Dissecting the complex Ne-Ar-N signature of asteroid Ryugu by step-heating analysis

Samples returned from the carbonaceous asteroid (162173) Ryugu show mineralogical, chemical, and isotopic similarities with Ivuna-type (CI) carbonaceous chondrites, which likely contributed to Earth's volatile inventory.To better understand the complex Ne-Ar-N signature of CI-type material, we analysed a single, mg-sized Ryugu particle by multi-step (n = 85) heating.Noble gases (Ne, Ar) are a mixture between implanted Solar Wind (SW), presolar component(s), and the carbonaceous phase Q, with negligible cosmogenic contributions.The δ 15 N variations observed during progressive heating reflect the presence of various N-bearing phases.The large number of heating steps provide key insights into the effect of thermal processing on the N abundance and isotopic ratio, and indicate that low temperatures can result in extensive N loss from CI-type material, without significantly affecting the bulk N isotopic composition.Nitrogen isotopes, therefore, remain a reliable and powerful tool for tracing volatile sources in the Solar System.