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On Saturday 20 October, BepiColombo blasted off on a seven-year journey to Mercury in an attempt to uncover the mysteries of the planet closest to the Sun.

BepiColombo is a joint endeavour between the European and Japanese space agencies (ESA and JAXA), and is a project which David Rothery (1974), Professor of Planetary Geosciences at The Open University, has been involved in for over 15 years. 

Professor Rothery heads ESA’s Mercury Surface & Composition Working Group and is the lead co-investigator for Geology for the Mercury Imaging X-ray Spectrometer (MIXS), the only UK-led instrument on board BepiColombo. MIXS will construct images of X-rays fluoresced from the planet’s surface to map what its surface is made of. This is a key aim of the mission, as one of Mercury’s biggest unsolved mysteries is how the rich and volatile substances which make up its surface are so abundant, despite its close proximity to the Sun.

Professor Rothery said: “I became keen on astronomy about the time I was in the Removes, and with two others (Clive Robinson and Ian Wilson) subsequently persuaded the School to enter us for Astronomy O-Level (which we’d taught ourselves) on top of the standard curriculum. We all passed, but I became a geologist rather than astronomer, and it was some years before I began to do geology on planets other than the Earth.

“We really need to understand Mercury better. So much about it seems wrong for a planet that close to the Sun, so maybe it originated further out. A collision with the proto-Earth or proto-Venus could be what robbed it of so much of its original rock.”

BepiColombo will enter into orbit around Mercury late in 2025 and will start collecting data in 2026. It is hoped that this will provide new insight into how the planet formed and evolved, and perhaps shed more light on our own planet and the formation of the Solar System.

Further information on the BepiColombo mission can be viewed in Professor Rothery's recent TEDx talk.