Mare Imbrium
The smooth, rolling plains to the east of this crater are called the Cayley Formation. It is somewhat similar to the lunar maria, but has a slightly higher albedo and is overlapped at the eastern edge by the Mare Tranquillitatis. Lunar scientists suspect that this plain may have resulted from deposits of ejecta from the formation of large impact basins such as Mare Imbrium or Mare Orientale. (The most likely source is the Mare Imbrium impact basin to the northwest.)