After eight years traversing the inner solar system, Europe’s BepiColombo mission reached Mercury’s arrival phase on September 3, 2026, completing a complex sequence of maneuvers to begin its scientific study of the planet.
The European Space Agency (ESA) and Japan Aerospace Exploration Agency (JAXA) joint mission, BepiColombo, finally entered its arrival phase on September 3, 2026, after a dramatic separation of its propulsion module. This milestone marked the end of an eight-year journey that involved six gravity-assist flybys of Mercury, two of Venus, and one of Earth, as well as a critical solar panel issue in 2024 that delayed its arrival.
The Final Approach and Module Separation
Ignacio Tanco, head of inner Solar System mission operations at ESA, emphasized the complexity of the maneuver: This is something that we will only see after separation if it has worked, and we will be using several new sensors and mechanisms as part of the attitude control system,
he said, adding that the operation was equivalent to launching a new spacecraft
with considerable risk.
The MTM’s removal required the rest of the spacecraft to take over power generation, propulsion and pointing, and thermal control, a critical step given Mercury’s harsh conditions.
Timeline of Arrival and Orbital Insertion
BepiColombo’s arrival at Mercury unfolded in stages. Following the MTM’s separation, the MPO and Mio entered a polar orbit around the planet on November 21, 2026. The two orbiters then separated in December, with Mio settling into a highly elliptical polar orbit and MPO descending to its own low polar orbit by March 10, 2027. The mission’s science phase, involving simultaneous observations from both orbiters, is set to begin on April 6, 2027.
The timeline includes 16 maneuvers to gradually lower and reshape BepiColombo’s orbit. Mio is scheduled to separate from MPO around December 9, 2026, while MPO will jettison Mio’s sunshield (MOSIF) on December 16, 2026, before continuing its descent. ESA’s timeline, published on its website, outlines these steps, though exact dates may shift due to operational adjustments.
Challenges and Technical Innovations
BepiColombo’s journey was fraught with technical challenges. In April 2024, a solar panel issue on the MTM reduced power for its electric thrusters, forcing engineers to adopt a lower-thrust trajectory that delayed Mercury arrival from December 2025 to November 2026. Despite these hurdles, the mission’s resilience paid off, with officials describing the separation as the best case scenario.
The spacecraft’s design includes innovative systems to survive Mercury’s extreme environment. MPO uses thermal blankets, heat pipes, and a sun-tracking solar array to manage temperatures exceeding 400°C / 752°F, while Mio employs a spin-stabilization mechanism to distribute heat across its reflective exterior. These measures are critical for the mission’s success, as Mercury’s proximity to the Sun makes it one of the most hostile environments in the solar system.
Scientific Goals and Historical Context
BepiColombo’s dual-orbiter strategy aims to address longstanding mysteries about Mercury, including the origins of its “hollows”—strange, shallow depressions peppering the surface—and why Mercury possesses an unexpectedly high density and an active magnetic field despite its small size. Previous missions, such as NASA’s Mariner 10 in the mid-1970s and MESSENGER from 2011 to 2015, provided limited data, but BepiColombo’s advanced instruments will offer unprecedented insights.
Elsa Montagnon, BepiColombo’s operations manager, noted the complexity of arriving at Mercury: Arriving to Mercury is not as simple as other missions that do a big maneuver and they are there.
Reactions and Future Implications
The successful separation of the MTM was met with relief and excitement. Montagnon expressed her satisfaction, stating, I’m again extremely relieved,
as telemetry confirmed the spacecraft’s correct configuration. The mission’s success marks a significant step forward in planetary science, with potential implications for understanding planetary formation and the dynamics of the inner solar system.
Looking ahead, BepiColombo’s findings could reshape our understanding of Mercury’s geology, magnetic field, and interaction with the solar wind. The mission’s data will be invaluable for future exploration, building on the legacy of past missions while pushing the boundaries of what is possible in space exploration.
