Premium
Martian atmospheric and indigenous components of xenon and nitrogen in the Shergotty, Nakhla, and Chassigny group meteorites
Author(s) -
MATHEW K. J.,
KIM J. S.,
MARTI K.
Publication year - 1998
Publication title -
meteoritics and planetary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.09
H-Index - 100
eISSN - 1945-5100
pISSN - 1086-9379
DOI - 10.1111/j.1945-5100.1998.tb01670.x
Subject(s) - martian , meteorite , xenon , atmosphere of mars , mars exploration program , isotopes of xenon , astrobiology , chemistry , radiogenic nuclide , achondrite , isotope , radiochemistry , chondrite , physics , nuclear physics , organic chemistry
— In a study of the isotopic signatures of trapped Xe in shock‐produced glass of shergottites and in ALH 84001, we observe three components: (1) modern Martian atmospheric Xe that is isotopically mass fractionated relative to solar Xe, favoring the heavy isotopes, (2) solar‐like Xe, as previously observed in Chassigny, and (3) an isotopically fractionated (possibly ancient) component with little or no radiogenic 129 Xe rad . In situ ‐produced fission and spallation components are observed predominantly in the high‐temperature steps. Heavy N signatures in ALH 84001, EET 79001 and Zagami reveal Martian atmospheric components. The low‐temperature release of ALH 84001 shows evidence for the presence of a light N component (δ 15 N ≤ ‐21%), which is consistent with the component observed in the other Shergotty, Nakhla and Chassigny (SNC) group meteorites. The highest observed 129 Xe/ 130 Xe ratio of 15.60 in Zagami and EET 79001 is used here to represent the present Martian atmospheric component, and the isotopic composition of this component is compared with other solar system Xe signatures. The 129 Xe/ 130 Xe ratios in ALH 84001 are lower but appear to reflect varying mixing ratios with other components. The consistently high 129 Xe/ 130 Xe ratios in rocks of different radiometric ages suggest that Martian atmospheric Xe evolved early on. As already concluded in earlier work, only a small fission component is observed in the Martian atmospheric component. Assuming that a chondritic 244 Pu/ 129 I initial ratio applies to Mars, this implies that either Pu‐derived fission Xe is retained in the solid planet (in fact, in situ ‐produced fission Xe is observed in ALH 84001) or may reflect a very particular degassing history of the planet.