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Ar-Ar Ages of Nakhlites Y000593, NWA998, and Nakhla and CRE Ages of NWA998The seven known Martian nakhlites are Nakhla, Lafayette, Governador Valadares, and four recent finds from hot and cold deserts: MIL03346 from the Transantarctic Mountains, a paired group from the Yamato Mountains (Y000593, Y000749, and Y000802, and two from Morocco (NWA998 and NWA817. Radiometric ages (Sm-Nd, Rb-Sr, U-Pb, and Ar-Ar) for the first three nakhlites, along with Chassigny, fall in the range of 1.19-1.37 Gyr and may suggest a common formation age. These meteorites also show very similar cosmic-ray (space) exposure ages, suggesting a single ejection event from Mars. The ages for nakhlites are different from those of Martian shergottites, whose radiometric ages vary by nearly a factor of three (approx. 165-475 Myr) and whose space exposure ages vary over a factor of approx. 20. Shergottite ages suggest that multiple locations on the Martian surface have been sampled, whereas nakhlite data imply sampling of only one Mars surface location. Because older Martian surfaces are expected to be more abundant, it seems surprising that all nakhlites would represent only one Martian impact event. To address this issue, we are measuring the (39)Ar-(40)Ar ages of Y-000593, NWA-998, Nakhla, and MIL-03346, and the space (CRE) exposure age of NWA998. Additional information is included in the original extended abstract.
Document ID
20050169505
Acquisition Source
Headquarters
Document Type
Conference Paper
Authors
Garrison, D. H.
(Lockheed Martin Corp. Houston, TX, United States)
Bogard, D. D.
(NASA Johnson Space Center Houston, TX, United States)
Date Acquired
September 7, 2013
Publication Date
January 1, 2005
Publication Information
Publication: Lunar and Planetary Science XXXVI, Part 7
Subject Category
Lunar And Planetary Science And Exploration
Distribution Limits
Public
Copyright
Public Use Permitted.
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