For most space missions, launch is the key moment. For BepiColombo, the real milestone comes years later. After spending nearly eight years in the inner solar system, the European-Japanese spacecraft is now getting closer to the point it was designed to reach from the beginning. As reported by ESA, in November 2026, the Mercury spacecraft is expected to finally be placed in orbit, ending one of the longest and most carefully managed planetary journeys ever undertaken. This wait is deliberate rather than unexpected. A trip to the planet closest to the Sun requires an approach unlike that of almost any other destination in space, requiring repeated gravity assists and constant adjustments rather than straight flight. Once BepiColombo is in orbit, scientists will begin a new chapter in the exploration of Mercury, a planet that remains surprisingly unknown despite being in Earth’s cosmic neighborhood.
Why does Mercury remain one of the least explored planets?
Mercury has never attracted the steady stream of missions seen at Mars or Venus. Its position close to the Sun makes every visit technically difficult, giving astronomers only a few close encounters over the past five decades.The first came via NASA’s Mariner 10 spacecraft in the mid-1970s. Those flybys provided humanity’s earliest detailed views of the scorched world, but the spacecraft were never intended to be placed in orbit. Decades later, NASA’s Messenger mission, orbiting Mercury between 2011 and 2015, transformed the understanding of its geology, magnetic field, and chemical composition.BepiColombo now becomes the third mission to reach Mercury and the second to orbit the planet, making its arrival an important contribution to the surprisingly short history of exploration.
Unusual route to the solar system’s innermost planet
Mercury may appear closer than Mars on a map of the Solar System, but distance alone tells little of the story. Any spacecraft moving inward toward the Sun picks up tremendous speed as solar gravity pulls it closer. That extra velocity becomes the main obstacle.Instead of running straight toward Mercury, BepiColombo has spent years doing almost the opposite. The mission has repeatedly slowed itself down through a carefully planned sequence of planetary encounters. One flyby of Earth, two close passes of Venus and six encounters with Mercury gradually reduced the spacecraft’s speed. At the same time, its ion propulsion system made continuous but gentle thrust, making small improvements over thousands of hours rather than relying on powerful blasts.The result has been a journey defined by patience rather than speed.
How BepiColombo was designed
Although commonly described as a single spacecraft, BepiColombo actually began its mission as a stack of three linked vehicles.The Mercury Transfer Module has propelled the mission through interplanetary space, providing the ion propulsion needed during the long journey. Above it are attached two independent science orbiters that will eventually separate once Mercury takes over the mission.The European-built Mercury Planetary Orbiter will focus on the planet itself, examining its surface, internal structure and geological history. In addition, Japan’s Mio spacecraft has a different function. Instead of looking down at Mercury, it will probe the planet’s magnetic environment, studying the interactions between Mercury, the solar wind, and surrounding charged particles.Operating together gives scientists the opportunity to observe the planet and its surrounding space at the same time, something previous missions could not achieve.
How engineers kept the mission on track
The original arrival schedule remained unchanged.During 2024, engineers identified an unexpected decrease in the performance of the spacecraft’s electric propulsion system. The investigation traced a problem to electrical currents affecting the power distribution system associated with the spacecraft’s solar arrays.The reduced thrust means that the current flight plan can no longer deliver the spacecraft to Mercury’s orbit on schedule. Mission specialists redesigned the remaining trajectory, making more use of Mercury’s own gravity during subsequent flybys to compensate for the weak propulsion.The revised route preserved the scientific goals of the mission, although it delayed entry into orbit by about a year. Instead of arriving in late 2025, BepiColombo is now expected to complete the process in November 2026.
How will BepiColombo enter orbit?
The mission passed another important milestone during 2026 when it completed the main phase of ion-powered rotation.Unlike missions that involve a dramatic braking maneuver with a large chemical engine, BepiColombo’s arrival unfolds very slowly. Small propulsion adjustments continue as Mercury’s gravity gradually takes over. The spacecraft will enter a temporary polar orbit before discarding the transfer module.Only then will the two science orbiters separate and begin moving toward their individual operational paths around the planet. Their full scientific program is expected to begin during 2027 after completion of commissioning and orbit adjustment.
Mercury still has many unanswered questions
Despite decades of research, Mercury remains a mystery to scientists.Its massive iron core occupies a much larger portion of the planet than any other rocky world in the Solar System. The reasons remain uncertain, with several competing theories attempting to explain how such an unusual interior developed.Despite its relatively small size, Mercury also has a global magnetic field. Exactly how that magnetic field survived for billions of years remains an active area of research.Perhaps the biggest surprise lies with the Poles. Although Mercury experiences the highest surface temperatures in the Solar System, permanently shadowed craters appear to be able to preserve water ice because sunlight never reaches their floors. Understanding the origin and stability of those frozen deposits is one of the objectives that awaits BepiColombo once its scientific observations begin.