BepiColombo snaps Mercury’s dark craters and volcanic plains

These are the last images we’ll see of Mercury’s marooned surface BepiColombo mission At the end of 2026 it starts orbiting the world inside the solar system.

Since its launch in 2018, the European and Japanese BepiColombo spacecraft have flown by Mercury six times, each using successive approach to reduce speed and adjust the flight path to facilitate entry into orbit. Although the mission’s main scientific instruments have yet to be used, the spacecraft’s monitoring cameras have given us some of the clearest views we’ve ever had of Planet Swift.

The European Space Agency (ESA) has released three of the most fascinating images from BepiColombo’s last flyby on January 8, taken about 300 kilometers below Mercury’s surface as it flew over the planet’s north pole and northern regions.

“It meant getting up at 5:30 in the morning, but when close-ups started popping up in our shared folder, it was worth it,” she says. David Rothery at the Open University, UK. “We looked at some simulated views beforehand and used these to figure out our imaging strategy, but what we saw was better than expected.”

The image above, taken at the planet’s north pole, shows the clear division between sunlight and darkness on Mercury, which researchers call the termination line. Mercury has some of the hottest temperatures in the solar system, where sunlight hits its scorched surface, but it also has some of the coldest, craters whose rims are permanently shadowed.

Some of these dark crater regions can be seen lying on the bottom line of the image. “It was amazing to look at Mercury’s north pole, and also to see the sunlit tip of the central peak inside Tolkien Crater, whose floor is in permanent shadow,” says Rothery.

Scientists have found it some evidence that these cratered regions contain frozen water. One of BepiColombo’s main mission objectives is to find out if this water actually exists and how much there is.

Mercury also has a vast volcanic plain known as the Borealis Planitia, which BepiColombo saw during the flyby. Researchers believe that these plains were formed by large lava flows that flooded craters over 3 billion years ago, some of which can be seen in the image above. Most of these submerged plains are smooth, with a few impact craters that must have been formed recently.

The Caloris Basin, the largest crater on Mercury at 1,500 kilometers across, appears as a lighter-colored semicircular patch of land extending from the horizon toward the lower left of the image. Scientists hope to learn how this crater, Borealis Planitia and solidified lava flows are connected when BepiColombo begins orbiting the planet.

The bright region near the top of the planet in this image is called Nathair Facula, which researchers believe is the remnant of Mercury’s largest volcanic eruption ever. At the center of the region is a 40-kilometer-wide crater that appears to have been the source of at least three major eruptions that spewed volcanic material hundreds of kilometers.

“(Nathair Facula) was on the cusp of what we would be able to see, but after NASA published images based on the previous mission to Mercury, it was exciting to see it again,” says Rothery. “Once we get into orbit, BepiColombo’s various instruments are a very important scientific goal because they offer our best chance to study what it is about Mercury’s composition that has allowed explosive volcanic eruptions to continue for much of the planet’s history.”