Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2024 September 16
The cratered surface of a large body is shown: Mercury.
The largest feature visible is a large impact crater with two
rings, near the image center. Arms from the BepiColumbo 
spacecraft that took the image are seen extending into the 
image from the top and the right. 
Please see the explanation for more detailed information.

Mercury's Vivaldi Crater from BepiColombo
Image Credit: ESA, JAXA, BepiColombo, MTM

Explanation: Why does this large crater on Mercury have two rings and a smooth floor? No one is sure. The unusual feature called Vivaldi Crater spans 215 kilometers and was imaged again in great detail by ESA's and JAXA's robotic BepiColombo spacecraft on a flyby earlier this month. A large circular feature on a rocky planet or moon is usually caused by either an impact by a small asteroid or a comet fragment, or a volcanic eruption. In the case of Vivaldi, it is possible that both occurred -- a heavy strike that caused a smooth internal lava flow. Double-ringed craters are rare, and the cause of the inner rings remains a topic of research. The speed-slowing gravity-assisted flyby of Mercury by BepiColombo was in preparation for the spacecraft entering orbit around the Solar System's innermost planet in 2026.

Tomorrow's picture: dusty heart


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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
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