Mercury is by far the least-explored rocky planet in the Solar System. BepiColombo is the third mission to ever visit the planet, and in 2026 it will be the second mission to enter orbit around Mercury. It is preceded only by NASA’s Mariner 10, which flew past three times between 1974 and 1975, and NASA’s Messenger, which orbited the planet from 2011 to 2015.

BepiColombo is on an eight-year journey to Mercury. Along the way, it relies on the gravity of Earth, Venus and Mercury to steer its course and slow it down. On 1 December 2024 at 15:23 CET, BepiColombo flew 37 626 km above Mercury's surface.

The mission used this flyby to gather more data on the mysterious planet and its surroundings. Aside from taking some ‘regular’ photos of the planet and measuring particles and electromagnetic fields in the space around it, this flyby was the first time that any spacecraft imaged Mercury in mid-infrared wavelengths of light.

The instrument making this flyby unique is the German-led Mercury Radiometer and Thermal Infrared Spectrometer, MERTIS for short.

"With MERTIS, we are breaking new ground and will be able to understand the composition, mineralogy and temperatures on Mercury much better,” notes Harald Hiesinger, the instrument's principal investigator from the University of Münster, Germany.

Jörn Helbert, who helped develop and supervise the instrument as co-principal investigator at the German Aerospace Center (DLR) in Berlin, is delighted: "After about two decades of development, laboratory measurements of hot rocks similar to those on Mercury and countless tests of the entire sequence of events for the mission duration, the first MERTIS data from Mercury is now available. It is simply fantastic!"