New, Stunning Images of Mercury’s North Pole Will Help Scientists Study the Planet’s Mysterious Permanent Shadows

The BepiColombo spacecraft—a joint endeavor between the European and Japanese space agencies—has just snapped stunning photographs of Mercury’s north pole during its recent flyby of the innermost planet.

The images, which reveal the depths of Mercury’s iconic polar craters, were captured by the craft’s monitoring cameras (M-CAMs) on January 8. European Space Agency (ESA) Director General Josef Aschbacher revealed the first image during a press briefing the next day.

“It meant getting up at 5:30 a.m., but once close-up images started to appear in our shared folder, it was worth it,” David Rothery, a planetary scientist at the Open University, tells New Scientist’s Alex Wilkins. “We had studied some simulated views in advance and used these to devise our imaging strategy, but what we saw was better than expected.”

M-CAM 1, the first of three monitoring cameras, captured a photograph of the shadowed north pole (above) from a distance of 489 miles above Mercury’s surface. The white hardware on the right side of the image is BepiColombo’s solar array, and part of the spacecraft’s Mercury Transfer Module is visible in the lower left. The image features Mercury’s terminator—the separation between day and night—at the center, nearly parallel to the Prokofiev, Kandinsky, Tolkien and Gordimer craters.

Because Mercury spins on an axis with a miniscule tilt of just 0.01 degrees—almost perpendicular to its plane of orbit around the sun—the rims of all four of these polar craters cast permanent shadows within their depths. Those eternally dark areas are some of the coldest places in the solar system, despite the fact that Mercury is the closest planet to the sun.

Previous observations suggested that these permanent shadows might host frozen water, an exciting hypothesis that the BepiColombo mission is set to investigate further. The mission and spacecraft are named in honor of Giuseppe (Bepi) Colombo, a 20th century Italian mathematician who contributed to previous space missions, per the Associated Press’ Marcia Dunn, including NASA’s Mariner 10, the first spacecraft sent to Mercury.

The area at the left of the craters and terminator is the Borealis Planitia, Mercury’s largest expanse of smooth volcanic plains, which was formed by large volcanic eruptions 3.7 billion years ago. The resulting lava flooded existing craters, including the Henri and Lismer craters marked in the image. Mercury’s wrinkle-like features across the left half of the image likely formed after those lava plains solidified and the planet’s interior cooled and contracted, according to an ESA statement.

Another M-CAM 1 photograph (above) highlights the Mendelssohn and Rustaveli craters, two of the ancient depressions in the Borealis Planitia that were flooded with lava billions of years ago. The Caloris basin is also visible in the bottom left of the photograph; with a span of more than 932 miles wide, it’s the planet’s largest impact crater, and it features linear troughs radiating from the point of impact.

Roughly in the center, Mercury’s surface is marked by a relatively bright boomerang-shaped streak of lava. According to the statement, this represents yet another astronomical question the BepiColombo mission aims to study: the direction of the lava flow. Did the lava move “into the Caloris basin, or out of it?”

BepiColombo snapped this second image just five minutes after the first.

Finally, the third photograph, captured by M-CAM 2, shows the relatively young Fonteyn crater (at 300 million years old) and the Nathair Facula, a feature that resulted from the largest volcanic eruption in Mercury’s history. It hosts a volcanic vent with a diameter of about 25 miles.

“[Nathair Facula] is a very important science target for several of BepiColombo’s instruments when we get into orbit, because it offers our best chance to work out what it is about Mercury’s composition that has allowed explosive volcanic eruptions to continue through much of the planet’s history,” Rothery says to New Scientist.

BepiColombo’s sixth flyby was the last gravity assist maneuver needed to propel the craft before it enters orbit around Mercury in late 2026, according to BBC News’ Danny Fullbrook. Built by Airbus and launched in 2018, the craft has flown by Earth, Venus and Mercury to reach its targeted speed and trajectory.

With its recent pass by the north pole being the last, the images are also the M-CAMs’ final close-up photographs of Mercury. The module they are attached to will separate from the craft’s two orbiters when they begin to loop around the planet.

“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,” says Geraint Jones, BepiColombo’s project scientist at the ESA, in the agency’s statement. “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.”

Margherita Bassi | READ MORE

Margherita Bassi is a freelance journalist and trilingual storyteller. Her work has appeared in publications including BBC Travel, Discover magazine, Live Science, Atlas Obscura and Hidden Compass.