Editing Valles Marineris (section)

== Regions of Valles Marineris ==
[[Image:Valles Marineris.jpg|thumb|500px|Valles Marineris with major features labeled.]]

=== Noctis Labyrinthus ===
[[File:Noctis Labyrinthus.jpg|thumb|300px|right|Morning water ice fog spills out of Noctis Labyrinthus (''[[Viking 1]]'' orbiter image)]] 
[[Noctis Labyrinthus]], on the western edge of the Valles Marineris Rift System, north of the [[Syria Planum]] and east of [[Pavonis Mons]], is a jumbled terrain composed of huge blocks which are heavily fractured. It also contains canyons that run in different directions surrounding large blocks of older terrain. Most of the upper parts of the blocks are composed of younger fractured material thought to be of volcanic origin associated with the Tharsis bulge. The other tops are composed of older fractured material thought also to be volcanic in origin, but differentiated from the younger material by more ruggedness and more impact craters. The sides of the blocks are composed of undivided material thought to be basement rock. The space between the blocks is composed mainly of either rough or smooth floor material. The rough floor material tends to be in the eastern portion of the Noctis Labyrinthus and is thought to be debris from the walls or maybe eolian features covering rough topography and landslides. The smooth floor material is thought to be composed of fluvial or basaltic material and/or eolian features covering an otherwise rough and jumbled terrain.<ref name="USGS I-2010">Witbeck, Tanaka and Scott, Geologic Map of the Valles Marineris Region, Mars; USGS I-2010; 1991.</ref> Terrains such as Noctis Labyrinthus are commonly found at the head of outflow channels, like the one explored by the Pathfinder mission and its Sojourner rover.  They are interpreted to be a place of downward block faulting associated with the removal of ground fluid in catastrophic flood sequences.<ref name="Rodriguez 2015">{{cite journal|last1=Rodriguez|first1=J. Alexis P.|last2=Kargel|first2=Jeffrey S.|last3=Baker|first3=Victor R.|last4=Gulick|first4=Virginia C.|date=8 September 2015|title=Martian outflow channels: How did their source aquifers form, and why did they drain so rapidly?|journal=Scientific Reports|volume=5|page=13404|doi=10.1038/srep13404|pmid=26346067|pmc=4562069|display-authors=etal|bibcode=2015NatSR...513404R}}</ref> The fluid could be either carbon-dioxide ice and gas, water or lava. The hypothesis of lava involvement is associated with a proposal that Noctis Labyrinthus is directly connected to lava tubes on the slope of Pavonis Mons.<ref name = "Leone2014" /> In 2024, scientists found evidence that the hypothesized lava came from a volcano they dubbed '''Noctis Mons''', which would be the seventh-highest mountain on Mars at {{cvt|9028|m|ft}}, and that the eastern part of its base was home to multiple [[glacier]]s with potential for hosting life, which could make it a highly valuable candidate target for [[astrobiology]] missions. <ref name="SETI Institute 2024">{{cite web | title=Giant Volcano Discovered on Mars | website=SETI Institute | date=March 13, 2024 | url=https://www.seti.org/press-release/giant-volcano-discovered-mars | access-date=March 22, 2024}}</ref><ref name="SETI Institute 2023">{{cite web | title=Remains of a Modern Glacier Found Near Mars' Equator Implies Water Ice Possibly Present at Low Latitudes on Mars Even Today | website=SETI Institute | date=March 15, 2023 | url=https://www.seti.org/press-release/remains-modern-glacier-found-near-mars-equator-implies-water-ice-possibly-present-low-latitudes | access-date=March 22, 2024}}</ref>

=== Ius and Tithonium chasmata ===
[[Image:Mars; Ius Chasma.jpg|right|thumb|400px|Ius Chasma image mosaic from ''[[2001 Mars Odyssey]]'', showing side canyons created by [[Groundwater sapping|sapping]]. On the northern (upper) rim, right of center, a canyon turns 90 degrees where it encounters a [[graben]].]]
Further to the east from Oudemans, [[Ius Chasma|Ius]] and [[Tithonium Chasma|Tithonium]] chasmata are located parallel to each other, Ius to the south and Tithonium to the north.  Ius is the wider of the two, leading to Melas Chasma. Ius has a ridge down the center of it by the name of Geryon Montes, composed of the undivided basement rock. The floor of Ius Chasma is mostly composed of pristine landslide material, not much degraded by cratering or erosion. The southern wall of Ius, and to a lesser extent the northern wall, has many short valleys stretching off roughly perpendicular to the line of the chasmas. These valleys have a stubby theater-headed leading edge very much like features seen on the Colorado Plateau near the [[Grand Canyon]] that appear from [[groundwater sapping]]. (Theater-headed means that, from above, the head of the valley is a well-defined U-shape). The valley is propagated by the continued erosion and the collapse of the wall.<ref>Howard, Kochel and Holt; Sapping Features of the Colorado Plateau: A Comparative Planetary Geology Field Guide; NASA; 1988.</ref> Tithonium Chasma is very similar to Ius, except it is lacking the sapping features on the south side and contains a small portion of material that is similar to the smooth floor features except that it appears to be an ash fall that has been eroded by the wind. Between the two canyons, the surface is composed of younger fractured material - lava flows and faults from crustal extension of the [[Tharsis Bulge]].<ref name="USGS I-2010"/>

=== Melas, Candor and Ophir chasmata ===
[[File:Ophir Chasma THEMIS mosaic.jpg|thumb|350px|Ophir Chasma THEMIS mosaic]]
The next portion of Valles Marineris to the east are three chasmata, that from south to north are [[Melas Chasma|Melas]], [[Candor Chasma|Candor]] and [[Ophir Chasma|Ophir]] chasmata. Melas is east of Ius, Candor is east of Tithonium and Ophir appears as an oval that runs into Candor. All three chasmata are connected.  The floor of Melas Chasma is about 70% younger massive material that is thought to be volcanic ash whipped up by the wind into eolian features. It also contains rough floor material from the erosion of the canyon walls. Also, in these central chasmata there is a portion of the floor that is higher than the rest of the floor, most likely left by the continued dropping of the other floor material. Around the edges of Melas is also a lot of slide material as seen in Ius and Tithonium chasmata.<ref name="USGS I-2010"/>

The material of the floor of the canyon system between Candor and Melas chasmata is grooved. This is interpreted to be [[alluvial]] deposits and/or material that has collapsed or contracted by the removal of ice or water. There are also portions of older and younger massive floor material of [[Pyroclastic rock|volcaniclastic]] origin - only separated in age by crater distribution. Also there is etched massive floor material that is like the younger and older massive material except that it has wind erosion features on it. There are also a few spires of undivided material composed of the same material as the canyon walls.<ref name="USGS I-2010"/>

=== Coprates Chasma ===
[[Image:PIA19805-SeasonalFlows-CopratesChasma-VallesMarineris-20150721.jpg|thumb|left|250px|[[Seasonal flows on warm Martian slopes|Seasonal flows]] on [[Coprates Chasma]] in Valles Marineris.]]
[[Image:Coprates Chasma landslides.jpg|right|thumb|260px|Deposits from landslides moving in opposite directions meet on the canyon floor near the junction of Melas and Coprates chasmata.]]
Further to the east, the canyon system runs into [[Coprates Chasma]], which is very similar to Ius and Tithonium chasmata. Coprates differs from Ius in the eastern end which contains alluvial deposits and [[Aeolian processes|eolian]] material<ref name="USGS I-2010"/> and like Ius, has layered deposits, although the deposits in the Coprates Chasma are much more well defined. These deposits pre-date the Valles Marineris system, suggesting erosion and sedimentary processes later cut by the Valles Marineris system. Newer data from [[Mars Global Surveyor]] suggest that the origin of this layering is either just a succession of [[landslide]]s, one over another, volcanic in origin, or it may be the bottom of a basin of either liquid or solid water ice suggesting that the peripheral canyons of the Valles Marineris system could have been at one time isolated lakes formed from erosional collapse. Another possible source of the layered deposits could be wind-blown, but the diversity of the layers suggests that this material is not dominant. Note that only the upper layers are thin, while the bottom layers are very big, suggesting that the lower layers were composed of mass wasted rock and the upper layers come from another source.<ref>{{Cite book |last=Cattermole |first=Peter John |url=https://archive.org/details/marsmysteryunfol00catt |title=Mars : the mystery unfolds |date=2001 |publisher=Oxford ; New York : Oxford University Press |others=Internet Archive |isbn=978-0-19-521726-1 |pages=113-114}}</ref> Some of this layering may have been transferred to the floor by landslides in which the layers are kept semi-intact, yet the layered section looks highly deformed with thickening and thinning beds that have multitudes of folds in them as seen in MOC image #8405. This complex terrain could also be just eroded sediment from an ancient Martian lake-bed and appear complex because all that we have is an aerial view like a geologic map and not enough elevation data to see if the beds are horizontal.

Near 60° W is the deepest point of the Valles Marineris system (as well as its lowest point by elevation) at {{convert|11|km|ft|abbr=on}} below the surrounding plateau. Eastward from here there is about a 0.03 degree slope upward before reaching the outflow channels, which means that if you poured fluid into this part of the canyon, it would form a lake with a depth of {{convert|1|km|ft|abbr=on}} before spilling over towards the northern plains.<ref>[https://archive.org/details/marsmysteryunfol00catt/page/105 Cattermole, 105]</ref>

A field of more than 100 pitted cones on the floor of Coprates Chasma has been interpreted as a set of small igneous [[cinder cone|cinder]] or [[tuff cone|tuff]] cones, with associated lava flows. Crater dating indicates they are of Middle to Late [[Amazonian (Mars)|Amazonian]] age, about 200 to 400 million years old.<ref name = "CzechAcad2017">{{cite web | url = http://www.avcr.cz/en/media/news-archive/Recent-volcanic-activity-and-hydrothermal-minerals-on-Mars/ | title = Recent volcanic activity and hydrothermal minerals on Mars | date =  2017-07-19 | publisher = [[Czech Academy of Sciences]] | access-date = 2017-07-27}}</ref><ref name="Brož2017">{{cite journal|last1= Brož|first1= P.|last2= Hauber|first2= E.|last3= Wray|first3=J. J.|last4= Michael|first4= G.|title= Amazonian volcanism inside Valles Marineris on Mars|journal= Earth and Planetary Science Letters|volume= 473|year= 2017|pages= 122–130|doi= 10.1016/j.epsl.2017.06.003|url=https://zenodo.org/record/889306|bibcode= 2017E&PSL.473..122B}}</ref>

=== Eos and Ganges chasmata ===
[[File:Ganges chasma closeup.jpg|thumb|Rim of Ganges chasma, closeup showing [[stratigraphy]] and small landslides. ]]
Further to the east lie [[Eos Chasma|Eos]] and [[Ganges Chasma|Ganges]] chasmata. Eos Chasma's western floor is mainly composed of an etched massive material composed of either volcanic or eolian deposits later eroded by the Martian wind. The eastern end of the Eos chasma has a large area of streamlined bars and longitudinal striations. This is interpreted to be stream-carved plateau deposits and material transported and deposited by flowing fluid.  Ganges Chasma is an offshoot chasma of Eos in a general east–west trend. The floor of Ganges is mainly composed of alluvial deposits from the canyon walls.<ref name="USGS I-2010"/>

=== Chryse region ===
East of Eos and Ganges, Valles Marineris empties out into the [[Chryse Planitia|Chryse]] region of the northern plains of Mars at an elevation only {{convert|1|km|ft|abbr=on}} above the deepest point of Valles Marineris in Melas Chasma. The outflow regions of the northern plains are similar to the terrain seen at the [[Mars Pathfinder]] landing site. A terrestrial counterpart of these [[outflow channels]] on Earth would be the [[Channeled Scablands|scablands]] of eastern [[Washington (state)|Washington]]. The eastern Washington scablands are a result of repeated catastrophic flooding due to the build-up of an ice dam at the head of [[Lake Missoula]] in the [[Late Pleistocene]]. The ice dam would block the water for a while, but when it broke, the ice would float on top of the ensuing flood and vast areas would be stripped of topsoil and vegetation, leaving a large barren area of 'teardrop' islands, longitudinal grooves and terraced margins. Many of these features are also seen in Martian outflow channels, but on a larger scale.<ref>[https://archive.org/details/marsmysteryunfol00catt/page/126 Cattermole, 126]</ref>

The outflow occurs successively through several regions of chaotic terrain, [[Aurorae Chaos]] and [[Hydraotes Chaos]], and finally through [[Simud Valles]] and [[Tiu Valles]] into Chryse Planitia.<ref name="Rodriguez 2015"/><ref name = "USGS map">[http://pubs.usgs.gov/imap/i2782/i2782_sh1.pdf United States Geological Survey Mars topographic map with feature names]</ref>