Britannica Sources used in this answer

When did the Caloris impact basin likely form?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Messenger: Mercury — Mercury Mercury as seen by the Messenger probe, January 14, 2008. This image shows half of the hemisphere missed by Mariner 10 in 1974–75 and was snapped by Messenger's Wide Angle Camera when it was about 27,000 km (17,000 miles) from the planet.

The Caloris impact basin is considered one of the youngest large multiring basins on Mercury. It likely formed approximately 3.9 billion years ago, around the same time as the last giant basins on the Moon.12