Rupes Tenuis (Latin:thin cliff) is aMartian north polarscarp.[1] It is named after one of theclassical albedo features on Mars.[2] Its name was officially approved byIAU in 1988. It extends from latitude 74.94°N to 82.2°N and from longitude 242.12°E to 300.77°E (59.23°W – 117.88°W).[2] Its centre is located at latitude 81.6°N longitude 85.47°W.[2] It marks the outer perimeter of Planum Boreum from longitude 242.12°E to 300.77°E, and it is formed by the eastern extension of the Olympia Cavi, a series of local troughs and depressions, which become longer and deeper as they merge to create the Rupes Tenuis scarp formation.[3] The scarp is located to the west ofChasma Boreale, at the base ofPlanum Boreum,[4] and its height varies from a few hundred metres to a maximum of approximately 1000 metres.[4][5][6]
Immediately to the south of Rupes Tenuis, approximately at 285ºE,[7] liesAbalos Mensa, a convex formation of approximately 180 kilometer span, shaped like a wedge when viewed from above.[3][7] The dune field ofAbalos Undae continues in a southwestward direction after it emerges from the western end of a narrow channel separating Rupes Tenuis from Abalos Mensa.[3]
Two named craters are located in the immediate area of Rupes Tenuis;Crotone, located at 82.2ºN, 290.0ºE with a 6.4 km diameter, is situated at the channel separating the scarp from Abalos Mensa, andBoola, located at 81.1ºN, 254.2ºE, with a 17 km diameter, is found close to the western boundary of the Rupes Tenuis scarp.[3] West of Abalos Mensa, parallel to and south of the Rupes Tenuis scarp, runs a narrow, low-altitude plain, named Tenuis Mensa, which exhibits a southward slope.[5]
The proposed erosion mechanism for the polarbasal unit in general, and Rupes Tenuis in particular, arekatabatic winds (FromGreek:katabasis, "descent", i.e. strong winds descending from Planum Boreum), and solarablation.[6][3] These mechanisms are also considered responsible for the modern-dayerosion and retreat of the Rupes Tenuis scarp, the existence of conical mounds and promontories in the immediate vicinity of the scarp, and the creation of the narrow channels that separate Abalos Mensa from the scarp.[6] This erosion process is theorised to have existed since the LateAmazonian period on Mars, and it is considered to have contributed to the continuous retreat of the polar scarp from an older southern latitude as low as 74ºN.[6]
It is further theorised that the Rupes Tenuisstratigraphic unit may have been a paleo-plateau that descended further South than the present-day Rupes Tenuis scarp.[6] Geological formations in the vicinity of the scarp, such as mounds, are considered to have been formed by erosion mechanisms rather than volcanic activity.[6] The horizontal attitude (inclination) of the layers of the Rupes Tenuis unit, further indicates the non-volcanic origin of these formations, since layers of volcanic origin are not typically horizontal.[6] Nearby formations such asAbalos Colles — a group of five, flat or concave top, mounds, less than 700 m high and less than 1 km in diameter —[5] are considered to be erosional remnants of a once-continuous stratigraphic unit, the Rupes Tenuis unit.[6]
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