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Fractionated martian atmosphere in the nakhlites?
M J Drake1, T D Swindle, T Owen
1Lunar and Planetary Laboratory, University of Arizona, Tucson 85721, USA.
Meteoritics
|January 1, 1994
Summary
Martian meteorites (SNCs) reveal noble gas signatures. The Nakhla meteorite shows an unusual xenon isotope ratio, suggesting interaction with a distinct Martian atmosphere reservoir, possibly within iddingsite.
Area of Science:
- Planetary Science
- Geochemistry
- Isotope Analysis
Background:
- Martian meteorites, specifically the Shergottite-Nakhlite-Chassignite (SNC) group, are strong candidates for a Martian origin.
- Noble gas isotopic compositions are crucial for understanding planetary evolution and atmospheric history.
Purpose of the Study:
- To investigate the origin of anomalous noble gas isotopic ratios in the Nakhla meteorite.
- To explore the implications of these findings for the presence of aqueous fluids and atmospheric reservoirs on Mars.
Main Methods:
- Analysis of noble gas (Xenon and Krypton) isotopic compositions in SNC meteorites.
- Comparison of isotopic ratios to identify mixing lines and anomalous components.
- Geochemical interpretation of mineral alteration products like iddingsite.
Main Results:
- A linear array of 129Xe/132Xe vs. 84Kr/132Xe ratios was observed in most SNC meteorites, interpreted as a mixing line between Martian mantle and atmosphere.
- The Nakhla meteorite exhibits a leachable component with an elevated 129Xe/132Xe ratio, deviating from this array.
- This anomalous component is likely linked to iddingsite, a low-temperature alteration product, suggesting elemental fractionation of the Martian atmosphere.
Conclusions:
- The elevated 129Xe/132Xe ratio in Nakhla's leachable component points to a distinct Martian atmospheric reservoir or elemental fractionation.
- The presence of iddingsite indicates interaction with aqueous fluids at temperatures below 150°C.
- These findings provide evidence for the existence of near-surface liquid water on Mars as recently as 1.3 billion years ago.
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