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This topic is available for NewMars members who might like to post updates on the Bepi Columbo Mission to Mercury.
The mission reached Mercury after a 6+ year journey, and two satellites have separated from their carrier. Months of patient celestial navigation remain before the satellites are safely installed in their planned orbits.
Post #3 will launch this topic with a report by CNN's Ashley Strickland.
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Post #3: Report on arrival at Mercury by CNN's Ashley Strickland
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This post is reserved for a report on the arrival of Bepi Columbo at Mercury by CNN's Ashley Strickland
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From CNN:
https://www.cnn.com/2026/09/03/science/ … on-arrival
The BepiColombo mission begins its arrival at Mercury after nearly 8 years
By
Ashley Strickland<the animation can be seen at the link above>
An animation shows the first step of BepiColombo's arrival to the vicinity of Mercury's orbit. ESA
An ambitious mission to reveal the secrets of the least explored planet in the inner solar system is taking the initial big step in arrival at its cosmic destination after a lengthy journey.
The BepiColombo mission, a joint effort between the European Space Agency and the Japan Aerospace Exploration Agency, intends to use two complementary orbiters to reveal insights into how Mercury formed and evolved so close to the sun.
The mission launched on an Ariane 5 rocket from Europe’s Spaceport near Kourou, French Guiana, in October 2018. Since then, it has traveled more than 6 billion miles (10 billion kilometers).
BepiColombo is named for Italian engineer and mathematician Giuseppe “Bepi” Colombo, who studied Mercury’s peculiar rotation and proposed trajectories that enabled NASA’s first flybys of the planet in 1974.
Earth is about 10 times closer to Mercury than it is to Jupiter, but BepiColombo has taken longer to reach the tiny planet than previous missions such as Galileo and Juno heading to the largest planet in our outer solar system.
“You can go faster to Mercury if you take a direct way to it,” said Frank Budnik, flight dynamics manager for the BepiColombo mission at the ESA. “But the problem is we want to insert into an orbit with respect to Mercury. You have to bring the spacecraft to the same velocity as Mercury has, and this is a very energy-demanding transfer.”
A combination of electric propulsion and gravitational boosts from a total of nine flybys of Earth, Venus and Mercury have aided BepiColombo in reaching the correct velocity on its long cruise.
BepiColombo snapped images during its sixth Mercury flyby, used to adjust the spacecraft's velocity, in January 2025. ESA/BepiColombo/MTM
The Mercury Transfer Module, which has powered the multiyear voyage, separated from BepiColombo’s stack of two science orbiters at 8 a.m. ET Thursday.The ESA hosted a live broadcast to share milestones of the nail-biting separation. Confirmation of separation arrived at ESA’s mission control at 9:53 a.m. ET, when the agency acquired a signal from BepiColombo. The mission team also confirmed that “the spacecraft is healthy and operating as expected.”
The mission’s flight dynamics team shared that the Mercury Transfer Module will remain in orbit around the sun for the foreseeable future and will not impact Mercury.
Ignacio Tanco, head of Inner Solar System Mission Operations at the ESA, compared the separation to launching a new spacecraft around a different planet. All went according to plan — but that’s just the beginning of a complex process.
“Unlike in other missions, BepiColombo’s arrival doesn’t mean a single event,” Tanco said. “We have about half a year of intense operations ahead of us.”
The challenges of venturing toward the sun
After nearly eight years, the Mercury Transfer Module (bottom) has finished its part of the mission. ESA/ATG medialab
Establishing an observational orbit around Mercury is even more difficult than the journey to get there.ESA’s Mercury Planetary Orbiter, or MPO, and JAXA’s Mercury Magnetospheric Orbiter, or MIO, will be captured by Mercury’s gravity and enter orbit around the planet on November 21.
The two orbiters will separate from one another between December 9 and 10, with the Mercury Planetary Orbiter moving into its orbital position on December 16 and the Mercury Magnetospheric Orbiter following on March 10.
Science operations will officially begin for both orbiters in April.
“It will be the first time that a mission releases two fully independent, fully operational separate spacecrafts around a different planet,” Tanco said.
BepiColombo's arrival at Mercury will occur sequentially through April. ESA
The MPO will observe the planet itself, while the MIO will focus on the space environment around Mercury, said Santa Martinez, BepiColombo mission manager at the ESA.
Mercury is about 36 million miles (58 million kilometers) from the sun on average, and completes one orbit around our star every 88 days, according to NASA. Such proximity means that the planet’s surface temperatures can reach about 800 degrees Fahrenheit (430 degrees Celsius) during the day.
Mercury’s close distance to the sun has made it a challenging planet to explore — and it’s the main driver of BepiColombo’s complexity. Only two previous missions, NASA’s Mariner 10 in 1974 and its MESSENGER mission in 2011, have been in the vicinity of the rocky world. Like BepiColombo, MESSENGER took nearly seven years to reach Mercury.
“The spacecraft in itself has been designed to operate within conditions which are extremely punishing,” Tanco said. “It’s essentially equivalent to operating with a very hot pizza oven running right on your back.”
Both orbiters are equipped with solar arrays to provide them with power, and they are at risk of overheating so close to the sun.
The MIO will spin 15 times a minute, while the MPO will position its array at an angle almost edge-on to the sun to receive just enough sunlight while also preventing solar radiation damage.
Solving Mercury’s mysteries
Putting two spacecraft in orbit around Mercury will provide unprecedented views of the planet and open a new chapter in scientists’ understanding of the solar system, Martinez said.
The orbiters will help map the planet in high resolution and answer questions that cropped up during MESSENGER’s detailed survey of Mercury.
An artist's impression depicts both orbiters in the dynamic near-sun environment. ESA
Each orbiter is equipped with a range of instruments to explore Mercury’s structure and composition, including craters and evidence of ancient volcanic activity on its surface, as well as the planet’s magnetic field and its exosphere, a thin cloud of gas that surrounds the planet, said Geraint Jones, lead project scientist for BepiColombo at the ESA.
One of the mysteries that scientists are hoping to probe are the so-called hollows spotted on Mercury by Mariner 10 and MESSENGER.
“There are depressions in the surface that look like the surface is being eaten away,” Jones said. “It might be possible that we can see changes in these regions over time.”
Hollows haven’t been found elsewhere on planets in our solar system, and with no wind or water to form the thousands of puzzling depressions, scientists want to know what forces sculpted them.
NASA’s MESSENGER spacecraft discovered strange "hollows" on the surface of Mercury. NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution for Science
The orbiters could also help uncover the truth behind why Mercury is so dense for its small size.
Some 4.5 billion years ago when the planets formed from the debris surrounding the sun, “it’s thought that Mercury started forming, created a modest-sized planet and then it was hit by another large planetesimal, which ripped off its outer crust,” Jones said. “So that means that the overall density of the material that was left behind was much higher, and that’s why it has the high density it has now.”
Learning more about Mercury’s surface and interior could uphold the theory or provide new answers, Jones said.
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The article at the link below is about shrinkage of Mercury over time, with a connection to the upcoming arrival of BepiColumbo in late 2026.
UrL >> https://www.cnn.com/2026/09/10/science/ … king-study
The closest planet to our sun is shrinking. Here’s what that means
By
Ashley Strickland
Sep 10, 2026A mosaic of images taken by NASA's MESSENGER spacecraft shows impact craters on Mercury in October 2008. NASA
Telltale wrinkles that cover Mercury, the closest planet to the sun, suggest it was once a larger world that has shrunk in size — and it may be shrinking more than scientists realized.
The smallest planet in our solar system is about 36 million miles (58 million kilometers) from the sun on average and completes one orbit around our star every 88 days, according to NASA.
The rocky world formed from swirls of gas and dust roughly 4.5 billion years ago. The early days of our solar system were chaotic, marked by violent interactions as a multitude of space rocks orbiting the sun crashed into other objects.
Newly formed planets are already hot, much like volcanic lava, but the energy from such collisions generate even more heat. As the heat escapes these worlds over time, the interiors of planets such as Mercury shrink.
Mercury’s cracked surface bears scars from such shrinkage — scientists call these ridges and cliffs shortening structures. Some of the cliffs can reach up to 1 mile (1.6 kilometers) in height and can extend for hundreds of miles in length.
But asteroids and comets have also bombarded Mercury, riddling it with impact craters, much like the pockmarked surface of Earth’s moon.
Debris from the impacts might have hidden just how much Mercury has contracted over time, according to a new study published Thursday in the journal Geophysical Research Letters.
Understanding Mercury’s shrink rate can shed light on how the planet has evolved and reveal secrets about its mysterious interior.
“There are lessons about the formation and evolution of large, rocky bodies like our Earth, that can be learned on Mercury better than anywhere else in our Solar System,” wrote Dr. Hannes Bernhardt, who was not involved in the study, in an email. Bernhardt is an assistant research scientist in the department of geological, environmental and planetary sciences at the University of Maryland, College Park.
The new study also highlights just how many questions linger about this tiny world — some of which could soon be answered by an unprecedented mission that will release two orbiters around Mercury in November.
A long cliff face runs through a large ancient crater on Mercury's scarred surface. NASA
A shrinking planet
As Mercury shrank, cracks likely appeared across its surface in a consistent way. But craters and debris from billions of years of impacts covered many of these fissures, said lead study author Gaku Nishiyama, a planetary scientist at the German Aerospace Center’s Institute of Space Research in Berlin.
Mercury’s proximity to the sun has made it a challenging planet to study and explore. Only two missions have ventured into this harsh environment in previous decades: NASA’s Mariner 10 in 1974 and the agency’s MESSENGER mission in 2011.
Mariner 10 conducted flybys of the planet that revealed Mercury’s intriguing wrinkles, while MESSENGER provided a more global portrait of the planet’s features, said Bernhardt, who has also studied Mercury’s shrinking.
Nishiyama and his team used data from MESSENGER to create a global map of Mercury’s surface roughness. They spotted a trend of fewer wrinkles in the roughest parts of Mercury, compared with smoother regions of the surface.
Contraction wrinkles can be seen on Mercury's otherwise smooth volcanic plains. NASA
“It made us think that there’s a process obscuring shortening structures,” Nishiyama said, such as debris cloaking signs of contraction on the surface.
The team estimated how many wrinkles might be present across Mercury’s surface if they weren’t hidden by debris. The computations determined that the planet may have shrunk 10% to 30% more than previously believed, or a radius change of about 7.2 miles (11.6 kilometers). Previous studies have suggested a change in radius between 0.6 to 1.2 miles (1 to 2 kilometers) and up to 4.3 miles (7 kilometers).
Dr. Paul Byrne, associate professor of Earth, environmental and planetary sciences at Washington University in St. Louis, said it’s plausible that previous studies of Mercury’s shrinking, including one of his own, missed geological cracks on the planet because they were hard to see in rough areas or because they hadn’t formed at all due to Mercury’s extremely rugged crust. Byrne was not involved in the latest study.
“Yet if we can accurately measure how much Mercury has contracted, we can make better estimates of its interior layering, the size and make-up of its core, its tectonic and volcanic histories, how its magnetic field is generated, and a whole lot more,” wrote Byrne, also the director of the NASA Planetary Data System Geosciences Node, in an email.
Wrinkle ridges formed on Mercury as the interior of the planet cooled. NASA
Mercury is the second densest planet in our solar system after Earth, mainly due to its large metallic core.
Calculating how much the planet has shrunk could provide a window into Mercury’s core and what has transpired inside the planet as it cooled.
“More shrinking means Mercury could have a larger metal core, less light elements like silicon mixed into the metal core, or a higher starting temperature,” Nishiyama said.
An unprecedented look at Mercury
The BepiColombo mission, which recently began its arrival at Mercury after traveling for nearly eight years, will position two orbiters near the planet at the end of this year.
Topography data that the mission collects could enable scientists to estimate more precisely how much Mercury has contracted over time and showcase the planet’s cliffs, craters and ridges like never before, said Nishiyama, who is a member of BepiColombo’s science team.
BepiColombo will make the first comprehensive global measurements of Mercury’s topographic properties, which is something MESSENGER couldn’t do, Byrne said.
An artist's impression depicts the two orbiters that BepiColombo will release near Mercury later this year. ESA
“Those new data will be key to testing whether this and other global contraction papers are right,” Byrne said. “But I suspect we’ll find that they are, and that we still have so very much to learn about the tiny innermost planet.”
While MESSENGER collected high-resolution data for Mercury’s northern hemisphere, BepiColombo’s Mercury Planetary Orbiter will also measure topography and surface roughness across the southern hemisphere, said Dr. Kelsey Crane, geologist at Seres Engineering and Services in Charleston, South Carolina. Crane was not involved in the new study but previously analyzed Mercury’s surface features using MESSENGER data.
“The instruments onboard will detect gravity anomalies, improve estimates of crustal thickness and interior structure, and detect elemental and mineral compositions of the surface,” Crane said. “All these types of data complement each other, helping scientists tell a more complete story of planetary evolution and spurring new questions for future missions to address.”
Mercury has likely shrunk more than any other planet because its core is much larger relative to the planet’s size than other rocky worlds in our solar system, Bernhardt said.
While he found the methodology and results of the paper to be compelling and sound, Bernhardt said he believes that such a dramatic decrease in Mercury’s size would have initiated visible large-scale buckling across the planet’s surface.
Bernhardt and his team are working on their own research to determine how much the planet has shrunk, but said orbital data alone might not answer the question.
“With all the things that government money can buy, maybe supporting our best engineers and scientists to put robotic boots into Mercury’s scorched dust is one of the most inspiring ones,” he said.
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