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| {{MarsGeo-Plains
| | I would like to introduce myself to you, I am Andrew and my wife doesn't like it at all. For years he's been living in Mississippi and he doesn't strategy on changing it. Distributing production is where her main earnings comes from. To climb is some thing she would by no means give up.<br><br>Also visit my blog - phone psychic ([http://mybrandcp.com/xe/board_XmDx25/107997 his explanation]) |
| |name=Planum Boreum
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| |image=[[Image:Mars NPArea-PIA00161 modest.jpg|200px]]
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| |caption=[[Viking (spacecraft)|Viking]] mosaic of Planum Boreum and surrounds
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| |location=
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| |latitude=88.0
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| |N_or_S=N
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| |longitude=15.0
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| |E_or_W=E
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| |area=
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| |discoverer
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| }}
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| '''Planum Boreum''' ([[Latin]]: "the northern plain") is the northern polar plain on [[Mars]]. It extends northward from roughly 80°N and is centered at {{Coord|88.0|15.0|globe:Mars}}. Surrounding the high polar plain is a flat and featureless lowland plain called [[Vastitas Borealis]] which extends for approximately 1500 kilometres southwards, dominating the northern hemisphere.<ref>[http://planetarynames.wr.usgs.gov/jsp/FeatureNameDetail.jsp?feature=64923] and [http://planetarynames.wr.usgs.gov/jsp/FeatureNameDetail.jsp?feature=66502] give Vastitas Borealis starting at 54.7°N and Planum Boreum at 78.5°N. The radius of Mars is approximately 3400 km, so <math>d=\frac{78.5 - 54.7}{360}\times 2 \pi\ \times 3400\mbox{ km} = 1412\mbox{ km} </math></ref>
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| ==Ice cap==
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| [[Image:MRO image of Mars North Pole.jpg|left|thumb|150px|False color [[Mars Reconnaissance Orbiter]] image of a side of the [[Chasma Boreale]], a canyon in the polar ice cap. Light browns are layers of surface dust greys and blues are layers of water and carbon dioxide ice. Regular geometric cracking is indicative of higher concentrations of water ice.]]
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| [[Image:PSP 001406 2680 ChasmaBoreale.jpg|right|200px|thumb|[[HiRISE]] image of a crater in the north polar ice cap]]
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| Planum Boreum is home to a permanent [[polar ice cap|ice cap]] consisting mainly of [[Ice|water ice]] (with a 1 m thick veneer of [[Dry ice|carbon dioxide ice]] during the winter).<ref name="darling_marspoles">{{cite web|last=Darling|first=David|title=Mars, polar caps|work=Encyclopedia of Astrobiology, Astronomy, and Spaceflight|url=http://www.daviddarling.info/encyclopedia/M/Marspoles.html|accessdate=2007-02-26}}</ref> It has a volume of 1.2 million cubic kilometres and covers an area equivalent to about 1.5 times the size of [[Texas]]. It has a radius of 600 km. The maximum depth of the cap is 3 km.<ref>{{cite web|url=http://ltpwww.gsfc.nasa.gov/tharsis/agu_f98.html|title=Laser provides first 3-D View of Mars' North Pole|accessdate=2006-11-01 |archiveurl = http://web.archive.org/web/20061017122112/http://ltpwww.gsfc.nasa.gov/tharsis/agu_f98.html <!-- Bot retrieved archive --> |archivedate = 2006-10-17}}</ref>
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| The spiral troughs in the ice cap are formed by [[katabatic wind]]s that entrain surface ice eroded from the equator-facing sides of the troughs, likely aided by solar ablation ([[Sublimation (phase transition)|sublimation]]), which is then redeposited on the colder pole-facing slopes. The troughs are roughly perpendicular to the wind direction, which is shifted by the [[Coriolis effect]], leading to the spiral pattern.<ref name = "Isaac_2010">{{cite journal | title=Onset and migration of spiral troughs on Mars revealed by orbital radar | author=Smith, Isaac B.; Holt, J. W. | journal=Nature | volume=465 | year=2010 | pages=450–453| url=http://www.nature.com/nature/journal/v465/n7297/full/nature09049.html | doi=10.1038/nature09049|bibcode = 2010Nature....32..450P | issue=4 }}</ref><ref>{{cite web|url=http://www.space.com/8494-mystery-spirals-mars-finally-explained.html|publisher=Space.com|title=Mystery Spirals on Mars Finally Explained|date=26 May 2010|accessdate=2010-05-26}}</ref> The troughs gradually migrate towards the pole over time; the central troughs have moved about 65 km in the last 2 million years.<ref name = "Isaac_2010"/> [[Chasma Boreale]] is a canyon-like feature older than the troughs, and in contrast is aligned parallel to the wind direction.<ref name = "Isaac_2010"/>
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| The surface composition of the northern ice cap in middle spring (after a winter's accumulation of seasonal dry ice) has been studied from orbit. The outer edges of the ice cap are contaminated with dust (0.15% by weight) and are mostly water ice. As one moves toward the pole, the surface water ice content decreases and is replaced by dry ice. The purity of the ice also increases. At the pole, the surface seasonal ice consists of essentially pure dry ice with little dust content and 30 [[parts per million]] of water ice.<ref>{{cite web|url=http://www-mars.lmd.jussieu.fr/granada2006/abstracts/Giuranna_Granada2006.pdf|title=Spatial variability and composition of the seasonal north polar cap on Mars|accessdate=2006-11-01}}</ref>
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| The [[Phoenix (spacecraft)|Phoenix]] lander, launched in 2007, arrived at Mars in May 2008 and successfully landed in the Vastitas Borealis region of the planet on May 25, 2008. The north polar cap of Mars has been proposed as a landing site for a human Mars expedition by [[Geoffrey A. Landis|Landis]]<ref>G. Landis, [http://www.sff.net/people/Geoffrey.Landis/pole.html Polar Landing Site for a First Mars Expedition] Founding Convention of the Mars Society, August 13–16, 1998, [[University of Colorado at Boulder|University of Colorado]] in [[Boulder, CO]]</ref> and by [[Charles Cockell]]<ref>[[Project Boreas]] C. Cockell (editor), [http://www.bis-spaceflight.com/sitesia.aspx/page/170/id/980/l/en-gbBoreas Project Boreas - A Station for the Martian Geographic North Pole], The [[British Interplanetary Society]] (2006)</ref>
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| ==Features==
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| [[Image:PoloNorteMarteTopologico.png|right|thumb|200px|Elevation map of the north pole. Note how Planum Boreum soars above the surrounding featureless terrain. Click to enlarge and for more info.]]
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| The main feature of the Planum Boreum is a large fissure or canyon in the polar ice cap called [[Chasma Boreale]]. It is up to {{convert|100|km}} wide and features scarps up to {{convert|2|km}} high.<ref>{{cite web|url=http://www.esa.int/SPECIALS/Mars_Express/SEM8T86Y3EE_0.html|title=Fly over the Chasma Boreale at Martian north pole|publisher=[[European Space Agency]]|accessdate=2006-11-01}}</ref><ref name=usgs>{{cite web|url=http://pubs.usgs.gov/sim/2005/2888/sim2888pamphlet.pdf|accessdate=2006-01-11|title=Geologic Map of the Northern Plains of Mars|publisher=[[United States Geological Survey]]}}</ref> By comparison, the [[Grand Canyon]] is approximately {{convert|1.6|km}} deep in some places and {{convert|446|km}} long but only up to {{convert|24|km}} wide. Chasma Boreale cuts through polar deposits and ice, such as those present at [[Greenland]].
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| Planum Boreum interfaces with Vastitas Borealis west of Chasma Boreale at an irregular scarp named [[Rupes Tenuis]]. This scarp reaches heights of up to 1 km. At other places, the interface is a collection of mesas and troughs.
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| Planum Boreum is surrounded by large fields of [[sand dune]]s spanning from 75°N to 85°N. These dune fields are named [[Olympia Undae]], [[Abalos Undae]] and [[Hyperboreae Undae]]. Olympia Undae, by far the largest, covers from 100°E to 240°E. Abalos Undae covers from 261°E to 280°E and Hyperboreale Undae spans from 311°E to 341°E.<ref>{{cite web|url=http://planetarynames.wr.usgs.gov/jsp/AdvanceSearch2.jsp?system=ALL&system=ALL&fname=undae&ft=ALL&diamgt=&diamlt=&nlat=&slat=&wlon=&elon=&lonDirection=null&adb=&ade=&as=ANY&cont=ðn=&refN=&refT=&quad=&map=&QuickSearch=true&sort=AP| title=USGS Astro: Search Planetary Nomenclature|accessdate=2006-11-01}}</ref> See also [[List of extraterrestrial dune fields]].
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| ==Avalanches==
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| [[Image:Mars avalanche Feb 19.jpg|thumb|200px|left|False color view of a Martian [[avalanche]].]]
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| A February 2008 HiRISE observation captured four [[avalanche]]s in progress off a {{convert|700|m}} cliff. The cloud of fine material is {{convert|180|m}} across and extends {{convert|190|m}} from the base of the cliff. The reddish layers are known to be rock rich in water ice while the white layers are seasonal carbon dioxide frost. The landslide is thought to have originated from the uppermost red layer. Follow-up observations are planned to characterize the nature of the landslide debris.<ref>{{cite web|url=http://www.sciam.com/gallery_directory.cfm?photo_id=7B82B079-C057-F0CF-D15B555DBA34B1CF|publisher=[[Scientific American]]|date=2008-03-04|accessdate=2008-03-05|title=Avalanche on Mars}}</ref><ref>{{cite web|url=http://www.jpl.nasa.gov/news/news.cfm?release=2008-036|accessdate=2008-03-05|date=2008-03-03|title=NASA Spacecraft Photographs Avalanches on Mars}}</ref>
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| ==Repeating annular cloud==
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| [[Image:Mars cyclone.jpg|thumb|right|Hubble view of the colossal polar cloud on Mars]]
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| A large doughnut shaped cloud appears in North polar region of Mars around the same time every Martian year and of about the same size.<ref name=mgs>[http://mpfwww.jpl.nasa.gov/mgs/gallery/20050912-repeatNPWIC.html Mars Global Surveyor - "8 Year Anniversary"]</ref> It forms in the morning, dissipates by the Martian afternoon.<ref name=mgs/> The outer diameter of the cloud is roughly {{convert|1000|mi|km|disp=flip|abbr=on}}, and the inner hole or eye is {{convert|320|km|mi|abbr=on}} across.<ref name=cornell/> The cloud is thought to be composed of water-ice,<ref name=cornell/> so it is white in color, unlike the more common dust storms.
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| It looks like a cyclonic storm, similar to hurricane, but it does not rotate.<ref name=mgs/> The cloud appears during the northern summer and at high latitude. Speculation is that this is due to unique climate conditions near the northern pole.<ref name=cornell>{{cite web | url=http://www.news.cornell.edu/releases/May99/mars.cyclone.deb.html | title=Colossal cyclone swirling near Martian north pole is observed by Cornell-led team on Hubble telescope | publisher=Cornell News | author=David Brand and Ray Villard | date=19 May 1999 | accessdate=2007-09-06}}</ref> Cyclone-like storms were first detected during the Viking orbital mapping program, but the northern annular cloud is nearly three times larger.<ref name=cornell/> The cloud has also been detected by various probes and telescopes including the [[Hubble Space Telescope|Hubble]] and [[Mars Global Surveyor]].<ref name=mgs/><ref name=cornell/>
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| When [[Hubble Space Telescope]] viewed it in 1999, it was thought to be [[cyclonic storm]]. The diameter was measured to be approximately 1750 km, and featured an "eye" 320 km in diameter.<ref>{{cite web|url=http://hubblesite.org/newscenter/archive/releases/1999/22/text/|title=Colossal Cyclone Swirls near Martian North Pole|accessdate=2006-11-01}}</ref>
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| ==See also==
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| *[[Martian polar ice caps]]
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| *[[Planum Australe]], the south polar plain
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| *[[Vastitas Borealis]]
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| ==References==
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| {{Reflist|2}}
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| ==External links==
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| *[http://www.esa.int/SPECIALS/Mars_Express/SEM8T86Y3EE_0.html Fly over the Chasma Boreale at Martian north pole] - courtesy of [[Mars Express]]
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| *[http://pubs.usgs.gov/sim/2005/2888/ Geologic Map of the Northern Plains of Mars]
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| *[http://hirise.lpl.arizona.edu/PSP_007338_2640 HiRISE image of Martian landslides]
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| *[http://hiroc.lpl.arizona.edu/images/PSP/PSP_001370_2505/ HiRISE image of permanent ice mound separated from cap]
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| *Various [[HiRISE]] images of the north polar ice cap: [http://hiroc.lpl.arizona.edu/images/PSP/PSP_001412_2650/] [http://hiroc.lpl.arizona.edu/images/PSP/PSP_001334_2645/color.html] [http://hiroc.lpl.arizona.edu/images/PSP/PSP_001513_2650/] [http://hiroc.lpl.arizona.edu/images/PSP/PSP_001406_2680/]
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| {{Mars}}
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| {{portal bar|Mars}}
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| [[Category:Plains on Mars]]
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| [[Category:Polar regions of Mars]]
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I would like to introduce myself to you, I am Andrew and my wife doesn't like it at all. For years he's been living in Mississippi and he doesn't strategy on changing it. Distributing production is where her main earnings comes from. To climb is some thing she would by no means give up.
Also visit my blog - phone psychic (his explanation)