Mineralogy of the RBT 04262 Martian meteorite as determined by micro-Raman and micro-X-ray fluorescence spectroscopies

Martian meteorites and terrestrial analogs represent the only samples available on Earth for studying mineralogy features of our neighbor planet Mars. This work characterizes the Roberts Massif (RBT) 04262 Martian meteorite by using mainly Raman spectroscopy. By means of this technique, it was confirmed that the meteorite matrix is composed by pyroxene and plagioclase (converted to maskelynite due to the shock pressure). Olivine-coarse grains embedded in the matrix were also observed. These grains were coated by hydrated magnesium and calcium sulfates, which would belong to the Mars sulfate deposits or to the terrestrial weathering. Although the sulfates could be formed on Mars due to the oxidation of sulfides or elemental sulfur along the sulfur Mars cycle, their distribution along cracks and fractures confirm that are weathering products. However, other S-bearing compounds that belong to Mars were found, such as elemental sulfur and a thermally transformed iron sulfide. Finally, the calcium phosphate merrillite and titanomagnetite were also detected. Taking this into account, the minerals found were classified into primary minerals that belong to Mars (pyroxene, olivine, elemental sulfur, and titanomagnetite), secondary ones that are alteration products of the primary minerals (maskelynite, iron sulfide, and merrillite), and terrestrial weathering products (sulfates gypsum and epsomite).