Chemical evolution of primordial salts and organic sulfur molecules in the asteroid 162173 Ryugu

Abstract

Samples from the carbonaceous asteroid (162173) Ryugu provide information on the chemical evolution of organic molecules in the early solar system. Here we show the element partitioning of the major component ions by sequential extractions of salts, carbonates, and phyllosilicate-bearing fractions to reveal primordial brine composition of the primitive asteroid. Sodium is the dominant electrolyte of the salt fraction extract. Anions and NH4+ are more abundant in the salt fraction than in the carbonate and phyllosilicate fractions, with molar concentrations in the order SO42− > Cl− > S2O32− > NO3− > NH4+. The salt fraction extracts contain anionic soluble sulfur-bearing species such as Sn-polythionic acids (n < 6), Cn-alkylsulfonates, alkylthiosulfonates, hydroxyalkylsulfonates, and hydroxyalkylthiosulfonates (n < 7). The sulfur-bearing soluble compounds may have driven the molecular evolution of prebiotic organic material transforming simple organic molecules into hydrophilic, amphiphilic, and refractory S allotropes.

Nitrogen K-edge X-ray adsorption near-edge structure spectroscopy of chemically adsorbed ammonia gas on clay minerals and the 15N/14N-nitrogen isotopic fractionation

“…Recent findings from the analysis of Ryugu samples suggest the important role of N-bearing organic chemical synthesis and diverse molecular profiles on asteroids (e.g., amino acids [ 5 , 45 ]; amines [ 6 ]; nucleobase [ 46 ]). Therefore, the successful identification of NH 3 on the carbonaceous asteroid Ryugu [ 47 ] and cometary NH 3 (67P/Churyumov-Gerasimenko [ 48 ]) is of great importance for the N-bearing chemical evolution and 15 N/ 14 N isotopic dynamics in the solar system.…”

Chemistry in Retrieved Ryugu Asteroid Samples Revealed by Non-Invasive X-ray Microanalyses: Pink-Beam Fluorescence CT and Tender-Energy Absorption Spectroscopy

“…Yet, sulfur chemistry, reactions, and the formation of sulfur-based compounds (especially S-bearing organic molecules) on carbonaceous asteroids are not well-constrained [19]. The varying abundance of sulfur in the "A" and "C" Ryugu samples (~3.3 ± 0.7 wt% and ~5.5 ± 0.7 wt%, respectively), indicates a heterogeneous distribution of sulfides [20]. XAS at the 5 µm scale identified the dominant sulfide as pyrrhotite, both in large grains and finer particles in the matrix.…”

Promethearchaeum syntrophicum gen. nov., sp. nov., an anaerobic, obligately syntrophic archaeon, the first isolate of the lineage ‘Asgard’ archaea, and proposal of the new archaeal phylum Promethearchaeota phyl. nov. and kingdom Promethearchaeati regn. nov.

“…Organic acids were measured using the ion-exclusion chromatography mode of the 930 Compact IC Flex (Metrohm) using a Metrosep Organic Acids - 250/7.8 column without a chemical suppressor module. Concentrations of sulphate, thiosulphate, and nitrate were determined by ion-exchange chromatography with electrical conductivity detection, on the same 930 Compact IC Flex system (Metrohm), as described previously [19].…”