In a thrilling close approach, the BepiColombo mission captured its final, stunning images of Mercury before its orbit insertion in 2026.
Revealing icy craters and expansive volcanic plains, these photographs from just hundreds of kilometers above the surface offer unprecedented details of the planet’s least understood features, suggesting the presence of water ice in shadowed craters and providing clues about Mercury’s volcanic and impact history.
Unveiling Mercury: The BepiColombo Mission’s Final Approach
On January 8, 2025, the ESA/JAXA BepiColombo mission completed its sixth flyby of Mercury, successfully performing the final “gravity assist maneuver” needed to guide the spacecraft into orbit around the planet by late 2026. During this maneuver, BepiColombo flew just a few hundred kilometers above Mercury’s north pole, capturing stunning close-up images of the planet’s permanently shadowed, potentially icy craters, as well as its vast, sunlit northern plains.
At 06:59 CET, the spacecraft passed within 295 kilometers (183 miles) of Mercury’s surface on the cold, dark night side of the planet. Just seven minutes later, it flew over the north pole, where it captured detailed views of Mercury’s sunlit northern region.
First Glimpses: Revealing Mercury’s Secrets
The first image from this flyby was unveiled on January 9 by ESA Director General Josef Aschbacher during his Annual Press Briefing. As with its previous flybys, BepiColombo’s monitoring cameras (M-CAMs) delivered remarkable images, continuing to reveal new details about the planet.
This flyby also marks the last time that the mission’s M-CAMs get up-close views of Mercury, as the spacecraft module they are attached to will separate from the mission’s two orbiters – ESA’s Mercury Planetary Orbiter and JAXA’s Mercury Magnetospheric Orbiter – before they enter orbit around Mercury in late 2026.
Celebrating the M-CAMs’ final hurrah, let’s explore the best three images from BepiColombo’s sixth close encounter with the little planet, and what they reveal about mysterious Mercury.
Peering Into Mercury’s Darkest Craters
After flying through Mercury’s shadow, BepiColombo’s monitoring camera 1 (M-CAM 1) got the first close views of Mercury’s surface. Flying over the ‘terminator’ – the boundary between day and night – the spacecraft got a unique opportunity to peer directly down into the forever-shadowed craters at planet’s north pole.
The rims of craters Prokofiev, Kandinsky, Tolkien and Gordimer cast permanent shadows on their floors. This makes these unlit craters some of the coldest places in the Solar System, despite Mercury being the closest planet to the Sun!
Excitingly, there is existing evidence that these dark craters contain frozen water. Whether there is really water on Mercury is one of the key Mercury mysteries that BepiColombo will investigate once it is in orbit around the planet.
Dynamic Landscape: Volcanic Plains and Impact Basins
To the left of Mercury’s north pole in M-CAM 1’s view lie the vast volcanic plains known as Borealis Planitia. These are Mercury’s largest expanse of ‘smooth plains’ and were formed by the widespread eruption of runny lava 3.7 billion years ago.
This lava flooded existing craters, such as the Henri and Lismer craters highlighted in the image. The wrinkles in the surface were formed over billions of years following the solidification of the lava, probably in response to the planet contracting as its interior cooled down.
Another M-CAM 1 image, taken just five minutes after the first, shows that these plains extend over a large part of Mercury’s surface. Prominently visible is the Mendelssohn crater, whose outer rim is barely visible above its flooded interior. Just a handful of smaller, more recent impact craters dent the smooth surface.
Further out, but still within the Borealis Planitia, the Rustaveli crater suffered a similar fate.
On the bottom left of the image lies the massive Caloris basin, Mercury’s largest impact crater, which spans more than 1500 km (932 miles). The impact that created this basin scarred Mercury’s surface up to thousands of kilometers away, as evidenced by the linear troughs radiating out from it.
Above a particularly large trough, a boomerang-shaped curve brightens the surface. This bright lava flow appears to connect to a deep trough below it. It appears similar in color to both the lava on the floor of the Caloris basin and the lava of Borealis Planitia further north. Yet another mystery that BepiColombo hopes to solve is which way this lava moved: into the Caloris basin, or out of it?
Illuminating the Dark: Young Features on Mercury
While M-CAM’s images might not always make it appear so, Mercury is a remarkably dark planet. At first glance, the cratered planet may resemble the Moon, but its cratered surface only reflects about two-thirds as much light.
On this dark planet, younger features on the surface tend to appear brighter. Scientists don’t yet know what exactly Mercury is made of, but it is clear that material brought up from beneath the outer surface gradually becomes darker with age.
BepiColombo’s third image selected from this flyby, taken by M-CAM 2, shows spectacular examples of the two things that bring bright material to the surface: volcanic activity and large impacts.
The bright patch near the planet’s upper edge in this image is the Nathair Facula, the aftermath of the largest volcanic explosion on Mercury. At its center is a volcanic vent of around 40 km (25 miles) across that has been the site of at least three major eruptions. The explosive volcanic deposit is at least 300 km (186 miles) in diameter.
And to the left lies the relatively young Fonteyn crater, which formed a ‘mere’ 300 million years ago. Its youth is apparent from the brightness of the impact debris that radiates out from it.
Throughout its mission, several BepiColombo instruments will measure the composition of both old and new parts of the planet’s surface. This will teach us about what Mercury is made of, and how the planet formed.
Concluding Insights: A Pre-orbit Preview
“This is the first time that we performed two flyby campaigns back-to-back. This flyby happens a bit more than a month after the previous one,” says Frank Budnik, BepiColombo Flight Dynamics Manager. “Based on our preliminary assessment, everything proceeded smoothly and flawlessly.”
“BepiColombo’s main mission phase may only start two years from now, but all six of its flybys of Mercury have given us invaluable new information about the little-explored planet. In the next few weeks, the BepiColombo team will work hard to unravel as many of Mercury’s mysteries with the data from this flyby as we can,” concludes Geraint Jones, BepiColombo’s Project Scientist at ESA.
About BepiColombo
Launched on October 20, 2018, BepiColombo is a collaborative mission between the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA), marking Europe’s first mission to Mercury. Led by ESA, the mission aims to unravel the mysteries of the Solar System’s innermost planet.
BepiColombo consists of two scientific orbiters: ESA’s Mercury Planetary Orbiter (MPO) and JAXA’s Mercury Magnetospheric Orbiter (Mio). These orbiters are being transported to Mercury by ESA’s Mercury Transfer Module (MTM). Upon reaching Mercury in late 2026, the spacecraft will separate, and the two orbiters will enter their designated polar orbits to begin a detailed scientific study of the planet.
Science operations are scheduled to commence in early 2027 and will continue for a nominal one-year mission, with the possibility of a one-year extension. The mission will provide unprecedented insights into Mercury’s surface, magnetosphere, and internal structure. All images captured by BepiColombo’s monitoring cameras (M-CAMs) will be made publicly available through the Planetary Science Archive, ensuring accessibility for researchers worldwide.
