Caloris Basin on Mercury

Mariner 10 found a huge impact feature on the surface of Mercury, which was named the Caloris Basin. Part of the motivation for the name is that the sun is directly over the basin every second time Mercury passes through its perihelion. It is the hottest place on the planet at that passage.

This major impact feature is just north of the planet's equator and is surrounded by circular mountain ridges up to 2 km (6500 ft) high. The diameter of the basin is 1300 km (810 mi).

Just south of the equator on the opposite side of the planet there is a collection of small jumbled hills. Since this feature is directly opposite the Caloris impact point, it is surmised that they are caused by propagating seismic waves from the impact.

Victoria Scarp

On its three flybys of Mercury, the Mariner 10 spacecraft photographed a remarkable long, high ridge in the northern hemisphere of the planet. Called the Victoria Scarp, it extends for several hundred kilometers and rises as much as 3 km (2 mi) above the surrounding plains. There are several such scarps and ridges on Mercury which are named for various sailing ships.

The scarps are thought to have their origin in contraction and wrinkling of the surface as the planet cooled.