Mِssbauer spectroscopy on the surface of Mars: constraints and expectations

Mِssbauer spectrometers will be included on the upcoming MER/Athena and Mars Express/Beagle rovers. These instruments have the exciting potential to characterize the surface mineralogy of Mars, but there are several complicating factors. It is difficult to differentiate minerals with similar structures, particularly if the rock or soil is multimineralic and the peaks overlap. Mineral modes cannot be determined from Mِssbauer spectra alone. The temperature dependence of Mِssbauer parameters for common rock-forming minerals and glasses is known for only a few minerals, but it is strong. No database of Mars surface temperature Mِssbauer spectra of minerals or glasses currently exists, with which Martian data can be compared. Peak areas in Mِssbauer spectroscopy do not directly correspond to the abundances of the minerals that give rise to them, and the calibration/correction factors to compensate for this problem are currently known for only a few minerals. We assess here the advantages and disadvantages of Mِssbauer spectroscopy for remote data acquisition, and describe work currently under way in our laboratory to address these potential complications.