ESA/JAXA spacecraft captures Mercury’s largest basin 'Caloris' during recent flyby: See Pics

Just a few minutes after the recent closest approach, the ESA/JAXA BepiColombo mission saw the largest basin on Mercury, the 1550 km-wide Caloris basin, for the first time. The spectacular basin is surrounded by a halo of less reflective (darker) lavas that are thought to post-date the formation of the basin itself by a hundred million years or so.

According to the European Space Agency (ESA), both the interior and exterior lavas are thought to post-date the formation of the basin by a hundred million years or so, and measuring and understanding the compositional differences between these is an important goal for BepiColombo when it begins its main science mission in orbit around Mercury in 2026.

One prominent dark patch inside Caloris is a 100 km-wide impact crater called Atget that cut through the basin-filling lavas from above and excavated underlying ‘low reflectance material’ that may be a relict of Mercury's early carbon-rich crust.

The images were captured by BepiColombo's three monitoring cameras (MCAM), which provide black-and-white snapshots in 1024 x 1024 pixel resolution. 

🆕 #BepiColombo's first sighting of the giant Caloris basin, shadows cast at sunrise, and a rare candidate volcano (hiding in this👇 image) are our top picks from yesterday's #MercuryFlyby. Explore more images and details 👉https://t.co/A2z4vxMQzk #ExploreFarther pic.twitter.com/MT1b7nFys0

— ESA Science (@esascience) June 24, 2022

BepiColombo's closest approach to Mercury took place on 23 June 2022, about 200 km above the planet's surface. This was the second gravity assist manoeuvre and the fifth of nine flybys overall the spacecraft will make during its seven-year cruise to the smallest and innermost planet of the Solar System. The spacecraft's next Mercury flyby will take place on 20 June 2023.

The spacecraft hosts two science orbiters – ESA's Mercury Planetary Orbiter and the Japan Aerospace Exploration Agency's (JAXA) Mercury Magnetospheric Orbiter – that will operate from complementary orbits to study all aspects of the mysterious planet.