After eight years in space, the European-Japanese mission BepiColombo is due to enter orbit around Mercury on 21 November 2026. The European Space Agency confirmed the date in its latest mission update. It will make BepiColombo only the third mission to visit the innermost planet, after NASA's Mariner 10 and MESSENGER.

Two spacecraft in one

BepiColombo is a stack of three modules that launched together in October 2018:

  • the Mercury Planetary Orbiter (MPO), built under ESA leadership, which will map the surface and study the interior;
  • Mio, the Mercury Magnetospheric Orbiter from the Japan Aerospace Exploration Agency (JAXA), which will study the planet's magnetic field;
  • the Mercury Transfer Module, which provided the electric propulsion for the journey.

After orbit insertion, the two orbiters are scheduled to separate on 9 and 10 December 2026. Science operations are due to start in April 2027, according to ESA.

Why it took so long

Mercury is hard to reach. A spacecraft falling toward the Sun gains a lot of speed, and it must lose that speed to be captured by a small planet. BepiColombo used nine planetary flybys, of Earth, Venus and Mercury itself, to slow down. In 2024, before the fourth Mercury flyby, engineers discovered a problem with the thrusters. The trajectory was redesigned, which delayed arrival by about a year, JAXA said.

What scientists want to learn

Mercury raises basic questions about how planets form:

  • A very large iron core, much larger in proportion than Earth's. Why?
  • A magnetic field, which is unusual for a small, slowly rotating planet.
  • Ice in permanently shadowed craters near the poles, despite the planet's closeness to the Sun.
  • Volatile elements on the surface that should have boiled away.

The German contribution

Germany is closely involved through the German Aerospace Center (DLR). Among other contributions, the MERTIS infrared spectrometer, developed with the University of Münster and DLR, will map the minerals on Mercury's surface by their heat signature.

The orbit insertion is a critical moment. Mission teams will confirm success only after tracking data show that the spacecraft has been captured by Mercury's gravity.