Lacus Somniorum (

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

''somniōrum'', "Lake of Dreams") is a basaltic plain located in the northeastern part of the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

's near side. It is located at selenographic coordinates 37.56° N, 30.8° E, and has a diameter of 424.76 kilometers. The name is

for Lake of Dreams, a title given to this feature by Giovanni Riccioli. It is the largest of the lunar features designated ''Lacus''. Lacus Somniorum is an irregular feature with complex, somewhat ill-defined borders. The surface has the same low

albedo Albedo ( ; ) is the fraction of sunlight that is Diffuse reflection, diffusely reflected by a body. It is measured on a scale from 0 (corresponding to a black body that absorbs all incident radiation) to 1 (corresponding to a body that reflects ...

as the larger

lunar mare The lunar maria ( ; mare ) are large, dark, basaltic plains on Earth's Moon, formed by lava flowing into ancient impact basins. They are less reflective than the "highlands" as a result of their iron-rich composition, and hence appear dark to ...

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

basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...

. The mare material contains what is described as, "unusually bright and red mare soils" of somewhat uncertain composition. It possesses reddish hues and higher than normal albedo. There may be a lower abundance of ferrous materials in these basalts compared to the nearby

Mare Serenitatis Mare Serenitatis (Latin ''serēnitātis'', the "Sea of Serenity") is a lunar mare located to the east of Mare Imbrium on the Moon. Its diameter is . Geology Mare Serenitatis is located within the Serenitatis basin, which is of the Nectarian ...

. The mare material shows a significant amount of contribution from deposited highland material. To the southwest this plain is joined to the Mare Serenitatis through a wide gap northwest of the crater

Posidonius Posidonius (; , "of Poseidon") "of Apameia" (ὁ Ἀπαμεύς) or "of Rhodes" (ὁ Ῥόδιος) (), was a Greeks, Greek politician, astronomer, astrologer, geographer, historian, mathematician, and teacher native to Apamea (Syria), Apame ...

. 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 In architecture, a hall is a relatively large space enclosed by a roof and walls. In the Iron Age and the Early Middle Ages in northern Europe, a mead hall was where a lord and his retainers ate and also slept. Later in the Middle Ages, the gre ...

, and a 150-km-long

rille Rille (German for 'groove') is typically used to describe any of the long, narrow depressions in the surface of the Moon that resemble channels. The Latin term is ''rima'', plural ''rimae''. Typically, a rille can be several kilometers w ...

named the Rima G. Bond for the small crater G. Bond south of Hall. The irregular eastern border comes close to the small crater Maury before continuing to the north until it reaches the crater remnant Williams. From there the edge continues to the west. A narrow border region separates the Lacus Somniorum from the smaller Lacus Mortis to the north. A buried crater with a 200 km diameter was detected in this locale by NASA's GRAIL experiment, forming part of the north wall of the mare. This strip of rough terrain includes the flooded

impact crater An impact crater is a depression (geology), depression in the surface of a solid astronomical body formed by the hypervelocity impact event, impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal c ...

s Mason and Plana. 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 is a surname. Notable people with the surname include: * Alexander Daniell (1599–1668), Cornish landowner * Alfred Daniell (1853–1937) * Ave Daniell (1914–1999), American (gridiron) footballer * Charles Daniell (1827–1889), Majo ...

, 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.

Gallery

G. Bond + Hall - LROC - WAC.JPG, Craters G. Bond and Hall in the eastern mare Rimae Daniell - LROC - WAC.JPG, Rimae Daniell in the southern mare Mare Serenitatis.jpg, Map of Mare Serenitatis showing the location of Lacus Somniorum in the upper right

References

{{Lunar maria Somniorum, Lacus

Gallery

See also

References