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The [[Mars Reconnaissance Orbiter]]'s [[HiRISE]] instrument has taken many images that strongly suggest that Mars has had a rich history of water related processes. A major discovery was finding evidence of hot springs. These may have contained life and may now contain well-preserved fossils of life.
Research, in the January 2010 issue of Icarus, described strong evidence for sustained precipitation in the area around Valles Marineris.<ref name="10.1016/j.icarus.2009.04.017">{{cite journal | doi = 10.1016/j.icarus.2009.04.017 | last1 = Weitz | first1 = C. | last2 = Milliken | year = 2010 | first2 = R.E. | last3 = Grant | first3 = J.A. | last4 = McEwen | first4 = A.S. | last5 = Williams | first5 = R.M.E. | last6 = Bishop | first6 = J.L. | last7 = Thomson | first7 = B.J. | title = Mars Reconnaissance Orbiter observations of light-toned layered deposits and associated fluvial landforms on the plateaus adjacent to Valles Marineris | url = | journal = Icarus | volume = 205 | issue = | pages = 73–102 | bibcode = 2010Icar..205...73W }}</ref><ref name="sciencedirect.com"/> The types of minerals there are associated with water. Also, the high density of small branching channels indicate a great deal of precipitation because they are similar to stream channels on the Earth.
<gallery>
Image:Ius Channels.jpg|Channels near the rim of Ius Chasma, as seen by HiRISE. The pattern and high density of these channels support precipitation as the source of the water. Location is [[Coprates quadrangle]].
Image:Candor Channels.jpg|Channels in Candor plateau, as seen by HiRISE. Location is [[Coprates quadrangle]]. Click on image to see many small, branched channels which are strong evidence for sustained precipitation.
</gallery>
Some places on Mars show [[Inverted Relief]]. In these locations, a stream bed appears as a raised feature, instead of a depression. The inverted former stream channels may be caused by the deposition of large rocks or due to cementation of loose materials. In either case erosion would erode the surrounding land and consequently leave the old channel as a raised ridge because the ridge will be more resistant to erosion. Images below, taken with HiRISE show sinuous ridges that are old channels that have become inverted.<ref>{{cite web|url=http://hiroc.lpl.arizona.edu/images/PSP/diafotizo.php?ID=PSP_002279_1735 |title=HiRISE | Sinuous Ridges Near Aeolis Mensae |publisher=Hiroc.lpl.arizona.edu |date=2007-01-31 |accessdate=2010-12-19}}</ref>
In an article published in January 2010, a large group of scientists endorsed the idea of searching for life in Miyamoto Crater because of inverted stream channels and minerals that indicated the past presence of water.<ref name="ReferenceB"/><ref name="sciencedirect.com"/>
<gallery>
Image:Antoniadi Crater Stream Channels.JPG|Inverted Stream Channels in [[Antoniadi Crater]]. Location is [[Syrtis Major quadrangle]].
Image:Juventae Chasma Inverted Channels.JPG|Inverted Channels near [[Juventae Chasma]]. Channels were once regular stream channels. Scale bar is 500 meters long. Location is [[Coprates quadrangle]].
Image:Miyamoto Crater.JPG| Inverted Channel in [[Miyamoto Crater]]. Image is located in [[Margaritifer Sinus quadrangle]]. The scale bar is 500 meters long.
Image:Inverted Channel 012435.jpg|Inverted Channel with many branches in [[Syrtis Major quadrangle]].
</gallery>
Using data from [[Mars Global Surveyor]], [[Mars Odyssey]] and the [[Mars Reconnaissance Orbiter]], scientists have found widespread deposits of [[chloride minerals]]. Usually chlorides are the last minerals to come out of solution. A picture below shows some deposits within the [[Phaethontis quadrangle]]. Evidence suggests that the deposits were formed from the evaporation of mineral enriched waters. Lakes may have been scattered over large areas of the Martian surface. [[Carbonate]]s, [[sulfate]]s, and [[silica]] should precipitate out ahead of them. Sulfates and silica have been discovered by the Mars Rovers. Places with chloride minerals may have once held various life forms. Furthermore, such areas should preserve traces of ancient life.<ref>{{cite journal | doi = 10.1126/science.1150690 | last1 = Osterloo | first1 = MM | last2 = Hamilton| year = 2008 | first2 = VE | last3 = Bandfield | first3 = JL | last4 = Glotch | first4 = TD | last5 = Baldridge | first5 = AM | last6 = Christensen | first6 = PR | last7 = Tornabene | first7 = LL | last8 = Anderson | first8 = FS | title = Chloride-Bearing Materials in the Southern Highlands of Mars | url = | journal = Science | volume = 319 | issue = 5870| pages = 1651–1654 | pmid = 18356522 | bibcode=2008Sci...319.1651O}}</ref>
[[Image:Chloride deposits on Mars.JPG|right|thumb|Evidence of water from chloride deposits in [[Phaethontis quadrangle]]. Picture from HiRISE. ]]
Rocks on Mars have been found to frequently occur as layers, called strata, in many different places. [[Columbus Crater]] is one of many craters that contain layers. Rock can form layers in a variety of ways. Volcanoes, wind, or water can produce layers.<ref>{{cite web|url=http://hirise.lpl.arizona.edu?PSP_008437_1750 |title=HiRISE | High Resolution Imaging Science Experiment |publisher=Hirise.lpl.arizona.edu?psp_008437_1750 |date= |accessdate=2010-12-19}}</ref> Many places on Mars show rocks arranged in layers. Scientists are happy about finding layers on Mars since layers may have formed under large bodies of water.
Sometimes the layers display different colors. Light-toned rocks on Mars have been associated with hydraded minerals like sulfates. The [[Mars Rover]] Opportunity examined such layers close-up with several instruments. Some layers are probably made up of fine particles because they seem to break up into fine dust. In contrast, other layers break up into large boulders so they are probably much harder. [[Basalt]], a volcanic rock, is thought to form layers composed of boulders. Basalt has been identified all over Mars. Instruments on orbiting spacecraft have detected [[clay]] (also called phyllosilicates) in some layers.<ref>[http://www.jhu.edu/~gazette/21jul08/21wetmars.html ]{{dead link|date=December 2010}}</ref><ref>{{cite web|url=http://www.itv.com/news/articles/Was-there-life-on-mars-930980581.html |title=Articles | Was there life on Mars? - ITV News |publisher=Itv.com |date= |accessdate=2010-12-19}}</ref> Scientists are excited about finding hydrated minerals such as sulfates and clays on Mars because they are usually formed in the presence of water.<ref>{{cite web|url=http://themis.asu.edu/features/nilosyrtis |title=Target Zone: Nilosyrtis? | Mars Odyssey Mission THEMIS |publisher=Themis.asu.edu |date= |accessdate=2010-12-19}}</ref> Places that contain clays and/or other hydrated minerals would be good places to look for evidence of life.<ref>http://hirise.lpl.arizona.edu/PSP_004046_2080</ref>
Below are a few of the many examples of layers that have been studied with HiRISE.
<gallery>
Image:Becquerel Crater layers.JPG|[[Becquerel (Martian crater)|Becquerel Crater]] layers. Click on image to see fault. Location is [[Oxia Palus quadrangle]].
Image:Eos Chaos.jpg|Light colored layers in [[Eos Chaos]]. Location is [[Coprates quadrangle]].
Image:Columbus Crater Layers.JPG|[[Columbus Crater]] Layers. This false-color image is about 800 feet across. Some of the layers contain hydrated minerals. Location is [[Memnonia quadrangle]].
Image:Asimov Crater Layers.jpg|Layers in west slope of Asimov Crater. Location is [[Noachis quadrangle]].
Image:Asimov Layers Close-up.JPG|Close-up of layers in west slope of Asimov Crater. Shadows show the overhang. Some of the layers are much more resistant to erosion, so they stick out. Location is [[Noachis quadrangle]].
Image:Ophir Chasma Wall.JPG|[[Ophir Chasma]] Wall. Location is [[Coprates quadrangle]].
Image:Tithonium Chasma Layers.JPG|[[Tithonium Chasma]]. Location is [[Coprates quadrangle]].
Image:Juventae Chasma Layers.JPG|Layers west of [[Juventae Chasma]]. Scale bar is 500 meters long. Location is [[Coprates quadrangle]].
</gallery>
Much of the surface of Mars is covered by a thick smooth mantle that is thought to be a mixture of ice and dust.<ref name="Head, J. 2003">{{cite journal| last1= Head| first1= James W.| last2= Mustard| first2= John F.| last3= Kreslavsky| first3= Mikhail A.| last4= Milliken| first4= Ralph E.| last5= Marchant| first5= David R.| title= Recent ice ages on Mars |journal= Nature| volume= 426| issue= 6968 |pages= 797–802| year= 2003| pmid= 14685228 | doi = 10.1038/nature02114 }}</ref> This ice-rich mantle, a few yards thick, smoothes the land. But in places it displays a bumpy texture, resembling the surface of a basketball. Because there are few craters on this mantle, the mantle is relatively young. The images below, all taken with HiRISE show a variety of views of this smooth mantle.
<gallery>
Image:Niger Vallis hirise.JPG|[[Niger Vallis]] with features typical of this latitude. Chevon pattern results from movement of ice-rich material. Click on image to see chevron pattern and mantle. Location is [[Hellas quadrangle]].
Image:Ptolemaeus Crater Rim.JPG|[[Ptolemaeus Crater]] Rim. Click on image to see excellent view of mantle deposit. Location is [[Phaethontis quadrangle]].
Image:Atlantis Chaos.JPG|[[Atlantis Chaos]]. Click on image to see mantle covering and possible gullies. The two images are different parts of the original image. They have different scales. Location is [[Phaethontis quadrangle]].
Image:Dissected Mantle.JPG|Dissected Mantle with layers. Location is [[Noachis quadrangle]].
Image:Layered mantle in Icaria Planum.JPG|Layers in mantle deposit, as seen by HiRISE, under the [[HiWish program]]. Mantle was probably formed from snow and dust falling during a different climate. Location is [[Thaumasia quadrangle]].
</gallery>
Changes in Mars's orbit and tilt cause significant changes in the distribution of water ice from polar regions down to latitudes equivalent to Texas. During certain climate periods water vapor leaves polar ice and enters the atmosphere. The water returns to the ground at lower latitudes as deposits of frost or snow mixed generously with dust. The atmosphere of Mars contains a great deal of fine dust particles.<ref>Head, J. et al. 2008. Formation of gullies on Mars: Link to recent climate history and insolation microenvironments implicate surface water flow origin. PNAS: 105. 13258-13263.</ref> Water vapor condenses on the particles, then they fall down to the ground due to the additional weight of the water coating. When ice at the top of the mantling layer goes back into the atmosphere, it leaves behind dust, which insulates the remaining ice.<ref name="sciencedaily.com"/>
HiRISE has carried out many observations of gullies that are assumed to have been caused by recent flows of liquid water. Many gullies are imaged over and over to see if any changes occur. Some repeat observations of gullies have displayed changes that some scientists argue were caused by liquid water over the period of just a few years.<ref>{{cite journal | doi = 10.1126/science.1135156 | last1 = Malin | first1 = M. | last2 = Edgett | year = 2006 | first2 = KS | last3 = Posiolova | first3 = LV | last4 = McColley | first4 = SM | last5 = Dobrea | first5 = EZ | title = Present-day impact cratering rate and contemporary gully activity on Mars | url = | journal = Science | volume = 314 | issue = 5805| pages = 1573–1577 | pmid = 17158321 |bibcode = 2006Sci...314.1573M }}</ref> Others say the flows were merely dry flows.<ref>{{cite journal | doi = 10.1016/j.icarus.2009.09.009 | last1 = Kolb | first1 = K. | last2 = Pelletier | year = 2010 | first2 = Jon D. | last3 = McEwen | first3 = Alfred S. | title = Modeling the formation of bright slope deposits associated with gullies in Hale Crater, Mars: Implications for recent liquid water | url = | journal = Icarus | volume = 205 | issue = | pages = 113–137 |bibcode = 2010Icar..205..113K }}</ref> These were first discovered by the Mars Global Surveyor.
Alternate theories for the creation of surface gullies and channels include wind erosion,<ref name=Leovy>{{cite journal | last1 = Leovy | first1 = C.B. | year = 1999 | title = Wind and climate on Mars | url = | journal = Science | volume = 284 | issue =5422 | page =1891 | doi = 10.1126/science.284.5422.1891a }}</ref> liquid carbon dioxide,<ref name=ReadandLewis /> and liquid methane.<ref name=Tang>{{cite journal | last1 = Tang | first1 = Y. | last2 = Chen | first2 = Q. | last3 = Huang | first3 = Y. | author-separator =, | author-name-separator= | year = 2006 | title = Early Mars may have had a methanol ocean | url = | journal = Icarus | volume = 181 | issue = | pages = 88–92 | doi = 10.1016/j.icarus.2005.09.013 | bibcode = 2006Icar..180...88T }}</ref>
Below are some of the many hundreds of gullies that have been studied with HiRISE.
<gallery>
Image:Crater wall inside Mariner Crater.JPG|Crater wall inside [[Mariner Crater]] showing a large group of gullies.
Image:Charitum Montes Gullies.JPG|[[Charitum Montes]] Gullies. Image located in [[Argyre quadrangle]].
Image:Jezza Crater.JPG|[[Jezza Crater]],as seen by HiRISE. North wall (at top) has gullies. Dark lines are dust devil tracks. Scale bar is 500 meters long. Image located in [[Argyre quadrangle]].
Image:Lohse Crater.JPG|[[Lohse Crater]] Gullies on Central Peak. Image located in [[Argyre quadrangle]].
Image:Green Crater Gullies.jpg|Gullies in [[Green Crater]].
Image:Close-up of Green Crater Gullies.JPG|Close-up of gullies in Green Crater. Image located in [[Argyre quadrangle]].
Image:Scalloped Terrain at Peneus Patera.JPG|Scalloped Terrain at [[Peneus Patera]]. Scalloped terrain is quite common in some areas of Mars.
Image:Maunder Crater.JPG|[[Maunder Crater]]. The overhang is part of the degraded south (toward bottom) wall of crater. The scale bar is 500 meters long.
Image:Asimov Crater.jpg|[[Asimov Crater]]. Bottom of picture shows southeastern wall of crater. Top of picture is edge of mound that fills most of the crater.
Image:Close-up of Asimov Crater.JPG|Gullies on mound in Asimov Crater. Location is [[Noachis quadrangle]].
Image:Gullies in trough and crater.jpg|Gullies in a trough and nearby crater, as seen by HiRISE under the [[HiWish program]]. Scale bar is 500 meters long. Location is [[Phaethontis quadrangle]].
Image:Gullies in crater under HiWish.JPG|Close-up of gullies in crater, as seen by HiRISE under the HiWish program. Location is [[Phaethontis quadrangle]].
Image:Gullies in trough.JPG|Close-up of gullies in trough, as seen by HiRISE under the HiWish program. These are some of the smaller gullies visible on Mars. Location is [[Phaethontis quadrangle]].
Image:Close up view of gullies.jpg|Gullies in [[Phaethontis quadrangle]]. Notice how channels curve around obstacles.
Image:Branched gullies.jpg|Gullies with branches in [[Phaethontis quadrangle]].
Image:ESP_020012gulliescropped.jpg|Gullies near Newton Crater, as seen by HiRISE, under the [[HiWish program]]. Place where there was an old glacier is labeled. Image from Phaethontis quadrangle.
Image:ESP_020330gulliesandmantlelayers.jpg|HiRISE image showing gullies. The scale bar is 500 meters. Picture taken under the [[HiWish program]]. Image from the [[Eridania quadrangle]].
</gallery>
Of interest from the days of the [[Viking]] Orbiters are piles of material surrounding cliffs. These deposits of rock debris are called '''lobate debris aprons''' (LDAs). These features have a convex topography and a gentle slope from cliffs or escarpments; this suggests flow away from the steep source cliff. In addition, lobate debris aprons can show surface lineations just as rock glaciers on the Earth.<ref name="Kieffer1992">{{cite book|author=Hugh H. Kieffer|title=Mars|url=http://books.google.com/books?id=NoDvAAAAMAAJ|accessdate=7 March 2011|year=1992|publisher=University of Arizona Press|isbn=9780816512577}}</ref> Recently, research with the Shallow Radar on the [[Mars Reconnaissance Orbiter]] has provided strong evidence that the LDAs in [[Hellas Planitia]] and in mid northern latitudes are [[glacier]]s that are covered with a thin layer of rocks. Radar from the Mars Reconnaissance Orbiter gave a strong reflection from the top and base of LDAs, meaning that pure water ice made up the balk of the formation (between the two reflections).<ref name="Holt, J. 2008" /><ref name="planetary.brown.edu"/> Based on the experiments of the [[Phoenix lander]] and the studies of the [[Mars Odyssey]] from orbit, frozen water is now know to exist a just under the surface of Mars in the far north and south (high latitudes). The discovery of water ice in LDA's demonstrates that water is found at even lower latitudes. Future colonists on Mars will be able to tap into these ice deposits, instead of having to travel to much higher latitudes. Another major advantage of LDA's over other sources of Martian water is that they can easily detected and mapped from orbit. Lobate Debris Aprons are shown below from the Phlegra Montes which are at a latitude of 38.2 degrees north. The Phoenix lander set down at about 68 degrees north latitude, so the discovery of water ice in LDA's greatly expands the range of easily available on Mars.<ref>[http://www.planetary.org/explore/topics/phoenix ]{{dead link|date=December 2010}}</ref> It is far easier to land a spaceship near the equator of Mars, so the closer water is available to the equator the better it will be for future colonists.
Below are examples of Lobate Debris Aprons that were studied with HiRISE.
<gallery>
Image:Lobate Debris Apron in Phlegra Montes.JPG|[[Lobate Debris Apron]] in [[Phlegra Montes]], [[Cebrenia quadrangle]]. The debris apron is probably mostly ice with a thin covering of rock debris, so it could be a source of water for future Martian colonists. Scale bar is 500 meters long.
Image:Lobate Debris Apron closeup.jpg|Close-up of surface of a Lobate Debris Apron. Note the lines that are common in rock glaciers on the Earth. Image located in [[Hellas quadrangle]].
Image:Wide view of Debris Apron.jpg|View of Lobate Debris Apron along a slope. Image located in [[Arcadia quadrangle]].
Image:Face of Lobate Debris Apron.jpg|Place where a lobate debris apron begins. Note stripes which indicates movement. Image located in [[Ismenius Lacus quadrangle]].
</gallery>
[[Image:Ice exposed by impact.jpg|right|thumb|Bright part is water ice that has been exposed by impact. The ice was identified using CRISM on the MRO. Location is [[Cebrenia quadrangle]]. ]]
Research, reported in the journal Science in September 2009,<ref>{{cite journal | last1 = Byrne | pmid = 19779195 | year = 2009 | first1 = S | last2 = Dundas | first2 = CM | last3 = Kennedy | first3 = MR | last4 = Mellon | first4 = MT | last5 = McEwen | first5 = AS | last6 = Cull | first6 = SC | last7 = Daubar | first7 = IJ | last8 = Shean | first8 = DE | last9 = Seelos | first9 = KD | title = Distribution of mid-latitude ground ice on Mars from new impact craters. | journal = Science | volume = 325 | issue = 5948 | pages=1674–1676 | doi = 10.1126/science.1175307 | bibcode = 2009Sci...325.1674B }}</ref> demonstrated that some new craters on Mars show exposed, pure, water ice. After a time, the ice disappears, evaporating into the atomsphere. The ice is only a few feet deep. The ice was confirmed with the Compact Imaging Spectrometer (CRISM) onboard the [[Mars Reconnaissance Orbiter]] (MRO). The ice was found in a total of 5 locations. Three of the locations are in the [[Cebrenia quadrangle]]. These locations are 55.57° N, 150.62° E; 43.28° N, 176.9° E; and 45° N, 164.5° E. Two others are in the [[Diacria quadrangle]]: 46.7° N, 176.8° E and 46.33° N, 176.9° E.<ref>{{cite web|url=http://www.space.com/scienceastronomy/090924-mars-crater-ice.html |title=Water Ice Exposed in Mars Craters |publisher=SPACE.com |date= |accessdate=2010-12-19}}</ref><ref>[http://news.aol.com/article/nasa-spacecraft-sees-ice-on-mars-exposed/686020 ]{{dead link|date=December 2010}}</ref><ref>http://nasa.gov/mission/MRO/news/mro20090924.html</ref>
This discovery proves that future colonists on Mars will be able to obtain water from a wide variety of locations. The ice can be dug up, melted, then taken apart to provide fresh [[oxygen]] and [[hydrogen]] for rocket fuel. Hydrogen is the powerful fuel used by the [[space shuttle]] main engines.
{{Clear}}
==Tham khảo==
{{Commonscat|Water on Mars}}
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