The noble gas concentrations of the Martian meteorites GRV 99027 and paired NWA 7906/NWA 7907

Stephenson, Peter; Lin, Yangting; Leya, Ingo (2017). The noble gas concentrations of the Martian meteorites GRV 99027 and paired NWA 7906/NWA 7907. Meteoritics & planetary science, 52(12), pp. 2505-2520. Meteoritical Society at the University of Arkansas, Dept. of Chemistry and Biochemistry 10.1111/maps.12950

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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 (1δ) 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 (1r), respectively, are in good agreement with the CRE age of ~5 Ma favored by Cartwright et al. (2014) for NWA 7034. The data, therefore, support the conclusion that all three basaltic regolith breccias are paired. The ⁴⁰Ar gas retention age for NWA 7907 of ~1.3 Ga is in accord with Cartwright et al. (2014). For NWA 7906, we were unable to determine a ⁴⁰Ar gas retention age. The ⁴He gas retention ages for NWA 7906 and 7907 are in the range of 200 Ma and are much shorter than the ⁴⁰Ar gas retention age of NWA 7907, indicating that about 86–88% of the radiogenic ⁴He 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.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences

UniBE Contributor:

Stephenson, Peter and Leya, Ingo

Subjects:

500 Science > 520 Astronomy
600 Technology > 620 Engineering
500 Science > 530 Physics

ISSN:

1086-9379

Publisher:

Meteoritical Society at the University of Arkansas, Dept. of Chemistry and Biochemistry

Language:

English

Submitter:

Dora Ursula Zimmerer

Date Deposited:

19 Dec 2017 10:16

Last Modified:

01 Jan 2019 02:30

Publisher DOI:

10.1111/maps.12950

Additional Information:

Due to an oversight, Beda Hofmann, curator of the Natural History Museum of Bern meteorite collection, was not properly credited as the provider of the NWA 7906 and NWA 7907 samples analyzed in this work. The authors regret the error.

BORIS DOI:

10.7892/boris.106981

URI:

https://boris.unibe.ch/id/eprint/106981

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