Vallis Alpes (

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 ...

for "Alpine Valley") is a lunar valley feature that bisects the

Montes Alpes Montes Alpes is a mountain range in the northern part of the Moon's near side. It was named after the Alps in Europe; the name was confirmed by the International Astronomical Union in 1935. It lies between the selenographic coordinates latitudes ...

range. It extends 166 km from the

Mare Imbrium Mare Imbrium (Latin ''imbrium'', the "Sea of Showers" or "Sea of Rains") is a vast lunar mare, lava plain within the Imbrium Basin on the Moon and is one of the larger craters in the Solar System. The Imbrium Basin formed from the collision ...

basin, trending east-northeast to the edge of the

Mare Frigoris Mare Frigoris (Latin ''frīgōris'', the "Sea of Cold") is a lunar mare in the far north of the Moon. It is located in the outer rings of the Procellarum basin, just north of Mare Imbrium, and stretches east to north of Mare Serenitatis. It is j ...

. The valley is narrow at both ends and widens to a maximum width of about 10 km along the middle stretch. The

selenographic coordinates The selenographic coordinate system is used to refer to locations on the surface of Earth's moon. Any position on the lunar surface can be referenced by specifying two numerical values, which are comparable to the latitude and longitude of Earth ...

of the center of this feature are . The valley floor is a flat,

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 ...

-flooded surface that is bisected by a slender, broken, cleft-like

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 ...

. The center rille is a challenging target for

telescope A telescope is a device used to observe distant objects by their emission, Absorption (electromagnetic radiation), absorption, or Reflection (physics), reflection of electromagnetic radiation. Originally, it was an optical instrument using len ...

observation from the

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

and described as, "notoriously hard to spot." The rille itself is longer than the valley proper, at 196.65 km ± 10.98 km, and has a width of 0.58 km ± 0.09 km and depth of 77.69 m ± 28.07 m. The sides of the valley rise from the floor to the surrounding highland terrain, a blocky, irregular surface. The southern face of the valley is straighter than the northern side, which is slightly bowed and uneven. The more rugged edges of the valley lie at the narrow west-southwest end that cuts through the mountain range. Most likely this valley is a

graben In geology, a graben () is a depression (geology), depressed block of the Crust (geology), crust of a planet or moon, bordered by parallel normal faults. Etymology ''Graben'' is a loan word from German language, German, meaning 'ditch' or 't ...

that was subsequently flooded with magma from Mare Imbrium and Mare Frigoris. However, the valley could have been formed by stress fractures due to expansion of the mantle or contraction after solidification of regolith. It is not dissimilar to other linear features radiating from Mare Imbrium, and the impact event which created the Imbrium basin may have also led to the stresses creating Vallis Alpes.

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 ...

flooding and thermal or tensional stress fractures are two causes of graben formation. This valley was discovered in 1727 by Francesco Bianchini. Its name was confirmed by the

International Astronomical Union The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...

in 1961.

References

Alpes, Vallis {{Valleys on the Moon