After eight years of travel, the BepiColombo mission successfully separated its propulsion module on September 3, 2026, marking a critical step toward orbiting Mercury. The European Space Agency (ESA) and Japan Aerospace Exploration Agency (JAXA) collaboration now faces its most perilous phase as the two science orbiters, MPO and Mio, prepare for Mercury’s extreme environment.
The BepiColombo spacecraft completed a pivotal maneuver on September 3, 2026, as its Mercury Transfer Module (MTM) detached from the ESA’s Mercury Planetary Orbiter (MPO) and JAXA’s Mercury Magnetospheric Orbiter (Mio). This separation, executed 63 million kilometers from the Sun, was described by ESA’s Ignacio Tanco as equivalent to launching a new spacecraft
due to the extreme risks involved. The MTM, which had propelled the stack for eight years, now drifts as inert debris, leaving the orbiters to navigate Mercury’s harsh conditions independently.
A Delicate Dance in Mercury’s Shadow
The separation occurred at 12:00 GMT, with the MTM’s four mechanical feet releasing via a spring-loaded mechanism. The two orbiters drifted apart at 40 cm per second, maintaining a close but safe distance.
Unveiling Mercury’s Secrets
BepiColombo’s dual-orbiter strategy aims to solve longstanding mysteries about Mercury, the least explored terrestrial planet. The MPO will map Mercury’s surface in high resolution, analyzing its composition and searching for water ice in shadowed craters. Mio will study the planet’s magnetic field, the only rocky planet in the solar system (besides Earth) to possess one. Fondamentalement, nous voulons comprendre les origines de cette planète et la manière dont elle est devenue ce qu’elle est,
said Geraint Jones, BepiColombo’s scientific project leader.
These features, first observed by NASA’s MESSENGER mission, remain poorly understood. The MPO and Mio will operate in complementary orbits, with Mio’s elliptical path allowing it to study Mercury’s magnetosphere while MPO focuses on the planet’s geology.
A Journey of Gravitational Ballet
BepiColombo’s 8-year voyage was a feat of gravitational engineering. Launching in October 2018, the spacecraft used nine gravity assists from Earth, Venus, and Mercury to slow its approach. Now, the orbiters must perform maneuvers to enter Mercury’s grasp by November 21, 2026.
The final phase includes a weak stability boundary capture, a technique to minimize risk during orbital insertion. After MPO and Mio enter orbit, they will separate in December, with Mio moving into its high elliptical orbit and MPO descending to a low polar orbit. The full scientific campaign is set to begin in April 2027, with MPO and Mio operating simultaneously.
The mission’s next critical test is Mercury’s orbital insertion on November 21, 2026. However, uncertainties remain: will the orbiters survive Mercury’s extreme conditions? How will their instruments perform in the intense radiation?
For scientists, the stakes are high. Mercury’s peculiarities—its dense iron core, magnetic field, and volatile-rich surface—could provide insights into exoplanet formation and the evolution of rocky worlds. The next chapter begins in November, with the world watching as BepiColombo takes its first steps into Mercury’s orbit.
