BepiColombo Begins Its Final Descent Toward Mercury

After eight years traveling through the inner solar system, the European Space Agency (ESA)-JAXA BepiColombo probe has entered the last phase of its mission. Ground control confirmed on September 3 that the propulsion module successfully separated from the spacecraft, clearing the way for the probe’s planned insertion into low Mercury orbit.

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The probe, named for the Italian scientist who pioneered the gravity-assist technique, was originally slated to reach Mercury a year earlier. A propulsion malfunction forced a course correction that delayed arrival by nearly twelve months. Over its voyage, BepiColombo covered roughly 6 billion miles (9.9 billion km), executing nine gravity-assist maneuvers—one around Earth, two around Venus, and six around Mercury—to shed excess velocity. Reaching Mercury is especially fuel-intensive because a spacecraft must brake against the Sun’s strong gravity rather than simply “fall” toward the planet.

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Once in position, BepiColombo will separate into two spacecraft: the Mercury Planetary Orbiter (MPO), tasked with mapping the planet’s surface and probing its interior, and the Mercury Magnetospheric Orbiter, nicknamed “Mio,” which will study Mercury’s magnetic field and thin exosphere. This will be the first instance of multiple probes orbiting Mercury simultaneously, allowing a more comprehensive data set than any single mission could achieve.

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Mercury has been visited only twice before, both times by NASA’s Mariner 10 and MESSENGER missions. BepiColombo’s dual-orbiter configuration promises new insights into the planet’s extreme temperature swings—exceeding 800 °F (430 °C) on the sun-facing side and dropping to –290 °F (-180 °C) at night—and its poorly understood magnetic environment. The mission’s successful progression marks a milestone for international collaboration in deep-space exploration and sets the stage for future studies of the solar system’s innermost world.

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