Extracting science from Mössbauer spectroscopy on Mars

Abstract

Deployment by the Mars Exploration Rovers of backscatter Mössbauer spectrometers offers an incredible opportunity to (1) elucidate the iron mineralogies of rocks, soils, and atmospheric dust and (2) gain insight into the physical event by which the mineralogy came into existence and consequently acquire information having potential for yielding ancient planetary history relevant to broad issues including the question of life. Determining the mineralogy is done by subjecting raw data to reduction algorithms and generating products known as Mössbauer parameters, which are highly characteristic. Mixed mineralogies are treated through deconvolution. Through being able to exploit Mössbauer measurements made at different temperatures during the Martian diurnal variation, and utilizing spectra obtained of the same sample with both the 6.4 and 14.4 keV energy channels, characteristics beyond oxidation state and stoichiometry are accessible. These include temperature sensitive magnetic transitions that can be either abrupt or gradual, variation of Mössbauer parameters with temperature, and variation of composition with depth, all of which can be dependent upon past processing affecting initial crystallization or subsequent alteration ("weathering"). The goal is to arrive at an understanding of environments including the very ancient. Copyright 2003 by the American Geophysical Union.