\t\t\t\t\t\t09\/12\/2024<\/span> On 1 December 2024, BepiColombo flew past Mercury for the fifth time. During this flyby, BepiColombo became the first spacecraft ever to observe Mercury in mid-infrared light. The new images reveal variations in temperature and composition across the planet’s cratered surface.<\/p>\n<\/div>\n 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\u2019s Mariner 10, which flew past three times between 1974 and 1975, and NASA\u2019s Messenger, which orbited the planet from 2011 to 2015.\u00a0<\/p>\n 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.\u00a0<\/p>\n The mission used this flyby to gather more data on the mysterious planet and its surroundings. Aside from taking some \u2018regular\u2019 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.\u00a0<\/p>\n The instrument making this flyby unique is the German-led Mercury Radiometer and Thermal Infrared Spectrometer, MERTIS for short. \u00a0<\/p>\n “With MERTIS, we are breaking new ground and will be able to understand the composition, mineralogy and temperatures on Mercury much better,\u201d notes Harald Hiesinger, the instrument’s principal investigator from the University of M\u00fcnster, Germany.\u00a0<\/p>\n J\u00f6rn 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!”<\/p>\n<\/p><\/div>\n \t\t\t\t<\/p>\n <\/figcaption><\/figure>\n MERTIS’s first Mercury image reveals which parts of the surface shine more brightly in mid-infrared light more than others, with a ground resolution of around 26\u201330 km. It covers a part of the Caloris Basin, and parts of a large volcanic plain in the northern hemisphere. \u00a0<\/p>\n The brightness of the surface depends on temperature, surface roughness and what minerals the cratered surface is made of. The imaging spectrometer is sensitive to mid-infrared light with wavelengths of 7\u201314 micrometres, a range known to be particularly suitable for distinguishing rock-forming minerals.\u00a0<\/p>\n The image highlights the Bash\u014d impact crater, a feature seen already by Mariner 10 and observed in detail by Messenger. Visible light images show that the Bash\u014d impact crater contains both very dark and very bright material. The MERTIS flyby observations reveal that the crater also stands out in infrared light.<\/p>\n \u201cThe 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 \u2013 surface features that have never been observed in this way before are waiting for us. We have never been this close to understanding the global surface mineralogy of Mercury with MERTIS ready for the orbital phase of BepiColombo,\u201d says Solmaz Adeli from DLR’s\u00a0Institute of Planetary Research in Berlin, who was instrumental in planning the current flyby as project lead. \u00a0<\/p>\n What the little planet’s surface is made of is one of Mercury’s many mysteries. MERTIS and other instruments on BepiColombo’s Mercury Planetary Orbiter will provide\u00a0better accuracy and resolution of the elemental composition compared to the Messenger data.\u00a0<\/p>\n Messenger revealed that the surface has relatively little iron in it, despite the planet’s iron-nickel core being unusually large. The mission also revealed that although Mercury orbits close to the Sun, some chemical elements that easily evaporate are present in unusually high concentrations. \u00a0<\/p>\n A related mystery is why the planet looks so dark. At a first glance, Mercury’s\u00a0crater-ridden dusty surface may look similar to the Moon, but its surface reflects only about two-thirds as much light as the Moon does.\u00a0<\/p>\n<\/p><\/div>\n To be able to interpret MERTIS’s measurements, one needs to know exactly how different minerals glow in mid-infrared light, and how this varies with temperature. The sunlit side of Mercury can get very hot: the MERTIS radiometer measured temperatures up to 420 \u00b0C during the flyby. \u00a0<\/p>\n In preparation for BepiColombo arriving at Mercury in 2026, the MERTIS team has been testing out many different materials and mineral mixtures in the lab, heating them to different temperatures and measuring how they glow in mid-infrared wavelengths. \u00a0\u00a0<\/p>\n \u201cBecause Mercury\u2019s surface is surprisingly poor in iron, we have been testing natural and synthetic minerals that lack iron,\u201d explains Solmaz. \u201cThe materials tested include rock-forming minerals to simulate what Mercury’s surface might be made of.\u201d\u00a0<\/p>\n MERTIS was built at DLR with participation from German industry. The MERTIS team consists of numerous scientists from several European countries and the USA, who are jointly studying the data from the flyby. \u201cIt is really a pleasure to work together with a fantastic team on evaluating the data. And the best is yet to come \u2013 when we enter orbit around Mercury in 2026, MERTIS will be able to exploit its full potential,” says Harald. \u00a0<\/p>\n After orbit insertion, MERTIS will provide a global map of the distribution of minerals on Mercury\u2019s surface\u00a0with a resolution down to 500 m.\u00a0<\/p>\n<\/p><\/div>\n The fact that MERTIS could already carry out observations at this early stage of the mission was only made possible by clever reprogramming of the instrument software. MERTIS was designed to observe Mercury through its so-called \u2018planet port\u2019 and to calibrate this data by looking out into cold space with its \u2018space port\u2019. \u00a0<\/p>\n But until BepiColombo arrives at Mercury in 2026, the spacecraft’s parts are \u2018stacked\u2019 together, and MERTIS’s planet port is blocked. Thanks to the reprogramming, its space port could now be used to generate data on the way to Mercury during this flyby. This has already proven successful during flybys of the Moon and Venus, allowing the team to test the instrument and to calibrate the data it produces.\u00a0<\/p>\n \u201cThese fascinating and valuable results from the MERTIS instrument are only a tantalising hint of the great results we\u2019re expecting from the entire BepiColombo science payload once both orbiters are operating in orbit around Mercury,\u201d says Geraint Jones, BepiColombo Project Scientist at ESA.<\/p>\n<\/p><\/div>\n Launched on 20 October 2018, BepiColombo is a joint mission between ESA and the Japan Aerospace Exploration Agency (JAXA), executed under ESA leadership. It is Europe’s first mission to Mercury.\u00a0<\/p>\n The mission comprises two scientific orbiters: ESA\u2019s Mercury Planetary Orbiter (MPO) and JAXA\u2019s Mercury Magnetospheric Orbiter (Mio). The European Mercury Transfer Module (MTM) carries the orbiters to Mercury. \u00a0<\/p>\n After arrival at Mercury in late 2026, the spacecraft will separate and the two orbiters will manoeuvre to their dedicated polar orbits around the planet. Starting science operations in early 2027, both orbiters will gather data during a one-year nominal mission, with a possible one-year extension.\u00a0<\/p>\n All M-CAM images are publicly available in the Planetary Science Archive. \u00a0<\/p>\n<\/p><\/div>\n For more information, please contact:<\/b>\u00a0<\/p>\n \nESA media relations
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<\/div>New eyes on Mercury’s mysterious surface<\/h4>\n
How much do you shine? <\/h2>\n
A clever sneak peak <\/h2>\n
\n\t\t\t\t\t\t\t\t<\/figcaption><\/figure>\n<\/p><\/div>\nAbout BepiColombo<\/h2>\n
media@esa.int\u00a0<\/p>\n<\/p><\/div>\n