Today in the history of astronomy, a mission to the understudied planet Mercury kicks off.
BepiColombo is only the third spacecraft to visit Mercury, following NASA's MESSENGER and Mariner 10. Credit: ESA/ATG medialab
BepiColombo, a joint mission of the European Space Agency and the Japan Aerospace Exploration Agency, launched Oct. 20, 2018. The spacecraft is actually two satellites in one, the Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (MMO), commissioned with investigating one of the least-visited planets in our solar system.
To reach its final position, BepiColombo received assistance from the gravity of the two inner planets, flying by Venus twice and Mercury six times. That sixth flyby of Mercury occurred Jan. 8, 2025, setting the spacecraft up to reach its destination in November 2026. When it arrives, the two orbiters will separate: The MPO will investigate Mercury’s surface and geophysical makeup, particularly its unusually large core. The MMO will examine the planet’s magnetic field and how it’s generated – another unusual feature of Mercury, since its slow rotation suggests its field should not be possible.
Elisa Neckar is senior production editor of Astronomy magazine, and the editor of the Today in the History of Astronomy feature on Astronomy.com.