Thermal alteration: A possible reason for the inconsistency between OMEGA/CRISM and TES detections of phyllosilicates on Mars?

Previous laboratory analyses have shown that high temperatures can modify the crystal structures of some phyllosilicates in such a way that their spectroscopic signatures appear different from various wavelength perspectives. This may be the case in the Nili Fossae region of Mars, where our analyses indicate that thermally altered (∼400°C) Fe-rich smectites might be possible mineral analogs to the phyllosilicate-bearing units in addition to mineral assemblages formed by Fe/Mg smectite and amorphous weathering products. We suggest that thermal alteration of phyllosilicates induced by impact shock or other heat sources might be a widespread process throughout Martian history. The mixing of altered and unaltered phyllosilicates might be partially responsible for the apparent disconnect between VNIR and TIR observations of Fe/Mg smectite-bearing surfaces on Mars.