BepiColombo achieves milestone with mid-infrared observations of Mercury

BepiColombo achieves milestone with mid-infrared observations of Mercury
by Erica Marchand
Paris, France (SPX) Dec 10, 2024

On December 1, 2024, the European Space Agency's BepiColombo mission completed its fifth flyby of Mercury, marking a historic first by capturing the planet in mid-infrared light. The unprecedented images provide fresh insights into the temperature and mineral composition of Mercury's cratered surface.

Mercury, the least-explored terrestrial planet in the Solar System, has only been visited by two previous missions: NASA's Mariner 10 in the 1970s and NASA's Messenger, which orbited the planet between 2011 and 2015. BepiColombo, launched on its eight-year journey to Mercury, is set to become the second mission to orbit the planet in 2026.

The December 1 flyby brought BepiColombo within 37,626 km of Mercury's surface, leveraging the planet's gravity for trajectory adjustments while gathering a wealth of scientific data. Among its suite of observations, the mission achieved a groundbreaking feat using the German-developed Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS).

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

After two decades of development and testing, MERTIS captured its first mid-infrared images of Mercury. "The first MERTIS data from Mercury is now available. It is simply fantastic!" added Jorn Helbert, co-principal investigator at the German Aerospace Center (DLR) in Berlin.

Illuminating Mercury's Surface

MERTIS's initial data reveal variations in the brightness of Mercury's surface in mid-infrared light, influenced by temperature, roughness, and mineral composition. The imaging spectrometer, capable of detecting wavelengths between 7-14 micrometers, identified distinct features, including the Basho impact crater.

"The moment when we first looked at the MERTIS flyby data and could immediately distinguish impact craters was breathtaking! There is so much to be discovered in this dataset," said Solmaz Adeli from DLR's Institute of Planetary Research.

BepiColombo's observations build on previous discoveries by NASA's Messenger mission, which revealed Mercury's unusually low surface iron content and unexpected concentrations of volatile elements despite its proximity to the Sun. These peculiarities contribute to the planet's unique darkness, reflecting significantly less light than the Moon despite its similar appearance.

Preparing for 2026 Orbit

To optimize MERTIS's performance, the team has been conducting laboratory tests on mineral samples under high temperatures, simulating Mercury's sunlit surface, which can reach up to 420 C. "We have been testing natural and synthetic minerals that lack iron," explained Adeli, referring to Mercury's notably iron-poor surface composition.

The innovative design of MERTIS allowed it to capture data during the flyby despite the spacecraft's stacked configuration, which blocks its primary observational port. Through clever software reprogramming, the instrument utilized its calibration port for observations, a method proven successful during earlier flybys of the Moon and Venus.

"When we enter orbit around Mercury in 2026, MERTIS will be able to exploit its full potential," said Hiesinger. The instrument will then produce high-resolution global maps of Mercury's surface mineral distribution, achieving a resolution as fine as 500 meters.

"These fascinating and valuable results from the MERTIS instrument are only a tantalising hint of the great results we're expecting from the entire BepiColombo science payload once both orbiters are operating in orbit around Mercury," commented Geraint Jones, BepiColombo Project Scientist at ESA.