Mössbauer spectroscopy showing large-scale inhomogeneity in the presumed martian meteorite Zagami

Abstract

A group of nine achondritic meteorites, the SNC-meteorites, are believed to be rocks from the planet Mars. With the planned exploration of Mars in mind, perhaps including in situ Mössbauer spectroscopy, the study of the SNC-meteorites takes on a specific significance. We have performed Mössbauer spectroscopy of specimens from one of these meteorites, Zagami. Surprisingly, the Mössbauer spectra of two separate samples from Zagami are very different. One of the samples shows no olivine, in agreement with the description of the meteorite Zagami in the literature. The other sample shows that about 23% of the iron is placed in olivine, and X-ray diffraction analysis confirms the existence of olivine as a major component in this sample. We are thus forced to conclude that the meteorite Zagami is inhomogeneous on a macroscopic scale. This result has evidently implications for the understanding of the igneous rocks on Mars, and thus for the interpretation of their Mössbauer spectra.