Abstract— In order to elucidate the formation of low-H kaersutites in Martian meteorites, the Fe3+/ΣFe ratio of Chassigny kaersutites in magmatic inclusions was directly determined by the synchrotron microXANES analysis. XANES analysis for standard kaersutites with known Fe3+/ΣFe ratios shows a linear relationship between centroid energy positions of XANES pre-edge spectra and the Fe3+/ΣFe ratio. Based on the linear relationship, the Fe3+/ΣFe ratio of Chassigny kaersutites is estimated to be about 0.05. The low Fe3+/ΣFe ratio clearly suggests that low-H kaersutites in Chassigny are not likely to be formed by the oxidation-dehydrogenation reactions. The low-H content of the Chassigny kaersutites is mainly due to the presence of a Ti oxy-component.