Thermal infrared spectroscopy to investigate the composition of mercury – The MERTIS instrument on BepiColombo

Telescopic measurements have shown that the surface composition of Mercury can be derived only indirectly from VIS-NIR-spectra: the spectral slopes and the absence of any feature in the range from 0.5 to 1 μm indicate feldspar as main component. [Hapke, B., Danielson, G.E., Jr., Klaasen, K., Wilson, L. Photometric observations of Mercury from Mariner 10. J. Geophys. Res. 80, 2431–2443, 1975; Hapke, B. Interpretations of optical observations of Mercury and the moon. Physics of the Earth and Planetary Interiors, vol. 15, no. 2–3, pp. 264–274, 1977.] suggested based on the analysis of albedo and color relationships on Mariner 10 images that very low contents of FeO (at about 3-6 wt%) and TiO2 (less than 1 wt%) could be present in the mercurian regolith. Feldspars are expected to compose the bulk of Mercury’s crust. In the NIR-range, however, pure feldspars have no specific spectral signature. In the Thermal Infrared (TIR), however, feldspars can be detected–and specified–by means of their diagnostic spectral signatures: Christiansen frequency, reststrahlen band, and transparency feature. In addition, pyroxenes and most other minerals can be detected and specified in this spectral range. Thermal infrared spectroscopy operating in the range between 7 and 14 μm will enable valuable mineral identification of feldspars and low-iron species that are expected to be prevailing on Mercury’s surface. Performing TIR measurements may make it possible to identify spectral features associated with the high radar backscattering efficiency of putative minerals and to differentiate between the proposed compositions (water ice, sulfur, and cold silicate glasses) for the high-latitude volatiles, something that cannot be done by ground based observing or near-infrared spectroscopy. In addition, TIR measurements will allow studying areas of geologic importance where composition can give significant new understanding to relative age of tectonic features. The MERTIS instrument, a TIR imaging spectrometer based on our suggestions, onboard of ESA’s BepiColombo mission will fulfil all the requirements needed to improve our knowledge about Mercury’s surface composition

MERTIS — a radiometer and thermal infrared spectrometer aboard BepiColombo

In cooperation, the Institut für Planetologie (IfP) at the Westfälische Wilhelms-Universität (WWU) of Münster and two DLR institutes located in Berlin are sending the Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) on a mission to the innermost planet. MERTIS is a sophisticated, miniaturized instrument and will be one of eleven payload items on the Mercury Planetary Orbiter (MPO), one of two separate spacecraft composing the BepiColombo mission. Launch is scheduled for 2013 with arrival currently foreseen to occur in 2019. The objectives of MERTIS are to study Mercury's surface composition, identify rock-forming minerals, map the surface mineralogy, and study surface temperatures and thermal inertia. </ul

MERTIS - MErcury Radiometer and Thermal Infrared Spectrometer- a novel thermal imaging spectrometer for the exploration of Mercury

The MERTIS instrument is a state of the art imaging spectrometer in the TIR range onboard ESA’s Bepi Colombo mission to the planet Mercury. MERTIS has four science goals: the study of Mercury’s surface composition, identification of rock-forming minerals, mapping of the surface mineralogy, and the study of surface temperature variations and of the thermal inertia. The instrument is designed to achieve a signal-to-noise-ratio above 100 in the 7-14 µm range with a spectral channel width of 90 nm and a nominal spatial ground resolution of 500 m within the complex thermal and radiation environment of Mercury