The ESA/JAXA BepiColombo mission has made its third of six gravity assist flybys at Mercury, snapping images of a newly named impact crater as well as tectonic and volcanic curiosities as it adjusts its trajectory for entering Mercury orbit in 2025.
The closest approach took place at 19:34 UTC (21:34 CEST) on 19 June 2023, about 236 km above the planet’s surface, on the night side of the planet.
“Everything went very smoothly with the flyby and images from the monitoring cameras taken during the close approach phase of the flyby have been transmitted to the ground,” says Ignacio Clerigo, ESA’s BepiColombo Spacecraft Operations Manager.
“While the next Mercury flyby isn’t until September 2024, there are still challenges to tackle in the intervening time: our next long solar electric propulsion ‘thruster arc’ is planned to start early August until mid-September. In combination with the flybys, the thruster arcs are critical in helping BepiColombo brake against the enormous gravitational pull of the Sun before we can enter orbit around Mercury.”
Geological curiosities
During last night’s close encounter, monitoring camera 3 snapped tens of images of the rocky planet. The images, which provide black-and-white snapshots in 1024 x 1024 pixel resolution, were downloaded overnight until early this morning. Three ‘early release’ images are presented here.
Approaching on the nightside of the planet, a few features started to appear out of the shadows about 12 minutes following the closest approach, when BepiColombo was already about 1800 km from the surface. The planet’s surface became more optimally illuminated for imaging from about 20 minutes after close approach and onwards, corresponding to a distance of about 3500 km and beyond. In these closer images, a bounty of geological features are visible, including a newly named crater.
Crater named for artist Edna Manley
A large 218 km-wide peak-ring impact crater visible just below and to the right of the antenna in the two closest images presented here has just been assigned the name Manley by the International Astronomical Union’s Working Group for Planetary System Nomenclature after Jamaican artist Edna Manley (1900–1987).
“During our image planning for the flyby we realised this large crater would be in view, but it didn’t yet have a name,” explains David Rothery, Professor of Planetary Geosciences at the UK’s Open University and a member of the BepiColombo MCAM imaging team. “It will clearly be of interest for BepiColombo scientists in the future because it has excavated dark ‘low reflectance material’ that may be remnants of Mercury’s early carbon-rich crust. In addition, the basin floor within its interior has been flooded by smooth lava, demonstrative of Mercury’s prolonged history of volcanic activity.”
While not apparent in these flyby images, the nature of the dark material associated with Manley Crater and elsewhere will be explored further by BepiColombo from orbit. It will seek to measure just how much carbon it contains and what minerals are associated with it, in order to learn more about Mercury’s geological history.
