formed by altering the first IOMA generation. Finally, using the same analytical technique, the molecular content of IOMA and that of the Paris IOM are compared, showing their molecular similarities for the first time. The molecular network application to the Paris SOM and IOM demonstrates that a possible connection related to photochemical ice processing is present, but that the overall history of IOM formation in meteorites is much more complex and might have been affected by additional factors (e.g., aqueous alteration). Conclusions. Our approach provides a new way to analyze the organic fraction of extraterrestrial material, giving new insights into the evolution of organic matter in the Solar System.

Uracil in the carbonaceous asteroid (162173) Ryugu

“…Variations in the concentrations of N-heterocyclic molecules including uracil between A0106 and C0107 samples may be related to the possible differences in the degree of alteration processes induced by energetic particles such as ultraviolet photons and cosmic rays since material in Chamber C may have been ~1 m below the surface of Ryugu for several million years 3,30 . Organic molecules in the surface materials would have experienced energetic processes more extensively than those in the subsurface materials, which potentially causes preferential degradation of molecules at the surface [31][32][33] (Fig. 8).…”

Dust traps in protoplanetary disks efficiently form organic macromolecular matter

“…Water-rich ice is expected to lead to oxygen-rich macromolecular material, inconsistent with IOM. Its formation may therefore rely on a preceding step where SOM is formed, and subsequently, water-ice is removed (e.g., by thermal desorption), and then heavy irradiation to form complex refractory macromolecules 13,41 . In our model, some of the smallest dust grains, which dominate the dust composition in the hot spot, reach temperatures at which solid-state water readily sublimates.…”

Molecular Diversity and Amino Acid Evolution in Simulated Carbonaceous Chondrite Parent Bodies

“…Comparisons between the amino acid content of such a preaccretional laboratory analogue and CM meteorites recovered after the same treatment with acid hydrolysis at 100 °C, a procedure generally used to recover amino acids in meteorites, reveal similarities between preaccretional laboratory analogues and the least altered CM chondrites. 21 However, preaccretional analogues still differ from the organic content of meteorites, 22 likely due to the secondary evolution happening in the meteorite parent bodies that influences the molecular inventory.…”