BepiColombo Set for Final Mercury Flybys to Solve Planet Secrets

Mercury, the smallest planet in our solar system and the closest neighbor to the sun, has long been a source of fascination and frustration for astronomers. Despite its proximity to Earth, the planet remains shrouded in mystery, largely because its location near the solar glare makes it incredibly difficult to observe and reach. However, a joint mission by the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) is about to change that, as the BepiColombo spacecraft prepares for a critical series of final flybys.

Launched in 2018, BepiColombo is currently on a seven-year journey to Mercury. The spacecraft is not yet in its final orbit; instead, it is performing a complex series of gravity-assist maneuvers around Earth, Venus, and Mercury itself. These flybys are essential for the spacecraft to shed the massive amount of orbital energy required to eventually settle into a stable path around the planet. By using the gravitational pull of these planets to slow down, the probe is effectively ‘braking’ its way toward its destination.

As BepiColombo nears its final arrival, scientists are eagerly anticipating the data these upcoming flybys will provide. Mercury is a world of extremes. Its surface temperature can soar to 800 degrees Fahrenheit (430 degrees Celsius) during the day and plummet to minus 290 degrees Fahrenheit (minus 180 degrees Celsius) at night. Despite the intense heat, planetary scientists have discovered evidence of water ice hidden within deep, permanently shadowed craters at the planet’s poles. Understanding how water can exist on such a scorched world is a primary goal for the mission.

Another enduring puzzle is the planet’s composition. Mercury is surprisingly dense, with a massive iron core that makes up a significant portion of its total volume. Scientists are still debating how such a small body could have such a large, metal-rich interior. Some theories suggest that a giant impact early in the solar system's history stripped away much of the planet's rocky outer crust, leaving only the dense core behind. BepiColombo’s sophisticated suite of instruments is designed to map the surface chemistry and magnetic field, which could finally provide the evidence needed to confirm or reject these theories.

Furthermore, Mercury possesses a magnetic field, which is rare for such a small, slow-rotating planet. The interactions between this magnetic field and the solar wind—a constant stream of charged particles flowing from the sun—create a unique environment that scientists call the magnetosphere. By studying this, researchers hope to learn more about how planetary magnetic fields evolve and how they protect (or fail to protect) the surfaces of planets from solar radiation.

This mission is a masterpiece of international cooperation and engineering. Surviving the proximity to the sun requires the spacecraft to endure extreme thermal conditions, protected by advanced shielding and specialized heat-resistant materials. The upcoming flybys serve as a trial run for the instruments, allowing mission teams to calibrate their sensors and refine their software before the true science phase begins.

Once the spacecraft enters its final orbit in 2025, it will begin an intensive year-long study of the planet. While we have visited Mercury before—most notably with NASA’s MESSENGER mission, which orbited the planet from 2011 to 2015—BepiColombo’s dual-probe design will offer a more comprehensive view than ever before. With two orbiters working in tandem, scientists will finally be able to decouple the planet's internal activity from the external effects of the sun. As the spacecraft edges closer, the scientific community prepares for a new era of understanding our solar system's most elusive neighbor.