Planet Mercury, during most recent encounter with probe BepiColomboImage ESA/BepiColombo/MTM

    Only 200 kilometers: on a cosmic scale, that’s nothing. At that distance, the European-Japanese spacecraft Bepicolombo flew past the cratered surface of Mercury. In technical terms, such a maneuver is called a ‘fly-by’: a route close to a planet.

    The move was one of many maneuvers needed to get the spacecraft into orbit around the planet. The team on Earth took the opportunity to shoot some pictures right away. The first of these came online on Thursday.

    ‘Spectacular’, is how space expert Erik Laan calls the new image. “We rarely get to see Mercury up close,” he adds. Only two probes preceded Bepicolombo.


    Traveling to Mercury is extremely difficult due to its proximity to the sun. It pulls on a probe with more gravity than a small planet like Mercury. In order to stay close to the planet, Bepicolombo has to slow down very precisely. This happens during the fly-by, where the probe gives off some of its speed to the planet.

    Thursday’s fly-by was the second, and four more are on the agenda before the probe remains permanently trapped in Mercury’s gravity. Bepicolombo takes its name from Giuseppe ‘Bepi’ Colombo, the man who first mapped out this complex flight in 1979.

    Spacecraft flying this close to the sun must withstand extreme temperatures. On the day side of Mercury, the temperature rises above 400 degrees Celsius, while the mercury on the shadow side can drop past 100 degrees below freezing. To ensure that the probe continues to operate during such large swings, Bepicolombo uses a type of titanium blinds that reflect sunlight and can fold in or out to regulate heat.


    Even though such a fly-by is only a fleeting encounter between probe and planet, it is a valuable moment to make new measurements, Johannes Benkhoff, project scientist at Bepicolombo, said in a press statement. Any measurement is welcome to solve Mercury’s puzzles, questions like: how do planets form so close to stars? And: how can the small planet generate a magnetic field?

    Bepicolombo will be in orbit around Mercury in three years, and will then spend about a year collecting measurement data – and more imagery.