Caloris Basin

Caloris Basin

Part of the Caloris Basin.

Caloris impact

Likely explanation of how the Caloris Basin and antipodal "weird" terrain formed.

Seen here is part of the enormous Caloris Basin on Mercury, which is thought to be similar to the large circular basins found on the Moon. It was probably formed by a giant impact early in Mercury's history, and then subsequently filled by lava flows. The nature of the wrinkle ridges on its floor is arguable: some scientists claim tectonics while others suggest they are due to volcanic flows escaping from fractures.


At the antipodal point to the Caloris Basin is found "weird" hilly terrain with lineated features. It is thought that the shock wave produced by the Caloris impact probably reflected and focused to the antipodal point (see lower diagram), thus jumbling the crust and breaking it into a series of complex blocks.