Mare Serenitatis (the "sea of serentity") is a
lunar mare that sits just to the east of
Mare Imbrium. It is located within the Serenitatis basin, which is of the
Nectarian[?] epoch. The material surrounding the mare is of the
Lower Imbrian[?] epoch, while the mare material is of the
Upper Imbrian[?] epoch. The mare
basalt covers a majority of the basin and overflows into
Lacus Somniorum[?] to the northeast. The most noticeable feature is the crater
Posidonius[?] on the northeast rim of the mare. The ring feature to the west of the mare is indistinct, except for
Montes Haemus. Mare Serenitatis connects with
Mare Tranquillitatis to the southeast.