The search for volcanoes (annotated)

The joint European-Japanese BepiColombo mission captured this view of Mercury on 23 June 2022 as the spacecraft flew past the planet for its second of six gravity assist manoeuvres at Mercury. This image was taken at 09:51:07 UTC by the Mercury Transfer Module’s Monitoring Camera 3, when the spacecraft was 1406 km from the surface of Mercury. Closest approach of 200 km took place shortly before, at 09:44 UTC. In this view, north is up.

The cameras provide black-and-white snapshots in 1024 x 1024 pixel resolution. This image has been 'block replicated' to 2048 x 2048 pixels. Some imaging artefacts such as vertical striping are also visible. The back of the high-gain antenna and part of the spacecraft’s body is also visible in front of Mercury in this image.

While clearly a heavily cratered region, this image also highlights some of Mercury’s volcanic history. Mercury’s smooth plains were formed by volcanic eruptions of runny lavas that spread across the planet 3.7 billion years ago – such as the plains visible between BepiColombo’s high-gain antenna and towards Mercury’s limb. 

The eruptions that formed these plains did not commonly build volcanoes that we are familiar with on Earth. The floor of the 125 km wide Heaney crater (next to BepiColombo’s high-gain antenna in the centre of this image) is covered in smooth volcanic plains, and a small mound is illuminated. This is a rare example of a candidate volcano on Mercury, which will be an important target for BepiColombo’s high resolution imaging suite once in orbit. 

North of Heaney, past the high-gain antenna, is Amaral crater (105 km wide) with a clearly defined rim and a central peak cluster. The region surrounding Amaral is pockmarked with so-called secondary craters caused by material ejected from Amaral during its formation re-impacting onto the surface nearby. This texture is common around fresh craters on Mercury.

Click here for a non-annotated version of this image.

The gravity assist manoeuvre was the second at Mercury and the fifth of nine flybys overall. During its seven-year cruise to the smallest and innermost planet of the Solar System, BepiColombo makes one flyby at Earth, two at Venus and six at Mercury to help steer on course for Mercury orbit in 2025. The Mercury Transfer Module carries two science orbiters: ESA’s Mercury Planetary Orbiter and JAXA’s Mercury Magnetospheric Orbiter. They will operate from complementary orbits to study all aspects of mysterious Mercury from its core to surface processes, magnetic field and exosphere, to better understand the origin and evolution of a planet close to its parent star.

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