BepiColombo Sheds Propulsion Module, Begins Descent to Mercury

Ground control confirmed on September 3 that BepiColombo's propulsion module separated from the rest of the spacecraft, starting the joint ESA-JAXA probe's final descent into low orbit around Mercury, according to Wired. The maneuver caps roughly eight years in space and puts the mission back on track after a propulsion malfunction forced a slower, lower-power route to the planet.

What happened on September 3?

The propulsion module — the section that carried BepiColombo's electric thrusters for most of the journey — detached from the spacecraft, marking what Wired describes as "the final phase" of the mission before orbit insertion. Telemetry after the separation showed the maneuver went smoothly despite the craft sitting more than 200 million kilometers from Earth.

Why is the probe arriving nearly a year late?

BepiColombo was originally scheduled to reach Mercury last year. A malfunction in its propulsion system forced controllers to reroute the craft onto a reduced-power trajectory, pushing arrival back by close to twelve months, per Wired's reporting. The delay adds to a mission already defined by its indirect path: reaching Mercury requires shedding enormous velocity as a spacecraft falls toward the sun's gravity well, and BepiColombo has relied on gravity-assist flybys rather than raw thrust to do most of that braking.

How did BepiColombo get here?

Over its journey, the spacecraft has traveled approximately 6 billion miles (9.9 billion kilometers), looping past Earth once, Venus twice, and Mercury itself six times — nine gravity-assist maneuvers in total, according to Wired. The technique is named for Giuseppe "Bepi" Colombo, the Italian scientist credited with developing gravity-assist trajectories, for whom the mission is named. Only two spacecraft have explored Mercury before, both NASA probes, underscoring how difficult the innermost planet remains to reach and survive.

What conditions will the probe face at Mercury?

Mercury's surface swings from more than 800 degrees Fahrenheit (about 430 Celsius) in daylight to roughly -290 Fahrenheit (-180 Celsius) at night, because the planet has essentially no atmosphere to hold heat. BepiColombo has to withstand not just those extremes but the daily transition between them as it settles into orbit.

What happens between now and full science operations?

Once positioned, BepiColombo will split into two separate spacecraft: the Mercury Planetary Orbiter (MPO), which will study the planet's surface and internal structure, and the Mercury Magnetospheric Orbiter, known as Mio, which will examine Mercury's magnetic field and thin atmosphere. Wired notes this marks the first time multiple probes will orbit Mercury at once, aimed at building a fuller picture than any single spacecraft could deliver alone.

Mio will settle into a higher elliptical orbit crossing the poles, while MPO lowers its altitude further and is scheduled to reach its final orbit in March 2027. After that positioning and instrument checkout, full-scale scientific observations are set to begin in April 2027 — roughly six months after this month's propulsion module separation.

Until then, the mission enters a quieter phase: orbital adjustments and calibration rather than headline-making maneuvers, as two spacecraft prepare to start returning the first simultaneous, dual-vantage data ever collected from Mercury's surface and magnetosphere.