BepiColombo Begins Months-Long Approach to Mercury

Two probes successfully separated from their transfer module on Thursday. The European-Japanese BepiColombo mission has thus begun its months-long approach to Mercury. The European Space Agency’s ESA Mercury Planetary Orbiter (MPO) and the Japanese space agency JAXA’s Mercury Magnetospheric Orbiter (Mio) are still approaching the planet together and remain connected.

The next fixed point is November 21: The probes are then scheduled to be captured by Mercury’s gravity. On December 9 or 10, they are expected to separate and enter different orbits. The MPO is scheduled to reach its final orbit on March 10, with the scientific phase of the mission set to begin in April. These are the mission’s planned next steps.

BepiColombo launched in October 2018, after preparations that had taken almost 20 years. In 2024, the transfer module’s solar panels no longer supplied enough power for the engines. Although the ion propulsion system’s thrust could be restored to 90% of its capacity, that was not enough for the originally planned route. The arrival was therefore delayed by a year.

The approach requires more than a long flight. On its way to the planet closest to the Sun, BepiColombo was continuously accelerated by the Sun and would normally have been traveling too fast to be captured by Mercury’s comparatively weak gravity. Several flybys of the planet helped reduce its energy and speed; the engines alone would not have been sufficient. Mercury is therefore the least explored rocky planet in the solar system. Before BepiColombo, only NASA’s Messenger mission had studied the planet from orbit.

What happens next? Once the separated probes have reached their orbits, they are scheduled to study Mercury’s surface and magnetic field. For researchers, this means new measurements of a planet whose difficult access has so far limited its exploration. The goal is to better understand the origins of the solar system.