Martian atmospheric and interior volatiles in the meteorite Nakhla

We report isotopic abundances of xenon, argon, and nitrogen for the observed distinct components in Martian meteorite Nakhla. In a stepwise release the 129Xe/132Xe ratios in the 800°C and 1000°C fractions show the signature of the modern atmosphere and other Xe ratios, when corrected for the cosmogenic component, confirm the isotopically fractionated modern atmospheric component. On the other hand, the Xe isotope ratios in the >1000°C steps reveal an isotopically unfractionated interior component, but with radiogenic 129Xe excesses. The isotopic composition of this interior component is consistent with Chass-S Xe (solar type), but is augmented by 244Pu-derived fission Xe. The fission components in interior trapped Xe (in both Nakhla and Chassigny) suggest that Mars effectively retained 244Pu-derived fission gas. A heavy (relative to interior N) nitrogen signature in the 600–900°C temperature steps also suggests a recent incorporation of Martian atmospheric gases. The N signatures in the high-temperature (>1000°C) steps are strongly affected by cosmic-ray-produced 15Nc and 36Ar and 38Ar abundances are dominated by the cosmogenic component. We discuss the signatures of Martian interior nitrogen and heavy noble gases and the constraints they provide on the evolutionary history of Mars.