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Rimae on the floor of the lunar crater Gassendi, from Apollo 16.
Mamers Valles rille on Mars.
Rima Ariadaeus is categorized as a straight rille (graben) and is over 300 km in length.
Hadley Rille at center is a sinuous rille visited by the Apollo 15 mission.
Detail of part of Hadley Rille

Rille /ˈrɪl/[1] (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 wide and hundreds of kilometers in length. However, the term has also been used loosely to describe similar structures on a number of planets in the Solar System, including Mars, Venus, and on a number of moons. All bear a structural resemblance to each other.

Structures

Three types of rille are found on the lunar surface:

Rilles which show more than one structure are termed hybrid rilles. Rima Hyginus in Sinus Medii is an example, initially formed through a fault and subsequently subject to volcanic activity.

Formation

Precise formation mechanisms of rilles have yet to be determined. It is likely that the different types are formed by different processes. Common features shared by lunar rilles and similar structures on other bodies suggest that common causative mechanisms operate widely in the solar system. Leading theories include lava channels, collapsed lava tubes, near-surface dike intrusion, nuée ardente (pyroclastic cloud), subsidence of lava-covered basin and crater floors, and tectonic extension. On-site examination would be necessary to clarify exact methods.

Sinuous rilles

According to NASA, the origin of lunar sinuous rilles remains controversial.[3] The Hadley Rille is a 1.5 km wide and over 300 m deep sinuous rille. It is thought to be a giant conduit that carried lava from an eruptive vent far to the south. Topographic information obtained from the Apollo 15 photographs supports this possibility; however, many puzzles about the rille remain.[3]

See also

References

  1. ^ "rille". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  2. ^ Hurwitz, D.M.; Head, J.W.; Kring, D.A. (2019). "Atlas of Lunar Sinuous Rilles". Lunar and Planetary Institute. Retrieved 20 July 2021.
  3. ^ a b "ch6.2". History.nasa.gov. Retrieved 2012-09-17.
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