Mercury is getting 2 new orbiters after more than a decade alone
BepiColombo will be the second mission to orbit Mercury and the first to study the planet with two spacecraft.
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After an eight-year journey through the inner solar system, a European-Japanese mission has begun its final approach to Mercury, clearing a critical milestone Thursday on its way to orbiting the planet.
The BepiColombo mission, led by the European Space Agency (ESA) in collaboration with the Japan Aerospace Exploration Agency (JAXA), is preparing to study the least-explored planet in the inner solar system.
The ESA-JAXA BepiColombo spacecraft captured these views of Mercury during its sixth and final flyby of the planet on Jan. 8, 2025. The spacecraft passed within 183 miles of Mercury’s surface, revealing its cratered north pole and vast volcanic plains. (Image credit: ESA/BepiColombo/MTM)
On Thursday, the spacecraft’s Mercury Transfer Module, or MTM, separated from the mission’s two science orbiters. The carefully choreographed maneuver marked the beginning of BepiColombo’s arrival phase.
ESA detected a preliminary Doppler signal indicating that the module had separated from the spacecraft stack as planned. An additional signal from the spacecraft fully confirmed the operation’s success.
A graphic showing the arrival timeline for the ESA-JAXA BepiColombo mission. (Image credit: ESA)
BepiColombo includes ESA’s Mercury Planetary Orbiter, or MPO, and JAXA’s Mercury Magnetospheric Orbiter, known as Mio. Together, the spacecraft carry a suite of instruments designed to study Mercury’s surface, interior, magnetic field and surrounding environment.
The two orbiters, still connected, are scheduled to enter a polar orbit around Mercury on Nov. 21. MPO and Mio will then separate Dec. 9-10 and begin moving into their individual science orbits.
After several months of calibration and commissioning, the mission’s science phase is scheduled to begin on April 6, 2027, according to ESA’s arrival timeline.
When was the last mission to study Mercury?
BepiColombo will be the first mission to orbit Mercury with two spacecraft and only the second mission to enter orbit around the planet, following NASA’s MESSENGER mission.
MESSENGER orbited Mercury for more than four years, providing the first detailed look at the planet’s surface composition, geological history and magnetic field. The mission ended in April 2015 when the spacecraft made a planned impact on Mercury’s surface.
NASA’s Mariner 10 was the first spacecraft to visit Mercury, completing three flybys in 1974 and 1975 but never entering orbit.
Subtle colors appear on Mercury's surface in this mosaic image created by filters within MESSENGER' s wide-angle camera. (Image: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie)
Although Mercury is relatively close to Earth, it is exceptionally difficult to study. From Earth, the planet always appears near the sun and can generally be seen only briefly around sunrise or sunset, while pointing powerful telescopes in its direction risks damaging their optics. Spacecraft traveling to Mercury must repeatedly slow down against the sun’s gravitational pull, requiring lengthy routes and multiple planetary flybys. Once there, they must withstand sunlight about 10 times more intense than near Earth, daytime temperatures as high as 842 degrees Fahrenheit and extreme temperature swings between Mercury’s day and night sides, according to ESA.
The mission is named for Italian mathematician and engineer Giuseppe “Bepi” Colombo, who proposed using a Venus gravity-assist flyby to allow NASA’s Mariner 10 to pass Mercury three times instead of the single encounter originally planned.
BepiColombo has already returned more recent views and scientific observations of Mercury during six flybys used to slow the spacecraft and prepare it for orbit around the solar system’s innermost planet.
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