Exploring Mercury with the MErcury Radiometer and Thermal infrared Imaging Spectrometer (MERTIS)

The MErcury Radiometer and Thermal infrared Imaging Spectrometer (MERTIS) is part of the payload of the Mercury Planetary Orbiter spacecraft of the ESA-JAXA BepiColombo mission. MERTIS combines an imaging spectrometer covering the wavelength range of 7-14 m with a radiometer covering the wavelength range of 7-40 m. The instrument will map the whole surface of Mercury with a spatial resolution of 500 m for the spectrometer channel and 2 km for the radiometer channel. The compositional map of Mercury provided by MERTIS will allow unique insights into the evolution of the least explored terrestrial planet and will directly address questions raised by the NASA MESSENGER mission. For example, MERTIS will be able to provide spatially resolved compositional information on the hollows and pyroclastic deposits and answer the question whether hollows are actually predominately composed of sulfide. MERTIS will also provide spatially resolved temperature maps inside the permanently shadowed craters, thereby potentially constraining the stability of water ice deposits in those craters.BepiColombo is currently in the final part of its 7-year journey to Mercury. The interplanetary cruise includes in total nine flybys for gravitational assists: one at Earth, two at Venus and six at Mercury. MERTIS could obtain so far observations during the Earth flyby in April 2020, the first Venus flyby (FB1) in October 2020 and the second Venus flyby (FB2) on August 10, 2021. The recently published results for FB2 show that MERTIS performed well beyond requirements and provided new insights into the long-term stability of the Venusian atmosphere.