The Moon observed by BepiColombo's MERTIS instrument during Earth flyby
The first ever measurements of the Moon's surface in the thermal infrared spectrum taken by the Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) aboard the European/Japanese BepiColombo mission.
MERTIS, a novel instrument for studying the surface composition of celestial objects, obtained the measurements during BepiColombo's Earth flyby on 10 April 2020. Each image in this sequence represents one observation. The colourful band in the middle is the Moon's reflection in thermal infrared against the colder surrounding space. Since various minerals absorb and emit thermal infrared radiation differently, scientists can get a clear picture of the surface composition of the studied celestial bodies from MERTIS data.
MERTIS was designed specifically to study Mercury, the closest planet to the Sun with surface temperatures of over 400 °C. Seeing such a clear signature of the much colder surface of the Moon proved to the science teams that the instrument will be able to obtain even higher quality data than expected once at its destination
The observations were performed from the distance of 700 000 km, which is up to 2000 times farther away than will be the orbit of ESA's Mercury Planetary Orbiter (MPO), one of the two orbiters comprising the BepiColombo mission, which carries the MERTIS instrument.
Moreover, MERTIS made the measurements using its calibration port and not the main port, currently hidden behind the Mercury Transfer Module (MTM), which carries MPO and the Mercury Magnetospheric Orbiter of the Japanese Aerospace Exploration Agency (JAXA) to their destination.