|Feature on||The Moon|
|Feature type||Mare (Lunar Sea)|
|Lunar coordinates||7 - 30° E, 16 - 38° N|
|Dimensions||Diameter 674km; area c.318,000 sq km|
|Bounding features||Montes Caucasus, Montes Haemus|
|Interior features||Banting, Bessel, Brackett, Deseilligny, Hornsby, Linné, Luther, Menelaus, Posidonius N, Sarabhai, Sulpicius Gallus|
A prominent sea in the northern hemisphere of the Moon. Though it is by no means the largest of the Moon's maria, its distinct circular shape marks it one of the most prominent seas on the Moon's nearside face. In renderings of the 'Man in the Moon' the Sea of Serenity typically forms the left eye.
The Mare Serenitatis falls between the Mare Imbrium or Sea of Rains to the west, and the Mare Tranquillitatis (Sea of Tranquility) to the southeast. The entire sea compromises a field of nearly featureless and flat basalt covering an area of some 318,000 square kilometres (making it a little smaller in area than the Caspian Sea on Earth).
On the western side of the sea, its basalt surface blends somewhat with the surface of the Mare Imbrium, with the two seas being separated by an irregular range of peaks known as the Montes Caucasus. To the north, Mare Serenitatis is bounded by a range of rough highlands that reach an end near its northeastern extent, where the sea breaks out into a small 'lake', Lacus Somniorum or the Lake of Dreams. At the southern extent of the sea's border with this lake lies the walled plain Posidonius.
Southward along the eastern edge of the sea, beyond Posidonius, is a mountainous region visited by several exploratory missions from Earth. The Lunokhod 2 rover explored the crater le Monnier a little to the south of Posidonius, and some kilometres further south still is the landing site of Apollo 17 among the Taurus Mountains.
The southeastern extent of the Sea of Serenity is marked by the peak of Argaeus Mons, and moving westward from this mountain its southern border is marked by a jumble of low-lying land and lunar rilles. At its southern point is promontory, Promontorium Archerusia, and from there the boundary is marked by higher land: a range of mountains known as Montes Haemus runs along its southwestern and western edge to meet Montes Caucasus and complete the circuit of the sea's boundaries.
The eastern and southern parts of the Sea of Serenity are marked by a collection of ridges, of which the most prominent in the Serpentine Ridge, meandering across the landscape from north to south in the sea's southeastern quarter.
Other than the Serpentine Ridge, the interior surface of the Mare Serenitatis is not notable for significant features. The largest crater at least partially within its boundaries is the 27km-diameter Menelaus, which extends out from the southern shores of the sea into the highlands beyond. Of craters entirely within the mare, the largest are Bessel (16km in diameter), and Sulpicius Gallus (12km in diameter) near the foothills of Montes Haemus near the sea's southwestern edge. The surface is dotted by a handful of smaller craters (including Banting, Deseilligny, Hornsby, Linné, Luther and Sarabhai) but none of these exceed a diameter of 10km.