BepiColombo mission will start to unpick Mercury’s secrets in 2026

We will finally begin to untangle Mercury’s mysteries in 2026, as the BepiColombo spacecraft descend into orbit around the solar system’s innermost planet.

BepiColombo consists of a pair of spacecraft from both the European Space Agency (ESA) and the Japanese Aerospace Exploration Agency (JAXA). The Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (Mio) are attached to a parent spacecraft, the Mercury Transfer Module (MTM).

Since launching in 2018, the MTM has flown by Mercury six times, using the planet’s gravity to slow its descent until it can easily slot into orbit, a technique invented by the mission’s namesake, physicist Giuseppe “Bepi” Colombo.

The mission has collected important scientific data, such as clues about the solar wind and high-resolution images of Mercury’s surface. But its most powerful instruments, such as a pair of X-ray spectrometers on ESA’s MPO, haven’t yet been used because their view has been obscured by the MTM.

In September 2026, MPO and Mio will detach from the MTM and begin their descent into orbit, which is expected to be complete by November, letting them finally set their eyes on the planet.

Charly Feldman at the University of Leicester, UK, worked on one of the MPO’s instruments. “There’s that anticipation of, is our instrument still working and is it going to work as we expect?” she says. “There’s nothing we can do if it’s broken. It’s been building for a very long time, so whilst it is incredibly exciting, it’s also a little bit nerve-wracking.”

As well as imaging Mercury’s magnetic environment in far more detail than any previous mission, Mercury’s surface will also be extensively mapped and analysed, using tools like the MPO’s spectrometers. “It will be taking the first X-ray images of a surface of another planetary body,” says Feldman.

This could help us solve mysteries such as the unexpectedly high amount of X-rays coming from the planet’s night side, facing away from the sun, which previous missions measured. It can also measure X-rays coming from the planet’s sun-facing side, which will allow scientists to work out what Mercury’s surface is made of, which can then tell us about how the planet evolved. “If you can understand how the different planets have come to be as they are, you can understand the dynamics of the whole solar system,” says Feldman.

Stargazing and space science in the land of the rising sun, Japan

Discover Japan through the lens of astronomy, from advanced research centres to skies that inspire both science and tradition. Visit world-class facilities including JAXA’s Tsukuba Space Center, Nobeyama Radio Observatory and Tanegashima Space Center, then stargaze under the pristine skies of the Japanese Alps and Yakushima Island.