BepiColombo’s Final Sprint: Two Spacecraft Near Mercury After an Eight‑Year Odyssey

It’s hard to imagine, but eight years ago on 20 October 2018 a pair of spacecraft lifted off from Kourou, France, bound for the tiniest rocky world in our solar system. That duo – the European Space Agency’s Mercury Planetary Orbiter (MPO) and Japan’s Mercury Magnetospheric Orbiter, nicknamed Mio – together form the ambitious BepiColombo mission.

Getting to Mercury isn’t as simple as pointing a rocket straight at it. The planet whirls around the Sun at a blistering 47 km s⁻¹, so any visitor must shed a massive amount of orbital speed. BepiColombo solved that puzzle with a painstaking choreography of nine planetary fly‑bys – one of Earth, two of Venus and six of Mercury itself – while using a solar‑electric propulsion system to nudge its path ever closer to the Sun.

Just this week, on 3 September, the Mercury Transfer Module that carried the two orbiters finally said goodbye. The deep‑space antenna at Cebreros in Spain picked up a clean signal confirming the separation, and engineers breathed a sigh of relief: the spacecraft were healthy and ready for the final approach.

The next big moment is slated for 21 November 2026, when both MPO and Mio will be captured by Mercury’s feeble gravity and settle into their respective orbits. It’s a delicate dance – the two vehicles will initially travel together, then part ways in December 2026 so each can focus on its own scientific agenda.

What will they look at? MPO will circle low, scanning the planet’s battered surface, probing the composition of its crust, and peering into the massive iron‑rich core that gives Mercury its surprisingly strong magnetic field. Meanwhile, Mio will swing higher, mapping the planet’s magnetosphere and measuring how the solar wind slams into it.

Scientists are especially excited about Mercury’s polar craters. Those permanently shadowed pits are thought to host deposits of water ice – a paradox on a world baked by the Sun. BepiColombo’s instruments should finally give us a high‑resolution picture of those hidden deposits, something earlier missions could only hint at.

There are also those mysterious “hollows” – bright, shallow depressions that seem to be forming even today. By studying their composition and distribution, researchers hope to learn how Mercury’s surface is still being reshaped.

After the spacecraft separate in December, MPO is expected to reach its final, low‑altitude science orbit by March 2027. Routine observations will kick off in April, marking the true start of the mission’s scientific phase after years of cruising.

In short, after a long commute across billions of kilometres, BepiColombo is finally pulling into the driveway. The real adventure – unraveling the secrets of the solar system’s innermost planet – is just beginning.