# BepiColombo’s blue ion glow goes dark as Mercury arrival begins

> The European Space Agency has announced that ESA and JAXA's BepiColombo spacecraft has permanently switched off its solar electric propulsion system, ending the long ion-powered cruise that carried it across the inner Solar System. The shutdown on June 15, 2026, moves the...

Canonical URL: https://www.argo.net/bepicolombos-blue-ion-glow-goes-dark-as-mercury-arrival-begins-2/
Byline: European Space Agency
Published: 2026-07-14T19:50:09+00:00
Categories: News, Space

![Planet Mercury against a dark space background](https://www.argo.net/wp-content/uploads/2026/06/mercury_planet_spacecraft.jpg)

The **European Space Agency** has [announced](https://www.esa.int/Enabling_Support/Operations/End_of_the_blue_glow_BepiColombo_turns_off_solar_electric_propulsion_for_Mercury_arrival) that ESA and **JAXA**'s **BepiColombo** spacecraft has permanently switched off its solar electric propulsion system, ending the long ion-powered cruise that carried it across the inner Solar System. The shutdown on June 15, 2026, moves the mission into its final approach toward Mercury, where arrival operations are now scheduled to unfold over the coming months.

For nearly eight years, BepiColombo traveled through one of the trickiest routes ever attempted by a planetary spacecraft. Its faint blue glow came from ion thrusters that slowly reshaped the spacecraft's path using electricity, xenon gas and extraordinary patience. That glow has now gone dark because the spacecraft has reached the trajectory needed for Mercury arrival.

The change marks a tense new phase for mission controllers. After years of slow electric thrust and carefully timed flybys, the spacecraft is now preparing for separation events and chemical engine burns that must happen with great precision. Mercury is close to the Sun, fast-moving and difficult to orbit, which makes the final months especially demanding.

## The end of solar electric propulsion

BepiColombo's **solar electric propulsion** system was the engine of its long cruise. Instead of relying on short, forceful rocket burns, the spacecraft used low but steady thrust for long stretches of time. ESA has described this capability in simple terms: "The solar electric propulsion is mission-enabling for the trip to Mercury."

The system was housed in the **Mercury Transfer Module**, the part of the spacecraft stack that supplied power and propulsion during the journey. Its four **QinetiQ T6 ion thrusters** used electricity from large solar arrays to turn xenon into plasma. The thrusters then accelerated that plasma to produce a gentle push.

That gentle push mattered because it accumulated over time. The thrust from an ion engine feels tiny compared with a chemical rocket engine, but it can operate for long periods while using propellant efficiently. Across millions of kilometers, small changes become mission-shaping changes.

ESA said the final shutdown occurred on June 15 at 15:24 CEST. From that moment onward, the blue ion glow became part of the mission's past. BepiColombo is now coasting along a carefully prepared route toward the next Mercury operations.

## Why Mercury is so hard to reach

Mercury looks like an easy target on a map of the Solar System because it orbits near Earth's neighborhood. Spaceflight tells a different story. A spacecraft leaving Earth already carries Earth's high orbital speed around the Sun and reaching Mercury requires shedding much of that speed.

The Sun adds another challenge. As a spacecraft moves inward, solar gravity pulls harder. A mission to Mercury has to drop closer to the Sun while also matching the motion of a small planet that races around its orbit. That combination makes orbital capture at Mercury unusually difficult.

BepiColombo solved the problem through a slow and carefully tuned route. Its ion propulsion system helped adjust the spacecraft's path between planetary encounters. Each adjustment helped mission planners guide the spacecraft toward Mercury without carrying the huge fuel load that a more direct approach would demand.

The result is a mission built around endurance. The spacecraft's long cruise was a central part of the design. Every low-thrust arc and planetary flyby contributed to the arrival geometry needed in 2026.

## Nine flybys and eight years of navigation

Nine planetary flybys shaped BepiColombo's route through the inner Solar System. The spacecraft flew past Earth once, Venus twice and Mercury six times. Each encounter used a planet's gravity to alter the spacecraft's speed and direction.

During those years, the spacecraft and ground teams worked through a navigation campaign that demanded constant precision. The flybys had to line up with long arcs of electric propulsion. Together, these maneuvers gradually adjusted the mission's orbit around the Sun.

The six Mercury flybys were especially important. They brought the spacecraft repeatedly past its destination before final arrival. These close passes helped reduce the spacecraft's relative speed and set up the later capture sequence.

Between flybys, **ionized xenon gas** provided the blue glow that became associated with the mission's cruise. The thrusters turned electrical power into a slow stream of motion control. That strategy allowed BepiColombo to complete an interplanetary route that began with launch in October 2018.

## The September separation

The **Mercury arrival phase** now moves toward a major hardware change. ESA's timeline places the separation of the Mercury Transfer Module on September 3, 2026. That event will remove the propulsion module that carried the spacecraft through its cruise.

After the transfer module separates, the remaining spacecraft stack will rely on different propulsion hardware. The **Mercury Planetary Orbiter**, ESA's science orbiter, carries a chemical propulsion system needed for the precise operations ahead. These burns will guide the spacecraft toward capture by Mercury's gravity.

The spacecraft stack also includes **Mio**, JAXA's Mercury Magnetospheric Orbiter. ESA describes the cruise configuration this way: "The Mercury Planetary Orbiter and the Mercury Magnetospheric Orbiter will voyage to Mercury together as a single composite spacecraft." That paired journey is now nearing the stage where the orbiters will begin taking on their final roles.

Separation operations are always sensitive because they change the spacecraft's mass, shape and handling. For BepiColombo, the event also signals the end of the cruise-era configuration. The mission will then be focused fully on Mercury capture and orbital deployment.

## The November capture burn

The most important maneuver is scheduled for **November 21, 2026**. On that date, BepiColombo must perform a carefully timed engine burn to become captured by Mercury's gravity. This operation is the key step that turns a long fly-in trajectory into a true orbital mission around the planet.

Precision will matter down to the details. The spacecraft must arrive at the right place, at the right speed and at the right time. A successful burn will allow mission controllers to begin the sequence of placing the two orbiters into their working paths around Mercury.

After capture, ESA's orbiter and JAXA's Mio will move toward separate operational roles. Mio is designed to study Mercury's magnetic environment. ESA's orbiter will later settle into a science orbit suited for close study of the planet itself.

By March 2027, the European orbiter is expected to reach its dedicated science orbit if the arrival sequence proceeds as planned. Routine science operations are expected after the spacecraft completes this carefully staged transition. The months between capture and full science operations will be filled with orbital adjustments, checks and deployments.

## What BepiColombo will study at Mercury

Mercury is the smallest planet in the Solar System and one of the least explored inner worlds. BepiColombo is designed to change that picture by studying the planet with two complementary orbiters. Together, they will investigate Mercury from its surface to its magnetic environment.

ESA's Mercury Planetary Orbiter will examine the planet's surface composition, interior structure, gravity and geology. These measurements could help scientists understand why Mercury has such a large iron core and how its surface changed over billions of years near the Sun.

JAXA's Mio will focus on Mercury's magnetosphere, the region controlled by the planet's magnetic field. Mercury has a global magnetic field, which makes it unusual among small rocky worlds. Mio will study how that field interacts with charged particles from the **solar wind**.

The mission also offers a rare chance to study a planet in extreme solar conditions. Mercury's surface faces intense heat, strong sunlight and constant particle bombardment. BepiColombo's instruments were built to operate in that environment while returning detailed measurements from orbit.

With the blue ion glow switched off, the spacecraft has entered the stage that its long cruise was built to reach. The next milestones will decide how smoothly ESA and JAXA can transform years of navigation into a working observatory at the innermost planet.