Integrated N₂–Ar measurements of trace extraterrestrial samples

As one of the major volatile components in extraterrestrial materials, nitrogen (N₂) 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 argon (Ar) isotopes by 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 high-efficiency, high-precision method for the integrated analysis of N₂ and 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 submilligram 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 cubic centimeters at standard temperature and pressure 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 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 N₂–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.