Other
Scientific paper
Oct 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007dps....39.1406g&link_type=abstract
American Astronomical Society, DPS meeting #39, #14.06; Bulletin of the American Astronomical Society, Vol. 39, p.435
Other
Scientific paper
CRISM has recently confirmed OMEGA's previous detection of clays on the surface of Mars, mainly in the Nili Fossae and Mawrth Vallis regions in the Noachian terrains. It has been proposed that transformations of clays through meteoritic impacts and thermal metamorphism may be responsible for Mars’ red color. We thermally treated several samples of nontronite (Fe-rich clay) and montmorillonite (Al-rich clay) in both air and in a CO2 atmosphere to various temperatures (from 500°C to 1100°C) for various durations (4 to 24 hrs) and impacted each clay sample at 2.5 km/s.
X-Ray Diffraction (XRD), infrared spectrometry (FT-IR), ESEM, TEM, and magnetic properties analyses were performed on each sample. XRD of heated samples showed the formation of hematite, sillimanite, and cristobalite in high temperature samples. The same phases with corundum and quartz formed in the medium temperature samples. ESEM and EDX analyses confirmed these results. No secondary phase was observed on the XRD spectra of the impacted samples. Magnetic analyses showed properties of hematite at high temperature, spinel only in the CO2 atmosphere at 850°C and the systematic formation of a distinct unknown magnetic phase around 900-1000°C, also observed in TEM. FT-IR analysis in the MIR range showed the loss of interlayer water and a quartz/silica-forming phase. NIR spectra of the shocked samples were of particular interest because of the formation of a pair of unidentified peaks at 3.4 and 3.5 μm. These two peaks did not appear in any other spectrum, indicating they are the result of the shock treatment only. Such result, combined with XRD results, suggests potential amorphisation of the impacted clays. Such a specific feature could help determine if clays were affected by shock on Mars.
Chevrier Vincent
Gavin Patricia
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