Water on Mars

From Wikipedia, the free encyclopedia
Jump to: navigation, search
page is in the middle of an expansion or major revamping
 This article or section is in the process of an expansion or major restructuring. You are welcome to assist in its construction by editing it as well. If this article or section has not been edited in several days, please remove this template.
This article was last edited by BatteryIncluded (talk | contribs) 3 seconds ago. (Purge)
For the music group, see Water on Mars (band). For the Doctor Who episode, see The Waters of Mars.
An artist's impression of what ancient Mars may have looked like, based on geological data
Dry channels near Warrego Valles

Water on Mars exists almost exclusively as water ice, and is located in the Martian polar ice caps and under the shallow Martian surface even at more temperate latitudes.[1][2] A small amount of water vapor is present in the atmosphere.[3]

There are no bodies of liquid water on the Martian surface because its atmospheric pressure at the surface averages 600 pascals (0.087 psi) —about 0.6% of Earth's mean sea level pressure— and because the temperature is far too low, (210 K (−63 °C)) leading to immediate freezing. Despite this, about 3.8 billion years ago,[4] there was a denser atmosphere, higher temperature, and vast amounts of liquid water flowed on the surface,[5][6] including large oceans.[7][8][9][10][11] It has been estimated that the primordial oceans on Mars would have covered between 36% [12][13] and 75% of the planet.[14]

There are a number of direct and indirect proofs of water presence either on or under the surface, e.g. dry stream beds,[15][16][17][18] polar caps, glaciers,[19][20][21][22][23] radar and spectroscopic measurements,[24] eroded craters or minerals directly connected to the past existence of liquid water.[25][26][27][28][29] Several Mars orbiters have detected basins of ancient lakes,[30][31][32][33][34][35][36] ancient river valleys,[16][37] and widespread glaciations,[20][38][39][40][41] while several landers and rovers directly analyzed soil and water ice from the shallow sub-surface.

Although the surface of Mars was wet and could have been hospitable to microbial life billions of years ago,[42] the present damaging effect of ionising radiation on cellular structure is one of the prime limiting factors on the survival of life on the surface.[43][44] Therefore, the best potential locations for discovering life on Mars may be at subsurface environments.[45][46][47]

Contents

History[edit]

Today, it is accepted that Mars had abundant water very early in its history.[48][49] All large areas of liquid water have disappeared, but deposited large amounts of water-rich materials , including clay and sulfates.[50][51][52][53][54] From these materials, glaciers and other forms of frozen ground came to be.

History of water on Mars numbers represent how many billion years ago

.

Mars areas have been extremely dry for long periods, as marked by the presence of olivine that would be decomposed by water. Olivine weathers to iddingsite readily in the presence of water. The presence of iddingsite on Mars suggest that liquid water once existed there, and might enable scientists to determine when there was last liquid water on the planet.[55][56][57][58][59] Studies of hydrogen isotopic ratios indicate that asteroids and comets from beyond 2.5 AU provide the source of Mars' water,[60] which currently totals 6% to 27% of the Earth's present ocean.[60]

Since several missions (Mars Odyssey, Mars Global Surveyor, Mars Reconnaissance Orbiter, Mars Express, Opportunity rover and Curiosity rover) are still sending back data from Mars, discoveries continue to be made.

Mars meteorites[edit]

Mars meteorite ALH84001

Over thirty meteorites have been found that came from Mars. Some of them contain evidence that they were exposed to water when on Mars. Some Mars meteorites called basaltic shergottites, appear (from the presence of hydrated carbonates and sulfates) to have been exposed to liquid water prior to ejection into space.[61][62] It has been shown that another class of meteorites, the nakhlites, were suffused with liquid water around 620 million years ago and that they were ejected from Mars around 10.75 million years ago by an asteroid impact. They fell to Earth within the last 10,000 years.[63]

In 1996, a group of scientists reported the possible presence of micro-fossils in the Allan Hills 84001, a meteorite from Mars.[64] Many studies disputed the validity of the fossils.[65][66] It was found that most of the organic matter in the meteorite was of terrestrial origin.[67]

Extinct water bodies[edit]

Lakes and river valleys[edit]

The Viking orbiters caused a revolution in our ideas about water on Mars. Huge river valleys were found in many areas. They showed that floods of water broke through dams, carved deep valleys, eroded grooves into bedrock, and traveled thousands of kilometers. Areas of branched streams, in the southern hemisphere, suggested that rain once fell.[68][69][70] Research published in June 2010, reported the detection of 40,000 river valleys on Mars, about four times the number of river valleys that have previously been identified.[13] The Martian water-worn features can be classified into two distinct classes: 1. dendritic (branched), terrestrial-scale, widely distributed, Noachian-age "valley networks" and 2. exceptionally large, long, single-thread, isolated, Hesperian-age "outflow channels".

Example of inverted terrain in Parana Valles region
Inverted stream channels in Antoniadi Crater. Location is Syrtis Major quadrangle

Some parts of Mars show inverted relief. This occurs when sediments are deposited on the floor of a stream and then become resistant to erosion, perhaps by cementation. Later the area may be buried. Eventually, erosion removes the covering layer and the former streams become visible since they are resistant to erosion. Mars Global Surveyor found several examples of this process.[71][72] Many inverted streams have been discovered in various regions of Mars, especially in the Medusae Fossae Formation,[73] Miyamoto Crater,[74] and the Juventae Plateau.[75][76]

A variety of lake basins have been discovered on Mars.[77] Some are comparable in size to the largest lakes on Earth, such as the Caspian Sea, Black Sea, and Lake Baikal. Lakes that were fed by valley networks are found in the southern highlands. There are places that are closed depressions with river valleys leading into them. These areas are thought to have once contained lakes; one is in Terra Sirenum which had its overflow move through Ma'adim Vallis into Gusev Crater, explored by the Mars Exploration Rover Spirit. Another is near Parana Valles and Loire Vallis.[78] Some lakes are thought to have formed by precipitation, while others were formed from groundwater.[30][31] Lakes are estimated to have existed in the Argyre basin,[32][33] the Hellas basin,[34][35] and maybe in Valles Marineris.[34][36][79][80]

Research, published in January 2010, suggests that Mars also had lakes along parts of the equator. 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 Mars Reconnaissance Orbiter, the researchers speculate that there may have been increased volcanic activity, meteorite impacts or shifts in Mars' orbit during this period to warm Mars' atmosphere enough to melt the abundant ice present in the ground. Volcanoes would have released gases that thickened the atmosphere for a temporary period, trapping more sunlight and making it warm enough for liquid water to exist. In this study, channels were discovered that connected lake basins near Ares Vallis. When one lake filled up, its waters overflowed the banks and carved the channels to a lower area where another lake would form.[81][82] These lakes would be another place to look for evidence (biosignatures) of past life.

On September 27, 2012, NASA scientists announced that the Curiosity rover found evidence for an ancient streambed in Gale Crater, suggesting an ancient "vigorous flow" of water on Mars.[83][84][85][86] In particular, analysis of the now dry streambed indicated that the water ran quickly (3.3 kilometer/hour (3 foot/second)), possibly at hip-depth. Proof of running water came in the form of rounded pebbles and gravel fragments that could have only been weathered by strong liquid currents. Their shape and orientation suggests long-distance transport from above the rim of the crater, where a channel named Peace Vallis feeds into the alluvial fan.

Lake deltas[edit]

Delta in Eberswalde crater

Researchers have found a number of examples of deltas that formed in Martian lakes.[12] Finding deltas is a major sign that Mars once had a lot of liquid 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 wide geographical range.[30]

Groundwater formations[edit]

Main article: Groundwater on Mars
Layers may be formed by groundwater rising up gradually

By 1979 it was thought that outflow channels formed in single, catastrophic ruptures of subsurface water reservoirs, possibly sealed by ice, discharging colossal quantities of water across an otherwise arid Mars surface.[87][88] In addition, evidence in favor of heavy or even catastrophic flooding is found in the giant ripples in the Athabasca Vallis.[89][90] This observation is supported by the sudden ending of the river networks in theatre shaped heads, rather than tapering ones. Additionally, some valleys are often discontinuous, with small sections of uneroded land separating the parts of the river.[91]

Despite the many gigantic flood channels and associated tree-like network of tributaries found on Mars, there are no smaller scale structures that would indicate the origin of the flood waters. It has been suggested that either weathering processes have denuded the geologic evidence, or that rather than floods, they were created by the slow seeping out of groundwater.[92][93] According to this hypothesis, groundwater with dissolved minerals came to the surface, in and around craters, and helped to form layers by adding minerals —especially sulfate— and cementing sediments.[94][95][96][97][98][99] In other words, some layers may be formed by groundwater rising up depositing minerals and cementing sediments. The hardened layers are consequently more protected from erosion. This process may occur instead of layers forming under lakes. A study published in 2011 using data from the Mars Reconnaissance Orbiter, show that the same kinds of sediments exist in a large area that includes Arabia Terra.[100]

Mars Ocean Hypothesis[edit]

Main article: Mars Ocean Hypothesis

The Mars Ocean Hypothesis proposes that the Vastitas Borealis basin was the site of a primordial ocean of liquid water 3.8 billion years ago,[4] and presents evidence that nearly a third of the surface of Mars was covered by a liquid ocean early in the planet's geologic history.[77][101] This primordial ocean, dubbed Oceanus Borealis,[4] would have filled the Vastitas Borealis basin in the northern hemisphere, a region which lies 4–5 km (2.5–3 miles) below the mean planetary elevation, at a time period of approximately 3.8 billion years ago. Early Mars would have required a warmer climate and denser atmosphere to allow liquid water to exist at the surface.[102][103] In addition, the large amount of valley networks strongly supports the possibility of a hydrological cycle on the planet in the past.[104][94]

Data from the Mars Orbiter Laser Altimeter (MOLA), which measures the altitude of all terrain on Mars, was used in 1999 to determine that the watershed for an ocean on Mars would have covered about 75% of the planet.[14] A similar study in June 2010 concluded that such an ocean would have covered 36% of Mars.[12][13] Two different shorelines have been proposed. One, the 'Arabia shoreline', can be traced all around Mars except through the Tharsis volcanic region. The second, the 'Deuteronilus', follows the Vastitas Borealis formation.

However, the existence of a primordial Martian ocean remains controversial among scientists, and the interpretations of some features as 'ancient shorelines' has been challenged.[105][10][10] One problem with the conjectured 2 billion years old (2 Ga) shoreline is that it is not flat — i.e. does not follow a line of constant gravitational potential. A 2007 research article points out that this could be due to a change in distribution in Mars' mass, perhaps due to volcanic eruption or meteor impact; the Elysium volcanic province or the massive Utopia basin that is buried beneath the northern plains have been put forward as the most likely causes.[94]

Present water ice[edit]

Ice patches[edit]

On July 28, 2005, the European Space Agency announced the existence of a crater partially filled with frozen water;[106] some then interpreted the discovery as an "ice lake".[107] Images of the crater, taken by the High Resolution Stereo Camera on board the European Space Agency's Mars Express orbiter, clearly show a broad sheet 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 scientists have attributed most of this height difference to sand dunes beneath the water ice, which are partially visible. While scientists do not refer to the patch as a "lake", the water ice patch is remarkable for its size and for being present throughout the year. Deposits of water ice and layers of frost have been found in many different locations on the planet.

Lake Vostok in Antarctica may have implications for liquid water still existing on Mars because if water existed before the polar ice caps on Mars, it is possible that there is still liquid water below the ice caps.[108]

Equatorial frozen sea[edit]

Surface features consistent with existing pack ice have been discovered in the southern Elysium Planitia.[77] 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 and that such lakes may still exist.[109] Not all scientists agree with these conclusions.[34][110][111]

Polar ice caps[edit]

Main article: Martian polar ice caps
The Mars Global Surveyor acquired this image of the Martian north polar ice cap in early northern summer.
Cross-section of a portion of the north polar ice cap of Mars. The ice depicted in this graphic is approximately 2 kilometers (1.2 miles) thick and 250 km (155 mi) across.

A significant amount of surface hydrogen has been observed globally by the Mars Odyssey GRS.[112] Stoichiometrically estimated water mass fractions indicate that - when free of carbon dioxide - the near surface at the poles consists almost entirely of water covered by a thin veneer of fine material.[112] This is reinforced by MARSIS observations, with an estimated 1.6x106 km3 of water at the southern polar region with Water Equivalent to a Global layer (WEG) 11 meters deep.[113] Additional observations at both poles suggest the total WEG to be 30 m, while the Mars Odyssey NS observations places the lower bound at ~14 cm depth.[114] Geomorphic evidence favors significantly larger quantities of surface water over geologic history, with WEG as deep as 500 m.[114] The current atmospheric reservoir of water, though important as a conduit, is insignificant in volume with the WEG no more than 10 µm.[114]

Both the northern polar cap (Planum Boreum) and the southern polar cap (Planum Australe) are thought to grow in thickness during the winter and partially sublime during the summer. Data obtained by the Mars Express satellite, made it possible in 2004 to confirm that the southern polar cap has ice at a depth of 3.7 kilometres (2.3 mi) below the surface[115] with varying contents of frozen water depending on its latitude. The polar cap is a mixture of CO2 ice and water ice. [15] The second part comprises steep slopes known as scarps, made almost entirely of water ice, that fall away from the polar cap to the surrounding plains.[15] The third part encompasses the vast permafrost fields that stretch for tens of kilometres away from the scarps.[15][116] NASA scientists calculate that the volume of water ice in the south polar ice cap, if melted, would be sufficient to cover the entire planetary surface to a depth of 11 metres (36 ft).[115]

On July 2008, NASA announced that Phoenix confirmed the presence of water ice at its landing site near the polar ice cap.[117] Research published in January 2010 using HiRISE images, stated that understanding the layers is more complicated than was formerly estimated. The brightness of the layers does not just depend on the amount of dust. The angle of the Sun together with the angle of the spacecraft greatly affects the brightness seen by the camera. This angle depends on factors such as the shape of the trough wall and its orientation. Furthermore, the roughness of the surface can greatly change the albedo (amount of reflected light). All of these factors are influenced by the wind which can erode surfaces. The HiRISE camera did not reveal layers that were thinner than those seen by the Mars Global Surveyor. However, it detected more detail within layers.[118]

The shallow radar on board the Mars Reconnaissance Orbiter took measurements of the north polar ice cap and determined that the volume of water ice in the cap is 821,000 cubic kilometers (197,000 cubic miles). That is equal to 30% of the Earth's Greenland ice sheet or enough to cover the surface of Mars to a depth of 5.6 meters.[119]

Ground ice[edit]

For many years, various scientists have suggested that some Martian surfaces look like periglacial regions on Earth.[24] Sometimes it is said that these are regions of permafrost. These observations suggest that frozen water lies right beneath the surface. A common feature in the higher latitudes, patterned ground, can occur in a number of shapes, including stripes and polygons. On the Earth, these shapes are caused by the freezing and thawing of soil.[120] There are other types of evidence for large amounts of frozen water under the surface of Mars, such as terrain softening which rounds sharp topographical features.[121] Besides landscape features that suggest water frozen in the ground, there is evidence from Mars Odyssey's Gamma Ray Spectrometer, theoretical calculations, and direct measurements with the Phoenix lander.[122]

Stages in scallop formation in Hellas quadrangle

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 through the lava and produces a cone. In the Athabasca Valles image, the larger cones were made when the steam passed through the thicker layers of lava. The difference between highest elevation (red) to lowest (dark blue) is 170 metres (560 ft).[123]

Scalloped topography

Certain regions of Mars display scalloped-shaped depressions. The depressions are suspected to be the remains of an ice-rich mantle deposit. Scallops were caused by ice sublimating from frozen soil. This mantle material probably fell from the atmosphere as ice formed on dust when the climate was different due to changes in the tilt of the Mars pole.[124][125] The scallops are typically tens of meters deep and from a few hundred to a few thousand meters across. They can be almost circular or elongated. Some appear to have coalesced causing a large heavily pitted terrain to form. The process of forming the terrain may begin with sublimation from a crack. There are often polygon cracks where scallops form. So the presence of scalloped topography is an indication of frozen ground.[76][126]

Glaciers[edit]

Main article: Glaciers on Mars
View of a 5-km-wide, glacial-like lobe deposit sloping up into a box canyon. The surface has 'moraines', deposits of rocks that show how the glacier advanced.

Many large areas of Mars have been shaped by glaciers. Much of the areas in high latitudes, especially the Ismenius Lacus quadrangle, are suspected to still contain enormous amounts of water ice.[127][128] Recent evidence has led many planetary scientists to believe that water ice still exists as glaciers with thin coverings of insulating rock.[19][23] In March 2010, scientists released the results of a radar study of an area called Deuteronilus Mensae that found widespread evidence of ice lying beneath a few meters of rock debris.[129] Glaciers are associated with fretted terrain, many volcanoes, and even some craters. Researchers have described glacial deposits on Hecates Tholus,[130] Arsia Mons,[12] Pavonis Mons,[131] and Olympus Mons.[132]

Ridges of debris on the surface of the glaciers indicate the direction of ice movement. The surface of some glaciers has rough textures due to sublimation of buried ice. The ice evaporates without melting and leaves behind an empty space. Overlying material then collapses into the void.[133] Glaciers are not pure ice; they contain sand and rocks. At times, they deposit their loads of material onto ridges called moraines. Some places on Mars have groups of ridges that are twisted around; this may have been due to more movement after the ridges were formed. Sometimes chunks of ice fall from the glacier and get buried in the land surface. When they melt, a more or less round hole remains.[134]

Moving ice carries rock material, then drops it as the ice disappears. On Mars, with its extremely thin atmosphere, ice does not usually melt but instead sublimes. As a result, the rock debris are just dropped, and melt water is not produced so the remains of these glaciers do not appear the same as on Earth. Various names have been applied to these ridged features. Depending on the author, they may be called arcuate ridges,[135] viscous flow features,[136] moraine-like ridges or Martian flow features. Many, but not all, seem to be associated with gullies on the walls of craters and mantling material.[137]

Reull Vallis with lineated floor deposits. Location is Hellas quadrangle

Lineated deposits are probably rock-covered glaciers which are found on the floors of some channels. Their surfaces have ridged and grooved materials that deflect around obstacles. Lineated floor deposits may be related to Lobate Debris Aprons, which have been proven to contain large amounts of ice by orbiting radar.[19][23] For many years, researchers interpreted that features called 'Lobate Debris Aprons' were glacial flows and it was thought that ice existed under a layer of insulating rocks.[20][21][22] With new instrument readings, it has been confirmed that Lobate Debris Aprons contain almost pure ice that is covered with a layer of rocks. [19][23]

Glaciers formed much of the observable surface in large areas of Mars. Much of the area in high latitudes, especially the Ismenius Lacus quadrangle, is suspected to still contain enormous amounts of water ice.[24][128] Recent evidence has led many planetary scientists to believe that water ice still exists as glaciers with a thin covering of insulating rock.[19][23][138] In March 2010, scientists released the results of a radar study of an area called Deuteronilus Mensae that found widespread evidence of ice lying beneath a few meters of rock debris. Glaciers are sometimes associated with fretted terrain, volcanoes,[34][139] and even some craters. Ridges of debris on the surface of the glaciers show the direction of ice movement.

Alpine glaciers[edit]

A terminal moraine of an alpine glacier. Location is Ismenius Lacus quadrangle

Using data acquired by the Mars Global Surveyor and Odyssey orbiters, 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 that flows over other deposits (debris-covered glacial ice). Researchers have described glacial deposits on Hecates Tholus,[130] Arisia Mons,[12] Pavonis Mons,[131] and Olympus Mons.[132]

Ice ages[edit]

North polar layered deposits of ice and dust
Dissected mantle with layers. Location is Noachis quadrangle

Ice ages on Mars are far different than the ones that the Earth experiences. During a Martian ice age, the poles get warmer, water ice then leaves the ice caps and is deposited in mid latitudes.[140] The moisture from the ice caps travels to lower latitudes in the form of deposits of frost or snow mixed with dust. The atmosphere of Mars contains a great deal of fine dust particles, the 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.[140] The total volume of water removed is about a few percent of the ice caps, or enough to cover the entire surface of the planet under one meter of water. Much of this moisture from the ice caps results in a thick smooth mantle with a mixture of ice and dust.[124][141][142] This ice-rich mantle, a few yards thick, smoothes the land at lower latitudes, but in places it displays a bumpy texture. Multiple stages of glaciations probably occurred.[139] Because there are few craters on the current mantle, it is thought to be relatively young. It is thought that this mantle was laid in place during a relatively recent ice age.

Ice ages are driven by changes in Mars's orbit and tilt. Orbital calculations show that Mars wobbles on its axis far more than Earth does. The Earth is stabilized by its proportionally large moon, so it only wobbles a few degrees. Mars, in contrast, may change its tilt by tens of degrees.[125] Its poles get much more direct sunlight and heat at times, which causes the ice caps to warm and become smaller as ice sublimes. Adding to the variability of the climate, the eccentricity of the orbit of Mars changes twice as much as Earth's eccentricity. Computer simulations have shown that a 45° tilt of the Martian axis would result in ice accumulation in areas that display glacial landforms.[143] A 2008 study provided evidence for multiple glacial phases during Late Amazonian glaciation at the dichotomy boundary on Mars.[144]

Recent seasonal flows[edit]

Main article: Seasonal flows on warm Martian slopes
Warm-season flows on slope in Newton Crater
Branched gullies
Group of deep gullies

Liquid water cannot exist on the surface of Mars with its present low atmospheric pressure and low temperature, except at the lowest elevations for a few hours.[145][116] So, a geological mystery commenced when observations from NASA's Mars Reconnaissance Orbiter revealed gully deposits that were not there ten years ago, possibly caused by flowing salty water (brine) during the warmest months on Mars.[146][147][148][149][150][151][149][152][153][154] The images were of two craters called Terra Sirenum and Centauri Montes which appear to show the presence of liquid water flows on Mars at some point between 1999 and 2001.[155][156][149][157] In August 2011, NASA announced the discovery by Nepalese student Lujendra Ojha[158] of current seasonal changes in gullies near crater rims on the Southern hemisphere. The researchers again suggested salty water (brines) flowing and then evaporating, possibly leaving some sort of residue.[159]

There is disagreement in the scientific community as to whether or not the recent gully streaks were formed by liquid water. A team suggests the flows were merely dry flows,[160] dry flows that were started by a rock fall in steep regions,[74] or liquid brine near the surface might explain this activity,[147][161][162] but the exact source of the water and the mechanism behind its motion are not understood.[125]

Habitability assessment[edit]

Main article: Life on Mars

Life is understood to require liquid water, but it is not the only essential requirement for life.[163][164] [165] The confirmation that liquid water once flowed on Mars, the existence of nutrients, and the previous discovery of a past magnetic field that protected the planet from cosmic and solar radiation,[166][167] together strongly suggest that Mars could have had the environmental factors to support life.[42] To be clear, the find of past habitability is not evidence that Martian life has ever actually existed.

An electron microscope reveals bacteria-like structures in meteorite fragment ALH84001

When there is a magnetic field, the atmosphere is protected from erosion by solar wind, and ensures the maintenance of a dense atmosphere, necessary for liquid water to exist on the surface of Mars.[168][169] The two current ecological approaches for predicting the potential habitability of the Martian surface use 19 or 20 environmental factors, with emphasis on water availability, temperature, presence of nutrients, an energy source, and protection from solar ultraviolet and galactic cosmic radiation.[164][165] In particular, the damaging effect of ionising radiation on cellular structure is one of the prime limiting factors on the survival of life in potential astrobiological habitats.[43][44] Even at a depth of 2 meters beneath the surface, any microbes would likely be dormant, cryopreserved by the current freezing conditions, and so metabolically inactive and unable to repair cellular degradation as it occurs.[43][44][165][170][171][172][46]

Therefore, the best potential locations for discovering life on Mars may be at subsurface environments that have not been studied yet.[46][47][173][174][175] The extensive volcanism in the past, possibly created subsurface cracks and caves within different strata, and liquid water could have been stored in these subterraneous places, forming large aquifers with deposits of saline liquid water, minerals, organic molecules, and geothermal heat – potentially providing a current habitable environment away from the harsh surface conditions.[46][45][176][177][178][179][93]

Findings by probes[edit]

Main article: Chronology of discoveries of water on Mars

Mariner 9[edit]

Meander in Scamander Vallis, as seen by Mariner 9. Such images implied that large amounts of water once flowed on the surface of Mars.

The images acquired by the Mariner 9 Mars orbiter, launched in 1971, revealed the first direct evidence of past water in the form of dry river beds, canyons (including the Valles Marineris, a system of canyons over about 4,020 kilometres (2,500 mi) long), evidence of water erosion and deposition, weather fronts, fogs, and more.[180] The findings from the Mariner 9 missions underpinned the later Viking program. The enormous Valles Marineris canyon system is named after Mariner 9 in honor of its achievements.

Viking program[edit]

Main article: Viking program
Streamlined islands in Maja Valles suggest that large floods occurred on Mars

By discovering many geological forms that are typically formed from large amounts of water, the two Viking orbiters and the two landers caused a revolution in our knowledge about water on Mars. Huge river valleys were found in many areas. They showed that floods of water broke through dams, carved deep valleys, eroded grooves into bedrock, and traveled thousands of kilometers.[16] Large areas in the southern hemisphere contained branched valley networks, suggesting that rain once fell.[181] Many craters look as if the impactor fell into mud. When they were formed, ice in the soil may have melted, turned the ground into mud, then the mud flowed across the surface.[182][24][68][69] Regions, called "Chaotic Terrain," seemed to have quickly lost great volumes of water which caused large channels to form downstream. Estimates for some channel flows run to ten thousand times the flow of the Mississippi River.[37] Underground volcanism may have melted frozen ice; the water then flowed away and the ground collapsed to leave chaotic terrain. Also, general chemical analysis by the two Viking landers suggested the surface has been either exposed to or submerged in water in the past.[183][184]

Mars Global Surveyor[edit]

Main article: Mars Global Surveyor
Map showing the distribution of hematite in Sinus Meridiani. This data was used to target the landing of the Opportunity rover that found definite evidence of past water.

The Mars Global Surveyor's Thermal Emission Spectrometer (TES) is an instrument able to determine the mineral composition on the surface of Mars. Mineral composition gives information on the presence or absence of water in ancient times. TES identified a large (30,000 km2) area in the Nili Fossae formation that contains the mineral olivine. It is thought that the ancient asteroid impact that created the Isidis basin resulted in faults that exposed the olivine. The discovery of olivine is strong evidence that parts of Mars have been extremely dry for a long time. Olivine was also discovered in many other small outcrops within 60 degrees north and south of the equator.[185] The probe has imaged several channels that suggest past sustained liquid flows, two of them are found in Nanedi Valles and in Nirgal Vallis.[150]

Inner channel (near top of the image) on floor of Nanedi Valles that suggests that water flowed for a fairly long period. Image from Lunae Palus quadrangle.

Mars Pathfinder[edit]

Main article: Mars Pathfinder

The Pathfinder lander recorded the variation of diurnal temperature cycle. It was coldest just before sunrise, about −78 °Celsius, and warmest just after Mars noon, about −8 °Celsius. These extremes occurred near the ground which both warmed up and cooled down fast. At this location, the highest temperature never reached the freezing point of water (0 °C), too cold for pure liquid water to exist on the surface.

Surface pressures varied diurnally over a 0.2 millibar range, but showed 2 daily minima and two daily maxima. The average daily pressure decreased from about 6.75 millibars to a low of just under 6.7 millbars, corresponding to when the maximum amount of carbon dioxide had condensed on the South Pole. The atmospheric pressure measured by the Pathfinder on Mars is very low —about 0.6% of Earth's, and it would not permit liquid water to exist on the surface.[186]

Other observations were consistent with water being present in the past. Some of the rocks at the Mars Pathfinder site leaned against each other in a manner geologists term imbricated. It is suspected that strong flood waters in the past pushed the rocks around until they faced away from the flow. Some pebbles were rounded, perhaps from being tumbled in a stream. Parts of the ground are crusty, maybe due to cementing by a fluid containing minerals.[187] There was evidence of clouds and maybe fog.[187]

Mars Odyssey[edit]

Main article: Evidence of water on Mars from Mars Odyssey
Complex drainage system in Semeykin Crater. Location is Ismenius Lacus quadrangle
Blocks in Aram showing a possible ancient source of water. Location is Oxia Palus quadrangle

The 2001 Mars Odyssey found much evidence for water on Mars in the form of images, and with its spectrometer, it proved that much of the ground is loaded with water ice. Mars has enough ice just beneath the surface to fill Lake Michigan twice.[1] In both hemispheres, from 55° 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.[2] Scientists think that much of this water is also locked up in the chemical structure of minerals, such as clay and sulfates.[188][189] Although the upper surface contains a few percent of chemically-bound water, ice lies just a few meters deeper, as it has been shown in Arabia Terra, Amazonis quadrangle, and Elysium quadrangle that contain large amounts of water ice.[190] Analysis of the data suggests that the southern hemisphere may have a layered structure, suggestive of stratified deposits beneath a now extinct large water mass.[191]

Branched channels near Warrego Valles

The instruments aboard the Mars Odyssey are only able to study the top meter of soil, while the radar aboard the Mars Reconnaissance Orbiter can measure a few kilometers deep. In 2002, available data were used to calculate that if all soil surfaces were covered by an even layer of water, this would correspond to a global layer of water (GLW) 0.5 to 1.5 km deep.[192]

Thousands of images returned from Odyssey orbiter also support the idea that Mars once had great amounts of water flowing across its surface. Some images show patterns of branching valleys; others show layers that may have been formed under lakes; even river and lake deltas have been identified.[30][193] For many years researchers thought that glaciers existed under a layer of insulating rocks.[20][21][22][19][23] Lineated valley fill is one example of these rock-covered glaciers. They are found on the floors of some channels. Their surfaces have ridged and grooved materials that deflect around obstacles. Lineated floor deposits may be related to lobate debris aprons, which have been shown by orbiting radar to contain large amounts of ice.[19][23][19]

Phoenix[edit]

Main article: Phoenix (spacecraft)
Permafrost polygons imaged by the Phoenix lander

The Phoenix lander also confirmed the existence of large amounts of water ice in the northern region of Mars.[194][195] This finding was predicted by previous orbital data and theory.[196] and was measured from orbit by the Mars Odyssey instruments.[2] On June 19, 2008, NASA announced that dice-sized clumps of bright material in the "Dodo-Goldilocks" trench, dug by the robotic arm, had vaporized over the course of four days, strongly implying that the bright clumps were composed of water ice which sublimes following exposure. Even though CO2 (dry ice) also sublimes under the conditions present, it would do so at a rate much faster than observed.[197] On July 31, 2008, NASA announced that Phoenix confirmed the presence of water ice at its landing site. During the initial heating cycle of a sample, the mass spectrometer detected water vapor when the sample temperature reached 0 °C.[117] Liquid water cannot exist on the surface of Mars with its present low atmospheric pressure and temperature, except at the lowest elevations for short periods.[145][116][194][198]

Perchlorate (ClO4), a strong oxidizer, was confirmed to be in the soil. The chemical, when mixed with water, can lower the water freezing point in a manner similar to how salt is applied to roads to melt ice. It has been hypothesized that perchlorate may be allowing small amounts of liquid water to form on Mars today and may have formed visible gullies by eroding soil on steep slopes.[199][200]

View underneath Phoenix lander showing water ice exposed by the landing retrorockets

Additionally, during 2008 and early 2009, a debate emerged within NASA over the presence of 'blobs' which appeared on photos of the vehicle's landing struts, which have been variously described as being either water droplets or 'clumps of frost'.[201][201][201][202][203][204]

For about as far as the camera can see, the landing site is flat, but shaped into polygons between 2 and 3 meters in diameter and are bounded by troughs that are 20 cm to 50 cm deep. These shapes are due to ice in the soil expanding and contracting due to major temperature changes. The microscope showed that the soil on top of the polygons is composed of rounded particles and flat particles, probably a type of clay.[205] 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 slowly sublimes.[198]

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 (CO2 or dry ice) because the temperature for forming carbon dioxide ice is much lower than −120 °C. As a result of mission observations, it is now suspected that water ice (snow) would have accumulated later in the year at this location.[206] The highest temperature measured during the mission, which took place during the Martian summer, was −19.6 °C, while the coldest was −97.7 °C. So, in this region the temperature remained far below the freezing point (0° C) of water.[207]

Mars Exploration Rovers[edit]

Main article: Mars Exploration Rover
Close up of a rock outcrop
Thin rock layers, not all parallel to each other
Hematite spherules
Partly embedded spherules

The Mars Exploration Rovers, Spirit and Opportunity found a great deal of evidence for past water on Mars. Designed to last only three months, Opportunity continues to provide scientific discovery. The Spirit rover landed in what was thought to be a large lake bed. However, the lake bed had been covered over with lava flows, so evidence of past water was initially hard to detect. On March 5, 2004, NASA announced that Spirit had found hints of water history on Mars in a rock dubbed "Humphrey".[208]

As Spirit traveled in reverse in December 2007, pulling a seized wheel behind, the wheel scraped off the upper layer of soil, uncovering a patch of white ground rich in silica. Scientists think that it must have been produced in one of two ways.[209] 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.[210] The Spirit rover also found evidence for water in the Columbia Hills of Gusev crater. In the Clovis group of rocks the Mossbauer spectrometer (MB) detected goethite,[211] that forms only in the presence of water.[212][213][214] iron in the oxidized form Fe+++,[215] carbonate-rich rocks, which means that regions of the planet once harbored water.[216][217]

The Opportunity rover was directed to a site that had displayed large amounts of hematite from orbit. Hematite often forms from water. The rover indeed found layered rocks and marble-like hematite concretions. In its years of continuous operation, Opportunity is still sending back evidence that this area on Mars was soaked in liquid water in the past.[218]

However, the MER rovers had been finding evidence for ancient wet environments that were very acidic. In fact, what Opportunity has mostly discovered, or found evidence for, was sulphuric acid, a harsh chemical for life.[26][27][219][220] But in May 17, 2013, NASA announced that Opportunity found clay deposits that typically form in wet environments that are near neutral acidity. This find provides additional evidence about a wet ancient environment possibly favorable for life.[27][26]

Mars Reconnaissance Orbiter[edit]

Main article: Evidence of water on Mars found by Mars Reconnaissance Orbiter
Springs in Vernal Crater, as seen by HIRISE. These springs may be good places to look for evidence of past life because hot springs can preserve evidence of life forms for a long time. Location is Oxia Palus quadrangle.

The Mars Reconnaissance Orbiter's HiRISE instrument has taken many images that strongly suggest that Mars has had a rich history of water-related processes. A major discovery was finding evidence of ancient hot springs. If they have hosted microbial life, they may contain biosignatures.[221] Research published in January 2010, described strong evidence for sustained precipitation in the area around Valles Marineris.[75][76] The types of minerals there are associated with water. Also, the high density of small branching channels indicates a great deal of precipitation.

Rocks on Mars have been found to frequently occur as layers, called strata, in many different places.[222] Layers form by various ways, including volcanoes, wind, or water.[223] Light-toned rocks on Mars have been associated with hydrated minerals like sulfates and clay.[28][224]

Layers on the west slope of Asimov Crater. Location is Noachis quadrangle.

The orbiter helped scientists determine that much of the surface of Mars is covered by a thick smooth mantle that is thought to be a mixture of ice and dust.[124][225][226]

The ice mantle under the shallow subsurface is thought to result from frequent, major climate changes. Changes in Mars' 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.[154] 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.[140]

In 2008, research with the Shallow Radar on the Mars Reconnaissance Orbiter provided strong evidence that the lobate debris aprons (LDA) in Hellas Planitia and in mid northern latitudes are glaciers that are covered with a thin layer of rocks. Its radar also detected a strong reflection from the top and base of LDAs, meaning that pure water ice made up the bulk of the formation.[23] The discovery of water ice in LDAs demonstrates that water is found at even lower latitudes.[24]

Research published in September 2009, demonstrated that some new craters on Mars show exposed, pure water ice.[227] After a time, the ice disappears, evaporating into the atmosphere. The ice is only a few feet deep. The ice was confirmed with the Compact Imaging Spectrometer (CRISM) on board the Mars Reconnaissance Orbiter.[228]

Curiosity rover[edit]

Main article: Timeline of MSL Curiosity mission
"Hottah" rock outcrop - an ancient streambed discovered by the Curiosity rover team (September 14, 2012) (close-up) (3-D version).
Rock outcrop on Mars - compared with a terrestrial fluvial conglomerate - suggesting water "vigorously" flowing in a stream.[83][84][85]

On October 2012, the first X-ray diffraction analysis of Martian soil was performed. The results revealed the presence of several minerals, including feldspar, pyroxenes and olivine, and suggested that the Martian soil in the sample was similar to the weathered basaltic soils of Hawaiian volcanoes. The sample used is composed of dust distributed from global dust storms and local fine sand. So far, the materials Curiosity has analyzed are consistent with the initial ideas of deposits in Gale Crater recording a transition through time from a wet to dry environment.[229]

On December 2012, NASA reported that Curiosity performed its first extensive soil analysis, revealing the presence of water molecules, sulfur and chlorine in the Martian soil.[230][231] And on March 2013, NASA reported evidence of mineral hydration, likely hydrated calcium sulfate, in several rock samples including the broken fragments of "Tintina" rock and "Sutton Inlier" rock as well as in veins and nodules in other rocks like "Knorr" rock and "Wernicke" rock.[232][233][234] Analysis using the rover's DAN instrument provided evidence of subsurface water, amounting to as much as 4% water content, down to a depth of 60 cm (2.0 ft), in the rover's traverse from the Bradbury Landing site to the Yellowknife Bay area in the Glenelg terrain.[232]

Image gallery[edit]

River valleys
Gullies
Glaciers

  • Glacier moving down valley, then spreading out on plain. Location is Ismenius Lacus quadrangle

  • This is the terminal moraine of a glacier. For scale, the box shows the approximate size of a football field. Location is Hellas quadrangle

  • Radar studies indicate that this glacier contains mostly pure water ice. It is moving from the right. Location is Ismenius Lacus quadrangle.

  • Tongue-Shaped Glacier. Location is Hellas quadrangle.

Other

  • The white area is water ice that has been exposed by an impact. Location is Cebrenia quadrangle.

See also[edit]

References[edit]

  1. ^ a b "Mars Odyssey: Newsroom". Mars.jpl.nasa.gov. May 28, 2002. Retrieved December 19, 2010. 
  2. ^ a b c Feldman, W. C. (2004). "Global distribution of near-surface hydrogen on Mars". J. Geographical Research 109. Bibcode:2004JGRE..10909006F. doi:10.1029/2003JE002160. 
  3. ^ "Mars Global Surveyor Measures Water Clouds". Retrieved March 7, 2009. 
  4. ^ a b c Baker, V. R.; Strom, R. G.; Gulick, V. C.; Kargel, J. S.; Komatsu, G.; Kale, V. S. (1991). "Ancient oceans, ice sheets and the hydrological cycle on Mars". Nature 352 (6348): 589–594. Bibcode:1991Natur.352..589B. doi:10.1038/352589a0. 
  5. ^ "Flashback: Water on Mars Announced 10 Years Ago". SPACE.com. June 22, 2000. Retrieved December 19, 2010. 
  6. ^ "Science@NASA, The Case of the Missing Mars Water". Retrieved March 7, 2009. 
  7. ^ ISBN 0-312-24551-3
  8. ^ "PSRD: Ancient Floodwaters and Seas on Mars". Psrd.hawaii.edu. July 16, 2003. Retrieved December 19, 2010. 
  9. ^ "Gamma-Ray Evidence Suggests Ancient Mars Had Oceans". SpaceRef. November 17, 2008. Retrieved December 19, 2010. 
  10. ^ a b c Carr, M., Head, J. (2003). "Oceans on Mars: An assessment of the observational evidence and possible fate". Journal of Geophysical Research 108: 5042. Bibcode:2003JGRE..108.5042C. doi:10.1029/2002JE001963. 
  11. ^ Harwood, William (January 25, 2013). "Opportunity rover moves into 10th year of Mars operations". Space Flight Now. Retrieved February 18, 2013. 
  12. ^ a b c d e Di Achille, Gaetano; Hynek, Brian M. (2010). "Ancient ocean on Mars supported by global distribution of deltas and valleys". Nature Geoscience 3 (7): 459. Bibcode:2010NatGe...3..459D. doi:10.1038/ngeo891. 
  13. ^ a b c "Ancient ocean may have covered third of Mars". Sciencedaily.com. June 14, 2010. Retrieved December 19, 2010. 
  14. ^ a b Smith, D. et al. (1999). "The Gravity Field of Mars: Results from Mars Global Surveyor". Science 284 (5437): 94–97. Bibcode:1999Sci...286...94S. doi:10.1126/science.286.5437.94. 
  15. ^ a b c d "Water at Martian south pole". European Space Agency (ESA). 17 March 2004. Retrieved 2009-09-11. 
  16. ^ a b c "ch4". History.nasa.gov. Retrieved December 19, 2010. 
  17. ^ Harrison, K, Grimm, R. (2005). "Groundwater-controlled valley networks and the decline of surface runoff on early Mars". Journal of Geophysical Research 110. Bibcode:2005JGRE..11012S16H. doi:10.1029/2005JE002455. 
  18. ^ Howard, A.; Moore, Jeffrey M.; Irwin, Rossman P. (2005). "An intense terminal epoch of widespread fluvial activity on early Mars: 1. Valley network incision and associated deposits". Journal of Geophysical Research 110. Bibcode:2005JGRE..11012S14H. doi:10.1029/2005JE002459. 
  19. ^ a b c d e f g h Plaut, Jeffrey J.; Safaeinili, Ali; Holt, John W.; Phillips, Roger J.; Head, James W.; Seu, Roberto; Putzig, Nathaniel E.; Frigeri, Alessandro (2009). "Radar Evidence for Ice in Lobate Debris Aprons in the Mid-Northern Latitudes of Mars". Geophysical Research Letters 36 (2). Bibcode:2009GeoRL..3602203P. doi:10.1029/2008GL036379. 
  20. ^ a b c d Head, JW; Neukum, G; Jaumann, R; Hiesinger, H; Hauber, E; Carr, M; Masson, P; Foing, B et al. (2005). "Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars". Nature 434 (7031): 346–350. Bibcode:2005Natur.434..346H. doi:10.1038/nature03359. PMID 15772652. 
  21. ^ a b c Source: Brown University Posted Monday, October 17, 2005 (2005-10-17). "Mars' climate in flux: Mid-latitude glaciers". Marstoday. Retrieved 2013-06-13. 
  22. ^ a b c Richard Lewis (2008-04-23). "Glaciers Reveal Martian Climate Has Been Recently Active". Brown University. Retrieved 2013-02-10. 
  23. ^ a b c d e f g h Holt, J. W.; Safaeinili, A.; Plaut, J. J.; Young, D. A.; Head, J. W.; Phillips, R. J.; Campbell, B. A.; Carter, L. M. et al. (2008). "Radar Sounding Evidence for Ice within Lobate Debris Aprons near Hellas Basin, Mid-Southern Latitudes of Mars". Lunar and Planetary Science. XXXIX: 2441. Bibcode:2008LPI....39.2441H. 
  24. ^ a b c d e Hugh H. Kieffer (1992). Mars. University of Arizona Press. ISBN 978-0-8165-1257-7. Retrieved March 7, 2011. 
  25. ^ "New Signs That Ancient Mars Was Wet". Space.com. 2008-10-28. Retrieved 2013-02-10. 
  26. ^ a b c "Old Opportunity Mars rover makes rock discovery". NASA (BBC News). 10 June 2013. Retrieved 2013-06-14. 
  27. ^ a b c "Mars Rover Opportunity Examines Clay Clues in Rock". NASA (Jet Propulsion Laboratory). May 17, 2013. Retrieved 2013-06-14. 
  28. ^ a b "Was there life on Mars? – ITV News". Itv.com. Retrieved December 19, 2010. 
  29. ^ Glotch, T. and P. Christensen. 2005. Geologic and mineralogical mapping of Aram Chaos: Evidence for water-rich history. J. Geophys. Res. 110. doi:10.1029/2004JE002389
  30. ^ a b c d Irwin, Rossman P.; Howard, Alan D.; Craddock, Robert A.; Moore, Jeffrey M. (2005). "An intense terminal epoch of widespread fluvial activity on early Mars: 2. Increased runoff and paleolake development". Journal of Geophysical Research 110. Bibcode:2005JGRE..11012S15I. doi:10.1029/2005JE002460. 
  31. ^ a b Fassett, C., Head, III (2008). "Valley network-fed, open-basin lakes on Mars: Distribution and implications for Noachian surface and subsurface hydrology". Icarus 198: 37–56. Bibcode:2008Icar..198...37F. doi:10.1016/j.icarus.2008.06.016. 
  32. ^ a b Parker, T.; Clifford, S. M.; Banerdt, W. B. (2000). "Argyre Planitia and the Mars Global Hydrologic Cycle" (PDF). Lunar and Planetary Science XXXI: 2033. Bibcode:2000LPI....31.2033P. 
  33. ^ a b Heisinger, H., Head, J. (2002). "Topography and morphology of the Argyre basin, Mars: implications for its geologic and hydrologic history". Planet. Space Sci. 50 (10–11): 939–981. Bibcode:2002P&SS...50..939H. doi:10.1016/S0032-0633(02)00054-5. 
  34. ^ a b c d e "The Surface of Mars" Series: Cambridge Planetary Science (No. 6) ISBN: 978-0-511-26688-1 Michael H. Carr, United States Geological Survey, Menlo Park
  35. ^ a b Moore, J., Wilhelms, D. (2001). "Hellas as a possible site of ancient ice-covered lakes on Mars". Icarus 154 (2): 258–276. Bibcode:2001Icar..154..258M. doi:10.1006/icar.2001.6736. 
  36. ^ a b Weitz, C.; Parker, T. (2000). "New evidence that the Valles Marineris interior deposits formed in standing bodies of water" (PDF). Lunar and Planetary Science XXXI: 1693. Bibcode:2000LPI....31.1693W. 
  37. ^ a b Morton, O. 2002. Mapping Mars. Picador, NY, NY
  38. ^ Head, J. and D. Marchant. 2006. Evidence for global-scale northern mid-latitude glaciation in the Amazonian period of Mars: Debris-covered glacial and valley glacial deposits in the 30 - 50 N latitude band. Lunar. Planet. Sci. 37. Abstract 1127
  39. ^ Head, J. and D. Marchant. 2006. Modifications of the walls of a Noachian crater in Northern Arabia Terra (24 E, 39 N) during northern mid-latitude Amazonian glacial epochs on Mars: Nature and evolution of Lobate Debris Aprons and their relationships to lineated valley fill and glacial systems. Lunar. Planet. Sci. 37. Abstract 1128
  40. ^ Head, J., et al. 2006. Modification if the dichotomy boundary on Mars by Amazonian mid-latitude regional glaciation. Geophys. Res Lett. 33
  41. ^ Garvin, J. et al. 2002. Lunar Planet. Sci: 33. Abstract # 1255.
  42. ^ a b Wall, Mike (25 March 2011). "Q & A with Mars Life-Seeker Chris Carr". Space.com. Retrieved 2011-03-25. 
  43. ^ a b c Dartnell, L.R.; Desorgher, Ward, Coates (30 January 2007). "Modelling the surface and subsurface Martian radiation environment: Implications for astrobiology". Geophysical Research Letters 34 (2). doi:10.1029/2006GL027494. Retrieved 2013-05-26. "The damaging effect of ionising radiation on cellular structure is one of the prime limiting factors on the survival of life in potential astrobiological habitats." 
  44. ^ a b c "Martian sub-surface ionising radiation: biosignatures and geology". Biogeosciences 4: 545–558. 2007. Retrieved 2013-06-01. "This ionising radiation field is deleterious to the survival of dormant cells or spores and the persistence of molecular biomarkers in the subsurface, and so its characterisation. [..] Even at a depth of 2 meters beneath the surface, any microbes would likely be dormant, cryopreserved by the current freezing conditions, and so metabolically inactive and unable to repair cellular degradation as it occurs." 
  45. ^ a b "A Possible Biochemical Model for Mars" (PDF). 43rd Lunar and Planetary Science Conference (2012). 2012. Retrieved 2013-06-05. "The extensive volcanism at that time much possibly created subsurface cracks and caves within different strata, and the liquid water could have been stored in these subterraneous places, forming large aquifers with deposits of saline liquid water, minerals organic molecules, and geothermal heat – ingredients for life as we know on Earth." 
  46. ^ a b c d "Scientists find evidence Mars subsurface could hold life". Digital Journal - Science. 21 January. Retrieved 2013-06-05. "There can be no life on the surface of Mars because it is bathed in radiation and it's completely frozen. However, life in the subsurface would be protected from that. - Prof. Parnell." 
  47. ^ a b Steigerwald, Bill (January 15, 2009). "Martian Methane Reveals the Red Planet is not a Dead Planet". NASA's Goddard Space Flight Center (NASA). Retrieved June 6 24, 2013. "If microscopic Martian life is producing the methane, it likely resides far below the surface, where it's still warm enough for liquid water to exist" 
  48. ^ Staff (July 2, 2012). "Ancient Mars Water Existed Deep Underground". Space.com. Retrieved July 3, 2012. 
  49. ^ Craddock, R.; Howard, A. (2002). "The case for rainfall on a warm, wet early Mars". J. Geophys. Res 107: E11. 
  50. ^ Head, J. et al. (2006). "Extensive valley glacier deposits in the northern mid-latitudes of Mars: Evidence for the late Amazonian obliquity-driven climate change". Earth Planet. Sci. Lett. 241: 663–671. 
  51. ^ Madeleine, J. et al. 2007. Mars: A proposed climatic scenario for northern mid-latitude glaciation. Lunar Planet. Sci. 38. Abstract 1778.
  52. ^ Madeleine, J. et al. (2009). "Amazonian northern mid-latitude glaciation on Mars: A proposed climate scenario". Icarus 203: 300–405. 
  53. ^ Mischna, M. et al. 2003. On the orbital forcing of Martian water and CO2 cycles: A general circulation model study with simplified volatile schemes. J. Geophys. Res. 108. (E6). 5062.
  54. ^ Source: NASA HQ Posted Tuesday, October 28, 2008 (2008-10-28). "NASA Mars Reconnaissance Orbiter Reveals Details of a Wetter Mars". SpaceRef. Retrieved 2013-02-10. 
  55. ^ Swindle, T. D.; Treiman, A. H.; Lindstrom, D. J.; Burkland, M. K.; Cohen, B. A.; Grier, J. A.; Li, B.; Olson, E. K. (2000). "Noble Gases in Iddingsite from the Lafayette meteorite: Evidence for Liquid water on Mars in the last few hundred million years". Meteoritics and Planetary Science 35 (1): 107–115. Bibcode:2000M&PS...35..107S. doi:10.1111/j.1945-5100.2000.tb01978.x. 
  56. ^ Gulick, V., Baker, V. (1989). "Fluvial valleys and martian palaeoclimates". Nature 341 (6242): 514–516. Bibcode:1989Natur.341..514G. doi:10.1038/341514a0. 
  57. ^ Head, J.; Kreslavsky, M. A.; Ivanov, M. A.; Hiesinger, H.; Fuller, E. R.; Pratt, S. (2001). "Water in Middle Mars History: New Insights From MOLO Data". American Geophysical Union. Bibcode:2001AGUSM...P31A02H. 
  58. ^ Head, J. et al. (2001). "Exploration for standing Bodies of Water on Mars: When Were They There, Where did They go, and What are the Implications for Astrobiology?". American Geophysical Union 21: 03. Bibcode:2001AGUFM.P21C..03H. 
  59. ^ "Mars Rover's Meteorite Discovery Triggers Questions". Space.com. Retrieved 2013-02-10. 
  60. ^ a b Lunine, Jonathan I.; John Chambers et al. (September 2003). "The Origin of Water on Mars". Icarus 165 (1). doi:10.1016/S0019-1035(03)00172-6. Retrieved 2013-06-10. 
  61. ^ "Shergotty Meteorite – JPL, NASA". .jpl.nasa.gov. Retrieved December 19, 2010. 
  62. ^ Hamiliton, W.; Christensen, Philip R.; McSween, Harry Y. (1997). "Determination of Martian meteorite lithologies and mineralogies using vibrational spectroscopy". Journal of Geophysical Research 102: 25593–25603. Bibcode:1997JGR...10225593H. doi:10.1029/97JE01874. 
  63. ^ Treiman, A (2005). "The nakhlite meteorites: Augite-rich igneous rocks from Mars". Chemie der Erde – Geochemistry 65 (3): 203. Bibcode:2005ChEG...65..203T. doi:10.1016/j.chemer.2005.01.004. Retrieved September 8, 2006. 
  64. ^ McKay, D.; Gibson Jr, EK; Thomas-Keprta, KL; Vali, H; Romanek, CS; Clemett, SJ; Chillier, XD; Maechling, CR et al. (1996). "Search for Past Life on Mars: Possible Relic Biogenic Activity in Martian Meteorite AL84001". Science 273 (5277): 924–930. Bibcode:1996Sci...273..924M. doi:10.1126/science.273.5277.924. PMID 8688069. 
  65. ^ Gibbs, W.; Powell, C. (August 19, 1996). "Bugs in the Data?". Scientific American. 
  66. ^ "Controversy Continues: Mars Meteorite Clings to Life – Or Does It?". SPACE.com. March 20, 2002. Retrieved December 19, 2010. 
  67. ^ Bada, J.; Glavin, DP; McDonald, GD; Becker, L (1998). "A Search for Endogenous Amino Acids in Martian Meteorite AL84001". Science 279 (5349): 362–365. Bibcode:1998Sci...279..362B. doi:10.1126/science.279.5349.362. PMID 9430583. 
  68. ^ a b Raeburn, P. 1998. Uncovering the Secrets of the Red Planet Mars. National Geographic Society. Washington D.C.
  69. ^ a b Moore, P. et al. 1990. The Atlas of the Solar System. Mitchell Beazley Publishers NY, NY.
  70. ^ ed, Hugh H. Kieffer ... (1994). Mars ([2. Aufl.]. ed.). Tucson [u.a.]: Univ. of Arizona Press. ISBN 0-8165-1257-4. 
  71. ^ Malin (2010). "An overview of the 1985–2006 Mars Orbiter Camera science investigation". The Mars Journal 5: 1. Bibcode:2010IJMSE...5....1M. doi:10.1555/mars.2010.0001. 
  72. ^ "Sinuous Ridges Near Aeolis Mensae". Hiroc.lpl.arizona.edu. January 31, 2007. Retrieved December 19, 2010. 
  73. ^ Zimbelman, J., Griffin, L. (2010). "HiRISE images of yardangs and sinuous ridges in the lower member of the Medusae Fossae Formation, Mars". Icarus 205: 198–210. Bibcode:2010Icar..205..198Z. doi:10.1016/j.icarus.2009.04.003. 
  74. ^ a b Newsom, H.; Lanza, Nina L.; Ollila, Ann M.; Wiseman, Sandra M.; Roush, Ted L.; Marzo, Giuseppe A.; Tornabene, Livio L.; Okubo, Chris H. et al. (2010). "Inverted channel deposits on the floor of Miyamoto crater, Mars". Icarus 205: 64–72. Bibcode:2010Icar..205...64N. doi:10.1016/j.icarus.2009.03.030. 
  75. ^ a b Weitz, C.; Milliken, R.E.; Grant, J.A.; McEwen, A.S.; Williams, R.M.E.; Bishop, J.L.; Thomson, B.J. (2010). "Mars Reconnaissance Orbiter observations of light-toned layered deposits and associated fluvial landforms on the plateaus adjacent to Valles Marineris". Icarus 205: 73–102. Bibcode:2010Icar..205...73W. doi:10.1016/j.icarus.2009.04.017. 
  76. ^ a b c "Icarus, Volume 210, Issue 2, Pages 539–1000 (December 2010)". ScienceDirect. Retrieved December 19, 2010. 
  77. ^ a b c Cabrol, N. and E. Grin (eds.). 2010. Lakes on Mars. Elsevier. NY
  78. ^ Goldspiel, J., Squires, S. (2000). "Groundwater sapping and valley formation on Mars". Icarus 148: 176–192. Bibcode:2000Icar..148..176G. doi:10.1006/icar.2000.6465. 
  79. ^ McCauley, J. 1978. Geologic map of the Coprates quadrangle of Mars. U.S. Geol. Misc. Inv. Map I-897
  80. ^ Nedell, S.; Squyres, Steven W.; Andersen, David W. (1987). "Origin and evolution of the layered deposits in the Valles Marineris, Mars". Icarus 70 (3): 409–441. Bibcode:1987Icar...70..409N. doi:10.1016/0019-1035(87)90086-8. 
  81. ^ "Spectacular Mars images reveal evidence of ancient lakes". Sciencedaily.com. January 4, 2010. Retrieved December 19, 2010. 
  82. ^ Gupta, Sanjeev; Warner, Nicholas; Kim, Rack; Lin, Yuan; Muller, Jan; -1#Jung-, Shih- (2010). "Hesperian equatorial thermokarst lakes in Ares Vallis as evidence for transient warm conditions on Mars". Geology 38: 71–74. doi:10.1130/G30579.1. 
  83. ^ a b Brown, Dwayne; Cole, Steve; Webster, Guy; Agle, D.C. (September 27, 2012). "NASA Rover Finds Old Streambed On Martian Surface". NASA. Retrieved September 28, 2012. 
  84. ^ a b NASA (September 27, 2012). "NASA's Curiosity Rover Finds Old Streambed on Mars - video (51:40)". NASAtelevision. Retrieved September 28, 2012. 
  85. ^ a b Chang, Alicia (September 27, 2012). "Mars rover Curiosity finds signs of ancient stream". Associated Press. Retrieved September 27, 2012. 
  86. ^ "NASA Rover Finds Conditions Once Suited for Ancient Life on Mars". NASA. 12 March 2013. Retrieved 2013-06-06. 
  87. ^ Carr, M.H. (1979). "Formation of Martian flood features by relaease of water from confined aquifers". J. Geophys. Res. 84: 2995–3007. Bibcode:1979JGR....84.2995C. doi:10.1029/JB084iB06p02995. 
  88. ^ Baker, V., Milton, D. (1974). "Erosion by Catastrophic Floods on Mars and Earth". Icarus 23: 27–41. Bibcode:1974Icar...23...27B. doi:10.1016/0019-1035(74)90101-8. 
  89. ^ "Mars Global Surveyor MOC2-862 Release". Msss.com. Retrieved 2012-01-16. 
  90. ^ Andrews-Hanna, Jeffrey C.; Phillips, Roger J.; Zuber, Maria T. (2007). "Meridiani Planum and the global hydrology of Mars". Nature 446 (7132): 163–6. Bibcode:2007Natur.446..163A. doi:10.1038/nature05594. PMID 17344848. 
  91. ^ Christensen, P. (2005). "The Many Faces of Mars". Scientific American 293 (1): 32–39. doi:10.1038/scientificamerican0705-32. PMID 16008291. 
  92. ^ Jakosky, Bruce M. (1999). "Water, Climate, and Life". Science 283 (5402): 648–649. doi:10.1126/science.283.5402.648. PMID 9988657. 
  93. ^ a b "Groundwater activity on Mars and implications for a deep biosphere". Nature Geoscience 6: 133–138. 20 January 2013. doi:10.1038/ngeo1706. Retrieved 2013-06-17. "Here we present a conceptual model of subsurface habitability of Mars and evaluate evidence for groundwater upwelling in deep basins." 
  94. ^ a b c Zuber, Maria T. (2007). "Planetary Science: Mars at the tipping point". Nature 447 (7146): 785–786. Bibcode:2007Natur.447..785Z. doi:10.1038/447785a. PMID 17568733. 
  95. ^ Andrews‐Hanna, J. C., M. T. Zuber, R. E. Arvidson, and S. M. Wiseman (2010), Early Mars hydrology: Meridiani playa deposits and the sedimentary record of Arabia Terra, J. Geophys. Res., 115, E06002, doi:10.1029/2009JE003485.
  96. ^ Grotzinger, J. P., et al. (2005), Stratigraphy and sedimentology of a dry to wet eolian depositional system, Burns formation, Meridiani Planum, Mars, Earth Planet. Sci. Lett., 240, 11–72, doi:10.1016/j.epsl.2005.09.039
  97. ^ McLennan, S. M., et al. (2005), Provenance and diagenesis of the evaporitebearing Burns formation, Meridiani Planum, Mars, Earth Planet. Sci. Lett., 240, 95–121, doi:10.1016/j.epsl.2005.09.041
  98. ^ Squyres, S. W., and A. H. Knoll (2005), Sedimentary rocks at Meridiani Planum: Origin, diagenesis, and implications for life on Mars, Earth Planet. Sci. Lett., 240, 1–10, doi:10.1016/j.epsl.2005.09.038.
  99. ^ Squyres, S. W., et al. (2006), Two years at Meridiani Planum: Results from the Opportunity rover, Science, 313, 1403–1407, doi:10.1126/science.
  100. ^ M. Wiseman, J. C. Andrews-Hanna, R. E. Arvidson, J. F. Mustard, K. J. Zabrusky. "Distribution of Hydrated Sulfates Across Arabia Terra Using CRISM Data: Implications for Martian Hydrology". 42nd Lunar and Planetary Science Conference (2011) 2133.pdf
  101. ^ Clifford, S. M., Parker, T. J. (2001). "The Evolution of the Martian Hydrosphere: Implications for the Fate of a Primordial Ocean and the Current State of the Northern Plains". Icarus 154: 40–79. Bibcode:2001Icar..154...40C. doi:10.1006/icar.2001.6671. 
  102. ^ Read, Peter L.; Lewis, S. R. (2004). The Martian Climate Revisited: Atmosphere and Environment of a Desert Planet (Paperback). Chichester, UK: Praxis. ISBN 978-3-540-40743-0. Retrieved December 19, 2010. 
  103. ^ "Martian North Once Covered by Ocean". Astrobio.net. Retrieved December 19, 2010. 
  104. ^ "New Map Bolsters Case for Ancient Ocean on Mars". SPACE.com. November 23, 2009. Retrieved December 19, 2010. 
  105. ^ "Mars Ocean Hypothesis Hits the Shore " Articles " NASA Astrobiology". Astrobiology.nasa.gov. January 26, 2001. Retrieved December 19, 2010. 
  106. ^ "Water ice in crater at Martian north pole" – July 27, 2005 ESA Press release. Retrieved March 17, 2006.
  107. ^ "Ice lake found on the Red Planet" – July 29, 2005 BBC story. Retrieved March 17, 2006.
  108. ^ Duxbury, N. S.; Zotikov, I. A.; Nealson, K. H.; Romanovsky, V. E.; Carsey, F. D. (2001). "A numerical model for an alternative origin of Lake Vostok and its exobiological implications for Mars". Journal of Geophysical Research 106: 1453. Bibcode:2001JGR...106.1453D. doi:10.1029/2000JE001254. Retrieved April 8, 2009. 
  109. ^ Murray, John B.; et al. (2005). "Evidence from the Mars Express High Resolution Stereo Camera for a frozen sea close to Mars' equator". Nature 434 (7031): 352–356. Bibcode:2005Natur.434..352M. doi:10.1038/nature03379. PMID 15772653. "Here we present High Resolution Stereo Camera images from the European Space Agency Mars Express spacecraft that indicate that such lakes may still exist." 
  110. ^ Orosei, R.; Cartacci, M.; Cicchetti, A.; Noschese, R.; Federico, C.; Frigeri, A.; Flamini, E.; Holt, J. W. et al. (2008). "Radar subsurface sounding over the putative frozen sea in Cerberus Palus, Mars" (PDF). Lunar and Planetary Science. XXXIX: 1. Bibcode:2007AGUFM.P14B..05O. doi:10.1109/ICGPR.2010.5550143. ISBN 978-1-4244-4604-9. 
  111. ^ ISBN 978-0-521-85226-5
  112. ^ a b Boynton, W. V. et al. (2007), Concentration of H, Si, Cl, K, Fe, and Th in the low and mid latitude regions of Mars, Journal of Geophysical Research Planets, in press doi 10.1029/2007JE002887
  113. ^ Plaut, J. J. et al. (2007), doi 10.1126/science.1139672
  114. ^ a b c Feldman, W. C. et al. (2004), doi 10.1029/2003JE002160
  115. ^ a b "Mars' South Pole Ice Deep and Wide". NASA News & Media Resources. NASA. March 15, 2007. Retrieved 2013-03-18. 
  116. ^ a b c Kostama, V.-P.; Kreslavsky, M. A.; Head, J. W. (June 3, 2006). "Recent high-latitude icy mantle in the northern plains of Mars: Characteristics and ages of emplacement". Geophysical Research Letters 33 (11): L11201. Bibcode:2006GeoRL..3311201K. doi:10.1029/2006GL025946. Retrieved 2008-08-01. 
  117. ^ a b Johnson, John (August 1, 2008). "There's water on Mars, NASA confirms". Los Angeles Times. Retrieved August 1, 2008. 
  118. ^ Fishbaugh, KE; Byrne, Shane; Herkenhoff, Kenneth E.; Kirk, Randolph L.; Fortezzo, Corey; Russell, Patrick S.; McEwen, Alfred (2010). "Evaluating the meaning of "layer" in the Martian north polar layered depsoits and the impact on the climate connection" (PDF). Icarus 205 (1): 269–282. Bibcode:2010Icar..205..269F. doi:10.1016/j.icarus.2009.04.011. 
  119. ^ "Radar Map of Buried Mars Layers Matches Climate Cycles". OnOrbit. Retrieved December 19, 2010. 
  120. ^ "Polygonal Patterned Ground: Surface Similarities Between Mars and Earth". SpaceRef. September 28, 2002. Retrieved December 19, 2010. 
  121. ^ Squyres, S. (1989). "Urey Prize Lecture: Water on Mars". Icarus 79 (2): 229–288. Bibcode:1989Icar...79..229S. doi:10.1016/0019-1035(89)90078-X. 
  122. ^ Lefort, A.; Russell, P.S.; Thomas, N. (2010). "Scaloped terrains in the Peneus and Amphitrites Paterae region of Mars as observed by HiRISE". Icarus 205: 259–268. Bibcode:2010Icar..205..259L. doi:10.1016/j.icarus.2009.06.005. 
  123. ^ "NASA – Turbulent Lava Flow in Mars' Athabasca Valles". Nasa.gov. January 11, 2010. Retrieved December 19, 2010. 
  124. ^ a b c Head, James W.; Mustard, John F.; Kreslavsky, Mikhail A.; Milliken, Ralph E.; Marchant, David R. (2003). "Recent ice ages on Mars". Nature 426 (6968): 797–802. doi:10.1038/nature02114. PMID 14685228. 
  125. ^ a b c "HiRISE Dissected Mantled Terrain (PSP_002917_2175)". Arizona University. Retrieved December 19, 2010. 
  126. ^ Lefort, A.; Russell, P.S.; Thomas, N. (2010). "Scalloped terrains in the Peneus and Amphitrites Paterae region of Mars as observed by HiRISE". Icarus 205: 259–268. Bibcode:2010Icar..205..259L. doi:10.1016/j.icarus.2009.06.005. 
  127. ^ Strom, R.G., Steven K. Croft, and Nadine G. Barlow, "The Martian Impact Cratering Record," Mars, University of Arizona Press, ISBN 0-8165-1257-4, 1992.
  128. ^ a b "ESA - Mars Express - Breathtaking views of Deuteronilus Mensae on Mars". Esa.int. 2005-03-14. Retrieved 2012-01-16. 
  129. ^ Ohanlon, Larry (4 March 2010). "Mars' Ice Age Revealed in Map". Discovery News. 
  130. ^ a b Hauber, E. et al. (2005). "Discovery of a flank caldera and very young glacial activity at Hecates Tholus, Mars". Nature 434 (7031): 356–61. Bibcode:2005Natur.434..356H. doi:10.1038/nature03423. PMID 15772654. 
  131. ^ a b Shean, D. et al. (2005). "Origin and evolution of a cold-based mountain glacier on Mars: The Pavonis Mons fan-shaped deposit". Journal of Geophysical Research 110 (E5): E05001. Bibcode:2005JGRE..11005001S. doi:10.1029/2004JE002360. 
  132. ^ a b Basilevsky, A. et al. (2006). "Geological recent tectonic, volcanic and fluvial activity on the eastern flank of the Olympus Mons volcano, Mars". Geophysical Research Letters 33. L13201. Bibcode:2006GeoRL..3313201B. doi:10.1029/2006GL026396. 
  133. ^ "Fretted Terrain Valley Traverse". Hirise.lpl.arizona.edu. Retrieved 2012-01-16. 
  134. ^ "Jumbled Flow Patterns". Arizona University. Retrieved 2012-01-16. 
  135. ^ Berman, D. et al. (2005). "The role of arcuate ridges and gullies in the degradation of craters in the Newton Basin region of Mars". Icarus 178 (2): 465–86. Bibcode:2005Icar..178..465B. doi:10.1016/j.icarus.2005.05.011. 
  136. ^ Milliken, R. et al. (2003). "Viscous flow features on the surface of Mars: Observations from high-resolution Mars Orbiter Camera (MOC) images". Journal of Geophysical Research 108. E6, 5057. 
  137. ^ Arfstrom, J.; W. Hartmann (2005). "Martian flow features, moraine-like ridges, and gullies: Terrestrial analogs and interrelationships". Icarus 174 (2): 321–35. Bibcode:2005Icar..174..321A. doi:10.1016/j.icarus.2004.05.026. 
  138. ^ "HiRISE | Glacier? (ESP_018857_2225)". Uahirise.org. Retrieved December 19, 2010. 
  139. ^ a b Shean, David E. (2005). "Origin and evolution of a cold-based tropical mountain glacier on Mars: The Pavonis Mons fan-shaped deposit". Journal of Geophysical Research 110. Bibcode:2005JGRE..11005001S. doi:10.1029/2004JE002360. 
  140. ^ a b c "Mars may be emerging from an ice age". ScienceDaily (MLA NASA/Jet Propulsion Laboratory). December 18, 2003. Retrieved February 19, 2009. 
  141. ^ Mustard, J. et al. (2001). "Evidence for recent climate change on Mars from the identification of youthful near-surface ground ice". Nature 412 (6845): 411–4. doi:10.1038/35086515. PMID 11473309. 
  142. ^ Kreslavsky, M.; J. Head (2002). "Mars: Nature and evolution of young latitude-dependent water-ice-rich mantle" (PDF). Geophysical Research Letters 29 (15). Bibcode:2002GeoRL..29o..14K. doi:10.1029/2002GL015392. 
  143. ^ Forget, F. et al. (2006). "Formation of Glaciers on Mars by Atmospheric Precipitation at High Obliquity". Science 311 (5759): 368–71. Bibcode:2006Sci...311..368F. doi:10.1126/science.1120335. PMID 16424337. 
  144. ^ Dickson, James L.; Head, James W.; Marchant, David R. (2008). "Late Amazonian glaciation at the dichotomy boundary on Mars: Evidence for glacial thickness maxima and multiple glacial phases". Geology 36 (5): 411–4. doi:10.1130/G24382A.1. 
  145. ^ a b Heldmann et al., Jennifer L. (May 7, 2005). "Formation of Martian gullies by the action of liquid water flowing under current Martian environmental conditions" (PDF). Journal of Geophysical Research 110: Eo5004. Bibcode:2005JGRE..11005004H. doi:10.1029/2004JE002261. Retrieved September 14, 2008.  'conditions such as now occur on Mars, outside of the temperature-pressure stability regime of liquid water' ... 'Liquid water is typically stable at the lowest elevations and at low latitudes on the planet because the atmospheric pressure is greater than the vapor pressure of water and surface temperatures in equatorial regions can reach 273 K (-53 °C) for parts of the day.
  146. ^ "Mars Gullies May Have Been Formed By Flowing Liquid Brine". Sciencedaily.com. 2009-02-15. Retrieved 2013-02-10. 
  147. ^ a b "NASA Finds Possible Signs of Flowing Water on Mars". voanews.com. Retrieved August 5, 2011. 
  148. ^ Jpl.Nasa.Gov (2006-12-06). "JPL news release 2006-145". Jpl.nasa.gov. Retrieved 2012-01-16. 
  149. ^ a b c Malin, Michael C.; Kenneth S. Edgett, Liliya V. Posiolova, Shawn M. McColley, Eldar Z. Noe Dobrea (8 December 2006). "Present-Day Impact Cratering Rate and Contemporary Gully Activity on Mars". Science 314 (5805): 1573–1577. Bibcode:2006Sci...314.1573M. doi:10.1126/science.1135156. PMID 17158321. Retrieved 2009-09-03. 
  150. ^ a b Malin, Michael C.; Edgett, Kenneth S. (2001). "Mars Global Surveyor Mars Orbiter Camera: Interplanetary cruise through primary mission". Journal of Geophysical Research 106: 23429–23570. Bibcode:2001JGR...10623429M. doi:10.1029/2000JE001455. 
  151. ^ "Mars Global Surveyor MOC2-1618 Release". Msss.com. doi:10.1126/science.288.5475.2330. Retrieved December 19, 2010. 
  152. ^ "Changing Mars Gullies Hint at Recent Flowing Water". SPACE.com. December 6, 2006. Retrieved December 19, 2010. 
  153. ^ "Mars Global Surveyor MOC2-239 Release". Mars.jpl.nasa.gov. Retrieved December 19, 2010. 
  154. ^ a b Head, JW; Marchant, DR; Kreslavsky, MA (2008). "Formation of gullies on Mars: Link to recent climate history and insolation microenvironments implicate surface water flow origin". PNAS 105 (36): 13258–63. Bibcode:2008PNAS..10513258H. doi:10.1073/pnas.0803760105. PMC 2734344. PMID 18725636. 
  155. ^ Henderson, Mark (December 7, 2006). "Water has been flowing on Mars within past five years, Nasa says". The Times (UK). Retrieved March 17, 2007. 
  156. ^ Mars photo evidence shows recently running water. The Christian Science Monitor. Retrieved on March 17, 2007
  157. ^ Malin, Michael C.; Edgett, Kenneth S. (2000). "Evidence for Recent Groundwater Seepage and Surface Runoff on Mars". Science 288 (5475): 2330–2335. Bibcode:2000Sci...288.2330M. doi:10.1126/science.288.5475.2330. PMID 10875910. 
  158. ^ Nepali Scientist Lujendra Ojha spots possible water on Mars. Nepali Blogger. (6 August 2011)
  159. ^ NASA Spacecraft Data Suggest Water Flowing on Mars, NASA, August 4, 2011
  160. ^ Kolb, K.; Pelletier, Jon D.; McEwen, Alfred S. (2010). "Modeling the formation of bright slope deposits associated with gullies in Hale Crater, Mars: Implications for recent liquid water". Icarus 205: 113–137. Bibcode:2010Icar..205..113K. doi:10.1016/j.icarus.2009.09.009. 
  161. ^ Source: Ames Research Center Posted Saturday, June 6, 2009 (June 6, 2009). "NASA Scientists Find Evidence for Liquid Water on a Frozen Early Mars". SpaceRef. Retrieved December 19, 2010. 
  162. ^ "Dead Spacecraft on Mars Lives on in New Study". SPACE.com. June 10, 2008. Retrieved December 19, 2010. 
  163. ^ "Essential requirements for life". CMEX-NASA. Retrieved 2013-5-26. 
  164. ^ a b "Biotoxicity of Marssoils:1. Dry deposition of analog soils on microbial colonies and survival under Martian conditions" (PDF). Elsevier -Planetary and Space Science. 20 July 2012. Retrieved 2013-06-06. 
  165. ^ a b c Beaty, David W.; et al. (July 14), "MEPAG SR-SAG (2006) Unpublished white paper" (PDF), Findings of the Mars Special Regions Science Analysis Group, Jet Propulsion Laboratory - NASA, p. 17, retrieved 2013-06-06 
  166. ^ Neal-Jones, Nancy; O'Carroll, Cynthia (October 12, 2005). "New Map Provides More Evidence Mars Once Like Earth". Goddard Space Flight Center. NASA. Retrieved 5 June 2013. 
  167. ^ "Martian Interior: Paleomagnetism". Mars Express. European Space Agency. 4 January 2007. 
  168. ^ "Planetary Magnetic Dynamo Effect on Atmospheric Protection of Early Earth and Mars". Space Sciences Series of ISSI 24: 279–300. 2007. Retrieved 2013-06-06. 
  169. ^ "What makes Mars so hostile to life?". BBC News. 7 January 2013. Retrieved 2013-06-15. 
  170. ^ "Study: Surface of Mars Devoid of Life". Space.com. 29 January 2007. Retrieved 28 May 2013. "After mapping cosmic radiation levels at various depths on Mars, researchers have concluded that any life within the first several yards of the planet's surface would be killed by lethal doses of cosmic radiation." 
  171. ^ Dartnell, L.R.; Desorgher, Ward, Coates (30 January 2007). "Modelling the surface and subsurface Martian radiation environment: Implications for astrobiology". Geophysical Research Letters 34 (2). doi:10.1029/2006GL027494. Retrieved 2013-05-26. "Bacteria or spores held dormant by freezing conditions cannot metabolise and become inactivated by accumulating radiation damage. We find that at 2 m depth, the reach of the ExoMars drill, a population of radioresistant cells would need to have reanimated within the last 450,000 years to still be viable. Recovery of viable cells cryopreserved within the putative Cerberus pack-ice requires a drill depth of at least 7.5 m." 
  172. ^ Richard A. Lovet (February 2, 2007). "Mars Life May Be Too Deep to Find, Experts Conclude". National Geographic News. "That's because any bacteria that may once have lived on the surface have long since been exterminated by cosmic radiation sleeting through the thin Martian atmosphere." 
  173. ^ NASA - Mars Rovers Sharpen Questions About Livable Conditions
  174. ^ "Mars: 'Strongest evidence' planet may have supported life, scientists say". BBC News. 20 January 2013. Retrieved 2013-01-22. 
  175. ^ "Groundwater activity on Mars and implications for a deep biosphere". Nature Geoscience. 20 January 2013. doi:10.1038/ngeo1706. Retrieved 2013-01-22. 
  176. ^ Anderson, Paul S. (15 December 2011). "New Study Says Large Regions of Mars Could Sustain Life". Universe Today. Retrieved 2013-06-05. "Most scientists would agree that the best place that any organisms could hope to survive and flourish would be underground." 
  177. ^ "Habitability and Biology: What are the Properties of Life?". Phoenix Mars Mission. The University of Arizona. Retrieved 2013-06-06. "If any life exists on Mars today, scientists believe it is most likely to be in pockets of liquid water beneath the Martian surface." 
  178. ^ "Possible New Mars Caves Targets in Search for Life". Space.com. 2 April 2007. Retrieved 2013-06-15. 
  179. ^ "Thermodynamic Stability of Liquid Water on Present‐Day Mars: Surface" (PDF), The Present-Day Habitability of Mars 2013, California, USA: The UCLA Institute for Planets and Exoplanets, February 4-6, 2013, retrieved 2013-06-17, "These results suggest that present day fluvial activity [gullies] on Mars may be associated with discharge from aquifers supplied during seasonal or inter‐annual climate cycles, rather than ubiquitous ground ice."  Unknown parameter |coeditors= ignored (help)
  180. ^ "Mars Exploration: Missions". Marsprogram.jpl.nasa.gov. Retrieved December 19, 2010. 
  181. ^ "ch5". History.nasa.gov. Retrieved December 19, 2010. 
  182. ^ "ch7". History.nasa.gov. Retrieved December 19, 2010. 
  183. ^ Arvidson, R; Gooding, James L.; Moore, Henry J. (1989). "The Martian surface as Imaged, Sampled, and Analyzed by the Viking Landers". Review of Geophysics 27: 39–60. Bibcode:1989RvGeo..27...39A. doi:10.1029/RG027i001p00039. 
  184. ^ Clark, B.; Baird, AK; Rose Jr, HJ; Toulmin P, 3rd; Keil, K; Castro, AJ; Kelliher, WC; Rowe, CD et al. (1976). "Inorganic Analysis of Martian Samples at the Viking Landing Sites". Science 194 (4271): 1283–1288. Bibcode:1976Sci...194.1283C. doi:10.1126/science.194.4271.1283. PMID 17797084. 
  185. ^ Hoefen, T.; Clark, RN; Bandfield, JL; Smith, MD; Pearl, JC; Christensen, PR (2003). "Discovery of Olivine in the Nili Fossae Region of Mars". Science 302 (5645): 627–630. Bibcode:2003Sci...302..627H. doi:10.1126/science.1089647. PMID 14576430. 
  186. ^ Atmospheric and Meteorological Properties, NASA
  187. ^ a b Golombek, M.; Cook, RA; Economou, T; Folkner, WM; Haldemann, AF; Kallemeyn, PH; Knudsen, JM; Manning, RM et al. (1997). "Overview of the Mars Pathfinder Mission and Assessment of Landing Site Predictions". Science 278 (5344): 1743–1748. Bibcode:1997Sci...278.1743G. doi:10.1126/science.278.5344.1743. PMID 9388167. 
  188. ^ Murche, S. et al. (1993). "Spatial Variations in the Spectral Properties of Bright Regions on Mars". Icarus 105 (2): 454–468. Bibcode:1993Icar..105..454M. doi:10.1006/icar.1993.1141. 
  189. ^ "Home Page for Bell (1996) Geochemical Society paper". Marswatch.tn.cornell.edu. Retrieved December 19, 2010. 
  190. ^ Feldman, WC; Boynton, WV; Tokar, RL; Prettyman, TH; Gasnault, O; Squyres, SW; Elphic, RC; Lawrence, DJ et al. (2002). "Global Distribution of Neutrons from Mars: Results from Mars Odyssey". Science 297 (5578): 75–78. Bibcode:2002Sci...297...75F. doi:10.1126/science.1073541. PMID 12040088. 
  191. ^ Mitrofanov, I.; Anfimov, D; Kozyrev, A; Litvak, M; Sanin, A; Tret'yakov, V; Krylov, A; Shvetsov, V et al. (2002). "Maps of Subsurface Hydrogen from the High Energy Neutron Detector, Mars Odyssey". Science 297 (5578): 78–81. Bibcode:2002Sci...297...78M. doi:10.1126/science.1073616. PMID 12040089. 
  192. ^ Boynton, W.; Feldman, WC; Squyres, SW; Prettyman, TH; Bruckner, J; Evans, LG; Reedy, RC; Starr, R et al. (2002). "Distribution of Hydrogen in the Near Surface of Mars: Evidence for Subsurface Ice Deposits". Science 297 (5578): 81–85. Bibcode:2002Sci...297...81B. doi:10.1126/science.1073722. PMID 12040090. 
  193. ^ "Dao Vallis (Released 7 August 2002) | Mars Odyssey Mission THEMIS". Themis.asu.edu. Retrieved December 19, 2010. 
  194. ^ a b Arvidson, P. H.; Tamppari, L.; Arvidson, R. E.; Bass, D.; Blaney, D.; Boynton, W.; Carswell, A.; Catling, D. et al. (2008). "Introduction to special section on the phoenix mission: Landing site characterization experiments, mission overviews, and expected science". J. Geophysical Research 113. Bibcode:2008JGRE..11300A18S. doi:10.1029/2008JE003083. 
  195. ^ NASA Data Shed New Light About Water and Volcanoes on Mars
  196. ^ Mellon, M., Jakosky, B. (1993). "Geographic variations in the thermal and diffusive stability of ground ice on Mars". J. Geographical Research 98: 3345–3364. Bibcode:1993JGR....98.3345M. doi:10.1029/92JE02355. 
  197. ^ "Confirmation of Water on Mars". Nasa.gov. June 20, 2008. Retrieved December 19, 2010. 
  198. ^ a b "The Dirt on Mars Lander Soil Findings". SPACE.com. Retrieved December 19, 2010. 
  199. ^ Hecht, MH; Kounaves, SP; Quinn, RC; West, SJ; Young, SM; Ming, DW; Catling, DC; Clark, BC et al. (2009). "Detection of Perchlorate and the Soluble Chemistry of Martian Soil at the Phoenix Lander Site". Science 325 (5936): 64–67. Bibcode:2009Sci...325...64H. doi:10.1126/science.1172466. PMID 19574385. 
  200. ^ "Audio Recording of Phoenix Media Telecon for Aug. 5, 2008". Jet Propulsion Laboratory (NASA). August 5, 2008. Retrieved July 14, 2009. 
  201. ^ a b c Chang, Kenneth (2009) Blobs in Photos of Mars Lander Stir a Debate: Are They Water?, New York Times (online), March 16, 2009, retrieved April 4, 2009;
  202. ^ "Liquid Saltwater Is Likely Present On Mars, New Analysis Shows". Sciencedaily.com. 2009-03-20. Retrieved 2011-08-20. 
  203. ^ Rennó, Nilton O.; Bos, Brent J.; Catling, David; Clark, Benton C.; Drube, Line; Fisher, David; Goetz, Walter; Hviid, Stubbe F. et al. (2009). "Possible physical and thermodynamical evidence for liquid water at the Phoenix landing site". Journal of Geophysical Research 114. Bibcode:2009JGRC..11400E03R. doi:10.1029/2009JE003362. 
  204. ^ "Astrobiology Top 10: Too Salty to Freeze". Astrobio.net. Retrieved December 19, 2010. 
  205. ^ Smith, PH; Tamppari, LK; Arvidson, RE; Bass, D; Blaney, D; Boynton, WV; Carswell, A; Catling, DC et al. (2009). "H2O at the Phoenix Landing Site". Science 325 (5936): 58–61. Bibcode:2009Sci...325...58S. doi:10.1126/science.1172339. PMID 19574383. 
  206. ^ Witeway, J.; Komguem, L; Dickinson, C; Cook, C; Illnicki, M; Seabrook, J; Popovici, V; Duck, TJ et al. (2009). "Mars Water-Ice Clouds and Precipation". Science 325 (5936): 68–70. Bibcode:2009Sci...325...68W. doi:10.1126/science.1172344. PMID 19574386. 
  207. ^ "CSA – News Release". Asc-csa.gc.ca. July 2, 2009. Retrieved December 19, 2010. 
  208. ^ "Mars Exploration Rover Mission: Press Releases". Marsrovers.jpl.nasa.gov. March 5, 2004. Retrieved December 19, 2010. 
  209. ^ "NASA - Mars Rover Spirit Unearths Surprise Evidence of Wetter Past". Nasa.gov. 2007-05-21. Retrieved 2013-02-10. 
  210. ^ Bertster, Guy (December 10, 2007). "Mars Rover Investigates Signs of Steamy Martian Past". Press Release. Jet Propulsion Laboratory, Pasadena, California. Retrieved December 12, 2007. 
  211. ^ Klingelhofer, G., et al. (2005) Lunar Planet. Sci. XXXVI abstr. 2349
  212. ^ Schroder, C., et al. (2005) European Geosciences Union, General Assembly, Geophysical Research abstr., Vol. 7, 10254, 2005
  213. ^ Morris,S., et al. Mossbauer mineralogy of rock, soil, and dust at Gusev crater, Mars: Spirit’s journal through weakly altered olivine basalt on the plains and pervasively altered basalt in the Columbia Hills. J. Geophys. Res: 111
  214. ^ Ming,D., et al. 2006 Geochemical and mineralogical indicators for aqueous processes in the Columbia Hills of Gusev crater, Mars. J. Geophys. Res.111
  215. ^ Bell, J (ed.) The Martian Surface. 2008. Cambridge University Press. ISBN 978-0-521-86698-9
  216. ^ "Outcrop of long-sought rare rock on Mars found". Sciencedaily.com. 2010-06-04. doi:10.1126/science.1189667. Retrieved 2013-02-10. 
  217. ^ Richard V. Morris, Steven W. Ruff, Ralf Gellert, Douglas W. Ming, Raymond E. Arvidson, Benton C. Clark, D. C. Golden, Kirsten Siebach, Göstar Klingelhöfer, Christian Schröder, Iris Fleischer, Albert S. Yen, Steven W. Squyres. Identification of Carbonate-Rich Outcrops on Mars by the Spirit Rover. Science, June 3, 2010 doi:10.1126/science.1189667
  218. ^ "Opportunity Rover Finds Strong Evidence Meridiani Planum Was Wet". Retrieved July 8, 2006. 
  219. ^ Benison, KC; Laclair, DA (2003). "Modern and ancient extremely acid saline deposits: terrestrial analogs for martian environments?". Astrobiology 3 (3): 609–618. Bibcode:2003AsBio...3..609B. doi:10.1089/153110703322610690. PMID 14678669. 
  220. ^ Benison, K; Bowen, B (2006). "Acid saline lake systems give clues about past environments and the search for life on Mars". Icarus 183 (1): 225–229. Bibcode:2006Icar..183..225B. doi:10.1016/j.icarus.2006.02.018. 
  221. ^ Osterloo, MM; Hamilton, VE; Bandfield, JL; Glotch, TD; Baldridge, AM; Christensen, PR; Tornabene, LL; Anderson, FS (2008). "Chloride-Bearing Materials in the Southern Highlands of Mars". Science 319 (5870): 1651–1654. Bibcode:2008Sci...319.1651O. doi:10.1126/science.1150690. PMID 18356522. 
  222. ^ Grotzinger, J. and R. Milliken (eds.) 2012. Sedimentary Geology of Mars. SEPM
  223. ^ "HiRISE | High Resolution Imaging Science Experiment". HiriUniversity of Arizona. Retrieved December 19, 2010. 
  224. ^ "Target Zone: Nilosyrtis? | Mars Odyssey Mission THEMIS". Themis.asu.edu. Retrieved December 19, 2010. 
  225. ^ Mellon, M. T., B. M. Jakosky, and S. E. Postawko (1997)The persistence of equatorial ground ice on Mars, J. Geophys. Res., 102(E8), 19357–19369, doi:10.1029/97JE01346.
  226. ^ John D. Arfstrom A Conceptual Model of Equatorial Ice Sheets on Mars. J Comparative Climatology of Terrestrial Planets (2012)
  227. ^ Byrne, S; Dundas, CM; Kennedy, MR; Mellon, MT; McEwen, AS; Cull, SC; Daubar, IJ; Shean, DE et al. (2009). "Distribution of mid-latitude ground ice on Mars from new impact craters". Science 325 (5948): 1674–1676. Bibcode:2009Sci...325.1674B. doi:10.1126/science.1175307. PMID 19779195. 
  228. ^ "Water Ice Exposed in Mars Craters". SPACE.com. Retrieved December 19, 2010. 
  229. ^ Brown, Dwayne (October 30, 2012). "NASA Rover's First Soil Studies Help Fingerprint Martian Minerals". NASA. Retrieved October 31, 2012. 
  230. ^ Brown, Dwayne; Webster, Guy; Jones, Nance Neal (December 3, 3012). "NASA Mars Rover Fully Analyzes First Martian Soil Samples". NASA. Retrieved December 3, 2012. 
  231. ^ Chang, Ken (December 3, 2012). "Mars Rover Discovery Revealed". New York Times. Retrieved December 3, 2012. 
  232. ^ a b Webster, Guy; Brown, Dwayne (March 18, 2013). "Curiosity Mars Rover Sees Trend In Water Presence". NASA. Retrieved March 20, 2013. 
  233. ^ Rincon, Paul (March 19, 2013). "Curiosity breaks rock to reveal dazzling white interior". BBC. Retrieved March 19, 2013. 
  234. ^ Staff (March 20, 2013). "Red planet coughs up a white rock, and scientists freak out". MSN. Retrieved March 20, 2013. 

External links[edit]

Wikimedia Commons has media related to: Water on Mars
Geography
Mars as seen by the Hubble Space Telescope
Moons
Specific
Common
Exploration
Current
and past
Proposed
Astronomy
Related


Category:Mars Category:Bodies of ice Category:Water and Mars

Retrieved from "http://en.wikipedia.org/w/index.php?title=Water_on_Mars&oldid=560335308"