Spectral analysis of silicate glasses analog of Mercury’s geochemical terrains and comparison with MESSENGER and BepiColombo data

Kurzfassung

Mercury, the closest planet to the Sun, has been studied by two NASA missions: Mariner 10 and MESSENGER (Mercury Surface, Space Environment, Geochemistry, and Ranging). They provided much information about the surface of the planet including the unique surface composition—characterized by a strong depletion in iron for example—and the identification of distinct regions with varying chemical compositions. However, one remaining question about Mercury is the mineralogical composition of its surface. Visible to near-infrared observations from the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) aboard MESSENGER lack absorption features of mafic minerals. One hypothesis for the absence of spectral signatures typically associated with mafic minerals is the low abundance of FeO [1]. Furthermore, Mercury's complex geological history, involving extensive volcanic activity, impact melting, and intense space weathering, likely resulted in the production of substantial amounts of glass at the surface, which may significantly influence the planet's spectral properties [2]. The ESA’s BepiColombo mission, launched in 2018, will soon be in its polar orbit around Mercury. Two key instruments will help characterize the surface mineralogy of the planet: MERTIS (Mercury radiometer and thermal infrared spectrometer), a radiometer and thermal infrared spectrometer operating between 7 and 14 µm and SIMBIO-SYS (Spectrometers and Imagers for MPO BepiColombo Integrated Observatory System), a high-resolution camera, a stereo camera and a near infrared hyperspectral imager operating between 0.4 and 2 µm. The aim of this study is to spectrally characterize glassy synthetic analogs with compositions similar to the five main geochemical regions of Mercury. This work is done at the Planetary Spectroscopy Laboratory (PSL) of the German Aerospace Center (DLR), Berlin. The spectral measurements will be compared to MASCS data and used for the interpretation of SIMBIO-SYS and MERTIS data. Thus, it will be possible to identify the effect of volcanic glass and their specific compositions characterized by a range of MgO content and low FeO.