BepiColombo Jettisons Transfer Module for Final Approach to Mercury

The BepiColombo mission has officially entered its final arrival phase at Mercury after jettisoning its Mercury Transfer Module on September 3, 2026. This critical maneuver marks the beginning of the end of an eight-year journey to the smallest planet in our solar system.

The joint effort between the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) is now on a trajectory to enter Mercury's orbit on November 21, 2026. Following orbital capture, the mission's two distinct spacecraft—the ESA-led Mercury Planetary Orbiter (MPO) and JAXA's Mercury Magnetospheric Orbiter (MMO), also known as Mio—are scheduled to separate from one another on December 9-10, 2026. Full science operations are expected to commence in April 2027.

A Complex Path to the Sun

Launched on October 20, 2018, BepiColombo represents one of the most complex missions ever attempted to orbit Mercury. Reaching the planet is a significant engineering challenge due to Mercury's proximity to the Sun and the immense velocity required to reach it. To slow down sufficiently for orbital capture, the spacecraft executed an unprecedented series of nine planetary flybys, including one Earth, two Venus, and six Mercury gravity assists.

Beyond these flybys, the mission relied on advanced ion propulsion to navigate the inner solar system. This approach follows the precedent set by NASA's MESSENGER mission, which orbited the planet from 2011 to 2015, but BepiColombo aims to provide a far more comprehensive analysis by deploying two specialized orbiters simultaneously.

Unlocking Mercury's Secrets

Mercury remains the least explored planet in the inner Solar System, and the dual-orbiter strategy is designed to fill critical gaps in planetary science. While the MPO focuses on surface mapping and composition, the MMO is dedicated to studying the planet's magnetosphere. Together, they will investigate the effects of solar wind and search for evidence of water ice at the poles.

According to ESA project scientist Geraint Jones, the fundamental goal is to learn about the origins of the planet and how it evolved into its current state. The data collected could reveal whether Mercury is still geologically active, providing a window into the early history of the solar system.

The Final Hurdles

Despite the successful jettison of the transfer module, the mission still faces high-stakes maneuvers. Ignacio Tanco, head of inner Solar System mission operations at ESA, noted that the success of certain attitude control systems, including several new sensors and mechanisms, will only be fully verified after the two orbiters separate in December.

Observers will now watch for the November orbital insertion, the most critical remaining milestone before the spacecraft begin their separate missions to map the surface and analyze the magnetic environment of the Sun's closest neighbor.