Mercury: a planet near the Sun with such a strange magnetic field

Space exploration often reveals unexpected surprises. In June 2023, during its flyby of Mercury, the BepiColombo mission collected information about the planet's magnetic field. These observations provide a glimpse of the discoveries to come when the probe places two orbiters around Mercury in 2026.

Mercury, though very small, has a magnetic field that creates a protective “bubble” around the planet: the magnetosphere. This field is about 100 times weaker than Earth's but interacts intensely with charged particles from the Sun, the solar wind.


BepiColombo, a collaborative project between the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA), aims to study this magnetosphere and explore how Mercury reacts to the extreme space environment near the Sun. At this distance, the interactions between the solar wind and the magnetosphere are more intense than anywhere else in the Solar System.

During the June 2023 flyby, some of the scientific instruments onboard BepiColombo captured significant data. Lina Hadid's team, which uses the instruments on the Mio orbiter, analyzed Mercury's magnetic environment, specifically mapping the particles present and their energy levels, over a brief period of 30 minutes.

The team observed some expected structures, such as the boundary where the free-flowing solar wind meets the magnetosphere. However, more surprising discoveries were also made, including the presence of a low-latitude plasma layer, revealing particle energies never before seen on Mercury.

Additionally, energetic ions were detected near the equator, suggesting the presence of a “ring current.” This type of current is well known around Earth, but for Mercury, the magnetosphere's small size makes it challenging to understand this phenomenon. This question will likely be answered once the probe is fully operational in 2026.

Another intriguing discovery involves the detection of cold ions at Mercury's surface, such as oxygen, sodium, and potassium. These particles are likely ejected by micrometeorites or the solar wind, providing a three-dimensional view of the small planet's surface composition.

These initial observations highlight the enormous potential of the BepiColombo mission to understand the complex interactions between Mercury and its space environment. Starting in 2026, the mission's two orbiters will provide continuous data that will allow a better understanding of the evolution of this unique magnetosphere and the real-time interactions that occur.

The BepiColombo Mission

BepiColombo is a joint space mission between the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) designed to explore Mercury, the closest planet to the Sun. Launched in October 2018, the mission aims to better understand Mercury's extreme environment and composition, particularly its magnetic field and its interaction with the solar wind.

The mission uses two orbiters: ESA's Mercury Planetary Orbiter (MPO) and JAXA's Mercury Magnetospheric Orbiter (MMO or Mio). These two probes are traveling together to Mercury and will separate in 2026 to enter orbit around the planet, enabling complementary observations.

BepiColombo aims to shed light on several mysteries about Mercury, including the formation of its magnetic field, the composition of its surface, and the interactions between the planet's thin atmosphere and charged particles from the Sun.