Lacus Somniorum is a plain located in the northeastern part of the Moon

Moon

The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

's near side. It is located at selenographic coordinates 38.0° N, 29.2° E, and has a diameter of 384 kilometers. (It is the largest of the lunar features designated Lacus.) The name is Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 for Lake of Dreams, a title given to this feature by Riccioli

Giovanni Battista Riccioli

Giovanni Battista Riccioli was an Italian astronomer and a Catholic priest in the Jesuit order...

.

Lacus Somniorum is an irregular feature with complex, somewhat ill-defined borders. The surface has the same low albedo

Albedo

Albedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it...

 as the larger lunar mare

Lunar mare

The lunar maria are large, dark, basaltic plains on Earth's Moon, formed by ancient volcanic eruptions. They were dubbed maria, Latin for "seas", by early astronomers who mistook them for actual seas. They are less reflective than the "highlands" as a result of their iron-rich compositions, and...

 found on the Moon, and its surface was formed by flows of basalt

Basalt

Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...

ic lava

Lava

Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...

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To the southwest this plain is joined to the Mare Serenitatis

Mare Serenitatis

Mare Serenitatis is a lunar mare that sits just to the east of Mare Imbrium on the Moon.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...

 through a wide gap northwest of the crater Posidonius

Posidonius (crater)

Posidonius is a lunar impact crater that is located on the western edge of Mare Serenitatis, to the south of Lacus Somniorum. The crater Chacornac is attached to the southeast rim, and to the north is Daniell....

. This crater forms the western end of the southern border, which extends eastward to about longitude 41° before turning northwest. Along this southern border is attached the flooded crater Hall

Hall (lunar crater)

Hall is a lunar crater named in honor of American astronomer Asaph Hall that is located in the southeast part of the Lacus Somniorum, a lunar mare in the northeast part of the Moon. This feature can be found to the west of the prominent walled plain Posidonius. Just to the south, and nearly...

, and a 150-km-long rille

Rille

Rille is typically used to describe any of the long, narrow depressions in the lunar surface that resemble channels. Typically a rille can be up to several kilometers wide and hundreds of kilometers in length...

 named the Rima G. Bond for the small crater G. Bond

G. Bond (crater)

G. Bond is a small lunar impact crater to the south of the Lacus Somniorum, a small lunar mare in the northeast part of the Moon's near side. It lies to the east of the larger crater Posidonius, and to the south of the flooded crater remnant Hall...

 south of Hall.

The irregular eastern border comes close to the small crater Maury

Maury (crater)

Maury is a small lunar impact crater named for two cousins. It was first named in honor of Lieutenant Matthew Fontaine Maury of the U. S. Naval Observatory and later shared to honor Antonia Maury of Harvard College Observatory. The crater lies in the northeastern part of the Moon, just to the east...

 before continuing to the north until it reaches the crater remnant Williams

Williams (lunar crater)

Williams is the remnant of a lunar crater that lies to the south of the prominent crater Hercules, in the northeastern part of the Moon. The southern rim borders the Lacus Somniorum, a small lunar mare that extends to the south and west. To the southwest is the sharp-rimmed crater Grove.Little...

. From there the edge continues to the west. A narrow border region separates the Lacus Somniorum from the smaller Lacus Mortis

Lacus Mortis

Lacus Mortis, latin for "Lake of Death", is a plain of basaltic lava flows in the northeastern part of the Moon. It lies just to the south of the elongated Mare Frigoris, being separated by a slender arm of rugged ground...

 to the north. This strip of rough terrain includes the flooded impact crater

Impact crater

In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...

s Mason

Mason (crater)

Mason is the remains of a lunar crater that lies in the northeastern part of the Moon. It is nearly attached to the eastern rim of the flooded crater Plana, and southeast of Bürg. Along the northern rim of Mason is the southern edge of the Lacus Mortis, a small lunar mare...

 and Plana

Plana (crater)

Plana is a lunar crater that lies on the boundary between two small lunar mare areas, with Lacus Mortis to the north and the larger Lacus Somniorum on the southern side. It is joined to the crater Mason to the east by a short stretch of rugged ground...

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Finally the lake curves back to the south, joining a region of rough terrain along the northern border of the Mare Serenitatis. In the southern half of this border area lies a rille system designated the Rimae Daniell. These were named for the crater Daniell

Daniell (crater)

Daniell is a lunar impact crater located in the southern half of the Lacus Somniorum. To the south-southeast is the much larger crater Posidonius. Nearby can be found the Rimae Daniell rille system....

, a small formation north of Posidonius that is encircled by the Lacus Somniorum. To the north of Daniell, near the northern edge of this feature, lies the small crater Grove

Grove (crater)

Grove is a small lunar impact crater that lies in the northern part of the Lacus Somniorum. It is located to the southeast of the crater remnant Mason. Grove is a relatively circular crater formation with a simple, sharp-edged rim. The unconsolidated material along the inner wall has slumped down...

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