BepiColombo Drops Its Transfer Module and Begins Final Approach to Mercury
After eight years and 9.9 billion kilometres of travel, BepiColombo has separated its Mercury Transfer Module and is now on final approach for orbital insertion around Mercury on November 21, 2026.
On September 3 at 15:49 CEST, ESA’s BepiColombo Mission Control Team confirmed that the Mercury Transfer Module had separated from the spacecraft stack — the first step in arriving at Mercury after nine years of travel and nine planetary flybys. The transfer module had done its job: it carried two science orbiters across 9.9 billion kilometres of interplanetary space, and now the stack doesn’t need it anymore.
BepiColombo is a joint European-Japanese mission, led by ESA with JAXA and US contributions, and it is also, by the standards of planetary science, a nearly $2 billion exercise in patience. The spacecraft launched in October 2018. It has been en route for eight years. It needed six Mercury flybys, two Earth flybys, and one Venus flybys just to lose enough orbital energy to fall inward toward the Sun — and the mission isn’t done yet.
The separation occurred 39 million miles from the Sun, in one of the harshest thermal environments any spacecraft has ever attempted this kind of operation in. Heat from the Sun at that distance is intense enough that the transfer module itself was wrapped in a solar shield designed to protect the rest of the stack during the long spiraling approach. That shield, the reason the module existed in the first place, has now been jettisoned along with it.
The spacecraft is now on track to enter orbit around Mercury on November 21, 2026. If that insertion goes as planned, the two orbiters — one ESA, one JAXA — will begin the most detailed study of Mercury ever attempted, mapping its surface composition, magnetic field, and exosphere in ways that MESSENGER, the only previous orbiter, could not.
Eight years is a long time to wait for a science mission to start doing science. But the approach profile that makes it possible — six flybys of the target planet itself, each one peeling off a little more velocity — is also what makes the mission’s arrival feel so deliberate. There was no shortcut to Mercury. The transfer module just delivered the payload to the threshold and stepped aside.