Mercury’s environment observed by BepiColombo mission and SERENA experiment.

Mercury’s environment is a complex system where the magnetosphere, the exosphere and the surface are inherently coupled and interact with the interplanetary medium that is particularly extreme for its close proximity to the Sun. Mercury lacks a thick atmosphere, and it possesses a weak internal magnetic field which is not able to effectively shield the planet. Previous explorations of this innermost planet include Mariner 10 and the NASA’s MESSENGER mission and ground-based observations of a few exospheric elements. Now we know that Mercury’s environment is highly dynamic. The magnetosphere can be fully reconfigured in a few minutes, and the exosphere shows a variability down to 10s minutes. But the new results have opened new unsolved questions about the functioning of this dynamic system, how the magnetosphere responds to the solar activity, and how the exosphere is connected to the surface and to the magnetosphere. For discriminating between space-time variations and for investigating the effects of external drivers to the planet, two spacecraft are needed. BepiColombo ESA-JAXA double-spacecraft mission is en route to Mercury. The two orbiters are MPO-Mercury Planetary Orbiter and Mio-Mercury Magnetospheric Orbiter. SERENA particle package on board MPO is a key experiment since it links the observations of near-planet particles both to the surface and to the magnetosphere. During the cruise phase, SERENA ion sensors, PICAM and MIPA, have collected interesting measurements during the swing-bys at Mercury. The BepiColombo orbit insertion will be performed in November 2026, and the scientific operations will start in 2027. We expect many fantastic results after this very long journey!