The Open UniversitySkip to content

Quantifying noble gas contamination during terrestrial alteration in Martian meteorites from Antarctica

Schwenzer, S. P.; Greenwood, R. C.; Kelley, S. P.; Ott, U.; Tindle, A. G.; Haubold, R.; Herrmann, S.; Gibson, J. M.; Anand, M.; Hammond, S. and Franchi, I. A. (2013). Quantifying noble gas contamination during terrestrial alteration in Martian meteorites from Antarctica. Meteoritics & Planetary Science, 48(6) pp. 929–954.

DOI (Digital Object Identifier) Link:
Google Scholar: Look up in Google Scholar


We investigated exterior and interior subsamples from the Martian shergottite meteorites Allan Hills (ALH) A77005 and Roberts Massif (RBT) 04261 for secondary minerals, oxygen isotopes, Ar-Ar, and noble gas signatures. Electron microprobe investigations revealed that RBT 04261 does not contain any visible alteration even in its most exterior fractures, whereas fracture fillings in ALHA77005 penetrate into the meteorite up to 300 μm, beyond which the fractures are devoid of secondary minerals. Light noble gases seem to be almost unaffected by terrestrially induced alteration in both meteorites. Thus, a shock metamorphic overprint of 30–35 GPa can be deduced from the helium measurements in RBT 04261. Oxygen isotopes also seem unaffected by terrestrially weathering and variations can easily be reconciled with the differences in modal mineralogy of the exterior and interior subsamples. The measurements on irradiated samples (Ar-Ar) showed a clear Martian atmospheric contribution in ALHA77005, but this is less apparent in our sample of RBT 04261. Exterior and interior subsamples show slight differences in apparent ages, but the overall results are very similar between the two. In contrast, krypton and xenon are severely affected by terrestrial contamination, demonstrating the ubiquitous presence of elementally fractionated air in RBT 04261. Although seemingly contradictory, our results indicate that RBT 04261 was more affected by contamination than ALHA77005. We conclude that irrespective of on which planet the alteration occurred, exposure of Martian rocks to atmosphere (or brine) introduces noble gases with signatures elementally fractionated relative to the respective atmospheric composition into the rock, and relationships of that process with oxygen isotopes or mineralogical observations are not straightforward.

Item Type: Journal Item
Copyright Holders: 2013 The Meteoritical Society
ISSN: 1945-5100
Keywords: Martian meteorite; noble gases; elementally fractionated air; xenon; krypton; contamination; Antarctica RBT 04261; ALH77005; alteration mineral
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Environment, Earth and Ecosystem Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Faculty of Science, Technology, Engineering and Mathematics (STEM) > Physical Sciences
Learning and Teaching Innovation (LTI) > Institute of Educational Technology (IET)
Learning and Teaching Innovation (LTI)
Research Group: Space
Item ID: 37799
Depositing User: Susanne Schwenzer
Date Deposited: 17 Jun 2013 08:10
Last Modified: 07 Dec 2018 10:16
Share this page:


Altmetrics from Altmetric

Citations from Dimensions

Actions (login may be required)

Policies | Disclaimer

© The Open University   contact the OU