Mineralogy of the LAR 12095 Martian shergottite as determined by micro-Raman and micro-X-ray fluorescence spectroscopies

Abstract

In this work, the geochemical characterization of the olivine-phyric Martian shergottite LAR 12095 was performed by using two complementary analytical techniques: micro-Raman and micro-energy dispersive X-ray fluorescence spectroscopies. Thanks to this methodology, olivine, pyroxene, and ilmenite were detected as primary minerals from Mars. Maskelynite, hematite, anatase, chromite, merrillite, oxidized mackinawite, pyrrhotite, elemental sulfur, marcasite, jarosite, epsomite, and gypsum were classified as secondary minerals. The major novelty of this work is that alterations under anaerobic and aerobic conditions of S-bearing minerals can be appreciated. In this sense, primary sulfides were altered to secondary sulfides, elemental sulfur and sulfates under the oxygen-free Martian atmosphere. However, in the Earth's oxidizing atmosphere, primary sulfides are weathered to iron oxides, such as hematite. In addition, it should be highlighted that the presence of ilmenite, mackinawite, elemental sulfur, and jarosite has been reported for the first time in this meteorite.