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The noble gas concentrations of the Martian meteorites GRV 99027 and paired NWA 7906/ NWA 7907
Author(s) -
Stephenson Peter C.,
Lin Yangting,
Leya Ingo
Publication year - 2017
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/maps.12950
Subject(s) - meteorite , martian , meteoroid , radiogenic nuclide , atmosphere of mars , geology , chemistry , astrobiology , geochemistry , mars exploration program , physics , mantle (geology)
Here we present the isotopic concentrations of He, Ne, Ar, Kr, and Xe for the three Martian meteorites, namely Grove Mountains 99027 (GRV 99027), Northwest Africa 7906 ( NWA 7906), and Northwest Africa 7907 ( NWA 7907). The cosmic ray exposure (CRE) age for GRV 99027 of 5.7 ± 0.4 Ma (1σ) is consistent with CRE ages for other poikilitic basaltic shergottites and suggests that all were ejected in a single event ~5.6 Ma ago. After correcting for an estimated variable sodium concentration, the CRE ages for NWA 7906 and NWA 7907 of 5.4 ± 0.4 and 4.9 ± 0.4 Ma (1σ), respectively, are in good agreement with the CRE age of ~5 Ma favored by Cartwright et al. ([Cartwright J. A., 2014]) for NWA 7034. The data, therefore, support the conclusion that all three basaltic regolith breccias are paired. The 40 Ar gas retention age for NWA 7907 of ~1.3 Ga is in accord with Cartwright et al. ([Cartwright J. A., 2014]). For NWA 7906, we were unable to determine a 40 Ar gas retention age. The 4 He gas retention ages for NWA 7906 and 7907 are in the range of 200 Ma and are much shorter than the 40 Ar gas retention age of NWA 7907, indicating that about 86–88% of the radiogenic 4 He has been lost. The Kr and Xe isotopic concentrations in GRV 99027 are composed almost exclusively of Martian interior (MI) gases, while for NWA 7906 and NWA 7907, they indicate gases from the MI, elementally fractionated air, and possibly Martian atmosphere.