Lacus Somniorum (

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

''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 is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

'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 Giovanni Battista Riccioli, SJ (17 April 1598 – 25 June 1671) was an Italian astronomer and a Catholic priest in the Jesuit order. He is known, among other things, for his experiments with pendulums and with falling bodies, for his discussion ...

. It is the largest of the lunar features designated ''Lacus''. Aldo Ferruggia - Lacus Mortis

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

albedo Albedo (; ) is the measure of the diffuse reflection of solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body that refl ...

as the larger

lunar mare The lunar maria (; singular: mare ) are large, dark, basaltic plains on Earth's Moon, formed by ancient asteroid impacts on the far side on the Moon that triggered volcanic activity on the opposite (near) side. They were dubbed , Latin for 'seas' ...

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

basalt Basalt (; ) is an 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 surface of a rocky planet or moon. More than 90 ...

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 moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...

. 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 epo ...

. 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 (; grc-gre, Ποσειδώνιος , "of Poseidon") "of Apameia" (ὁ Ἀπαμεύς) or "of Rhodes" (ὁ Ῥόδιος) (), was a Greek politician, astronomer, astrologer, geographer, historian, mathematician, and teacher nativ ...

. 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, 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 wi ...

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 Lacus Mortis (Latin ''mortis'', "Lake of Death") is a hexagonal-shaped plain of basaltic lava flows in the northeastern part of the Moon's near face. It was formed as a floor-fractured crater during the pre-Imbrian epoch, then flooded during the ...

to the north. A buried crater with a 200 km diameter was detected in this locale by NASA's

GRAIL The Gravity Recovery and Interior Laboratory (GRAIL) was an American lunar science mission in NASA's Discovery Program which used high-quality gravitational field mapping of the Moon to determine its interior structure. The two small spacecraf ...

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 circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact crater ...

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, 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