Integrated N2-Ar measurements of trace extraterrestrial samples

As one of the major volatile components in extraterrestrial materials, nitrogen isotopes serve not only as tracers for the formation and evolution of the Solar System, but also play a critical role in assessing planetary habitability and the search for extraterrestrial life. The integrated measurement of N₂ and Ar isotopes using noble gas mass spectrometry represents a state-of-the-art technique for such investigations. To support the growing demands of planetary science research in China, we have developed a method for high-efficiency, high-precision method for the integrated analysis of nitrogen (N) and argon (Ar) isotopes. This was achieved by enhancing gas extraction and purification systems and integrating them with a static noble gas mass spectrometer. This method enables integrated N₂–Ar isotope measurements on sub-milligram samples, significantly improving sample utilization and reducing the impact of sample heterogeneity on volatile analysis. The system integrates CO₂ laser heating, a modular two-stage Zr–Al getter pump, and a CuO furnace-based purification process, effectively reducing background levels (N₂ blank as low as 0.35 × 10⁻⁶ ccSTP). Analytical precision is ensured through calibration with atmospheric air and CO corrections. To validate the reliability of the method, we performed N₂–Ar isotope analyses on the Allende carbonaceous chondrite, one of the most extensively studied meteorites internationally. The measured N₂ concentrations range from 19.2 to 29.8 ppm, with δ¹⁵N values between −44.8‰ and −33.0‰. Concentrations of ⁴⁰Ar, ³⁶Ar, and ³⁸Ar are (12.5–21.1) × 10⁻⁶ ccSTP/g, (90.9–150.3) × 10⁻⁹ ccSTP/g, and (19.2–30.7) × 10⁻⁹ ccSTP/g, respectively. These values correspond to cosmic-ray exposure (CRE) ages of 4.5–5.7 Ma, consistent with previous reports. Step-heating experiments further reveal distinct release patterns of N and Ar isotopes, as well as their associations with specific mineral phases in the meteorite. In summary, the combined N–Ar isotopic system offers significant advantages for tracing volatile sources in extraterrestrial materials and will provide essential analytical support for upcoming Chinese planetary missions, such as Tianwen-2.