{{Short description|Geologic feature of Mars}} [[File:Nilokeras Scopulus.jpg|thumb|right|360 px|False color oblique view of Nilokeras Scopulus looking north. The cratered plateau at top is [[Tempe Terra]]. The dark greenish, smooth area at bottom is [[floodplain]] of [[Kasei Valles]]. The light blue area at bottom left is a portion of the (younger) central channel of N. Kasei Vallis. Image is [[Mars Orbital Laser Altimeter]] (MOLA) colorized elevation overlying [[Thermal Emission Imaging System]] (THEMIS) Infrared (IR) daytime mosaic from [[Mars Odyssey]] spacecraft. Yellow and light green represent high elevations; dark green and blue are lower elevations. Image is approximately 175 km across. Vertical exaggeration is 3X.]]

[[File:Nilokeras Scopulus based on day THEMIS.png|thumb|Nilokeras Scopulus based on [[THEMIS]] day-time image]] '''Nilokeras Scopulus''' is a long [[scopulus|escarpment]] (cliff) in the northern hemisphere of the planet [[Mars]]. It is located along the southeastern boundary of the [[Tempe Terra]] plateau and forms the northern valley wall (wallrock boundary) of the downstream portion of the immense [[Kasei Valles]] [[outflow channel]] system. The escarpment is 765&nbsp;km long{{citation needed|date=November 2016}}<ref name=USGS>USGS Gazetter of Planetary Nomenclature. https://planetarynames.wr.usgs.gov/Feature/4277.</ref> and ranges from 1 to a little over 2&nbsp;km (3300–6600&nbsp;ft) in height.<ref name=JMars>Mars Orbital Laser Altimeter (MOLA) gridded dataset from JMars. (cf. Christensen, P. et al. (2007). New Insights about Mars from the Creation and Analysis of Mars Global Datasets. American Geophysical Union, abstract #P11E-01. http://adsabs.harvard.edu/abs/2007AGUFM.P11E..01C.)</ref>

For most of its length, Nilokeras Scopulus lies between lat. 31° and 32° N. It trends west-east, extending from approximately long. 297° to 309° E.<ref name=USGS /> The escarpment curves northward at the eastern edge of Tempe Terra where the northern segment of Kasei Valles [[debouch]]es into [[Chryse Planitia|Chryse]] and southwestern [[Acidalia Planitia|Acidalia]] Planitiae.

==Name origin== Nilokeras, which is Greek for "horn of the [[Nile]]," was the name given by astronomer [[E. M. Antoniadi]] in 1930 to a telescopic [[Classical albedo features on Mars|albedo feature]] and [[Martian canals|canal]] centered at lat. 30° N., long. 55° W. (See [[List of Martian canals]].) [[Scopulus]] is a [[descriptor term]] used in planetary geology for an irregular escarpment or cliff. The [[International Astronomical Union]] (IAU) formally adopted the name Nilokeras Scopulus in 1976.<ref name=USGS /> [[Scopulus]] is the Latin term for "crag" or cliff.

==Geology== In [[geomorphology]], an escarpment (usually shortened to scarp) is any steep, abrupt slope or cliff along the margin of a [[plateau]], [[terrace (geology)|terrace]], or other [[bench (geology)|topographic bench]]. A scarp may be formed by [[tectonics|tectonic]], [[erosion]]al, or [[deposition (geology)|depositional]] processes.<ref name =Bloom>Bloom, A.L. (1978) ''Geomorphology: A Systematic Analysis of Late Cenozoic Landforms;'' Prentice-Hall: Englewood Cliffs, NJ, p. 28.</ref> The term carries no implication of geologic origin.

Nilokeras Scopulus likely formed from a combination of faulting and erosion from flood waters that formed Kasei Valles. Recent geologic mapping of the Kasei Valles region<ref name=Chapman1>{{cite journal | last1 = Chapman | first1 = M.G. | display-authors = etal | year = 2010a | title = Noachian–Hesperian Geologic History of the Echus Chasma and Kasei Valles System on Mars: New Data and Interpretations | url = https://elib.dlr.de/67494/1/Chapman_et_al.Kasei_Noachian-Hesperian.EPSL_2010.pdf| journal = Earth Planet. Sci. Lett. | volume = 294 | issue = 3–4| pages = 256–271 | doi = 10.1016/j.epsl.2009.11.032 | bibcode=2010E&PSL.294..256C}}</ref><ref name= Chapman2>{{cite journal | last1 = Chapman | first1 = M.G. | display-authors = etal | year = 2010b | title = Amazonian Geologic History of the Echus Chasma and Kasei Valles System on Mars: New Data and Interpretations | journal = Earth Planet. Sci. Lett. | volume = 294 | issue = 3–4| pages = 238–255 | doi = 10.1016/j.epsl.2009.11.034 | bibcode=2010E&PSL.294..238C}}</ref> indicates that the west-to-east flow of the Kasei Valles floods followed the existing [[structural geology|structural]] trend of [[rift valley]]s in southern Tempe Terra. Thus, the proto-Nilokeras Scopulus was probably an east-west oriented fault scarp or fracture zone (or zone of weakness<ref>Jöns, H-P. (1995). A Fossil Linear Zone of Weakness Beneath the Kasei Valles, Mars? 26th Lunar and Planetary Science Conference, Abstract #1351. http://www.lpi.usra.edu/meetings/lpsc1995/pdf/1351.pdf.</ref>) that was eroded and further downcut by at least one (and possibly two) episodes of early catastrophic flooding from the northern [[Tharsis]] region. (See [[outflow channels]].) These floods occurred in [[Hesperian]] time between about 3.6 and 3.4 billion years ago (Gya).

After initial flooding, the northern Kasei valley was covered by extensive late Hesperian-aged basaltic lava flows from [[Tharsis]]. Two final episode of flooding from the [[Echus Chasma]] region to the south occurred in Kasei Valles during [[Amazon period|Amazonian]] times (<1.8 Gya). The later floods carved the channels south of Nilokeras Scopulus and may not have strongly influenced development of the scarp.

During the course of its history, Nilokeras Scopulus has been subjected to glacial/[[periglacial]] processes and modified by [[groundwater sapping]], slumping, collapse, and other [[mass wasting]] processes. Rocks making up the scarp face are Noachian or Early Hesperian in age (>3.6 Gya). They probably consist of ancient [[impact breccia]]s and volcanic materials. Layered bedrock is visible at the top of the escarpment in some medium and high resolution spacecraft images, but the scarp face is largely covered by [[scree|talus]] aprons and dust.

==See also== *[[Outflow channels]] *[[Scopulus]] *[[Kasei Valles]] *[[Tempe Terra]]

== References == {{commons category|Nilokeras Scopulus}} {{reflist}}

{{Geography of Mars}}

[[Category:Cliffs on Mars]] [[Category:Geology of Mars]] [[Category:Mare Acidalium quadrangle]]