Infrared Spectroscopy of Lithologically Different Areas of a Piece of the Zagami Meteorite

Kurzfassung

Zagami belongs to the SNC-meteorites which are believed to be rocks from the planet Mars. With the planned mineralogical inspection of its surface in mind, spectral data of this meteorite are significant as a base of comparison. Zagami is a basalt/diabase whose dominant constituents are pigeonite, augite, an maskelynite (a diaplectic glass). This achondrite chrystallized apparently on or near the surface of its parent body. Thus, it is a good reprensentative of a volcanic rock which may be encountered on Mars. We measured infrared diffuse reflectance spectra of a piece of the Zagami meteorite in the NIR region. The measured spectra stem from individual mineral grains and more extendend surface regions (8 mm diameter) of a sawed surface. On this base, the goals of this study are to - continue our first measurements of the Zagami meteorite, now using an other and greater piece, - determine the spectroscopically measureable diversity of the main mineralogical phases, - characterize different lithologies present in the meteorite. Spectra from three texturally different areas (8 mm diameter) are shown in Fig. 1. These composite spectra exhibit strong absorptions near 1 muem and 2 muem with band minima at 0.97 - 0.99 muem and 2.11 - 2.18 muem which are characteristic of Ca- and Fe-bearing clinopyroxenes. The small but distinctive differences in band positions in the three spectra are interpreted to be the result of slightly different portions of pigeonite and augite in the three measured areas. The spectra measured may help to constrain the surface mineralogy of the planet Mars. Particularly Zagami, besides other Shergottites, seems to be a type of rock accessible by remote infrared spectroscopy of this planet.