Diacria quadrangle

{{Short description|Map of Mars}} {{Infobox feature on celestial object |name = Diacria [[quadrangle (geography)|quadrangle]] |image = [[File:USGS-Mars-MC-2-DiacriaRegion-mola.png|300px]] |caption = Elevation map of Diacria quadrangle from [[Mars Orbiter Laser Altimeter]] (MOLA) data |coordinates = {{coord|47.5|N|150|W|globe:mars_type:landmark|display=inline,title}} |eponym = [[Diacria]] highlands around [[Marathon, Greece|Marathon]] in Greece }} [[File:PIA00162-Mars-MC-2-DiacriaRegion-19980604.jpg|thumb|right|300px|Image of the Diacria Quadrangle (MC-2). The southeastern part is marked by aureole deposits of the largest known volcano in the Solar System, [[Olympus Mons]].]] The '''Diacria quadrangle''' is one of a series of [[list of quadrangles on Mars|30 quadrangle maps of Mars]] used by the [[United States Geological Survey]] (USGS) [[Astrogeology Research Program]]. The [[Quadrangle (geography)|quadrangle]] is located in the northwestern portion of Mars' western hemisphere and covers 180° to 240° east longitude (120° to 180° west longitude) and 30° to 65° north latitude. The quadrangle uses a [[Lambert conformal conic projection]] at a nominal scale of 1:5,000,000 (1:5M). The Diacria quadrangle is also referred to as '''MC-2''' (Mars Chart-2).<ref>Davies, M.E.; Batson, R.M.; Wu, S.S.C. "Geodesy and Cartography" in Kieffer, H.H.; Jakosky, B.M.; Snyder, C.W.; Matthews, M.S., Eds. ''Mars.'' University of Arizona Press: Tucson, 1992.</ref> The Diacria quadrangle covers parts of [[Arcadia Planitia]] and [[Amazonis Planitia]].

The southern and northern borders of the Diacria quadrangle are approximately {{convert|3065|km|mi|abbr=on}} and {{convert|1500|km|mi|abbr=on}} wide, respectively. The north to south distance is about {{convert|2050|km|mi|abbr=on}} (slightly less than the length of Greenland).<ref>Distances calculated using NASA World Wind measuring tool. {{cite web| url = http://worldwind.arc.nasa.gov/.| title = NASA WorldWind}}</ref> The quadrangle covers an approximate area of 4.9 million square km, or a little over 3% of Mars' surface area.<ref>Approximated by integrating latitudinal strips with area of R^2 (L1-L2)(cos(A)dA) from 30° to 65° latitude; where R = 3889 km, A is latitude, and angles expressed in radians. See: {{cite web| url = https://stackoverflow.com/questions/1340223/calculating-area-enclosed-by-arbitrary-polygon-on-earths-surface.| title = Calculating area enclosed by arbitrary polygon on Earth's surface - Stack Overflow}}</ref> The ''[[Phoenix (spacecraft)|Phoenix]]'' lander's landing site (68.22° N, 234.25° E) lies about {{convert|186|km|mi|abbr=on}} north of the northeastern quarter of the Diacria quadrangle. The landscape viewed by the ''Phoenix'' lander is probably representative of a large portion of the terrain in the northern Diacria quadrangle.

==Etymology== Diacria is the name of a [[classical albedo features on Mars|telescopic albedo feature]] located at 48° N and 190° E on Mars. The feature was named by Greek astronomer E. M. Antoniadi in 1930 after [[Diacria]], the highlands around [[Marathon, Greece|Marathon]] in north-west [[Attica]], Greece. The name was approved by the [[International Astronomical Union]] (IAU) in 1958.<ref>USGS Gazetteer of Planetary Nomenclature. Mars. {{cite web| url = http://planetarynames.wr.usgs.gov/.| title = Planetary Names: Welcome}}</ref>

==Physiography and geology== The Diacria quadrangle is located at the northwestern edge of the [[Tharsis]] volcanic plateau. Topographic, volcanic, and tectonic features associated with the large volcanoes [[Olympus Mons]] (south of map area) and [[Alba Mons]] (east of map area) characterize the southeastern and east central portions of the quadrangle. The northern and western areas of the quadrangle lie in the northern lowland plains of Mars and cover portions of [[Amazonis Planitia]] (in the south), [[Arcadia Planitia]] (west central) and [[Vastitas Borealis]] (in the north). The large crater Milankovič (118.4 km in diameter) is located in the north central portion of the quadrangle at 54.7° N, 213.3° E.

Elevation data from the [[Mars Orbital Laser Altimeter]] (MOLA) instrument on the [[Mars Global Surveyor]] spacecraft shows that the regional terrain slopes gently downward to the northwest, with the highest elevation about {{convert|3.5|km|mi|abbr=on}} above datum (Mars "sea level") on the western flank of the Alba Mons volcano in the southeastern portion of the quadrangle. The lowest points in the quadrangle are about 4.5 km below datum (-4,500 m) in Vastitas Borealis in the northwest corner.<ref>JMARS MOLA elevation database. Christensen, P.; Gorelick, N.; Anwar, S.; Dickenshied, S.; Edwards, C.; Engle, E. "New Insights About Mars From the Creation and Analysis of Mars Global Datasets;" American Geophysical Union, Fall Meeting 2007, (abstract #P11E-01).</ref> The regional relief is thus about 8 km, but at a local scale, slopes are very shallow; the portion of Amazonis Planitia in the south central part of the quadrangle contains some of the flattest terrain on the entire planet.<ref>Goddard Spaceflight Center. Global Slope and Roughness Maps of Mars from MOLA. [https://web.archive.org/web/20090321025947/http://ssed.gsfc.nasa.gov/tharsis/slopes.html].</ref>

== Placeholder == The western flank of the Alba Mons volcano makes up the eastern and southeastern edge of the quadrangle. In terms of area, Alba Mons (formerly, Alba Patera) is the largest volcanic feature on Mars. The flank has a very low slope (l° or less) and is characterized by lava flows and an outwardly radiating array of ridges and channels. Some of the channels have a drainage pattern that resembles that formed by rain water on the slopes of terrestrial volcanoes. However, many other channels on the flanks of Alba Mons were clearly formed by flowing lava.<ref>Carr, M.H. ''The Surface of Mars;'' Cambridge University Press: New York, 2006.</ref> The western flank of the volcano also contains some NW-SE trending [[graben]]s ([[Cyane Fossae]]). An image from High Resolution Imaging Science Experiment ([[HiRISE]]) on the [[Mars Reconnaissance Orbiter]] (MRO) beautifully shows a line of rimless pit craters in Cyane Fossae. The pits may have formed by the collapse of surface materials into open fractures created as magma intruded the subsurface rock to form [[dike (geology)|dikes]].<ref>University of Arizona HiRISE Website. {{cite web| url = http://hirise.lpl.arizona.edu/PSP_010345_2150.| title = HiRISE {{!}} High Resolution Imaging Science Experiment}}</ref>

===Acheron Fossae=== {{main|Acheron Fossae}}

Near the southeast corner of the quadrangle (37° N, 225° E) lies a southward sloping, semicircular block of ancient, heavily cratered, highland crust that is dissected by numerous, [[:wikt:arcuate|arcuate]] troughs ([[Acheron Fossae]]).

===Lycus Sulci (Olympus Mons Aureole)=== Lycus Sulci (24.6° N, 219° E) is the name applied to the northwestern portion of a larger terrain feature that partially encircles Olympus Mons and extends up to 750 km from the giant [[shield volcano|shield volcano's]] base. This feature, called the Olympus Mons aureole, consists of several large lobes and has a distinctive corrugated or grooved surface texture. East of Olympus Mons, the aureole is partially covered by lava flows, but where it is exposed it goes by different names ([[Gigas Sulci]], for example). The origin of the aureole remains debated, but it was likely formed by huge landslides or gravity-driven [[thrust fault|thrust sheets]] that sloughed off the edges of the Olympus Mons shield.<ref>Cattermole P. ''Mars: the Mystery Unfolds;'' Oxford University Press: New York, 2001.</ref>

===Erebus Montes=== {{main|Erebus Montes}}

[[File:Erebus Montes.JPG|thumb|300px|right|Erebus Montes, as seen by HiRISE. Grooves indicate movement.]] Westward from Lycus Sulci, across the flat plains of Amazonis Planitia, lies an elongated region of knobby terrain called [[Erebus Montes]] (Erebus Mountains). The region contains hundreds of clustered to isolated hillocks that stand 500 to 1,000 m above the surrounding plains. The presence of numerous partly filled "ghost" craters in the area indicates that the hills represent the high-standing remnants of ancient highland crust that was inundated by lava flows and (possibly) alluvial sediments from Tharsis in the southeast and the [[Elysium Planitia|Elysium]] volcanic province to the west.<ref>Tanaka, K.L.; Skinner, J.A.; Hare, T.M. Geologic Map of the Northern Plains of Mars. Scientific Investigations Map 2888, U.S. Geological Survey, 2005.</ref>

===Arcadia Planitia and Southern Vastitas Borealis=== North and east of the Erebus Montes are low-lying plains that characterize a large part of the Diacria Quadrangle and of the Martian northern hemisphere in general. Medium resolution [[Mariner 9]] and [[Viking program|Viking]] spacecraft images from the 1970s show that large portions of Arcadia Planitia have an overall mottled (blotchy light and dark) appearance. At higher resolution, landforms commonly consist of lobate flow fronts; small channel segments; [[wrinkle-ridge|wrinkle ridges]]; [[pedestal craters]]; and low, isolated volcano-like hills with summit craters.<ref>Tanaka, K.L.; Scott, D.H.; Greely, R. "Global Stratigraphy" in Kieffer, H.H.; Jakosky, B.M.; Snyder, C.W.; Matthews, M.S., Eds. ''Mars;'' University of Arizona Press: Tucson, 1992.</ref> MOLA images reveal numerous large, shallowly buried craters, suggesting that an old cratered surface lies under a layer of younger material.

At the resolution of the Mars Orbital Camera (MOC) on the Mars Global Surveyor spacecraft (around several m per pixel), much of the northern plains has a distinctly stippled, pitted texture that causes the ground to resemble the surface of a basketball or orange rind. This texture is likely caused by a mantle of ice and dust covering the landscape. The small hollows and pits formed as the ice evaporated (sublimed).

The geologic history and origin of the northern plains are complex and still poorly understood. Many of the landforms resemble [[periglacial]] features seen on Earth, such as [[moraines]], [[ice wedge|ice-wedged polygons]], and [[pingo]]s. Arcadia Planitia and Vastitas Borealis likely consist of a hodgepodge of old lava flows, ice-related features, and reworked sediments of diverse origin. Some theorize that the northern plains were once covered by oceans or large lakes.

==See also== {{div col|colwidth=30em}}

* [[Dark slope streak]] * [[Dust Devil Tracks]] * [[Expanded Craters]] * [[Fossa (geology)]] * [[HiRISE]] * [[HiWish program]] * [[Inverted relief]] * [[List of quadrangles on Mars]] * [[List of rocks on Mars]] * [[Martian Gullies]] * [[Milankovic (Martian crater)]] * [[Outflow channels]] * [[Valley networks (Mars)]] * [[Phoenix Lander|''Phoenix'' lander]] * [[Polygonal patterned ground]] * [[Volcanism on Mars]] * [[Water on Mars]] {{div col end}}

==References== {{reflist|colwidth=30em}}

== External links == * [https://www.flickr.com/photos/136797589@N04/33566282890/ High resolution video] by Seán Doran of a flyover of crater Domoni (51.7° N, 125.6° W) *[https://www.youtube.com/watch?v=1plIgTG9x-A Chris McKay: Results of the Phoenix Mission to Mars and Analog Sites on Earth]

{{DEFAULTSORT:Diacria Quadrangle}} [[Category:Diacria quadrangle| ]] [[Category:Mars]]