During the first visit BepiColombo on Mercury, the field of view of surveillance cameras two and three is tracked across the planet. The triple camera shows part of the southern hemisphere, starting with a view of the sun rising over the Astrolabe Rupes, a striking feature named after the French Antarctic cruiser.
Astrolabe Rupes is lobate scarp 250 km long, a long curved structure that marks where one part of the planet’s crust has been pushed into the nearest field, as the entire planet contracts as it slowly cools. There are some much smaller equivalent features on the Moon, but Mercury is the only nearby celestial body where lobate scarps are known to occur on a large scale.
Four minutes later, the perspective has changed enough to reveal a wider area. These include flooded lava, the 251km-wide Haydn crater, and Pampu Facula, one of the many bright spots that may have been formed by an explosive volcanic eruption.
Both features attest to Mercury’s long volcanic history, most active more than three billion years ago but probably surviving until about a billion years ago. Meanwhile, the dual camera focuses on Mercury’s northern hemisphere, including the region around the Calvino crater or important locations for deciphering what is in Mercury’s crust.
It also shows the Lermontov crater, a region that appears rosy because it hosts volcanic deposits and vents, where currently unknown crustal volatiles are lost to space through a mysterious process. The American Space Agency’s (NASA) MESSENGER mission orbited Mercury between 2011 and 2015, revealing about the planet that remains fraught with questions.
Among them is why Mercury has features such as explosive volcanoes and strange and unique holes in its surface is just one of the problems that we hope further research will solve. Once in orbit, the payload of BepiColombo’s advanced scientific instrument will help us understand more about how Mercury was formed and what it’s made of.