Mare Marginis
Mare Marginis is a lunar mare that lies on the very edge of the lunar nearside. The selenographic coordinates of this feature are 13.3° N, 86.1° E, and the diameter is 358 km.
This mare differs from most of the nearside maria; it has an irregular outline and appears fairly thin. It has small circular and elongated features in the mare plains that
probably mark impact craters buried by less than 1000 to 1700 feet of lava. Further, Mare Marginis is not centered on any clear, large impact basin. Thus, Mare Marginis marks a low-lying highlands region where mare lavas could reach the surface. Several large mare-floored craters also occur nearby. In these craters, the crater floors lie below the surrounding highland surface. Thus, they mark sites around Mare Marginis where lavas were close to the lunar surface. The major crater north of Marginis is Al-Biruni, with Ibn Yunus to the southeast and Goddard to the northwest.
The surface of this mare displays some lunar swirls; higher albedo deposits are similar to the Reiner Gamma feature on the Oceanus Procellarum. This feature is associated with a relatively strong magnetic field. It is also located at the antipode of the Mare Orientale impact basin, and may be associated with forming that feature. Other possible explanations for the formation include a cometary impact, venting of volcanic gases, or just normal surface markings shielded from space weathering due to the magnetic field. However, the exact cause of albedo features such as this is not completely understood.