Wikipedia
Mairan is a lunar impact crater that is located on a highland peninsula between Oceanus Procellarum to the west and Mare Imbrium to the east. To the north-northeast is the comparably sized crater Sharp. Northwest of Mairan is the heavily eroded Louville.
The outer rim of Mairan has not been significantly eroded or impacted, and retains a sharp edge. The surface around Mairan is rough and irregular, with a multitude of many tiny craters, particularly to the south and west. The inner walls display some terracing, and flow down to a relatively flat interior floor.
In the mare, due west of Mairan, is a small lunar dome designated Mairan T with tiny crater at the summit (in official IAU nomenclature this name refers only to the crater). Its width is about 7 km, and height is about 800 m. It is one of unusually steep and bright domes which are thought to be formed by very viscous, high- Si lava. There is also a sinuous rille along the southwest edge of the highland peninsula containing Mairan. It is designated Rima Mairan, and follows a north–south course for a length of about 100 kilometers.