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Water on Mars 1 Water on Mars An artist's impression of what ancient Mars may have looked like, based on geological data Water on Mars exists almost exclusively as water ice. The Martian polar ice caps consist primarily of water ice, and further ice is contained in Martian surface rocks at more temperate latitudes (permafrost). A small amount of water vapor is present in the atmosphere. [1] There are no bodies of liquid water on the Martian surface. Current conditions on the planet surface do not support the long-term existence of liquid water. The average atmospheric pressure and temperature are far too low, leading to immediate freezing and resulting sublimation. Despite this, research suggests that in the past there was liquid water flowing on the surface, [2][3] creating large areas similar to Earth's oceans. [4][5][6][7] There are a number [8] of direct and indirect proofs of water's presence either on or under the surface, e.g. stream beds, [9][10][11] polar caps, spectroscopic measurement, [12] eroded craters or minerals directly connected to the existence of liquid water (such as goethite), grey, crystalline hematite, phyllosilicates, opal, [13] and sulfate. [14][15] With the improved cameras on advanced Mars orbiters such as Viking, Mars Odyssey, Mars Global Surveyor, Mars Express, and the Mars Reconnaissance Orbiter pictures of ancient lakes, [16][17][18][19][20][20][21][22] ancient river valleys, [9][23] and widespread glaciation [24][25][26][27][28] have accumulated. Besides the visual confirmation of water from a huge collection of images, an orbiting Gamma Ray Spectrometer found ice just under the surface of much of the planet. [29][30] Also, radar studies discovered pure ice in formations that were thought to be glaciers. [31][32][33][34][35][36] The Phoenix lander exposed ice as it landed, watched chunks of ice disappear, [37][38][39] detected snow falling, [40] and even saw drops of liquid water. [41][42][43] Today, it is generally believed that Mars had abundant water very early in its history [44] during which snow and rain fell on the planet and created rivers, lakes, and possibly oceans. [45][46][47] Large clay deposits were produced. Life may even have come into existence. Large areas of liquid water have disappeared, but climate changes have frequently deposited large amounts of water-rich materials in mid-latitudes. [48][49][50][51] From these materials, glaciers and other forms of frozen ground came to be. Small amounts of water probably melt on steep slopes from time to time and produce gullies. [52][53] Recent images have also detected yearly changes on some slopes that may have been caused by liquid water. [54][55] Although Mars is very cold at present, water could exist as a liquid if it contains salts. [56] Salt is expected to be on the Martian surface. [57] Details of how water has been discovered can be found in the sections that follow on the various orbiting and landing robots that have been sent to Mars. In addition, many bits and pieces of indirect evidence are listed here. Since several missions (Mars Odyssey, Mars Global Surveyor, Mars Reconnaissance Orbiter, Mars Express, Mars Opportunity Rover and Mars Curiosity Rover) are still sending back data from the Red Planet, discoveries continue to be made. One recent discovery, announced by NASA scientists on September 27, 2012, is that the Curiosity Rover found evidence for an ancient streambed suggesting a "vigorous flow" of water on Mars. [][][]

Water on Mars

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Page 1: Water on Mars

Water on Mars 1

Water on Mars

An artist's impression of what ancient Mars mayhave looked like, based on geological data

Water on Mars exists almost exclusively as water ice. The Martianpolar ice caps consist primarily of water ice, and further ice iscontained in Martian surface rocks at more temperate latitudes(permafrost). A small amount of water vapor is present in theatmosphere.[1] There are no bodies of liquid water on the Martiansurface.

Current conditions on the planet surface do not support the long-termexistence of liquid water. The average atmospheric pressure andtemperature are far too low, leading to immediate freezing andresulting sublimation. Despite this, research suggests that in the pastthere was liquid water flowing on the surface,[2][3] creating large areassimilar to Earth's oceans.[4][5][6][7]

There are a number[8] of direct and indirect proofs of water's presenceeither on or under the surface, e.g. stream beds,[9][10][11] polar caps,spectroscopic measurement,[12] eroded craters or minerals directly connected to the existence of liquid water (such asgoethite), grey, crystalline hematite, phyllosilicates, opal,[13] and sulfate.[14][15] With the improved cameras onadvanced Mars orbiters such as Viking, Mars Odyssey, Mars Global Surveyor, Mars Express, and the MarsReconnaissance Orbiter pictures of ancient lakes,[16][17][18][19][20][20][21][22] ancient river valleys,[9][23] andwidespread glaciation[24][25][26][27][28] have accumulated. Besides the visual confirmation of water from a hugecollection of images, an orbiting Gamma Ray Spectrometer found ice just under the surface of much of theplanet.[29][30] Also, radar studies discovered pure ice in formations that were thought to beglaciers.[31][32][33][34][35][36] The Phoenix lander exposed ice as it landed, watched chunks of ice disappear,[37][38][39]

detected snow falling,[40] and even saw drops of liquid water.[41][42][43]

Today, it is generally believed that Mars had abundant water very early in its history[44] during which snow and rainfell on the planet and created rivers, lakes, and possibly oceans.[45][46][47] Large clay deposits were produced. Lifemay even have come into existence. Large areas of liquid water have disappeared, but climate changes havefrequently deposited large amounts of water-rich materials in mid-latitudes.[48][49][50][51] From these materials,glaciers and other forms of frozen ground came to be. Small amounts of water probably melt on steep slopes fromtime to time and produce gullies.[52][53] Recent images have also detected yearly changes on some slopes that mayhave been caused by liquid water.[54][55] Although Mars is very cold at present, water could exist as a liquid if itcontains salts.[56] Salt is expected to be on the Martian surface.[57]

Details of how water has been discovered can be found in the sections that follow on the various orbiting and landingrobots that have been sent to Mars. In addition, many bits and pieces of indirect evidence are listed here. Sinceseveral missions (Mars Odyssey, Mars Global Surveyor, Mars Reconnaissance Orbiter, Mars Express, MarsOpportunity Rover and Mars Curiosity Rover) are still sending back data from the Red Planet, discoveries continueto be made. One recent discovery, announced by NASA scientists on September 27, 2012, is that the Curiosity Roverfound evidence for an ancient streambed suggesting a "vigorous flow" of water on Mars.[][][]

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Water on Mars 2

Interactive maps of MarsThe following interactive map of the planet Mars has embedded links to geographical features in addition to thenoted Rover and Lander locations. Click on the features and you will be taken to the corresponding article pages.North is at the top; Elevations: red (higher), yellow (zero), blue (lower).

Spirit Opportunity <<<<<Sojourner Viking 1 Viking 2 Phoenix Mars 3 Curiosity

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Water on Mars 3

Map of quadrangles

The following interactive map of the planet Mars is divided into the 30 quadrangles defined by the United StatesGeological Survey[58][59] The quadrangles are numbered with the prefix "MC" for "Mars Chart."[60] Click on thequadrangle and you will be taken to the corresponding article pages. North is at the top; 0°N 180°W is at the far lefton the equator. The map images were taken by the Mars Global Surveyor.

0°N 180°W0°N 0°W90°N 0°W

MC-01Mare Boreum

MC-02DiacriaMC-03ArcadiaMC-04

Mare AcidaliumMC-05

Ismenius LacusMC-06CasiusMC-07

CebreniaMC-08

Amazonis

Page 4: Water on Mars

Water on Mars 4

MC-09TharsisMC-10

Lunae PalusMC-11

Oxia PalusMC-12ArabiaMC-13

Syrtis MajorMC-14

AmenthesMC-15ElysiumMC-16

MemnoniaMC-17

PhoenicisMC-18

CopratesMC-19

MargaritiferMC-20SabaeusMC-21IapygiaMC-22

TyrrhenumMC-23AeolisMC-24

PhaethontisMC-25

ThaumasiaMC-26ArgyreMC-27NoachisMC-28HellasMC-29Eridania

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Water on Mars 5

MC-30Mare Australe

Findings from probes

Mariner 9

Meander in Scamander Vallis, as seen by Mariner9. Such images implied that large amounts of

water once flowed on the surface of Mars.

Mariner 9 imaging revealed the first direct evidence of water in theform of river beds, canyons (including the Valles Marineris, a systemof canyons over about 4,020 kilometres (2,500 mi) long), evidence ofwater erosion and deposition, weather fronts, fogs, and more.[61] Thefindings from the Mariner 9 missions underpinned the later Vikingprogram. The enormous Valles Marineris canyon system is namedafter Mariner 9 in honor of its achievements. Launched in 1971, itsmission ended the following year.

Viking program

By discovering many geological forms that are typically formed fromlarge amounts of water, Viking orbiters caused a revolution in ourideas about water on Mars. Huge river valleys were found in manyareas. They showed that floods of water broke through dams, carveddeep valleys, eroded grooves into bedrock, and traveled thousands ofkilometers.[9] Large areas in the southern hemisphere containedbranched valley networks, suggesting that rain once fell. The flanks ofsome volcanoes are believed to have been exposed to rainfall becausethey resemble those occurring on Hawaiian volcanoes.[62] Many craterslook as if the impactor fell into mud. When they were formed, ice inthe soil may have melted, turned the ground into mud, then the mud flowed across the surface.[63] Normally, materialfrom an impact goes up, then down. It does not flow across the surface, going around obstacles, as it does on someMartian craters.[12][64][65] Regions, called "Chaotic Terrain,"seemed to have quickly lost great volumes of waterwhich caused large channels to form downstream. The amount of water involved was almost unthinkable—estimatesfor some channel flows run to ten thousand times the flow of the Mississippi River.[23] Underground volcanism mayhave melted frozen ice; the water then flowed away and the ground just collapsed to leave chaotic terrain.

The images below, some of the best from the Viking orbiters, are mosaics of many small, high resolution images.

Page 6: Water on Mars

Water on Mars 6

Streamlinedislands in MajaValles suggest

that large floodsoccurred on

Mars.

Tear-drop shapedislands caused byflood waters fromMaja Vallis. The

islands are formed inthe ejecta of Lod

Crater, Bok Crater,and Gold Crater.

Large amountsof water would

have beenrequired to

carry out theerosion shownin this imageof Dromore

Crater.

Networks ofbranched channels

in Thaumasiaquadrangle arestrong evidencefor rain on Mars

in the past.

The ejectafrom ArandasCrater acted

like mudsuggestingthat large

amounts offrozen waterwere melted

by theimpact.

Channels &troughs on theflank of Alba

Patera. Some areassociated with

lava flows, othersare probably

caused by runningwater.

Frost at the Viking 2 landing site in UtopiaPlanitia

Results from Viking lander experiments strongly suggest the presenceof water in the present and in the past of Mars. All samples heated inthe gas chromatograph-mass spectrometer (GSMS) gave off water.However, the way the samples were handled prohibited an exactmeasurement of the amount of water. But, it was around 1%.[66]

General chemical analysis suggested the surface had been exposed towater in the past. Some chemicals in the soil contained sulfur andchlorine that were like those remaining after sea water evaporates.Sulfur was more concentrated in the crust on top of the soil, than in thebulk soil beneath. So it was concluded that the upper crust wascemented together with sulfates that were transported to the surfacedissolved in water. This process is common on Earth's deserts. Thesulfur may be present as sulfates of sodium, magnesium, calcium, oriron. A sulfide of iron is also possible.[67]

Using results from the chemical measurements, mineral models suggest that the soil could be a mixture of about 80%iron-rich clay, about 10% magnesium sulfate (kieserite?), about 5% carbonate (calcite), and about 5% iron oxides(hematite, magnetite, goethite?). These minerals are typical weathering products of mafic igneous rocks. Thepresence of clay, magnesium sulfate, kieserite, calcite, hematite, and goethite strongly suggest that water was once inthe area.[68] Sulfate contains chemically bound water, hence its presence suggests water was around in the past.Viking 2 found similar group of minerals. Because Viking 2 was much farther north, pictures it took in the wintershowed frost.

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Mars Global Surveyor

Map showing distribution of hematite in SinusMeridiani, as seen by TES. This data was used to

target the landing of Opportunity Rover.Hematite is usually formed in the presence of

water. Opportunity landed here and founddefinite evidence for water.

The Mars Global Surveyor's Thermal Emission Spectrometer (TES) isan instrument able to detect mineral composition on Mars. Mineralcomposition gives information on the presence or absence of water inancient times. TES identified a large (30,000 square-kilometer) area (inthe Nili Fossae formation) that contained the mineral olivine. It isthought that the ancient impact that created the Isidis basin resulted infaults that exposed the olivine. Olivine is present in many maficvolcanic rocks; in the presence of water it weathers into minerals suchas goethite, chlorite, smectite, maghemite, and hematite. The discoveryof olivine is strong evidence that parts of Mars have been extremelydry for a long time. Olivine was also discovered in many other smalloutcrops within 60 degrees north and south of the equator.[69] Olivinehas been found in the SNC (shergottite, nakhlite, and chassigny)meteorites that are generally accepted to have come from Mars.[70]

Later studies have found that olivine-rich rocks cover more than113,000 square kilometers of the Martian surface. That is 11 timeslarger than the five volcanoes on the Big Island of Hawaii.[71]

On December 6, 2006 NASA released photos of two craters called Terra Sirenum and Centauri Montes which appearto show the presence of liquid water on Mars at some point between 1999 and 2001.[72][73]

Hundreds of gullies have been discovered that were formed from liquid water, possible in recent times. These gulliesoccur on steep slopes and mostly in certain bands of latitude.[74][75][76][77][78]

Below are some examples of gullies that were photographed by Mars Global Surveyor.

Group of gullies on north wall ofcrater that lies west of the craterNewton (41.3047 degrees southlatitude, 192.89 east longitide).

Image is located in thePhaethontis quadrangle.

Gullies in a crater in Eridaniaquadrangle, north of the large

crater Kepler. Features that maybe remains of old glaciers are

present. One, to the right, has theshape of a tongue.

Gullies on one wall ofKaiser Crater. Gulliesusually are found inonly one wall of acrater. Location is

Noachis quadrangle.

Full color image of gullieson wall of Gorgonum Chaos.

Image is located in thePhaethontis quadrangle.

A few channels on Mars displayed inner channels that suggest sustained fluid flows. The most well-known is the onein Nanedi Valles. Another was found in Nirgal Vallis.[74]

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Water on Mars 8

Inner channel (near top of the image) on floor ofNanedi Valles that suggests that water flowed for

a fairly long period. Image from Lunae Palusquadrangle.

Many places on Mars show dark streaks on steep slopes, such ascrater walls. Dark slope streaks have been studied since the Marinerand Viking missions.[79] It seems that streaks start out being dark, thenthey become lighter with age. Often they originate with a small narrowspot, then widen and extend downhill for hundreds of meters. Streaksdo not seem to be associated with any particular layer of materialbecause they do not always start at a common level along a slope.Although many of the streaks appear very dark, they are only 10% orless darker than the surrounding surface. Mars Global Surveyor foundthat new streaks have formed in less than one year on Mars.

Several ideas have been advanced to explain the streaks. Some involvewater,[80] or even the growth of organisms.[81][82] The generallyaccepted explanation for the streaks is that they are formed from theavalanching of a thin layer of bright dust that is covering a darkersurface. Bright dust settles on all Martian surfaces after a period oftime.[74]

Dark streaks can be seen in the images below, as seen from MarsGlobal Surveyor.

Layers in Tikonravev Crater inArabia. Layers may form from

volcanoes, the wind, or bydeposition under water. The

craters on the left are pedestalcraters. Dark slope streaks areseen to originate from certain

layers (you may need to click onimage to see the streaks).

Tikonravev Crater floor in Arabiaquadrangle. Click on image to

see dark slope streaks and layers.

Dark streaks in Diacriaquadrangle.

Dark Streaks in Arabiaquadrangle. Crater is aboutthe size of Earth's Meteor

Crater in Arizona.

Some parts of Mars show inverted relief. This occurs when materials are deposited on the floor of a stream thenbecome resistant to erosion, perhaps by cementation. Later the area may be buried. Eventually erosion removes thecovering layer. The former streams become visible since they are resistant to erosion. Mars Global Surveyor foundseveral examples of this process.[83] Many inverted streams have been discovered in various regions of Mars,especially in the Medusae Fossae Formation,[84] Miyamoto Crater,[85] and the Juventae Plateau.[86][87]

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Water on Mars 9

Inverted Streams near Juventae Chasma, as seenby Mars Global Surveyor. These streams begin at

the top of a ridge then run together.

Mars Pathfinder

Pathfinder found temperatures varied on a diurnal cycle. It was coldestjust before sunrise (about −78 Celsius) and warmest just after Marsnoon (about −8 Celsius). These extremes occurred near the groundwhich both warmed up and cooled down fastest. At this location, thehighest temperature never reached the freezing point of water (0 °C),so Mars Pathfinder confirmed that where it landed it is too cold forliquid water to exist. However, water could exist as a liquid if it weremixed with various salts.[88]

Surface pressures varied diurnally over a 0.2 millibar range, butshowed 2 daily minimums and two daily maximums. The average dailypressure decreased from about 6.75 millibars to a low of just under 6.7millbars, corresponding to when the maximum amount of carbondioxide had condensed on the south pole. The pressure on the Earth isgenerally close to 1000 millibars, so the pressure on Mars is very low.The pressures measured by Pathfinder would not permit water or ice toexist on the surface. But, if ice were insulated with a layer of soil, itcould last a long time.[89]

Other observations were consistent with water being present in thepast. Some of the rocks at the Mars Pathfinder site leaned against eachother in a manner geologists term imbricated. It is believed strong flood waters in the past pushed the rocks arounduntil they faced away from the flow. Some pebbles were rounded, perhaps from being tumbled in a stream. Parts ofthe ground are crusty, maybe due to cementing by a fluid containing minerals.[90]

There was evidence of clouds and maybe fog.[90]

Mars OdysseyMars Odyssey found much evidence for water on Mars in the form of pictures and with a spectrometer it proved that much of the ground is loaded with ice. In July 2003, at a conference in California, it was announced that the Gamma Ray Spectrometer (GRS) on board the Mars Odyssey had discovered huge amounts of water over vast areas of Mars. Mars has enough ice just beneath the surface to fill Lake Michigan twice.[29] In both hemispheres, from 55 degrees latitude to the poles, Mars has a high density of ice just under the surface; one kilogram of soil contains about 500 g of water ice. But, close to the equator, there is only 2 to 10% of water in the soil.[30] Scientists believe that much of this water is locked up in the chemical structure of minerals, such as clay and sulfates. Previous studies with infrared spectroscopes have provided evidence of small amounts of chemically or physically bound water.[91][92] The Viking landers detected low levels of chemically bound water in the Martian soil.[66] It is believed that although the upper surface only contains a percent or so of water, ice may lie just a few feet deeper. Some areas, Arabia Terra, Amazonis quadrangle, and Elysium quadrangle contain large amounts of water.[93] Analysis of the data suggest that the southern hemisphere may have a layered structure.[94] Both of the poles showed buried ice, but the north pole had none close to it because it was covered over by seasonal carbon dioxide (dry ice). When the measurements were gathered, it was winter at the north pole so carbon dioxide had frozen on top of the water ice.[29] There may be much more water further below the surface; the instruments aboard the Mars Odyssey are only able to study the top meter or so of soil. If all holes in the soil were filled by water, this would correspond to a global layer of water 0.5 to 1.5 km deep.[95] The Phoenix lander confirmed the initial findings of the Mars Odyssey.[96] It found ice a few inches below the surface and the ice is at least 8 inches deep. When the ice is exposed to the Martian atmosphere it slowly

Page 10: Water on Mars

Water on Mars 10

sublimates. In fact, some of the ice was exposed by the landing rockets of the craft.[97]

View underneath Phoenix lander towards southfoot pad, showing patchy exposures of a brightsurface that was later proven to be water ice, as

predicted by theory and detected by MarsOdyssey.

Thousands of images returned from Odyssey support the idea thatMars once had great amounts of water flowing across its surface. Somepictures show patterns of branching valleys. Others show layers thatmay have formed under lakes. Deltas have been identified.[16] Formany years researchers believed that glaciers existed under a layer ofinsulating rocks.[98][99][100][101][102] Lineated valley fill is one exampleof these rock-covered glaciers. They are found on the floors of somechannels. Their surfaces have ridged and grooved materials that deflectaround obstacles. Some glaciers on the Earth show such features.Lineated floor deposits may be related to Lobate debris aprons, whichhave been proven to contain large amounts of ice by orbitingradar.[101][102][103] The pictures below, taken with the THEMIS instrument on board the Mars Odyssey, showexamples of features that are associated with water present in the present or past.[104]

Reull Vallis with lineated floordeposits. Click on image to seerelationship to other features.

Floor deposits are believed to beformed from ice movement.

Location is Hellas quadrangle.

Auqakuh Vallis. At one time adark layer covered the wholearea, now only a few pieces

remain as buttes. Click on imageto see layers. Layers may haveformed from deposition on the

bottom of lakes.

Channelsnear

WarregoValles.These

branchedchannels

arestrong

evidencefor

flowingwater on

Mars,perhapsduring a

muchwarmerperiod.

Semeykin Crater Drainage.Click on image to see detailsof beautiful drainage system.Location is Ismenius Lacus

quadrangle.

Page 11: Water on Mars

Water on Mars 11

Erosion features inAres Vallis – thestreamlined shape

was probablyformed by running

water.

Delta in Lunae Palus quadrangle. Athabasca Vallesshowing source ofits water, Cerberus

Fossae. Notestreamlined islands

which showdirection of flow tosouth. AthabascaValles is in the

Elysium quadrangle.

Branchingchannels

on floor ofMelas

Chasma.Image is inCoprates

quadrangle.

Dao Vallis, as seen by THEMIS. Click on image to see relationship of Dao Vallis to othernearby features

Dao Vallis begins near a large volcano, called Hadriaca Patera, so it is thought to have received water when hotmagma melted huge amounts of ice in the frozen ground. The partially circular depressions on the left side of thechannel in the image above suggests that groundwater sapping also contributed water.[105] In some areas large rivervalleys begin with a landscape feature called "Chaos" or Chaotic Terrain." It is thought that the ground collapsed, ashuge amounts of water were suddenly released. Examples of Chaotic terrain, as imaged by THEMIS, are shownbelow.

Page 12: Water on Mars

Water on Mars 12

Blocks in Aram showing possible source of water. The groundcollapsed when large amounts of water were released. The large blocks

probably still contain some water ice. Location is Oxia Palusquadrangle.

Huge canyons in Aureum Chaos. Click on image to seethe gullies which may have formed from recent flows of

water. Gullies are rare at this latitude. Location isMargaritifer Sinus quadrangle.

PhoenixThe Phoenix lander confirmed the existence of large amounts of water ice in the northern regions of Mars.[96] Thisfinding was predicted by theory.[106] and was measured from orbit by the Mars Odyssey instruments.[30] On June 19,2008, NASA announced that dice-sized clumps of bright material in the "Dodo-Goldilocks" trench, dug by therobotic arm, had vaporized over the course of four days, strongly implying that the bright clumps were composed ofwater ice which sublimated following exposure. Even though dry ice also sublimates under the conditions present, itwould do so at a rate much faster than observed.[37][38][39]

On July 31, 2008, NASA announced that Phoenix confirmed the presence of water ice on Mars. During the initialheating cycle of a new sample, the Thermal and Evolved-Gas Analyzer's (TEGA) mass spectrometer detected watervapor when the sample temperature reached 0 °C.[107] Liquid water cannot exist on the surface of Mars with itspresent low atmospheric pressure, except at the lowest elevations for short periods.[108][109]

Results published in the journal Science after the mission ended reported that chloride, bicarbonate, magnesium,sodium potassium, calcium, and possibly sulfate were detected in the samples. Perchlorate (ClO4), a strong oxidizer,was confirmed to be in the soil. The chemical when mixed with water can greatly lower freezing points, in a mannersimilar to how salt is applied to roads to melt ice. Perchlorate may be allowing small amounts of liquid water to formon Mars today. Gullies, which are common in certain areas of Mars, may have formed from perchlorate melting iceand causing water to erode soil on steep slopes.[110]

Additionally, during 2008 and early 2009, a debate emerged within NASA over the presence of 'blobs' whichappeared on photos of the vehicle's landing struts, which have been variously described as being either waterdroplets or 'clumps of frost'.[111] Due to the lack of consensus within the Phoenix science project, the issue had notbeen raised in any NASA news conferences.[111] One scientist's view poised that the lander's thrusters splashed apocket of brine from just below the Martian surface onto the landing strut during the vehicle's landing. The saltswould then have absorbed water vapor from the air, which would have explained how they appeared to grow in sizeduring the first 44 Martian days before slowly evaporating as Mars temperature dropped.[111][112] Some images evensuggest that some of the droplets darkened, then moved and merged; this is strong physical evidence that they wereliquid.[41][42][43][113]

Page 13: Water on Mars

Water on Mars 13

Dice-sized clumps of bright materialin the enlarged "Dodo-Goldilocks"trench vanished over the course offour days, implying that they werecomposed of ice which sublimated

following exposure.[37]

Color versions of the photos showing ice sublimation, with thelower left corner of the trench enlarged in the insets in the upper

right of the images.

For about as far as the camera can see, the land is flat, but shaped into polygons between 2–3 meters in diameter andare bounded by troughs that are 20 cm to 50 cm deep. These shapes are due to ice in the soil expanding andcontracting due to major temperature changes.

Comparison between polygonsphotographed by Phoenix on

Mars...

 ... and as photographed (in false color)from Mars orbit...

 ... with patterned ground on Devon Island inthe Canadian Arctic, on Earth.

The microscope showed that the soil on top of the polygons is composed of flat particles (probably a type of clay)and rounded particles. Clay is a mineral that forms from other minerals when water is available. So, finding clayproves the existence of past water.[114] Ice is present a few inches below the surface in the middle of the polygons,and along its edges, the ice is at least 8 inches deep. When the ice is exposed to the Martian atmosphere it slowlysublimates.[115]

Snow was observed to fall from cirrus clouds. The clouds formed at a level in the atmosphere that was around −65 °C, so the clouds would have to be composed of water-ice, rather than carbon dioxide-ice (dry ice) because the temperature for forming carbon dioxide ice is much lower—less than −120 °C. As a result of mission observations, it is now believed that water ice (snow) would have accumulated later in the year at this location.[40] The highest

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Water on Mars 14

temperature measured during the mission was −19.6 °C, while the coldest was −97.7 °C. So, in this region thetemperature remained far below the freezing point (0°) of water. Bear in mind that the mission took place in the heatof the Martian summer.[116]

Interpretation of the data transmitted from the craft was published in the journal Science. As per the peer revieweddata the site had a wetter and warmer climate in the recent past. Finding calcium carbonate in the Martian soil leadsscientists to believe that the site had been wet or damp in the geological past. During seasonal or longer perioddiurnal cycles water may have been present as thin films. The tilt or obliquity of Mars changes far more than theEarth; hence times of higher humidity are probable.[117] The data also confirms the presence of the chemicalperchlorate. Perchlorate makes up a few tenths of a percent of the soil samples. Perchlorate is used as food by somebacteria on Earth.[118] Another paper claims that the previously detected snow could lead to a buildup of water ice.

Mars RoversThe Mars Rovers Spirit and Opportunity found a great deal of evidence for past water on Mars. Designed to last onlythree months, both were still operating after more than six years. Although Spirit got trapped in a sand pit,Opportunity continues to provide scientific discovery.The Spirit rover landed in what was thought to be a huge lake bed. However, the lake bed had been covered overwith lava flows, so evidence of past water was initially hard to detect. As the mission progressed and the Rovercontinued to move along the surface more and more clues to past water were found.On March 5, 2004, NASA announced that Spirit had found hints of water history on Mars in a rock dubbed"Humphrey". Dr. Raymond Arvidson, PhD, the McDonnell University Professor and chair of Earth and planetarysciences at Washington University in St. Louis, reported during a NASA press conference: "If we found this rock onEarth, we would say it is a volcanic rock that had a little fluid moving through it." In contrast to the rocks found bythe twin rover Opportunity, this one was formed from magma and then acquired bright material in small crevices,which look like crystallized minerals. If this interpretation holds true, the minerals were most likely dissolved inwater, which was either carried inside the rock or interacted with it at a later stage, after it formed.[119]

By Sol 390 (Mid-February 2005), as Spirit was advancing towards "Larry's Lookout", by driving up the hill inreverse, it investigated some targets along the way, including the soil target, "Paso Robles", which contained thehighest amount of salt found on the red planet. The soil also contained a high amount of phosphorus in itscomposition, however not nearly as high as another rock sampled by Spirit, "Wishstone". Squyres said of thediscovery, "We're still trying to work out what this means, but clearly, with this much salt around, water had a handhere".As Spirit traveled with a dead wheel in December 2007, pulling the dead wheel behind, the wheel scraped off theupper layer of the martian soil, uncovering a patch of ground that scientists say shows evidence of a pastenvironment that would have been perfect for microbial life. It is similar to areas on Earth where water or steamfrom hot springs came into contact with volcanic rocks. On Earth, these are locations that tend to teem with bacteria,said rover chief scientist Steve Squyres. "We're really excited about this," he told a meeting of the AmericanGeophysical Union (AGU). The area is extremely rich in silica – the main ingredient of window glass. Theresearchers have now concluded that the bright material must have been produced in one of two ways.[120] One:hot-spring deposits produced when water dissolved silica at one location and then carried it to another (i.e. a geyser).Two: acidic steam rising through cracks in rocks stripped them of their mineral components, leaving silica behind."The important thing is that whether it is one hypothesis or the other, the implications for the former habitability ofMars are pretty much the same," Squyres explained to BBC News. Hot water provides an environment in whichmicrobes can thrive and the precipitation of that silica entombs and preserves them. Squyres added, "You can go tohot springs and you can go to fumaroles and at either place on Earth it is teeming with life – microbial life.[121][122]

Opportunity rover was directed to a site that had displayed large amounts of hematite from orbit. Hematite often forms from water. When Opportunity landed, layered rocks and marble-like hematite concretions ("blueberries")

Page 15: Water on Mars

Water on Mars 15

were easily visible. In its years of continuous operation, Opportunity sent back much evidence that a wide area onMars was soaked in liquid water.During a press conference in March 2006, mission scientists discussed their conclusions about the bedrock, and theevidence for the presence of liquid water during their formation. They presented the following reasoning to explainthe small, elongated voids in the rock visible on the surface and after grinding into it (see last two imagesbelow).[123] These voids are consistent with features known to geologists as "vugs". These are formed when crystalsform inside a rock matrix and are later removed through erosive processes, leaving behind voids. Some of thefeatures in this picture are "disk-like", which is consistent with certain types of crystals, notably sulfate minerals.Additionally, mission members presented first data from the Mössbauer spectrometer taken at the bedrock site. Theiron spectrum obtained from the rock El Capitan shows strong evidence for the mineral jarosite. This mineralcontains hydroxide ions, which indicates the presence of water when the minerals were formed. Mini-TES data fromthe same rock showed that it consists of a considerable amount of sulfates. Sulfates also contain water.

Close up of a rockoutcrop.

Thin Rock layers, not allparallel to each other

Section of hole createdby RAT

Voids or "vugs" inside the rock

Spirit Rover found evidence for water in the Columbia Hills of Gusev crater. In the Clovis group of rocks theMossbauer spectrometer(MB) detected goethite.[124] Goethite forms only in the presence of water, so its discovery isthe first direct evidence of past water in the Columbia Hills's rocks. In addition, the MB spectra of rocks andoutcrops displayed a strong decline in olivine presence,[125] although the rocks probably once contained mucholivine.[126] Olivine is a marker for the lack of water because it easily decomposes in the presence of water. Sulfatewas found, and it needs water to form. Other rock groups also contained sulfates. One type of soil, called PasoRobles, from the Columbia Hills, may be an evaporate deposit because it contains large amounts of sulfur,phosphorus, calcium, and iron.[127] In addition, the MB found that much of the iron in Paso Robles soil was of theoxidized, Fe+++ form, which would happen if water had been present.[128]

After Spirit stopped working scientists studied old data from the Miniature Thermal Emission Spectrometer, orMini-TES and confirmed the presence of large amounts of carbonate-rich rocks, which means that regions of theplanet may have once harbored water. The carbonates were discovered in an outcrop of rocks called"Comanche."[129][130]

On September 27, 2012, NASA scientists announced that the Curiosity rover found evidence for an ancientstreambed suggesting a "vigorous flow" of water on Mars.[][][]

Page 16: Water on Mars

Water on Mars 16

Peace Vallis and related alluvial fan near the Curiosity rover landing ellipse and landing site (noted by +).

"Hottah" rock outcrop on Mars - an ancient streambed viewed by the Curiosity rover (September 14, 2012) (close-up [131]) (3-D version [132]).

"Link" rock outcrop on Mars - compared with a terrestrial fluvial conglomerate - suggesting water "vigorously" flowing in a stream.

Mars Reconnaissance OrbiterThe Mars Reconnaissance Orbiter's HiRISE instrument has taken many images that strongly suggest that Mars hashad a rich history of water-related processes. A major discovery was finding evidence of hot springs. These mayhave contained life and may now contain well-preserved fossils of life. Research, in the January 2010 issue ofIcarus, described strong evidence for sustained precipitation in the area around Valles Marineris.[86][87] The types ofminerals there are associated with water. Also, the high density of small branching channels indicates a great deal ofprecipitation because they are similar to stream channels on the Earth.

Page 17: Water on Mars

Water on Mars 17

Springs in Vernal Crater, as seen by HIRISE.These springs may be good places to look forevidence of past life because hot springs can

preserve evidence of life forms for a long time.Location is Oxia Palus quadrangle.

Channels near the rim of Ius Chasma, as seenby HiRISE. The pattern and high density ofthese channels support precipitation as thesource of the water. Location is Coprates

quadrangle.

Example of inverted terrain in ParanaValles region, as seen by HiRISE under

the HiWish program.

Inverted Stream Channels inAntoniadi Crater. Location is

Syrtis Major quadrangle.

Some places on Mars show inverted relief. In these locations, a stream bed appears as a raised feature, instead of adepression. The inverted former stream channels may be caused by the deposition of large rocks or due tocementation of loose materials. In either case erosion would erode the surrounding land and consequently leave theold channel as a raised ridge because the ridge will be more resistant to erosion. Images below, taken with HiRISEshow sinuous ridges that are old channels that have become inverted.[133]

Using data from Mars Global Surveyor, Mars Odyssey and the Mars Reconnaissance Orbiter, scientists have foundwidespread deposits of chloride minerals. Usually chlorides are the last minerals to come out of solution. A picturebelow shows some deposits within the Phaethontis quadrangle. Evidence suggests that the deposits were formedfrom the evaporation of mineral-enriched waters. Lakes may have been scattered over large areas of the Martiansurface. Carbonates, sulfates, and silica should precipitate out ahead of them. Sulfates and silica have beendiscovered by the Mars Rovers. Places with chloride minerals may have once held various life forms. Furthermore,such areas should preserve traces of ancient life.[57]

Rocks on Mars have been found to frequently occur as layers, called strata, in many different places. Layers form byvarious ways. Volcanoes, wind, or water can produce layers.[134] Many places on Mars show rocks arranged inlayers. 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 hydratedminerals like sulfates. Instruments on orbiting spacecraft have detected clay (also called phyllosilicates) in somelayers.[14] Scientists are excited about finding hydrated minerals such as sulfates and clays on Mars because they areusually formed in the presence of water.[135] Below are a few of the many examples of layers that have been studiedwith HiRISE.

Page 18: Water on Mars

Water on Mars 18

Evidence of water from chloride deposits inPhaethontis quadrangle. Picture from HiRISE.

Becquerel Crater layers.Click on image to see fault.

Location is Oxia Palusquadrangle.

Close-up of layers in west slopeof Asimov Crater. Shadows

show the overhang. Some of thelayers are much more resistant to

erosion, so they stick out.Location is Noachis quadrangle.

Dark slope streaks near the top of a pedestalcrater, as seen by HiRISE under the HiWish

program.

Much of the surface of Mars is covered by a thick smooth mantle that is thought to be a mixture of ice and dust.[136]

This ice-rich mantle, a few yards thick, smoothes the land. But in places it displays a bumpy texture, resembling thesurface of a basketball. Because there are few craters on this mantle, the mantle is relatively young. The imagesbelow, all taken with HiRISE, show a variety of views of this smooth mantle.

Niger Vallis with features typical ofthis latitude. Chevron pattern results

from movement of ice-richmaterial. Click on image to see

chevron pattern and mantle.Location is Hellas quadrangle.

Dissected Mantle with layers. Locationis Noachis quadrangle.

Layers in mantle deposit, as seen by HiRISE,under the HiWish program. Mantle was

probably formed from snow and dust fallingduring a different climate. Location is

Thaumasia quadrangle.

The mantle is thought to result from frequent, major climate changes. 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.[137] 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.[138] HiRISE has carried out many observations of gullies that

Page 19: Water on Mars

Water on Mars 19

are assumed to have been caused by recent flows of liquid water. Many gullies are imaged over and over to see ifany changes occur. Some repeat observations of gullies have displayed changes that some scientists argue werecaused by liquid water over the period of just a few years.[139] Others say the flows were merely dry flows.[140]

These were first discovered by the Mars Global Surveyor. Below are some of the many hundreds of gullies that havebeen studied with HiRISE.

Gullies near Newton Crater, asseen by HiRISE, under the

HiWish program. Place wherethere was an old glacier is

labeled. Image from Phaethontisquadrangle.

Gullies nearNewton

Crater, asseen byHiRISE

under theHiWish

Program.

Gullies in acrater in

TerraSirenum, as

seen byHiRISE

under theHiWish

Program.

Close-up of gully showingmultiple channels and

patterned ground, as seen byHiRISE under the HiWish

program.

Of interest from the days of the Viking Orbiters are piles of material surrounding cliffs. These deposits of rock debrisare called lobate debris aprons (LDAs). These features have a convex topography and a gentle slope from cliffs orescarpments; this suggests flow away from the steep source cliff. In addition, lobate debris aprons can show surfacelineations just as rock glaciers on the Earth.[12] In 2008, research with the Shallow Radar on the MarsReconnaissance Orbiter provided strong evidence that the LDAs in Hellas Planitia and in mid northern latitudes areglaciers that are covered with a thin layer of rocks. Radar from the Mars Reconnaissance Orbiter gave a strongreflection from the top and base of LDAs, meaning that pure water ice made up the bulk of the formation (betweenthe two reflections).[102][103]). The discovery of water ice in LDAs demonstrates that water is found at even lowerlatitudes. Future colonists on Mars will be able to tap into these ice deposits, instead of having to travel to muchhigher latitudes. Another major advantage of LDAs over other sources of Martian water is that they can easilydetected and mapped from orbit. Below are examples of lobate debris aprons that were studied with HiRISE.

Bright part is water ice that has been exposed byimpact. The ice was identified using CRISM on

the MRO. Location is Cebrenia quadrangle.

Page 20: Water on Mars

Water on Mars 20

View of lobate debris apron along aslope. Image located in Arcadia

quadrangle.

Place where a lobate debris apron begins. Note stripes which indicatemovement. Image located in Ismenius Lacus quadrangle.

Research, reported in the journal Science in September 2009,[141] demonstrated that some new craters on Mars showexposed, pure, water ice. After a time, the ice disappears, evaporating into the atmosphere. The ice is only a few feetdeep. The ice was confirmed with the Compact Imaging Spectrometer (CRISM) on board the Mars ReconnaissanceOrbiter (MRO). The ice was found in five locations. Three of the locations are in the Cebrenia quadrangle. Theselocations are 55.57° N, 150.62° E; 43.28° N, 176.9° E; and 45° N, 164.5° E. Two others are in the Diacriaquadrangle: 46.7° N, 176.8° E and 46.33° N, 176.9° E.[142][143][144] This discovery proves that future colonists onMars will be able to obtain water from a wide variety of locations. The ice can be dug up, melted, then taken apart toprovide fresh oxygen and hydrogen for rocket fuel. Hydrogen is the powerful fuel used by the space shuttle mainengines.

Columnar jointing

Columnar jointing in basalt, Marte Vallis

In 2009, HiRISE discovered columnar jointing in rocks on Mars.[145]

Such jointing is accepted as having involved water. To make theparallel cracks of columnar jointing, more cooling is necessary, andwater is the most logical choice. Scientists calculate that the water waspresent intermittently for a few months to a few years.[146]

Light-toned layered deposits

HiRISE has sent back many images of large surface areas that are termed "light-toned layered deposits." These30–80 meter thick deposits are believed to have been formed from the action of water. They contain evidence ofstream channel systems.[147] Furthermore, chemical data from the Compact Reconnaissance Imaging Spectrometerorbiting the planet have shown water related mineral forms: opal (hydrated silica) and iron sulfates.[148] These can beformed from the action of low temperature acid solutions reacting with basaltic rocks. These features of light-tonedlayered deposits strongly suggest that there was long lasting precipitation and surface runoff during the Hesperianepoch of Martian history.[86][149]

Page 21: Water on Mars

Water on Mars 21

Sources of Martian water

Map of the Tharsis region on Mars, whichcontains many volcanoes.

Volcanoes give off great amounts of gas when they erupt. The gasesare usually water vapor and carbon dioxide. Estimates put the amountof gas released into the atmosphere as enough to make the Martianatmosphere thicker than the Earth's. The water vapor from thevolcanoes could have made enough water to place all of Mars under120 meters of water. In addition, all the carbon dioxide released wouldhave raised the temperature of the planet due to the greenhouse effect,by trapping heat in the form of infrared radiation. So the eruption oflava on Tharsis could have made Mars Earth-like in the past. With athicker atmosphere, oceans and/or lakes may have been present.[150]

Groundwater on MarsOne group of researchers proposed that some of the layers on Mars were caused by groundwater rising to the surfacein many places, especially inside of craters. According to the hypothesis, groundwater with dissolved minerals cameto the surface, in and later around craters, and helped to form layers by adding minerals (especially sulfate) andcementing sediments. This hypothesis is supported by a groundwater model and by sulfates discovered in a widearea.[151][152] At first, by examining surface materials with Opportunity Rover, scientists discovered thatgroundwater had repeatedly risen and deposited sulfates.[123][153][154][155][156] Later studies with instruments onboard the Mars Reconnaissance Orbiter showed that the same kinds of materials exist in a large area that includedArabia.[157]

Evidence of frozen water

Ice patchesOn July 28, 2005, the European Space Agency announced the existence of a crater partially filled with frozenwater;[158] some then interpreted the discovery as an "ice lake".[159] Images of the crater, taken by the HighResolution Stereo Camera on board the European Space Agency's Mars Express spacecraft, clearly show a broadsheet of ice in the bottom of an unnamed crater located on Vastitas Borealis, a broad plain that covers much of Mars'far northern latitudes, at approximately 70.5° North and 103° East. The crater is 35 km wide and about 2 km deep.The height difference between the crater floor and the surface of the water ice is about 200 metres. ESA scientistshave attributed most of this height difference to sand dunes beneath the water ice, which are partially visible. Whilescientists do not refer to the patch as a "lake", the water ice patch is remarkable for its size and for being presentthroughout the year. Deposits of water ice and layers of frost have been found in many different locations on theplanet.

Equatorial frozen seaSurface features consistent with pack ice have been discovered in the southern Elysium Planitia.[160] What appear to be plates of broken ice, ranging in size from 30 m to 30 km, are found in channels leading to a flooded area of approximately the same depth and width as the North Sea. The plates show signs of break up and rotation that clearly distinguish them from lava plates elsewhere on the surface of Mars. The source for the flood is thought to be the nearby geological fault Cerberus Fossae which spewed water as well as lava aged some 2 to 10 million years. It was suggested that the water exited the Cerberus Fossae then pooled and froze in the low, level plains.[161] Not all

Page 22: Water on Mars

Water on Mars 22

scientists agree with these conclusions.[20][162][163]

GlaciersGlaciers formed much of the observable surface in large areas of Mars. Much of the area in high latitudes, especiallythe Ismenius Lacus quadrangle, is believed to still contain enormous amounts of water ice.[12][164] Recent evidencehas led many planetary scientists to believe that water ice still exists as glaciers with a thin covering of insulatingrock.[98][99][100][101][102][165] In March 2010, scientists released the results of a radar study of an area calledDeuteronilus Mensae that found widespread evidence of ice lying beneath a few meters of rock debris.[166] Glaciersare believed to be associated with Fretted terrain, many volcanoes,[20][167] and even some craters. Ridges of debrison the surface of the glaciers show the direction of ice movement. The surface of some glaciers has a rough texturedue to sublimation of buried ice. The ice goes directly into a gas (this process is called sublimation) and leavesbehind an empty space. Overlying material then collapses into the void.[168] Other pictures below show variousfeatures that appear to be connected with the existence of glaciers.

Gullies andpossible remains of

old glaciers in acrater in Eridaniaquadrangle, northof the large crater

Kepler. Onesuspected glacier,

to the right, has theshape of a tongue.Image was taken

by the Mars GlobalSurveyor under the

Public Targetprogram.

Glacier asseen byHiRISE

under theHiWish

program.Area in

rectangle isenlarged in

the nextphoto. Zone

ofaccumulation

of snow atthe top.

Glacier ismoving

down valley,then

spreadingout on plain.Evidence forflow comes

from themany lineson surface.Location is

in ProtonilusMensae inIsmenius

Lacusquadrangle.

Enlargement of areain rectangle of the

previous image. OnEarth, the ridge wouldbe called the terminalmoraine of an alpineglacier. Picture takenwith HiRISE under

the HiWish program.Image from Ismenius

Lacus quadrangle.

Context for the next image of theend of a flow feature or glacier.Location is Hellas quadrangle.

Picture taken with HiRISE underthe HiWish program.

Page 23: Water on Mars

Water on Mars 23

Close-up of thearea in the box in

the previous image.This may be called

by some theterminal moraine ofa glacier. For scale,the box shows the

approximate size ofa football field.

Image taken withHiRISE under theHiWish program.Location is Hellas

quadrangle.

Possible moraine on the end of apast glacier on a mound in

Deuteronilus Mensae, as seen byHiRISE, under the HiWish

program.

Possible Glacial Cirquein Hellas Planitia, as

seen by HiRISE, underthe HiWish program.

Lines are probably dueto downhill movement.

Glaciers, asseen byHiRISE,

underHiWish

program.Glacier onleft is thinbecause ithas lost

much of itsice. Glacieron the righton the other

hand is thick;it still

contains a lotof ice that isunder a thinlayer of dirtand rock.

Location isHellas

quadrangle.

Remains of glaciers,as seen by HiRISEunder the HiWish

program. Image fromIsmenius Lacus

quadrangle.

Probable glacier as seen byHiRISE under HiWish program.Radar studies have found that itis made up of almost completelypure ice. It appears to be movingfrom the high ground (a mesa) on

the right. Location is IsmeniusLacus quadrangle.

Page 24: Water on Mars

Water on Mars 24

Polar ice caps

The Mars Global Surveyor acquired this image ofthe Martian north polar ice cap in early northern

summer.

Both the northern polar cap (Planum Boreum) and the southern polarcap (Planum Australe) are believed to grow in thickness during thewinter and partially sublime during the summer. Data obtained by theMars Express satellite made it possible in 2004 to confirm that thesouthern polar cap has an average of 3 kilometres (1.9 mi) thick slab ofice[169] with varying contents of frozen water, depending on itslatitude; the polar cap is a mixture of 85% CO2 ice and 15% waterice.[170] The second part comprises steep slopes known as 'scarps',made almost entirely of water ice, that fall away from the polar cap tothe surrounding plains.[170] The third part encompasses the vastpermafrost fields that stretch for tens of kilometres away from thescarps.[170][171] NASA scientists calculate that the volume of water icein the south polar ice cap, if melted, would be sufficient to cover theentire planetary surface to a depth of 11 metres.[169]

Results, published in 2009, of shallow radar measurements of the North Polar ice cap determined that the volume ofwater ice in the cap is 821,000 cubic kilometers (197,000 cubic miles). That's equal to 30% of the Earth's Greenlandice sheet or enough to cover the surface of Mars to a depth of 5.6 meters (dividing the ice cap volume by the surfacearea of Mars is how this number is found). The radar instrument is on board the Mars Reconnaissance Orbiter.[172]

Ground iceFor many years, various scientists have suggested that some Martian surfaces look like periglacial regions onEarth.[12] Sometimes it is said that these are regions of permafrost. These observations suggest that frozen water liesright beneath the surface. A common feature in the higher latitudes, patterned ground, can occur in a number ofshapes, including stripes and polygons. On the Earth, these shapes are caused by the freezing and thawing ofsoil.[173][174] There are other types of evidence for large amounts of frozen water under the surface of Mars, such asterrain softening which rounds sharp topographical features.[175] Besides landscape features that suggest waterfrozen in the ground, there is evidence from Mars Odyssey's Gamma Ray Spectrometer, theoretical calculations, anddirect measurements with the Phoenix lander.[176]

Permafrostpolygons in the

Arctic

Flatterrain

near thenorth

pole ofMars

showingwhat

appear tobe

polygonalpatterns.

Patterned groundin the Canadian

Arctic

Patternedground on Mars

at 45 degreesnorth

Cones inAthabasca Vallesformed from lavainteracting with

ice.

These rings on Marsmay have beencaused by crust

moving over steamproduced by lavainteracting with

water ice.

Some areas of Mars are covered with cones that resemble those on Earth where lava has flowed on top of frozen ground. The heat of the lava melts the ice, then changes it into steam. The powerful force of the steam works its way

Page 25: Water on Mars

Water on Mars 25

through the lava and produces a cone. In the Athabasca Valles image above, the larger cones were made when thesteam went through the thicker layers of lava. The difference between highest elevation (red) to lowest (dark blue) is170 metres (560 ft).[177]

Scalloped topography

Stages in scallop formation in Hellas quadrangle

Certain regions of Mars display scalloped-shaped depressions. Thedepression are believed to be the remains of an ice-rich mantle deposit.Scallops were caused by ice sublimating from frozen soil. This mantlematerial probably fell from the air as ice formed on dust when theclimate was different due to changes in the tilt of the Marspole.[136][178] The scallops are typically tens of meters deep and from afew hundred to a few thousand meters across. They can be almostcircular or elongated. Some appear to have coalesced causing a largeheavily pitted terrain to form. The process of forming the terrain maybegin with sublimation from a crack. There are often polygon crackswhere scallops form. So the presence of scalloped topography is an indication of frozen ground.[87][179]

Possible evidence of flowing waterIn August 2011, NASA announced the discovery of seasonal changes in gullies near crater rims on the Southernhemisphere. This suggests salty water flowing and then evaporating, possibly leaving some sort of residue.[180]

On September 27, 2012, NASA scientists announced that the Curiosity rover found evidence for an ancientstreambed suggesting a "vigorous flow" of water on Mars.[][][]. In particular, analysis of an ancient streambedindicated that the water ran quickly, possibly at hip depth. The discovery marks an important achievement forCuriosity, and supports the notion that Mars was once capable of harboring life.Remnants of the now dried-up stream were found inside the Gale Crater within which Curiosity is working. Proof ofrunning water came in the form of rounded pebbles and gravel fragments that could have only been weathered bystrong currents. Their shape and orientation suggests long-distance transport from above the rim of the crater, wherea channel named Peace Vallis feeds into the alluvial fan. Because there are many channels like this, NASA scientistsbelieve the flows were continuous or repeated for long durations, and not intermittent."From the size of gravels it carried, we can interpret the water was moving about 3 feet per second, with a depthsomewhere between ankle and hip deep," noted Curiosity scientist William Dietrich speaking through NASA'sofficial release. "Plenty of papers have been written about channels on Mars with many different hypotheses aboutthe flows in them. This is the first time we're actually seeing water-transported gravel on Mars. This is a transitionfrom speculation about the size of streambed material to direct observation of it."

Page 26: Water on Mars

Water on Mars 26

Mars meteorites

Mars meteorite ALH84001

Over thirty meteorites have been found that came from Mars.Some of them contain evidence that they were exposed to waterwhen on Mars.Some Mars meteorites called basaltic shergottites, appear (fromthe presence of hydrated carbonates and sulfates) to have beenexposed to liquid water prior to injection into space.[181]

It has been shown that another class of meteorites, the nakhlites,were suffused with liquid water around 620 million years ago andthat they were ejected from Mars around 10.75 million years agoby an asteroid impact. They fell to Earth within the last 10,000years.[182]

In 1996, a group of scientists reported on chemical fossils in Allan Hills 84001, a meteorite from Mars.[183] Manystudies disputed the validity of the fossils.[184][185] It was found that most of the organic matter in the meteorite wasof terrestrial origin.[186]

LakesA variety of lake basins have been discovered on Mars.[187] Some are comparable in size to the largest lakes onEarth, such as the Caspian Sea, Black Sea, and Lake Baikal. Lakes that are fed by valley networks are found in thesouthern highlands. There are places that are closed depressions with river valleys leading into them. These areas arethought to have once contained lakes. One is in Terra Sirenum which had its overflow move through Ma'adim Vallisinto Gusev Crater, which was explored by the Mars Exploration Rover Spirit. Another is near Parana Valles andLoire Vallis.[188] Some lakes are believed to have formed by precipitation, while others were formed fromgroundwater.[16][17] Lakes are believed to have existed in the Argyre basin,[18][19] the Hellas basin,[20][21] and maybein Valles Marineris.[20][22][189][190]

Research, published in January 2010, suggests that Mars had lakes, each around 20 km wide, along parts of theequator. Although earlier research showed that Mars had a warm and wet early history that has long since dried up,these lakes existed in the Hesperian Epoch, a much earlier period. Using detailed images from NASA's MarsReconnaissance Orbiter, the researchers speculate that there may have been increased volcanic activity, meteoriteimpacts or shifts in Mars' orbit during this period to warm Mars' atmosphere enough to melt the abundant ice presentin the ground. Volcanoes would have released gases that thickened the atmosphere for a temporary period, trappingmore sunlight and making it warm enough for liquid water to exist. In this new study, channels were discovered thatconnected lake basins near Ares Vallis. When one lake filled up, its waters overflowed the banks and carved thechannels to a lower area where another lake would form.[191][192] These lakes would be another place to look forevidence of present or past life.

Page 27: Water on Mars

Water on Mars 27

Lake deltasResearchers have found a number of examples of deltas that formed in Martian lakes.[193] Finding deltas is a majorsign that Mars once had a lot of water. Deltas usually require deep water over a long period of time to form. Also,the water level needs to be stable to keep sediment from washing away. Deltas have been found over a widegeographical range and several are pictured below.[16]

Delta in Ismenius Lacusquadrangle

Delta in Lunae Palusquadrangle

Delta in Margaritifer Sinusquadrangle

Probable delta inEberswalde crater

Mars Ocean HypothesisThe Mars Ocean Hypothesis states that nearly a third of the surface of Mars was covered by an ocean of liquid waterearly in the planet’s geologic history.[194] [195] This primordial ocean, dubbed Oceanus Borealis,[196] would havefilled the Vastitas Borealis basin in the northern hemisphere, a region which lies 4–5 km (2.5–3 miles) below themean planetary elevation, at a time period of approximately 3.8 billion years ago. Early Mars would require awarmer climate and thicker atmosphere to allow liquid water to remain at the surface.[197]

Observational evidenceThere are several physical features in the present geography of Mars that suggest the existence of an ocean.Networks of valleys that merge into larger channels imply erosion by a liquid agent, and resemble ancient riverbedson Earth. Enormous channels, 25 km wide and several hundred meters deep, appear to direct flow from undergroundaquifers in the Southern uplands into the Northern plains.[197]

Research published in the Journal of Geophysical Research – Planets, shows a much higher density of flow pathsthan formerly believed (more than twice as many). Regions on Mars with the most valleys are comparable to what isfound on our Earth. In the research, the team developed a computer program to identify valleys by searching forU-shaped structures in topographical data.[198] The large amount of valley networks strongly supports rain on theplanet in the past. The global pattern of the martian valleys could be explained with a big northern ocean. A largeocean in the northern hemisphere would explain why there is a southern limit to valley networks; the southernmostregions of Mars, located farthest from the water reservoir, would get little rainfall and would not develop valleys. Ina similar fashion the lack of rainfall would explain why Martian valleys become shallower as you go from north tosouth.[199]

Much of the northern hemisphere of Mars is located at a significantly lower elevation than the rest of the planet (theMartian dichotomy), and is unusually flat. Along the margins of this region are physical features indicative ofancient shorelines.[196] Sea level must follow a line of constant gravitational potential. After adjustment for polarwander caused by mass redistributions from volcanism, the Martian paleo-shorelines meet this criterion.[200] TheMars Orbiter Laser Altimeter (MOLA), which accurately determined the altitude of all parts of Mars, found that thewatershed for an ocean on Mars covers three-quarters of the planet.[201]

A study, published in Nature, in June 2010 concluded that an Ocean covered 36% of Mars. The study was based ondozens of deltas that were at the same elevation.[193][202]

Although phyllosilicates, i.e. clay, have been observed on Mars, the northern lowlands are known to show only few such abundances in early geological layers, a fact that has so far contradicted the theory of a northern ocean on Mars. A 2011 numerical simulation study found though that an ocean of water on the northern hemisphere would have had

Page 28: Water on Mars

Water on Mars 28

a temperature near the freezing point "which would have hindered the formation of phyllosilicate minerals in theocean basin" and would therefore explain the relative absence of clay minerals on the northern hemisphere.[203]

Theoretical issuesThe existence of liquid water on the surface of Mars requires both a warmer and thicker atmosphere. Atmosphericpressure on the present day Martian surface only exceeds that of the triple point of water (6.11 hPa) in the lowestelevations; at higher elevations water can exist only in solid or vapor form. Annual mean temperatures at the surfaceare currently less than 210 K, significantly less than what is needed to sustain liquid water. However, early in itshistory Mars may have had conditions more conducive to retaining liquid water at the surface.Calculations of the volume of one of the supposed oceans yielded a number that would mean that Mars was coveredwith as much water as the Earth.The water that was in this ocean may have escaped into space, been deposited in the ice caps, or have been trapped inthe soil.[7]

Alternative ideasThe existence of a primordial Martian ocean remains controversial among scientists.[204] The Mars ReconnaissanceOrbiter's High Resolution Imaging Science Experiment has discovered large boulders on the site of the ancientseabed, which should contain only fine sediment.[205] The interpretations of some features as ancient shorelines hasbeen challenged. Some have been shown to be of volcanic origin.[7]

Possibility of Mars having enough water to support lifeLife is generally understood to require liquid water. Some evidence suggests that Mars had enough water to formlakes and to carve huge river valleys.[206][207] Vast quantities of water have been discovered frozen beneath much ofthe Martian surface. Nevertheless, many significant issues remain.• History. When did the water once flow on Mars?[208][209][210] Mars areas have been extremely dry for long

periods, as marked by the presence of olivine that would be decomposed by water.[211] On the other hand, manyother areas contain clay and/or sulfates, which indicate the presence of liquid water on the surface.[212]

• Sulfates. While the presence of sulfates bolsters the case for surface water, they present problems of their own.Sulfates form under acid conditions.[213] On Earth some organisms can survive in acidic environment, butquestions remain about the possibility of life forming under such conditions.[214][215] Even allowing foradaptation to acidic environments, could life actually originate in acidic waters?[216] On the other hand,carbonates, which do not form in acid solutions, have been found in Martian meteorites by the Phoenix lander andby the Compact Reconnaissance Imaging Spectrometer, an instrument aboard the NASA Mars ReconnaissanceOrbiter.[217]

• Salts. The saltiness of the soil could be a major obstacle for life.[218] Salt has been used by the human race as amajor preservative since most organisms can not live in highly salted water (halophile bacteria being anexception).[219]

• Oxidizers. The Phoenix mission discovered perchlorate, a highly oxidizing chemical in the soil. Although someorganisms use perchlorate, the chemical could be hostile to life. Other research from different sources show thatsome areas of Mars may not be that hostile to life.[220][221]

Benton Clark III, a member of the Mars Exploration Rover (MER) team, surmises that Martian organisms could be adapted to a sort of suspended animation for millions of years.[222] Indeed, some organisms can endure extreme environments for a time. Measurements performed on Earth under 50 meters of permafrost, showed that half of the microorganisms would accumulate enough radiation from radioactive decay in rocks to die in 10 million years, but if organisms come back to life every few million years they could repair themselves and reset any damaged systems,

Page 29: Water on Mars

Water on Mars 29

especially DNA.[223][224] Other scientists are in agreement.The discovery of organisms living in extreme conditions on Earth has brought renewed hope that life exists, or onceexisted on Mars.[225][226][227] Colonies of microbes have been found beneath almost 3 kilometers of glaciers in theCanadian Arctic and in Antarctica.[228] Could microbes live under the ice caps of Mars? In the 1980s, it was thoughtthat microorganisms might live up to a depth of a few meters under ground.[229] Today, we know that a wide varietyof organisms grow to a depth of over a mile. Some live on gases like methane, hydrogen, and hydrogen sulfide thatoriginate from volcanic activity. Mars has had widespread volcanic activity.[230] It is entirely possible that life existsnear volcanoes or underground reservoirs of hot magma.[231] Some organisms live inside of basalt (the mostcommon rock on Mars) and produce methane. Methane has been tracked on Mars.[232] Some believe there must besome (possibly biological) mechanism that is producing methane since it will not last long in the present atmosphereof Mars.[233] Other organisms eat sulfur compounds; the same chemicals that have been found in many regions ofMars. Scientists have suggested that whole communities of organisms could thrive near areas heated by volcanicactivity. Studies have shown that certain forms of life have adapted to extremely high temperatures (80° to 110°C).[234] With all the volcanic activity on Mars, one would suppose that certain places have not yet cooled down.[235]

An underground magma chamber might melt ice, then circulate water through the ground. Remains of hot springslike the ones in Yellowstone National Park have actually been spotted by the Mars Reconnaissance Orbiter.[236][237]

Minerals accociated with hot springs, such as opal and silica have been studied on the ground by Spirit Rover andmapped from orbit by the Mars Reconnaissance Orbiter.[212] Some volcanoes, like Olympus Mons, seem relativelyyoung to the eyes of a geologist. However, no warm areas have ever been found on the surface. The Mars GlobalSurveyor scanned most of the surface in infrared with its TES instrument. The Mars Odyssey's THEMIS, alsoimaged the surface in wavelengths that measure temperature.The possibility of liquid water on Mars has been examined. Although water would quickly boil or evaporate away,lake-sized bodies of water would quickly be covered with an ice layer which would greatly reduce evaporation. Witha cover of dust and other debris, water under ice might last for some time and could even flow to significantdistances as ice-covered rivers.[238] Lake Vostok in Antarctica may have implications for liquid water still being onMars because if the lake existed before the perennial glaciation began, is likely that the lake did not freeze all theway to the bottom. Accordingly if water existed before the polar ice caps on Mars, it is likely that there is still liquidwater below the ice caps.[239] Large quantities of water could be released, even today, by an asteroid impact. It hasbeen suggested that life has survived over millions of years by periodic impacts which melted ice and allowedorganisms to come out of dormancy and live for a few thousands of years.[240][241] But if impacts brought the water,maybe liquid water did not exist on the surface very long. Large river valleys could have been made in short periodsof time (maybe just days) when impacts caused water to flow as a giant flood.[242] We suppose that Mars had greatamounts of water because of the existence of so many large river valleys.[10][11] Maybe, valleys did not takethousands to millions of years to form as on the Earth.[243] It is accepted that a vast network of channels, resemblingmany Martian channels, were formed in a very short time period in eastern Washington State when floods werecaused by a breakout of an ice-dammed lake. So, perhaps not that much water was involved and maybe it did not lastlong enough for life to develop.Studies have shown that various salts present in the Martian soil could act as a kind of antifreeze—keeping water liquid well below its normal freezing point.[88][244] Some calculations suggest that tiny amounts of liquid water may be present for short periods of time (hours) in some locations.[245][246] Some researchers have calculated that when taking into consideration insolation and pressure factors that liquid water could exist in some areas for about 10% of the Martian year;[247] others estimate that water could be a liquid for only 2% of the year.[248] Either way, that may be enough liquid water to support some forms of hardy organisms. It may not take much liquid water for life; organisms have been found on Earth living on extremely thin layers of unfrozen water in below-freezing locations.[249] Research described in December 2009, showed that liquid water could form in the daytime inside of snow on Mars. As light heats ice, it may be warming up dust grains located inside. These grains would then store heat and form water by melting some of the ice. The process has been already been observed in Antarctica. Enough

Page 30: Water on Mars

Water on Mars 30

water may be produced for physical, chemical, and biological processes.[250][251]

Valleys and channelsFurther information: Atmosphere of MarsThe Viking Orbiters caused a revolution in our ideas about water onMars. Huge river valleys were found in many areas. They showed thatfloods of water broke through dams, carved deep valleys, erodedgrooves into bedrock, and traveled thousands of kilometers. Areas ofbranched streams, in the southern hemisphere, suggested that rain oncefell.[64][65][252]

The images below, some of the best from the Viking Orbiters, aremosaics of many small, high resolution images. Click on the imagesfor more detail. Some of the pictures are labeled with place names.

Streamlined Islands seen byViking showed that largefloods occurred on Mars.Image is located in Lunae

Palus quadrangle.

Tear-drop shaped islands causedby flood waters from Maja

Vallis, as seen by Viking Orbiter.Image is located in Oxia Palus

quadrangle. The islands areformed in the ejecta of Lod

Crater, Bok Crater, and GoldCrater.

Scour Patterns, located inLunae Palus quadrangle, were

produced by flowing waterfrom Maja Vallis, which liesjust to the left of this mosaic.

Detail of flow around DromoreCrater is shown on the next

image.

Great amounts of waterwere required to carryout the erosion shownin this Viking image.Image is located in

Lunae Palusquadrangle. The erosion

shaped the ejectaaround Dromore Crater.

Page 31: Water on Mars

Water on Mars 31

Waters from Vedra Vallis,Maumee Vallis, and Maja Valleswent from Lunae Planum on the

left, to Chryse Planitia on theright. Image is located in LunaePalus quadrangle and was taken

by Viking Orbiter.

Area aroundNorthern KaseiValles, showing

relationshipsamong Kasei

Valles, BahramVallis, Vedra

Vallis, MaumeeVallis, and Maja

Valles. Maplocation is inLunae Palus

quadrangle andincludes parts ofLunae Planum

and ChrysePlanitia.

The ejectafrom

ArandasCrater actslike mud.It movesaroundsmallcraters

(indicatedby

arrows),instead ofjust fallingdown on

them.Craterslike thissuggest

that largeamountsof frozen

water weremelted

when theimpact

crater wasproduced.Image islocated in

MareAcidaliumquadrangle

and wastaken byVikingOrbiter.

This view of theflank of AlbaPatera shows

severalchnnels/troughs.Some channelsare associated

with lava flows;others are

probably causedby running

water. A largetrough or

graben turnsinto a line ofcollapse pits.

Image is locatedin Arcadia

quadrangle andwas taken by

Viking Orbiter.

Page 32: Water on Mars

Water on Mars 32

Branched channelsin Thaumasia

quadrangle, as seenby Viking Orbiter.

Networks ofchannels like this arestrong evidence forrain on Mars in the

past.

The branchedchannels seen byViking from orbitstrongly suggested

that it rained on Marsin the past. Image is

located in MargaritiferSinus quadrangle.

Ravi Vallis, as seen by VikingOrbiter. Ravi Vallis was probablyformed when catastrophic floods

came out of the ground to theright (chaotic terrain). Imagelocated in Margaritifer Sinus

quadrangle.

Channelsnear

WarregoValles.These

branchedchannels

arestrong

evidencefor

flowingwater on

Mars,perhapsduring a

muchwarmerperiod.

Semeykin CraterDrainage. Click on

image to see details ofdrainage system.

Location is IsmeniusLacus quadrangle.

Channels in Candor plateau, asseen by HiRISE. Location is

Coprates quadrangle. Click onimage to see many small,

branched channels which arestrong evidence for sustained

precipitation.

Channels near the rim of IusChasma, as seen by HiRISE. Thepattern and high density of thesechannels support precipitation asthe source of the water. Location

is Coprates quadrangle.

The high resolution Mars Orbiter Camera on the Mars Global Surveyor has taken pictures which give much moredetail about the history of liquid water on the surface of Mars. Despite the many gigantic flood channels andassociated tree-like network of tributaries found on Mars, there are no smaller scale structures that would indicate theorigin of the flood waters. It has been suggested that weathering processes have denuded these, indicating the rivervalleys are old features. Another theory about the formation of the ancient river valleys is that rather than floods,they were created by the slow seeping out of groundwater. This observation is supported by the sudden ending of theriver networks in theatre shaped heads, rather than tapering ones. Additionally, valleys are often discontinuous, smallsections of uneroded land separating the parts of the river.[253]

On the other hand, evidence in favor of heavy or even catastrophic flooding is found in the giant ripples in theAthabasca Vallis.[254]

Research, published in the Journal of Geophysical Research in June 2010, reported the detection of 40,000 rivervalleys on Mars, about four times the number of river valleys that have previously been identified by scientists.[255]

Page 33: Water on Mars

Water on Mars 33

Many Mars researchers now agree that the Martian water worn features can be divided into two distinct classes: 1.dendritic (branched), terrestrial-scale, widely distributed, Noachian-age "valley networks" and 2. exceptionally large,long, single-thread, isolated, uncommon, Hesperian-age "outflow channels". Consensus seems to be emerging thatthe latter formed in single, catastrophic ruptures of subsurface water reservoirs, possibly sealed by ice, dischargingcolossal quantities of water across an otherwise ultra-arid Mars surface.[256] The former, however, probably indicateprolonged "wet" (though still arid by terrestrial standards) conditions on Noachian-era Mars, with an active ongoinghydrological cycle.[257]

Higher resolution observations from spacecraft like Mars Global Surveyor also revealed at least a few hundredfeatures along crater and canyon walls that appear similar to terrestrial seepage gullies.[258] The gullies tended to beEquator facing and in the highlands of the southern hemisphere, and all greater than 30° north or south latitude.[259]

The researchers found no partially degraded (i.e. weathered) gullies and no superimposed impact craters, indicatingthat these are very young features.

Group of gullies on northwall of crater that lies west

of the crater Newton(41.3047 degrees south

latitude, 192.89 eastlongitide). Image taken withMars Global Surveyor under

the public target program.

Crater wall inside MarinerCrater showing a large group of

gullies, as seen by HiRISE.

Gullies with branches. Group of deep gullies, as seen byHiRISE.

Liquid water

Mosaic shows some spherules partly embedded. Photo of Microscopic rock forms indicating past signs of water, taken by Opportunity

Liquid water cannot exist on the surface of Mars with its present low atmospheric pressure, except at the lowestelevations for short periods.[260][261] Recently, the discovery of gully deposits that were not seen ten years agoprovided evidence to support the popular belief that liquid water flowed on the surface in the recent past.[262][263]

There is some disagreement in the scientific community as to whether or not the new gully deposits were formedfrom liquid water. A paper, published in the January 2010 issue of Icarus, concluded that the observed deposits wereprobably dry flows that were started by a rockfall in steep regions.[85][264]

Among the findings from the Opportunity rover is the presence of hematite on Mars in the form of small spheres on the Meridiani Planum. The spheres are only a few millimetres in diameter and are believed to have formed as rock

Page 34: Water on Mars

Water on Mars 34

deposits under watery conditions billions of years ago. Other minerals have also been found containing forms ofsulfur, iron, or bromine such as jarosite. This and other evidence led a group of 50 scientists to conclude in theDecember 9, 2004 edition of the journal Science that "Liquid water was once intermittently present at the Martiansurface at Meridiani, and at times it saturated the subsurface. Because liquid water is a key prerequisite for life, weinfer conditions at Meridiani may have been habitable for some period of time in Martian history." Later studiessuggested that this liquid water was actually acid because of the types of minerals found at the location.[265][266] Onthe opposite side of the planet, the mineral goethite, which (unlike hematite) forms only in the presence of water,along with other evidence of water, has also been found by the Spirit rover in the "Columbia Hills".On July 31, 2008, NASA announced that the Phoenix lander confirmed the presence of water ice on Mars,[267] aspredicted on 2002 by the Mars Odyssey orbiter.Studies have shown that various salts present in the Martian soil could act as a kind of antifreeze—keeping waterliquid at temperatures far below its normal freezing point.[268][269] Some calculations suggest that tiny amounts ofliquid water may be present for short periods of time (hours) in some locations.[270] Some researchers havecalculated that when taking into consideration insolation and pressure factors that liquid water could exist in someareas for about 10% of the Martian year;[271] others estimate that water could be a liquid for only 2% of the year.[272]

Either way, that may be enough liquid water to support some forms of hardy organisms. It may not take much liquidwater for life—organisms have been found on Earth living on extremely thin layers of unfrozen water inbelow-freezing locations.[273] Research in December 2009 showed that liquid water could form in the daytime insideof snow on Mars. As light heats ice, it may be warming up dust grains located inside. These grains would then storeheat and form water by melting some of the ice. This process has already been observed in Antarctica. Enough watermay be produced for physical, chemical, and biological processes.[274][275]

Polar ice caps

The Mars Global Surveyor acquired this image ofthe Martian north polar ice cap in early northern

summer.

Both the northern polar cap (Planum Boreum) and the southern polarcap (Planum Australe) are believed to grow in thickness during thewinter and partially sublime during the summer. Data obtained by theMars Express satellite, made it possible in 2004 to confirm that thesouthern polar cap has an average of 3 kilometres (1.9 mi) thick slab ofCO2 ice[169] with varying contents of frozen water. Depending on itslatitude, the polar cap can be a mixture of 85% CO2 ice and 15% waterice.[170] The second part comprises steep slopes known as scarps,made almost entirely of water ice, that fall away from the polar cap tothe surrounding plains.[170] The third part encompasses the vastpermafrost fields that stretch for tens of kilometres away from thescarps.[170][276] NASA scientists calculate that the volume of water icein the south polar ice cap, if melted, would be sufficient to cover theentire planetary surface to a depth of 11 metres.[277]

Research, published in January 2010 using HiRISE images, says that understanding the layers is more complicatedthan was formerly believed. The brightness of the layers does not just depend on the amount of dust. The angle of thesun together with the angle of the spacecraft greatly affect the brightness seen by the camera. This angle depends onfactors such as the shape of the trough wall and its orientation. Furthermore, the roughness of the surface can greatly

Page 35: Water on Mars

Water on Mars 35

North polar layered deposits can be seen on thetrough wall imaged here by HiRISE.

change the albedo (amount of reflected light). In addition, many timeswhat one is seeing is not a real layer, but a fresh covering of frost. Allof these factors are influenced by the wind which can erode surfaces.The HiRISE camera did not reveal layers that were thinner than thoseseen by the Mars Global Surveyor. However, it did see more detailwithin layers.[278]

Ice patchesOn July 28, 2005, the European Space Agency announced the existence of a crater partially filled with frozenwater,[158] which some then interpreted as an "ice lake".[159] Images of the crater, taken by the High ResolutionStereo Camera on board the European Space Agency's Mars Express spacecraft, clearly show a broad sheet of ice inthe bottom of an unnamed crater located on Vastitas Borealis, a broad plain that covers much of Mars' far northernlatitudes, at approximately 70.5° North and 103° East. The crater is 35 km wide and about 2 km deep.The height difference between the crater floor and the surface of the water ice is about 200 metres. ESA scientistshave attributed most of this height difference to sand dunes beneath the water ice, which are partially visible. Whilescientists do not refer to the patch as a "lake", the water ice patch is remarkable for its size and for being presentthroughout the year. Deposits of water ice and layers of frost have been found in many different locations on theplanet.

Equatorial frozen seaSurface features consistent with pack ice have been discovered in the southern Elysium Planitia. What appear to beplates of broken ice, ranging in size from 30 m to 30 km, are found in channels leading to a flooded area ofapproximately the same depth and width as the North Sea. The plates show signs of break up and rotation that clearlydistinguish them from lava plates elsewhere on the surface of Mars. The source for the flood is thought to be thenearby geological fault, Cerberus Fossae, which spewed water as well as lava some 2 to 10 million years ago.[161]

Ancient coastlineA striking feature of the topography of Mars is the flat plains of the northern hemisphere. With the increasingamounts of data returning from the current set of orbiting probes, what seems to be an ancient shoreline severalthousands of kilometres long has been discovered. Actually, two different shorelines have been proposed. One, theArabia shoreline, can be traced all around Mars except through the Tharsis volcanic region. The second, theDeuteronilus, follows the Vastitas Borealis Formation. Some researchers do not agree that these formations are realshorelines.[279][280] One major problem with the conjectured 2 Ga old shoreline is that it is not flat — i.e. does notfollow a line of constant gravitational potential. However, a 2007 Nature article points out that this could be due to achange in distribution in Mars' mass, perhaps due to volcanic eruption or meteor impact—the Elysium volcanicprovince or the massive Utopia basin that is buried beneath the northern plains have been put forward as the mostlikely causes.[281] The Mars Ocean Hypothesis conjectures that the Vastitas Borealis basin was the site of aprimordial ocean of liquid water 3.8 billion years ago.[196]

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Water on Mars 36

Glaciers and ice ages

Perspective view of a 5-km-wide, glacial-likelobe deposit sloping up into a box canyon alongthe crustal dichotomy boundary on Mars. The

surface has moraines, deposits of rocks that showhow the glacier advanced.

Many large areas of Mars have been shaped by glaciers. Much of thearea in high latitudes, especially the Ismenius Lacus quadrangle, arebelieved to still contain enormous amounts of water ice.[282][283]

Recent evidence has led many planetary scientists to believe that waterice still exists as glaciers with thin coverings of insulatingrock.[98][99][100][101][102] In March 2010, scientists released the resultsof a radar study of an area called Deuteronilus Mensae that foundwidespread evidence of ice lying beneath a few meters of rockdebris.[284] Glaciers are believed to be associated with Fretted terrain,many volcanoes, and even some craters. Researchers have describedglacial deposits on Hecates Tholus,[285] Arsia Mons,[193] PavonisMons,[286] and Olympus Mons.[287]

Ridges of debris on the surface of the glaciers indicate the direction ofice movement. The surface of some glaciers have rough textures due tosublimation of buried ice. The ice goes directly into a gas (this processis called sublimation) and leaves behind an empty space. Overlying material then collapses into the void.[288]

Glaciers are not pure ice; they contain dirt and rocks. At times, they dump their loads of material into ridges. Suchridges are called moraines. Some places on Mars have groups of ridges that are twisted around; this may have beendue to more movement after the ridges were put into place. Sometimes chunks of ice fall from the glacier and getburied in the land surface. When they melt, a more or less round hole remains.[289] On Earth we call these featureskettles or kettle holes. Mendon Ponds Park in upstate NY has preserved several of these kettles. The picture fromHiRISE below shows possible kettles in Moreux Crater.

Pictures below show various features that appear to be connected with the existence of glaciers.

Page 37: Water on Mars

Water on Mars 37

Moreux Crater morainesand kettle holes, as seen by

HIRISE. Location isIsmenius Lacus quadrangle.

Niger Vallis with features typicalof this latitude. Chevron pattern

results from movement ofice-rich material. Click on image

to see chevron pattern andmantle. Location is Hellas

quadrangle.

Mesa in IsmeniusLacus

quadrangle, asseen by CTX.

Mesa has severalglaciers eroding

it. One of theglaciers is seen ingreater detail in

the next twoimages from

HiRISE.

Glacier as seenby HiRISE under

the HiWishprogram. Area in

rectangle isenlarged in the

next photo. Zoneof accumulationof snow at thetop. Glacier ismoving downvalley, then

spreading out onplain. Evidencefor flow comesfrom the many

lines on surface.Location is in

ProtonilusMensae in

Ismenius Lacusquadrangle.

Enlargement of area in rectangleof the previous image. On Earth

the ridge would be called theterminal moraine of an alpine

glacier. Picture taken withHiRISE under the HiWish

program.

Many mid-latitude craters contain straight and/or curved ridges of material that resemble glacial moraines on theEarth. Moving ice carries rock material, then drops it as the ice disappears. On Mars, with its extremely thinatmosphere, ice does not usually melt but instead sublimates. As a result, the rock debris is just dropped, and meltwater is not produced so the remains of these glaciers do not appear the same as on the Earth. Various names havebeen applied to these ridged features. Depending on the author, they may be called arcuate ridges,[290] viscous flowfeatures,[291] Martian flow features, or moraine-like ridges. Many, but not all, seem to be associated with gullies onthe walls of craters and mantling material.[292]

Page 38: Water on Mars

Water on Mars 38

Gullies and possibleremains of old

glaciers in a crater inEridania quadrangle,

north of the largecrater Kepler. One

suspected glacier, tothe right, has the

shape of a tongue.Image taken with

Mars GlobalSurveyor, under the

Public Targetprogram.

Tongue-Shaped Glacier,as seen by Mars GlobalSurveyor. Location is

Hellas quadrangle.

Tongue-shaped glacier, as seenby HiRISE under the HiWishprogram. Ice may exist in the

glacier, even today, beneath aninsulating layer of dirt. Location

is Hellas quadrangle.

Close-up of tongue-shapedglacier, as seen by HiRISE underthe HiWish program. Resolutionis about 1 meter, so one can seeobjects a few meters across in

this image. Ice may exist in theglacier, even today, beneath an

insulating layer of dirt. Locationis Hellas quadrangle.

Lineated deposits are probably rock-covered glaciers which are found on the floors of some channels. Their surfaceshave ridged and grooved materials that deflect around obstacles, similar to some glaciers on the Earth. Lineated floordeposits may be related to Lobate Debris Aprons, which have been proven to contain large amounts of ice byorbiting radar.[101][102][103]

For many years, researchers believed that on Mars features called Lobate Debris Aprons looked like glacial flows. Itwas thought that ice existed under a layer of insulating rocks.[98][99][100] With new instrument readings, it has beenconfirmed that Lobate Debris Aprons contain almost pure ice that is covered with a layer of rocks.[101][102]

Reull Vallis with lineated floor deposits. Click on image to seerelationship to other features. Floor deposits are believed to be formed

from ice movement. Location is Hellas quadrangle.

Coloe Fossae Lineated Valley Fill, as seen by HiRISE. Scale bar is500 meters long. Location is Ismenius Lacus quadrangle.

Ice ages on Mars are far different than the ones that our Earth experiences. Ice ages on Mars, that is when ice accumulates, occur during warmer periods.[293] During a Martian ice age, the poles get warmer. Water ice leaves the ice caps and is deposited in mid latitudes. The moisture from the ice caps travels to lower latitudes in the form of deposits of frost or snow mixed generously with dust. The atmosphere of Mars contains a great deal of fine dust particles. Water vapor condenses on these particles, which then fall down to the ground due to the additional weight of the water coating. When ice at the top of the mantling layer returns to the atmosphere, it leaves behind dust which serves to insulate the remaining ice.[138] The total volume of water removed is about a few percent of the ice caps, or

Page 39: Water on Mars

Water on Mars 39

enough to cover the entire surface of the planet under one meter of water. Much of this moisture from the ice capsresults in a thick smooth mantle that is thought to be a mixture of ice and dust.[294][295][296] This ice-rich mantle, afew 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. It is believed that this mantle was put inplace during a relatively recent ice age. The mantle covers areas to the equivalent latitude of Saudi Arabia and thesouthern United States.The images below, all taken with HiRISE show a variety of views of this smooth mantle.

Ptolemaeus Crater Rim. Click on image tosee excellent view of mantle deposit.Location is Phaethontis quadrangle.

Atlantis Chaos. Click on image to see mantlecovering and possible gullies. The two imagesare different parts of the original image. Theyhave different scales. Location is Phaethontis

quadrangle.

Dissected mantle with layers. Location isNoachis quadrangle.

Ice ages are driven by changes in Mars's orbit and tilt. Orbital calculations show that Mars wobbles on its axis farmore than Earth. Earth is stabilized by its proportionally large moon, so it only wobbles a few degrees. Mars, incontrast, may change its tilt by tens of degrees.[297] Its poles get much more direct sunlight at times, which causes theice caps to warm and become smaller as ice sublimes. Adding to the variability of the climate, the eccentricity of theorbit of Mars changes twice as much as Earth's eccentricity. Computer simulations have shown that a 45° tilt of theMartian axis would result in ice accumulation in areas that display glacial landforms.[298] A 2008 study providedevidence for multiple glacial phases during Late Amazonian glaciation at the dichotomy boundary on Mars.[299]

Glaciers on volcanoesUsing new MGS and Odyssey data, combined with recent developments in the study of cold-based glaciers,scientists believe glaciers once existed and still exist on some volcanoes. The evidence for this are concentric ridges(these are moraines dropped by the glacier), a knobby area (caused by ice sublimating), and a smooth section thatflows over other deposits (debris-covered glacial ice). The ice could have been deposited when the tilt of Marschanged the climate, thereby causing more moisture to be present in the atmosphere. Studies suggest the glaciationhappened in the Late Amazonian period, the latest period in Mars history. Multiple stages of glaciations probablyoccurred.[300] The ice present today represents one more resource for the possible future colonization of the planet.Researchers have described glacial deposits on Hecates Tholus,[285] Arisia Mons,[193] Pavonis Mons,[286] andOlympus Mons.[287]

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External links• NASA - Curiosity Rover Finds Evidence For An Ancient Streambed - September, 2012 (http:/ / science. nasa.

gov/ science-news/ science-at-nasa/ 2012/ 27sep_streambed/ )• Images - Signs Of Water On Mars (http:/ / marsoweb. nas. nasa. gov/ HiRISE/ hirise_images/ ) (HiRISE)• Video (02:01) - Liquid Flowing Water Discovered on Mars - August, 2011 (http:/ / www. youtube. com/

watch?v=HQKnDdB36zY)• Video (04:32) - Evidence: Water "Vigorously" Flowed On Mars - September, 2012 (http:/ / www. youtube. com/

watch?v=Jr1Xu2i-Uc0)

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Article Sources and Contributors 51

Article Sources and ContributorsWater on Mars  Source: http://en.wikipedia.org/w/index.php?oldid=525913910  Contributors: Acalamari, Airplaneman, Albertiam, AnemoneProjectors, Arjayay, BD2412, BatteryIncluded,Beao, Ben MacDui, Bgpaulus, Brian Everlasting, Bubba73, Cb6, Ccacsmss, Chmee2, Chocodum, ClamDip, Cogiati, Colonies Chris, CommonsDelinker, Crosscountry511, Cu3ps, Cyclopia,DanHobley, Dav3395, De728631, Debresser, Drbogdan, Dthomsen8, Dunner99, Edgepedia, Edokter, Eumolpo, Fences and windows, Fotaun, Frankie816, Funandtrvl, Furrykef, GVnayR, GobLofa, GoingBatty, Gunmetal Angel, Holmst3dT, Ioannes Pragensis, JMK, JZCL, Jimmarsmars, John of Reading, Khazar2, Kingpin13, Kokoon, Krasss, Ktsquare, LilHelpa, M4gnum0n,Magioladitis, Mgiganteus1, Mild Bill Hiccup, Msnader11, NBardy34, Niceguyedc, NovaDog, Ohconfucius, Ohnoitsjamie, Oknazevad, Op47, Optimist on the run, PartTimeGnome, Paul H.,Pedro, Petr Kopač, PhilKnight, Pt, R'n'B, RA0808, RHaworth, Rabbabodrool, Reaper Eternal, Rich Farmbrough, Rjwilmsi, Roentgenium111, Ruslik0, Scebert, Scientist1234smart, Silvergoat,SpaceChimp1992, Staszek Lem, Steorra, Surajt88, Surv1v4l1st, Sémhur, The.aviation.expert, The2crowrox, Trkiehl, Van der Hoorn, Vauhtimato, Viriditas, Wingman4l7, WolfmanSF, Xession,Гатерас, 104 anonymous edits

Image Sources, Licenses and ContributorsFile:AncientMars.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:AncientMars.jpg  License: Creative Commons Attribution-Sharealike 3.0  Contributors: IttizImage:Mars Map.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Mars_Map.JPG  License: Public Domain  Contributors: NASA/JPL-CaltechFile:RoverIcon.png  Source: http://en.wikipedia.org/w/index.php?title=File:RoverIcon.png  License: Public Domain  Contributors: NASAFile:SojournerIcon.png  Source: http://en.wikipedia.org/w/index.php?title=File:SojournerIcon.png  License: Public Domain  Contributors: NASAFile:VikingIcon.png  Source: http://en.wikipedia.org/w/index.php?title=File:VikingIcon.png  License: Public Domain  Contributors: NASAFile:PhoenixIcon.png  Source: http://en.wikipedia.org/w/index.php?title=File:PhoenixIcon.png  License: Public Domain  Contributors: NASAFile:Mars3Icon.png  Source: http://en.wikipedia.org/w/index.php?title=File:Mars3Icon.png  License: Public Domain  Contributors: NASAFile:CuriosityIcon.png  Source: http://en.wikipedia.org/w/index.php?title=File:CuriosityIcon.png  License: Public Domain  Contributors: NASAImage:MGS_MOC_Wide_Angle_Map_of_Mars_PIA03467.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:MGS_MOC_Wide_Angle_Map_of_Mars_PIA03467.jpg  License:Public Domain  Contributors: NASA/JPL/MSSSFile:Scamander Vallis from Mariner9.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Scamander_Vallis_from_Mariner9.jpg  License: Public Domain  Contributors: Jim Secoskyselected nasa image.Image:Streamlined Islands in Maja Vallis.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Streamlined_Islands_in_Maja_Vallis.jpg  License: Public Domain  Contributors: JimSecosky modified nasa image.Image:Viking Teardrop Islands.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Viking_Teardrop_Islands.jpg  License: Public Domain  Contributors: Jim Secosky modified nasaimage.Image:Detail of Maja Vallis Flow.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Detail_of_Maja_Vallis_Flow.jpg  License: Public Domain  Contributors: Jim Secosky modifiednasa image.Image:Branched Channels from Viking.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Branched_Channels_from_Viking.jpg  License: Public Domain  Contributors: Jim Secoskyselected nasa image.Image:Flow from Arandas Crater.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Flow_from_Arandas_Crater.jpg  License: Public Domain  Contributors: Jim Secosky modifiednasa image.Image:Alba Patera Channels.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Alba_Patera_Channels.jpg  License: Public Domain  Contributors: Jim Secosky modified nasa image.File:Mars Viking 21i093.png  Source: http://en.wikipedia.org/w/index.php?title=File:Mars_Viking_21i093.png  License: Public domain  Contributors: "Roel van der Hoorn (Van der Hoorn)"File:Hematite region Sinus Meridiani sur Mars.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Hematite_region_Sinus_Meridiani_sur_Mars.jpg  License: Public Domain Contributors: Original uploader was Almak at fr.wikipediaImage:Gully in Phaethontis.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Gully_in_Phaethontis.jpg  License: Public Domain  Contributors: Jim Secosky modified NASA image.Original uploader was Jimmarsmars at en.wikipediaImage:Gullies and tongue-shaped glacier.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Gullies_and_tongue-shaped_glacier.jpg  License: Public Domain  Contributors: JimSecosky modified NASA photo. Original uploader was Jimmarsmars at en.wikipediaImage:Kaiser Gullies.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Kaiser_Gullies.JPG  License: Public Domain  Contributors: Jim Secosky selected nasa image.Image:Gullies in Gorgonum.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Gullies_in_Gorgonum.jpg  License: Public Domain  Contributors: Jim Secosky modified nasa image.File:Nanedi channel.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Nanedi_channel.JPG  License: Public Domain  Contributors: Jim Secosky modified nasa image.Image:Layers in a crater in Arabia.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Layers_in_a_crater_in_Arabia.JPG  License: Public Domain  Contributors: jim secoskymodified a NASA image. Original uploader was Jimmarsmars at en.wikipediaImage:Tikonravev Crater Floor.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Tikonravev_Crater_Floor.JPG  License: Public Domain  Contributors: Jim Secosky modifiedNASA imagesImage:Dark streaks in Diacria.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Dark_streaks_in_Diacria.JPG  License: Public Domain  Contributors: Jim Secosky modified NASAimage. Original uploader was Jimmarsmars at en.wikipediaImage:Dark Streaks in Crater.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Dark_Streaks_in_Crater.JPG  License: Public Domain  Contributors: Jim Secosky modified nasaimage.Image:Inverted Streams in Juventae Chasma.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Inverted_Streams_in_Juventae_Chasma.jpg  License: Public Domain  Contributors:Jim Secosky, NASA/JPL/Malin Space Science SystemsFile:PIA10741 Possible Ice Below Phoenix.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:PIA10741_Possible_Ice_Below_Phoenix.jpg  License: Public Domain  Contributors:NASA/Jet Propulsion Lab-Caltech/University of Arizona/Max Planck InstituteImage:Reull Vallis lineated deposits.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Reull_Vallis_lineated_deposits.JPG  License: Public Domain  Contributors: Jim Secoskymodified NASA imageImage:Wikiauquakuh.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Wikiauquakuh.JPG  License: Public Domain  Contributors: Jim Secosky modified NASA image.. Originaluploader was Jimmarsmars at en.wikipediaImage:Channels near Warrego in Thaumasia.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Channels_near_Warrego_in_Thaumasia.JPG  License: Public Domain  Contributors:Jim Secosky modified NASA image. Original uploader was Jimmarsmars at en.wikipediaImage:Semeykin Crater Drainage.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Semeykin_Crater_Drainage.JPG  License: Public Domain  Contributors: Jim Secosky modifiedNASA image.Image:Erosion features in Ares Vallis.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Erosion_features_in_Ares_Vallis.JPG  License: Public Domain  Contributors: Jim Secoskymodified NASA image.Image:Delta in Lunae Palus.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Delta_in_Lunae_Palus.jpg  License: Public Domain  Contributors: Jim Secosky modified nasa image.Image:Athabasca Valles.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Athabasca_Valles.JPG  License: Public Domain  Contributors: Jim Secosky modified NASA image.Original uploader was Jimmarsmars at en.wikipediaImage:Melas Chasma channels.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Melas_Chasma_channels.JPG  License: Public Domain  Contributors: Jim Secosky selected nasaimage.

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Image:Dao Vallis.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Dao_Vallis.JPG  License: Public Domain  Contributors: Jim Secosky modified NASA image. Original uploaderwas Jimmarsmars at en.wikipediaImage:Blocks in Aram.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Blocks_in_Aram.JPG  License: Public Domain  Contributors: Jim Secosky modified NASA image. Originaluploader was Jimmarsmars at en.wikipediaImage:Canyons and Mesas of Aureum Chaos in Oxia Palus.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Canyons_and_Mesas_of_Aureum_Chaos_in_Oxia_Palus.JPG License: Public Domain  Contributors: Jim Secosky modified NASA photo Original uploader was Jimmarsmars at en.wikipediaImage:Ice_sublimating_in_the_Dodo-Goldilocks_trench.gif  Source: http://en.wikipedia.org/w/index.php?title=File:Ice_sublimating_in_the_Dodo-Goldilocks_trench.gif  License: PublicDomain  Contributors: NASA/JPL-Caltech/University of Arizona/Texas A&M UniversityImage:Evaporating ice on Mars Phoenix lander image.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Evaporating_ice_on_Mars_Phoenix_lander_image.jpg  License: PublicDomain  Contributors: NASA/JPLImage:Phoenix_Sol_0_horizon.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Phoenix_Sol_0_horizon.jpg  License: Public Domain  Contributors: NASA/JPL-Caltech/University ofArizonaImage:PSP 008301 2480 cut a.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:PSP_008301_2480_cut_a.jpg  License: Public Domain  Contributors: NASA/Jet PropulsionLab/University of ArizonaImage:Patterned_ground_devon_island.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Patterned_ground_devon_island.jpg  License: Creative Commons Attribution-Sharealike 3.0 Contributors: AnthonaresImage:Opportunity photo of Mars outcrop rock.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Opportunity_photo_of_Mars_outcrop_rock.jpg  License: Public Domain Contributors: Original uploader was Awolf002 at en.wikipediaImage:Opp layered sol17-B017R1 br.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Opp_layered_sol17-B017R1_br.jpg  License: Public Domain  Contributors: Original uploaderwas Awolf002 at en.wikipediaImage:Xpe First Opp RAT-B032R1 br.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Xpe_First_Opp_RAT-B032R1_br.jpg  License: Public Domain  Contributors: Originaluploader was Awolf002 at en.wikipediaImage:17-jg-03-mi2-B035R1_br.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:17-jg-03-mi2-B035R1_br.jpg  License: unknown  Contributors: -Image:PIA16158-Mars Curiosity Rover-Water-AlluvialFan.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:PIA16158-Mars_Curiosity_Rover-Water-AlluvialFan.jpg  License:Public Domain  Contributors: Drbogdan, 1 anonymous editsImage:PIA16156-Mars Curiosity Rover-Water-AncientStreambed.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:PIA16156-Mars_Curiosity_Rover-Water-AncientStreambed.jpg License: Public Domain  Contributors: ComputerHotline, DrbogdanImage:PIA16189 fig1-Curiosity Rover-Rock Outcrops-Mars and Earth.jpg  Source:http://en.wikipedia.org/w/index.php?title=File:PIA16189_fig1-Curiosity_Rover-Rock_Outcrops-Mars_and_Earth.jpg  License: Public Domain  Contributors: ComputerHotline, DrbogdanFile:Springs in Vernal Crater.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Springs_in_Vernal_Crater.jpg  License: Public Domain  Contributors: Jim Secosky modified NASAimage.Image:Ius Channels.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Ius_Channels.jpg  License: Public Domain  Contributors: Jim Secosky modified nasa image.Image:Inverted terrain in Parana Valles.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Inverted_terrain_in_Parana_Valles.JPG  License: Public Domain  Contributors: JimSecosky modified nasa image.Image:Antoniadi Crater Stream Channels.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Antoniadi_Crater_Stream_Channels.JPG  License: Public Domain  Contributors: JimSecosky modified NASA image. Original uploader was Jimmarsmars at en.wikipediaFile:Chloride deposits on Mars.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Chloride_deposits_on_Mars.JPG  License: Public Domain  Contributors: Jim Secosky modifiedNASA image. Original uploader was Jimmarsmars at en.wikipediaImage:Becquerel Crater layers.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Becquerel_Crater_layers.JPG  License: Public Domain  Contributors: Jim Secosky modified NASAimage.Image:Asimov Layers Close-up.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Asimov_Layers_Close-up.JPG  License: Public Domain  Contributors: Jim Secosky modified nasaimage.Image:Pedestaltop22919.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Pedestaltop22919.jpg  License: Public Domain  Contributors: Jim Secosky modified nasa image.Image:Niger Vallis hirise.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Niger_Vallis_hirise.JPG  License: Public Domain  Contributors: Jim Secosky modified NASA image.Image:Dissected Mantle.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Dissected_Mantle.JPG  License: Public Domain  Contributors: Jim Secosky modified nasa image.Image:Layered mantle in Icaria Planum.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Layered_mantle_in_Icaria_Planum.JPG  License: Public Domain  Contributors: JimSecosky modified nasa image.Image:ESP_020012gulliescropped.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:ESP_020012gulliescropped.jpg  License: Public Domain  Contributors: Jim Secosky modifiednasa image.Image:Gullies near Newton Crater.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Gullies_near_Newton_Crater.jpg  License: Public Domain  Contributors: Jim Secosky modifiednasa image.Image:Gullies in Terra Sirenum.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Gullies_in_Terra_Sirenum.jpg  License: Public Domain  Contributors: Jim Secosky modified nasaimage.Image:21845gulliespatt.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:21845gulliespatt.jpg  License: Public Domain  Contributors: Jim Secosky modified nasa image.File:Ice exposed by impact.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Ice_exposed_by_impact.jpg  License: Public Domain  Contributors: NASA/JPL-Caltech/University ofArizona.Image:Wide view of Debris Apron.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Wide_view_of_Debris_Apron.jpg  License: Public Domain  Contributors: Jim Secosky modifiednasa image.Image:Face of Lobate Debris Apron.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Face_of_Lobate_Debris_Apron.jpg  License: Public Domain  Contributors: Jim Secoskymodified nasa image.File:Columnar jointing, Marte Vallis.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Columnar_jointing,_Marte_Vallis.jpg  License: Public Domain  Contributors: NASA EarthObservatoryFile:Olympus Mons Region map-la.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Olympus_Mons_Region_map-la.svg  License: Creative Commons Attribution-Share Alike Contributors: SémhurImage:Wide view of glacier showing image field.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Wide_view_of_glacier_showing_image_field.JPG  License: Public Domain Contributors: Jim Secosky modified nasa image.Image:Glacier close up with hirise.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Glacier_close_up_with_hirise.JPG  License: Public Domain  Contributors: User:RonhjonesImage:ESP_020319flowcontext.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:ESP_020319flowcontext.jpg  License: Public Domain  Contributors: Jim Secosky modified nasaimage.Image:ESP_020319flowsclose-up.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:ESP_020319flowsclose-up.jpg  License: Public Domain  Contributors: Jim Secosky modified nasaimage.Image:Glacier moraine in Deuteronilus Mensae.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Glacier_moraine_in_Deuteronilus_Mensae.JPG  License: Public Domain Contributors: Jim Secosky modified nasa image.Image:Glacial Cirque in Hellas.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Glacial_Cirque_in_Hellas.JPG  License: Public Domain  Contributors: Jim Secosky modified nasaimage.Image:ESP020886 with tongue shaped glacier.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:ESP020886_with_tongue_shaped_glacier.jpg  License: Public Domain  Contributors:Jim Secosky modified nasa image.Image:20769flow features .jpg  Source: http://en.wikipedia.org/w/index.php?title=File:20769flow_features_.jpg  License: Public Domain  Contributors: Jim Secosky modified nasa image.

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Image:Lobate feature with hiwish.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Lobate_feature_with_hiwish.JPG  License: Public Domain  Contributors: Jim Secosky modifiednasa imageFile:Martian north polar cap.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Martian_north_polar_cap.jpg  License: Public Domain  Contributors: NASA/JPL/Malin Space ScienceSystemsImage:Permafrost - polygon.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Permafrost_-_polygon.jpg  License: Public Domain  Contributors: Ktz, MushiHoshiIshi, Wst, 1anonymous editsImage:Phoenix horizon view.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Phoenix_horizon_view.jpg  License: Public Domain  Contributors: NASA/Jet PropulsionLab/University of ArizonaImage:Permafrost pattern.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Permafrost_pattern.jpg  License: Creative Commons Attribution-Sharealike 3.0  Contributors: BrockenInagloryImage:Patternedground.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Patternedground.JPG  License: Public Domain  Contributors: Jim Secosky modified NASA image..Original uploader was Jimmarsmars at en.wikipediaImage:Athabasca Cones.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Athabasca_Cones.jpg  License: Public Domain  Contributors: Jim Secosky modified nasa image.Image:Rootless Cones.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Rootless_Cones.jpg  License: Public Domain  Contributors: Jim Secosky modified nasa image.File:Scalop formation.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Scalop_formation.jpg  License: Public Domain  Contributors: Jim Secosky modified nasa image.File:ALH84001.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:ALH84001.jpg  License: Public Domain  Contributors: NASAImage:Delta in Ismenius Lacus.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Delta_in_Ismenius_Lacus.jpg  License: Public Domain  Contributors: Jim Secosky modified nasaimage.Image:Delta in Margaritifer Sinus.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Delta_in_Margaritifer_Sinus.jpg  License: Public Domain  Contributors: Jim Secosky modifiednasa image.Image:Distributary fan-delta.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Distributary_fan-delta.jpg  License: Public Domain  Contributors: Jim Secosky modified nasa image.File:History of water on Mars.jpeg  Source: http://en.wikipedia.org/w/index.php?title=File:History_of_water_on_Mars.jpeg  License: Public Domain  Contributors: Chmee2, DragonFire1024,Yakuzai, Zoz, 4 anonymous editsImage:Chryse Planitia Scour Patterns.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Chryse_Planitia_Scour_Patterns.jpg  License: Public Domain  Contributors: Jim Secoskymodified nasa image.Image:Vedra, Maumee, and Maja Vallis.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Vedra,_Maumee,_and_Maja_Vallis.JPG  License: Public Domain  Contributors: JimSecosky modified nasa image.Image:Kasei Valles topolabled.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Kasei_Valles_topolabled.JPG  License: Creative Commons Attribution-Sharealike 3.0,2.5,2.0,1.0 Contributors: Kasei_Valles_topo.jpg: Areong derivative work: Aldaron (talk) 20:26, 4 September 2012 (UTC)Image:Dissected Channels, as seen by Viking.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Dissected_Channels,_as_seen_by_Viking.jpg  License: Public Domain  Contributors:Jim Secosky selected nasa image.Image:Ravi Vallis.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Ravi_Vallis.jpg  License: Public Domain  Contributors: Jim Secosky selected nasa image.Image:Candor Channels.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Candor_Channels.jpg  License: Public Domain  Contributors: Jim Secosky modified nasa image.Image:Crater wall inside Mariner Crater.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Crater_wall_inside_Mariner_Crater.JPG  License: Public Domain  Contributors: JimSecosky modified NASA image.Image:Branched gullies.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Branched_gullies.jpg  License: Public Domain  Contributors: Jim Secosky modified nasa image.Image:Deep Gullies.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Deep_Gullies.jpg  License: Public Domain  Contributors: Jim Secosky modified nasa image.Image:07-ml-3-soil-mosaic-B019R1 br.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:07-ml-3-soil-mosaic-B019R1_br.jpg  License: Public Domain  Contributors: Originaluploader was Sennheiser at en.wikipediaImage:nasa mars opportunity rock water 150 eng 02mar04.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Nasa_mars_opportunity_rock_water_150_eng_02mar04.jpg  License:Public Domain  Contributors: NASA/JPL/US Geological SurveyFile:North Polar Layers of Mars.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:North_Polar_Layers_of_Mars.jpg  License: Public Domain  Contributors: NASA/JPL/University ofArizonaFile:Mars glacial-like lobe deposit.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Mars_glacial-like_lobe_deposit.jpg  License: Public Domain  Contributors: NASA/JPL/MSSSImage:Moreux Crater moraines.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Moreux_Crater_moraines.JPG  License: Public Domain  Contributors: Jim Secosky modifiedNASA image.Image:Glacier as seen by ctx.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Glacier_as_seen_by_ctx.JPG  License: Public Domain  Contributors: User:RonhjonesImage:Tongue Glacier.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Tongue_Glacier.JPG  License: Public Domain  Contributors: Jim Secosky modified nasa image.Image:Tongue23141.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Tongue23141.jpg  License: Public Domain  Contributors: Jim Secosky modified nasa image.Image:Tongue23141close.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Tongue23141close.jpg  License: Public Domain  Contributors: Jim Secosky modified nasa image.Image:Coloe Fossae Lineated Valley Fill.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Coloe_Fossae_Lineated_Valley_Fill.JPG  License: Public Domain  Contributors: JimSecosky modified nasa image.Image:Ptolemaeus Crater Rim.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Ptolemaeus_Crater_Rim.JPG  License: Public Domain  Contributors: Jim Secosky modified NASAimage.Image:Atlantis Chaos.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Atlantis_Chaos.JPG  License: Public Domain  Contributors: Jim Secosky modified nasa image.. Originaluploader was Jimmarsmars at en.wikipedia

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