Comparative Planetary Science
Water and the evolution of NWA 8114 Martian Regolith
J. L. MacArthur
J. C. Bridges (University of Leicester), L. J. Hicks (University of Leicester), L. Paget (University of Leicester), R. Burgess (University of Manchester), K.H. Joy (University of Manchester)
University of Leicester
NWA8114 (a pair of NWA7034) is a martian regolith breccia with varied clasts in a fine grained matrix [1]. It is the most hydrated martian meteorite discovered and isotope analyses support the martian origin of water [2]. The majority of the water is suggested to be hosted by hydrous Fe oxides, with a minor contribution from Cl-apatite [1]. The ferric phases maghemite and goethite have been detected, making this potentially the most oxidised known martian meteorite [3].
The meteorite was likely formed as a result of an impact event which may have led to hydrothermal systems causing further alteration to it. Using FIB-TEM and XANES we have shown partial breakdown and oxidation of pyroxene clasts. These pyroxenes have recrystallised to form magnetite and amorphous aluminium silicate. This shows effect of high temperature and presence of H2O during high temperature alteration.
We have also used synchrotron transmission XRD, synchrotron FTIR and Ar-Ar dating to show the presence of goethite within pyroxene clasts, indicating that water was also present at a later, low temperature stage in the regolith’s history, likely as it was cooling on Mars. The 40Ar-39Ar potential age of 1.1-1.2 Ga may relate to the high temperature phase of regolith formation.
[1] Muttik N. et al. (2014) GRL 41, 8235-8244. [2] Agee C. B. et al. (2013) Science 339, 780-785. [3] Gattacceca J. et al. (2014) GRL 41, 4859-4864.
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