Almost all water on Mars today exists as ice, although it also exists in small amounts as vapor in the atmosphere and sometimes as low-volume salt water in shallow Mars land. The only place where water ice is visible on the surface is at the polar ice pole. The abundant water ice also lies beneath the permanent carbon dioxide ice cap at Mars' southern pole and beneath a shallow surface in temperate climates. More than five million cubic kilometers of ice have been identified on or near the surface of modern Mars, enough to cover the entire planet to a depth of 35 meters (115 feet). Even more ice is likely to be locked below the surface.
Some liquid water may occur temporarily on the surface of Mars today, but is limited to the trace of dissolved moisture from the atmosphere and thin film, which is a challenging environment for life as we know it. No large body of water stands, because atmospheric pressure on the surface averages only 600 pascals (0.087 psi) - about 0.6% of the Earth's mean sea surface pressure - leading to rapid evaporation (sublimation) or rapid freezing. Before about 3.8 billion years ago, Mars may have a denser atmosphere and higher surface temperatures, allowing large quantities of liquid water on the surface, possibly including large oceans that may cover a third of the planet. Water also seems to flow across the surface for a short time at various more recent intervals in Mars history. On December 9, 2013, NASA reported that, based on evidence from the Curiosity rover studying Aeolis Palus, Gale Crater contains an ancient fresh water lake that could be a friendly environment for microbial life.
Many lines of evidence show that water is abundant on Mars and has played an important role in the planet's geological history. The current water inventory on Mars can be estimated from the image of the spacecraft, remote sensing techniques (spectroscopic measurements, radar, etc.), and surface investigation of landers and inventors. Geological evidence from past water including large outlets carved by floods, ancient river valley networks, delta, and lakes; and detection of rocks and minerals on surfaces that can only form in liquid water. Many geomorphic features indicate the presence of soil ice (permafrost) and ice movement on glaciers, both in the past and present. Ditches and slope lines along the cliffs and crater walls show that the flowing water continues to form the surface of Mars, albeit to a much lower level than in the ancient past.
Although the Martian surface is periodically wet and could be friendly for microbial life billions of years ago, the current environment on dry and subfreezing surfaces may present an insurmountable obstacle to living organisms. In addition, Mars lacks a thick atmosphere, ozone layer, and magnetic field, allowing solar and cosmic radiation to attack the surface unhindered. The destructive effect of ionizing radiation on cellular structures is one of the major limiting factors on surface survival. Therefore, the best potential location for finding life on Mars may be in the subsurface environment. On November 22, 2016, NASA reported finding large amounts of underground ice on Mars; the volume of water detected is equivalent to the volume of water in Lake Superior.
Understanding the extent and situation of water on Mars is very important to assess the planet's potential to save lives and to provide resources that can be used for future human exploration. For this reason, "Follow the Water" is the science theme of the NASA Mars Exploration Program (MEP) in the first decade of the 21st century. The discovery by Mars Odyssey 2001, Mars Exploration Rovers (MERs), Mars Reconnaissance Orbiter (MRO), and Mars Phoenix landers has been instrumental in answering key questions about the abundance and distribution of water on Mars. Mars Express ESA orbiter has also provided important data in this search. Mars Odyssey, Mars Express, MER Opportunity explorer, MRO, and Mars Science Lander Curiosity rover still send back data from Mars, and the discovery continues.
Video Water on Mars
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The idea of ​​water on Mars precedes the age of space by hundreds of years. Early telescopic observers correctly assumed that white polar caps and clouds were an indication of the presence of water. This observation, coupled with the fact that Mars has a 24-hour day, led by astronomer William Herschel to declare in 1784 that Mars may offer its inhabitants "the situation in many ways resembles us."
At the beginning of the 20th century, most astronomers admit that Mars is much colder and drier than Earth. The presence of the oceans is no longer acceptable, so the paradigm transforms into the image of Mars as a "dying" planet with little water. Dark areas, which can be seen changing seasonally, are now considered as vegetation channels. The person most responsible for popularizing this Martian outlook was Percival Lowell (1855-1916), who envisioned the race of Martians building a network of canals to bring water from the poles to the population at the equator. Despite generating tremendous public enthusiasm, Lowell's ideas were rejected by most astronomers. The consensus of scientific formation at the time was probably best summarized by the English astronomer Edward Walter Maunder (1851-1928) who compared the Martian climate with conditions at the top of twenty thousand feet on the polar islands where only lichen might be expected. to survive.
Meanwhile, many astronomers perfected the planet's spectroscopic devices in the hope of determining the composition of Mars's atmosphere. Between 1925 and 1943, Walter Adams and Theodore Dunham at the Mount Wilson Observatory tried to identify oxygen and water vapor in the Martian atmosphere, with generally negative results. The only known component of Mars's atmosphere is the carbon dioxide (CO 2 ) spectroscopically identified by Gerard Kuiper in 1947. Water vapor was undetectable on Mars until 1963.
The composition of the polar cap, assumed water ice since the time of Cassini (1666), was questioned by some scientists in the late 1800s who favored CO 2 ice, because the whole planet is low in temperature and obviously lacks sufficient water. This hypothesis was confirmed theoretically by Robert Leighton and Bruce Murray in 1966. Today we know that winter caps in both poles are mainly made up of CO 2 ice, but it is a permanent (or lasting) water cap. ice remains there during the summer at the north pole. At the south pole, a small cap CO 2 ice stays during the summer, but this hat is also grounded by ice water.
The final piece of the Martian climate puzzle was provided by Mariner 4 in 1965. The crude television images of the spacecraft show the surface dominated by the crater, which implies that the surface is very old and has not experienced the level of erosion and tectonic activity seen in the world. Small erosion means that liquid water may not play a major role in planetary geomorphology for billions of years. Furthermore, variations in radio signals from the spacecraft as it passes behind the planet allow scientists to calculate atmospheric densities. The results show atmospheric pressure of less than 1% of the Earth at sea level, effectively blocking the presence of liquid water, which will rapidly boil or freeze at such low pressures. Thus, Mars's vision was born from a world like the Moon, but with only a glimmer of atmosphere to blow the dust around it. This view of Mars will last almost a decade longer until Mariner 9 shows a much more dynamic Mars with hints that the planet's past environment is more clement than it is now.
On January 24, 2014, NASA reported that the current study on Mars by Rovers would now look for evidence of ancient life, including an autotrophic biosphere, chemotrophic microorganisms and/or chemolithoautotrophic , as well as ancient water, including the fluvio-lacustrine environment (plains associated with ancient rivers or lakes) that may be inhabited.
Over the years, it has been estimated that observed flood waters are caused by water discharges from a global water table, but research published in 2015 reveals precipitated regional deposits and ice deposited 450 million years earlier as the source. "Sedimentary sediments from rivers and glacial catfish fill giant canyons beneath the ancient oceans contained in the northern lowlands of the planet, which is water preserved in canyon sediments that are then released as massive floods, whose effects can be seen today."
Maps Water on Mars
Evidence from rocks and minerals
It has been widely accepted that Mars has abundant water at the beginning of its history, but all the large areas of liquid water have been lost. A small part of this water is retained on modern Mars as ice and is locked into abundant water-rich material structures, including clay minerals (phyllosilicates) and sulfates. The study of hydrogen isotope ratios shows that asteroids and comets from outside 2.5 astronomical units (AU) provide a Mars water source, which currently totals 6% to 27% of the oceans now on Earth.
Water in weathering products (aqueous mineral)
The main rock types on the surface of Mars are basalt, fine-grained frozen rocks composed mostly of olivine mafic minerals, piroksen, and plagioclase feldspar. When exposed to water and atmospheric gases, these minerals chemically weather into new (secondary) minerals, some of which can combine water into their crystal structure, either as H 2 O or as hydroxyl (OH). Examples of hydrated (or oxidized) minerals include iron hydroxide goetite (common component of terrestrial soils); mineral gypsum and kieserit evaporate; silica opalina; and phyllosilicates (also called clay minerals), such as kaolinite and montmorillonite. All of these minerals have been detected on Mars.
One of the immediate effects of chemical weathering is to consume water and other reactive chemical species, extracting them from mobile reservoirs such as atmospheres and hydrospheres and sequestering them in rocks and minerals. The amount of water in Mars's crust stored in hydrated minerals is currently unknown, but may be substantial. For example, rocky mineralogy models examined by instruments at Explosion probabilities in Meridiani Planum show that sulphate deposits there can contain up to 22% water by weight.
On Earth, all chemical weathering reactions involve water to some extent. Thus, many secondary minerals do not actually enter water, but still need water to form. Some examples of anhydrous secondary minerals include many carbonates, some sulfates (eg, anhydrics), and metal oxides such as iron oxide iron hematite. On Mars, some of these weathering products can in theory be formed without water or with little amounts present as ice or in thin-molecular-scale films (monolayers). The extent to which such exotic weathering processes operate on Mars remains uncertain. Minerals that combine water or shapes in the presence of water are generally called "aqueous minerals."
Aqueous minerals are a sensitive indicator of the type of environment that exists when minerals are formed. The ease of aqueous reaction (see Gibbs free energy) depends on the pressure, temperature, and concentration of the gas and soluble species involved. Two important properties are potential pH and oxidation reduction (Eh). For example, mineral sulphate jarosite only forms at a low (very acidic) pH of water. Phyllosilicates usually form in neutral water to a high pH (alkaline). Eh is the size is the oxidation state of an aqueous system. Together Eh and pH show the most likely type of thermodynamic mineral to form from a given set of aqueous components. Thus, past environmental conditions on Mars, including those conducive to life, can be inferred from the types of minerals present in the rocks.
Hydrothermal changes
The aqueous mineral can also form beneath the surface by hydrothermal fluids that migrate through the pores and cracks. The heat source that drives the hydrothermal system may be close to the magma or the residual heat from a major impact. One of the most important types of hydrothermal changes in Earth's oceanic crust is serpentinization, which occurs when sea water migrates through ultramafic and basaltic rocks. The water-rock reaction produces iron oxidation of iron in olivine and pyroxene to produce ferric iron (as a mineral magnetite) that produces molecular hydrogen (H 2 ) as a by-product. This process creates a very alkaline and reduced (low Eh) environment that supports the formation of phyllosilicates (mineral serpentine) and various carbonate minerals, which together form a rock called serpentinite. The resulting hydrogen gas can be an important energy source for the chemosynthtic organism or it can react with CO 2 to produce methane gas, a process that has been considered a non-biological source for trace amounts of methane. reported in the atmosphere of Mars. Serpentine minerals can also store a lot of water (as hydroxyl) in their crystal structure. A recent study argues that hypothetical serpentinites in ancient Martian plateau crust could withstand as much as 500 meters (1,600 ft) of global equivalent black layer (GEL) of water. Although some serpentine minerals have been detected on Mars, there is no widespread bulge that is evident from remote sensing data. This fact does not preclude the presence of a large number of sepentinites hidden in the depths of Mars's crust.
Weathering speed
The rate at which the major minerals are converted into secondary aqueous minerals varies. Primary silicate minerals crystallize from magma under pressure and temperature much higher than conditions on the surface of the planet. When exposed to the surface environment these minerals are out of balance and will tend to interact with available chemical components to form a more stable mineral phase. In general, silicate minerals crystallize at the highest temperature (compacted first in the cooling magma) of the fastest weather. On Earth and Mars, the most common mineral to meet this criterion is olivine, which is ready to become clay mineral in the presence of water.
Olivin is widespread on Mars, suggesting that the surface of Mars has not changed widely by water; abundant geological evidence suggests otherwise.
Meteorite Mars
More than 60 meteorites have been discovered from Mars. Some of them contain evidence that they are exposed to water when on Mars. Some meteorites of Mars called basaltic shergottites, emerging (from the presence of hydrated carbonate and sulfate) have been exposed to liquid water before being expelled into space. It has been shown that another class of meteorites, nakhlites, which were covered with liquid water about 620 million years ago and that they were removed from Mars about 10.75 million years ago by asteroid impacts. They fell to Earth in the last 10,000 years. The Mars NWA 7034 meteorite has an order of magnitude more water than most other Mars meteorites. It is similar to the basal studied by rover missions, and it was formed in the early Amazonian era.
In 1996, a group of scientists reported the possibility of a microfossil presence in Allan Hills 84001, a meteorite from Mars. Many studies have denied the validity of fossils. It was found that most of the organic matter in meteorites came from land. Moreover, the scientific consensus is that "morphology alone can not be used unambiguously as a tool for the detection of primitive life." Morphological interpretation is very subjective, and its own use has caused many misinterpretations.
Geomorphic evidence
Lakes and river valleys
The 1971 Mariner 9 spacecraft caused a revolution in our ideas about water on Mars. The great river valleys are found in many areas. The pictures show that water floods break the dam, carve deep valleys, scrape the grooves to bedrock, and travel thousands of miles. The branched stream area, in the southern hemisphere, suggests that the rain once descended. The number of recognized valleys has increased over time. The study, published in June 2010 mapped 40,000 river valleys on Mars, about four times the number of previously identified river valleys. The typical water characteristics of Martia can be classified into two distinct classes: 1) dendritic, terrestrial-scale, widely distributed, Noachian-age valve tissue and 2) very large, long, single-threaded, isolated, Hesperian- age outflow channel. Recent work suggests that there may also be a class of channels currently enigmatic, smaller, younger (Hesperian to Amazonian) in midlatitudes, possibly linked to local ice melt.
Some parts of Mars show an upside-down aid. This occurs when the sediment is deposited on the bottom of the river and then becomes resistant to erosion, possibly by cementation. Then the area may be buried. Finally, erosion removes the cover layer and the former rivers become visible as they are resistant to erosion. Mars Global Surveyor found several examples of this process. Many inverse streams have been found in various regions of Mars, especially in the Fossae Medusae Formation, Miyamoto Crater, Saheki Crater, and Plateau Juventae.
Various lake basins have been found on Mars. Some are comparable to the largest lake size on Earth, such as the Caspian Sea, Black Sea, and Lake Baikal. The lake is fed by a network of valleys found in the southern highlands. There are places covered with depression with river valleys leading to them. These areas are considered to have contained lakes; one on the overflowing Terra Sirenum moving through Ma'adim Vallis to Gusev Crater, explored by Mars Exploration Rover Spirit. Other nearby Parana Valles and Loire Vallis. Some lakes are thought to be formed by rainfall, while others are formed from groundwater. The lake is thought to have existed in the Argyre basin, Hellas basin, and probably in the Valles Marineris. It is likely that sometimes in Noachian, many crater lakes. These lakes are consistent with a cold, dry (standard Earth) hydrological environment, somewhat similar to the Great West United Basin during the Last Glacial Maximum.
Research from 2010 shows that Mars also has lakes along the equator. Although previous research has shown that Mars has a warm, wet, early history, these lakes are at the Hesperian Epoch, a much slower period. Using detailed images from NASA's Mars Reconnaissance Orbiter, the researchers speculate that there may be increased volcanic activity, meteorite impact or shifts in Mars orbit during this period to warm the Mars atmosphere enough to melt the abundant ice in the ground. Volcanoes release gas that thickens the atmosphere for a while, trapping more sunlight and making it warm enough for the presence of liquid water. In this study, channels were found linking the lakes near Ares Vallis. When one lake is filled, the water overflows to the river's edge and carves the channel to the lower area where another lake will form. This dry lake will be the target to look for evidence (biosignatures) of past lives.
On September 27, 2012, NASA scientists announced that Curiosity rover found immediate evidence for the ancient streambed at Gale Crater, showing the ancient "powerful flow" of water on Mars. In particular, the dry streambed analysis now shows that water ran at 3.3 km/h (0.92 m/s), probably at the depth of the hip. Evidence of the flowing water comes in the form of round pebbles and gravel shards that can only be passed by a strong liquid stream. Their form and orientation shows long-distance transport from the top of the crater rim, where a channel called Peace Vallis enters the alluvial fan.
Eridania Lake is an ancient lake theorized with a surface area of ​​about 1.1 million square kilometers. Its maximum depth is 2,400 meters and its volume is 562,000 km 2 . It's bigger than Earth's largest landlocked sea, Caspian Sea and contains more water than any other Mars lake together. The Eridania Sea has more than 9 times more water than all the Great Lakes in North America. The upper surface of the lake is assumed to be at the height of the valley network surrounding the lake; they all end at the same height, indicating that they empty themselves into the lake.
Research with CRISM found thick deposits, over 400 meters thick, containing mineral saponites, talc-saponite, Fe rich mica (eg, glauconite-nontronite), Fe- and Mg-serpentine, Mg-Fe-Ca-carbonate and Fe -sulfide. Fe-sulphides may form in deep water from water heated by volcanoes. Such a process, classified as hydrothermal might be the place where life on Earth begins.
delta lake
Researchers have found a number of examples of deltas formed in Mars lakes. Finding the delta is a major sign that Mars once had plenty of liquid water. Delta usually requires deep water for long periods of time to form. In addition, the water level should be stable to keep the sediment from washing away. Delta has been found on a wide geographical range, although there are some indications that the delta may be concentrated around the previously expected edges of Mars's oceans.
Ground water
In 1979 it was estimated that the outlet channels formed in one, the disastrous submarine reservoir spray, possibly sealed by ice, the colossal water usage on the otherwise arid surface of Mars. In addition, the evidence supporting a large or even catastrophic flood is found in the giant ripples within Athabasca Vallis. Many outlets start in Chaos or Chasma features, providing evidence for rupture that could penetrate ice seals beneath the surface.
The network of valleys branched off on Mars are inconsistent with formations by the sudden release of groundwater, both in terms of their dendritic forms that do not originate from a single point of outflow, and in terms of the discharge that seems to flow along them. In contrast, some authors argue that they are formed by the slow seepage of groundwater from below the surface essentially as springs. To support this interpretation, the upstream end of many valleys in the network begins with a box canyon or "amphitheater" head, which on Earth is usually associated with groundwater seepage. There is also little evidence of a finer scale channel or valley at the end of the duct, which some authors have interpreted as showing the flow appearing suddenly from below the surface with enough discharge, rather than accumulating gradually on the surface. Others have debated the relationship between the amphitheater heads of the valleys and the formation by groundwater for terrestrial examples, and argue that the lack of a fine-scale head to the valley tissue is due to their displacement by weathering or the impact of gardening. Most authors accept that most of the valley tissues are at least partially influenced and shaped by groundwater soaking processes.
Groundwater also plays an important role in controlling the patterns and processes of large-scale sedimentation on Mars. According to this hypothesis, groundwater with dissolved minerals appears to the surface, in and around the crater, and helps form layers by adding minerals - especially sulfates - and cementing sediments. In other words, some layers may have been formed by groundwater accumulating minerals and cementing existing, loose, and aeolian deposits. The hard layers consequently are more protected from erosion. A study published in 2011 using data from the Mars Reconnaissance Orbiter, shows that the same type of sediment exists in large areas that include Arabia Terra. It has been argued that regions rich in sedimentary rocks are also areas that are likely to experience groundwater increases on a regional scale.
Ocean ocean hypothesis
The Mars oceanic hypothesis proposes that the Vastitas Borealis basin is the location of a sea of ​​liquid water at least once, and presents evidence that nearly a third of the Martian surface is covered by a liquid ocean at the start of the planet's geological history. This ocean, dubbed Oceanus Borealis , will fill the Vastitas Borealis basin in the northern hemisphere, an area located 4-5 kilometers (2.5-3.1 mi) below the average planetary altitude. The two main coastlines thought to have been proposed: higher, dating to a time period of about 3.8 billion years ago and along with the formation of valley networks in the Highlands, and lower, may be correlated with younger outflows. The higher, the 'coastline of Arabia', can be traced all over Mars except through the volcanic region of Tharsis. The lower, 'Deuteronilus', follows the Vastitas Borealis formation.
A study in June 2010 concluded that more ancient oceans would cover 36% of Mars. Data from the Mars Orbiter Laser Altimeter (MOLA), which measures the altitudes of all the plains on Mars, was used in 1999 to determine that such a waterline for such oceans would cover about 75% of the planet. Early Mars will require a warmer climate and a denser atmosphere to allow liquid water to exist on the surface. In addition, a large number of valley networks strongly support the possibility of hydrological cycles on the planet in the past.
The existence of the primordial oceans of Mars remains controversial among scientists, and the interpretation of some features as 'ancient coastlines' has been challenged. One problem with the 2 billion year coastline (2G) is that it is not flat - that is, it does not follow the constant gravitational potential line. This could be due to changes in Mars' mass distribution, possibly due to volcanic eruptions or meteor impacts; The Elysium volcanic province or the massive Utopia basin buried beneath the northern plains has been suggested as the most likely cause.
In March 2015, scientists claimed that evidence exists for ancient Mars seas, possibly in the northern hemisphere of the planet and about the size of the Arctic Ocean Earth, or about 19% of the surface of Mars. This finding comes from the ratio of water and deuterium in the modern Mars atmosphere compared to the ratio found on Earth. Eight times more deuterium is found on Mars than on Earth, indicating that ancient Mars had significantly higher water levels. Results from previous Curiosity rover have found a high deuterium ratio in Gale Crater, although not significant enough to show the presence of oceans. Other scientists caution that the new study has not been confirmed, and suggests that the model of the Martian climate has not yet shown that the planet was warm enough in the past to support the body of liquid water.
Additional evidence for the northern oceans was published in May 2016, illustrating how some surfaces in the square of Ismius Lacus have been altered by two Tsunamis. Tsunamis are caused by asteroids that attack the oceans. Both are considered strong enough to make the crater 30 km in diameter. The first tsunami took and carried stones the size of cars or small houses. The backwash of the waves forms a channel by rearranging the rocks. The second comes when the oceans are 300 m lower. The second brought a lot of ice dropped in the valleys. Calculations show that the average wave height is 50 m, but its height will vary from 10 m to 120 m. Numerical simulations show that in certain parts of the oceans two craters impacting by 30 sq km will be formed every 30 million years. The implication here is that the great northern oceans may have existed for millions of years. One argument against the oceans is the lack of coastline features. These features may have been swept away by these tsunami events. The parts of Mars studied in this study were Chryse Planitia and Northwestern Arabia Terra. This tsunami affects several surfaces in the squares of Ismius Lacus and in the Mare Acidalium quadrangle.
Attend water ice
A large number of surface hydrogens have been observed globally by the Mars Odyssey neutron spectrometer and the gamma ray spectrometer. This hydrogen is thought to be incorporated into the molecular structure of the ice, and through stoichiometric calculations, the observed flux has been converted to a concentration of water ice in the upper meters of the Martian surface. This process has revealed that ice is widespread and abundant on this surface. Below 60 degrees latitude, ice is concentrated in some areas, particularly around Elysium volcanoes, Terra Sabaea, and northwest Terra Sirenum, and exists in concentrations of up to 18% ice below the surface. Above 60 degrees latitude, ice is very abundant. Polewards at 70 degrees latitude, ice concentrations exceeding 25% almost everywhere, and close to 100% at the poles. The SHARAD and MARSIS radar sound instruments also confirm that the surface features of ice-rich individuals. Due to the icy instability known to the current Martian surface conditions, it is estimated that almost all of this ice is covered by a thin layer of rocky or dusty material.
The observation of the Mars Odyssey neutron spectrometer shows that if all the ice on the top of the Martian surface is evenly distributed, it will provide a layer of Global Equivalent Water (WEG) of at least - 14 cm (5.5 inches) - in other words, the global average is about 14% water. The water ice that is currently locked in both poles of Mars corresponds to a 30-meter WEG (98Ã, ft), and geomorphic evidence prefers a larger amount of surface water than geological history, with a 500-meter (1,600 ft) WEG. It is thought that parts of this past water have been lost to subsurface, and part to space, although the detailed mass balance of these processes is still poorly understood. Current atmospheric water reservoirs are important as channels allowing the gradual migration of ice from one part of the surface to another on a seasonal and longer time scale, but the volume is insignificant, with WEG not exceeding 10 micrometers (0.00039 di).
Polar ice cap
Both the North Polar cap (Planum Boreum) and South Pole cap (Planum Australe) have been observed growing thick during the winter and are partly sublime during the summer. In 2004, MARSIS radar detectors at Mars Express satellites targeted the south pole, and can confirm that the ice there extends to a depth of 3.7 kilometers (2.3 miles) below the surface. That same year, the OMEGA instrument on the same orbiter revealed that the hat was divided into three distinct parts, with various frozen water contents depending on the latitude. The first part is the brightest part of the polar cap shown in the image, centered on a pole, which is a mixture of 85% CO 2 ice to 15% water ice. The second part consists of a steep slope known as scarps, almost entirely made of water ice, which rings and falls from the polar cap to the surrounding plain. The third section covers a wide permafrost field that stretches tens of kilometers away from the scarps, and is not clearly part of the lid until the surface composition is analyzed. NASA scientists calculated that the volume of water ice in the polar ice cap, if melted, would be enough to cover the entire surface of the planet to a depth of 11 meters (36 feet).
The ancient icebergs that have been proposed for the southern polar region may contain 20 million km <3> ice water, which is equivalent to a layer of 137 m above the planet.
In July 2008, NASA announced that the Phoenix lander had confirmed the presence of water ice at its landing site near the north polar ice pole (at 68.2 Â ° latitude). This is the first direct observation of the ice from the surface. Two years later, a shallow radar on the Mars Reconnaissance Orbiter takes the measurement of the polar ice cap and determines that the total volume of water ice in its cap is 821,000 cubic kilometers (197,000 cuÃ, mi). That equals 30% of Earth's Greenland ice sheets, or enough to cover the surface of Mars to a depth of 5.6 meters (18 feet). Both polar caps reveal a nice internal layer when examined in HiRISE and Mars Global Surveyor images. Many researchers have studied this coating to understand the structure, history, and nature of the lid flow, although their interpretation is not direct.
Vostok Lake in Antarctica may have implications for liquid water that still exists on Mars, because if water existed before the polar ice at Mars, there is the possibility that there is still liquid water under the ice sheet.
Ice ground
Over the years, various scientists have suggested that some of the Martian surfaces look like periglasia areas on Earth. By analogy with these terrestrial features, it has been argued for years that this is a permafrost region. This will show that the frozen water is located just below the surface. General characteristics in higher latitudes, patterned soils, can occur in a number of forms, including lines and polygons. On Earth, these forms are caused by freezing and liquefaction of the soil. There is another kind of evidence for large amounts of frozen water beneath the surface of Mars, such as field softening, which stretches sharp topographic features. Evidence from the Mars Odyssey gamma ray spectrometer and direct measurements with Phoenix landers has corroborated that many of these features are closely related to the presence of ground ice.
Using HiRISE cameras on the Mars Reconnaissance Orbiter (MRO), the researchers found that by 2017 at least eight erosion slopes show a 100-meter open water ice sheet, covered by a layer of 1 or 2 meters thick of soil. The site is located at a latitude of about 55 to 58 degrees, indicating that there is shallow ground ice under about a third of the Martian surface. This image confirms what was previously detected by the spectrometer at 2001 Mars Odyssey, ground penetrating radar on the MRO and on Mars Express, and by the in situ Phoenix lander . This ice sheet stores easily accessible clues about the history of the Martian climate and makes frozen water accessible to future robotic or human explorers. Some researchers suggest this sediment could be a remnant of glaciers that existed millions of years ago when the axes of planetary rotation and their orbits differed. (See the Ice section below.)
- Toothed topography
Certain areas on Mars display a shell-shaped depression. Depression is thought to be the remains of a very rich ice coat deposit. Scallops are caused by ice sublimated from frozen soil. The toothed topographic landscape can be formed by the loss of ice-water surface with sublimation under present-day Martian climates. A model predicts a similar shape when the ground has large amounts of pure ice, up to tens of meters deeper. This mantle material may be deposited from the atmosphere when ice is formed in dust when climate is different due to changes in the slope of the Mars pole (see "Ice age", below). Shells are usually tens of meters and from several hundred to several thousand meters. They can be almost circular or elongated. Some seem to have united causing large terrain to be pitted against. The process of terrain formation can begin with the sublimation of the cracks. Often there are polygonal cracks in which scallops are formed, and the presence of toothed topography appears to be an indication of frozen soil.
On November 22, 2016, NASA reported discovering large quantities of underground ice in the Utopian region of Mars Planitia. The volume of water detected has been estimated to be equivalent to the volume of water in Lake Superior.
The volume of water ice in the area is based on measurements of a ground-penetrating radar instrument on the Mars Reconnaissance Orbiter, called SHARAD. From data obtained from SHARAD, "dielectric permittivity", or dielectric constant is determined. The value of the dielectric constant is consistent with the large concentration of water ice.
These toothed features are superficially similar to Swiss cheese features, found around the south polar cap. The specialty of Swiss cheese is thought to be caused by the formation of the cavity in the surface layer of solid carbon dioxide, rather than water ice - although the floor of this hole may be H 2 O-rich.
- Es patch
On July 28, 2005, the European Space Agency announced the existence of a crater partially filled with frozen water; some then interpreted the discovery as an "icy lake". The image of the crater, taken by the High Resolution Stereo Camera over the orbiter Mars Express of the European Space Agency, clearly shows a large sheet of ice at the base of an unnamed crater located at Vastitas Borealis, a vast plain covering most of Mars' latitudes far north, at about 70.5 Â ° North and 103 Â ° east. The crater is 35 kilometers (22 miles) wide and about 2 kilometers (1.2 mi) deep. The height difference between the crater floor and the water ice surface is about 200 meters (660 feet). ESA scientists attribute most of this height difference to the dunes under water ice, which are partly visible. While scientists do not refer to patches as "lakes", the ice water patch is amazing for its size and to be present throughout the year. Deposits of ice and ice water have been found in many different locations on the planet.
As more and more Martian surfaces have been imaged by the modern generation of orbits, it is increasingly clear that there may be more ice fillings scattered on the surface of Mars. Many of these alleged patches of ice are concentrated at the midline of Mars (30-60 Â ° N/S from the equator). For example, many scientists think that the widespread features in latitudinal bands that are variously described as "dependent mantle" or "occupied field" consist of an ice sheet covered with dust or debris, which is slowly demeaning. The debris sheath is necessary both to explain the blunt surface seen on the image that does not reflect the ice, and also allows the patch to exist for a long period of time without fully refining. These fractures have been proposed as a possible water source for some mysterious flow features such as trenches also seen in the latitudes.
Surface features consistent with existing ice packs have been found on the southern Elysium Planitia. What appears to be plates, ranging in size from 30 meters (98Ã, ft) to 30 kilometers (19 mi), is found on the channel leading to a large flood area. Plates show clear breaking and rotation markings that distinguish them from lava plates elsewhere on the surface of Mars. The source of the flood is suspected to be a geological error of Cerberus Fossae that spewed water and lava aged between 2 and 10 million years. It is recommended that the water coming out of Cerberus Fossae then gather and freeze in the lowlands, lowlands, and such frozen lakes may still exist.
Glacier
Many large areas of Mars appear as hosts of glaciers, or carry evidence that they once existed. Most of the areas in high latitudes, especially the squares of Ismius Lacus, allegedly still contain large amounts of water ice. Recent evidence has led many planet scientists to conclude that water ice still exists as a glacier in many mid and high latitudes of Mars, protected from sublimation by thin layers of insulating rock and/or dust. An example of this is a feature like a glacier called apron lobe remnants in an area called Deuteronilus Mensae, which features extensive evidence of ice that lies beneath a few feet of stone debris. The glacier is associated with a restless terrain, and many volcanoes. Researchers have described the glacial deposits at Hecates Tholus, Arsia Mons, Pavonis Mons, and Olympus Mons. Glaciers have also been reported in a number of larger Martian craters in the midlatitudes and above.
Glacier-like features on Mars are known to feature various viscous flows, feature Mars streams, apron lobe debris, or fill the valley lined, depending on the shape of the feature, its location, the landscape it is associated with, and the author describes it. Many, but not all, small glaciers seem to be associated with trenches in the crater wall and mantle material. The lined sediments known as the lined valley fillers are probably glaciers covered by rocks found on the ducts of the channels in the field encountered around Arabia Terra in the northern hemisphere. Their surfaces have jagged and grooved material that bends around obstacles. Striped floor deposits may be associated with apron lobosi debris, which has been shown to contain large amounts of ice by orbiting radar. Over the years, researchers have interpreted that the so-called 'apron lobes' feature is a glacial flow and it is thought that ice is under layers of insulating rock. With the reading of new instruments, it has been confirmed that apron lobosi debris contains almost pure ice that is covered with a layer of stone.
Ice that moves with rock material, then drops it as ice disappears. This usually occurs on the muzzle or the edge of the glacier. On Earth, such features will be called moraines, but on Mars they are usually known as moraine-like mountains, concentric mountains, or fiery mountains >. Because ice tends to be sublime rather than melt on Mars, and because low temperatures Mars tends to make glaciers "cold based" (freeze to their beds, and can not slide), the remnants of glaciers and backs they leave do not appear exactly to normal glaciers on earth. In particular, Martian moraines tend to be kept without being deflected by the underlying topography, which is thought to reflect the fact that the ice on Mars glaciers is usually frozen and can not slide. Rows of debris on the surface of the glacier indicate the direction of ice movement. The surface of some glaciers has a rough texture due to the buried ice sublimation. Ice evaporates without melting and leaving empty space. The material on it then collapses into the void. Sometimes ice blocks fall from glaciers and buried on the ground. As they melt, the round holes are more or less fixed. Many of these "boiler holes" have been identified on Mars.
Despite strong evidence for glacial flow on Mars, there is little convincing evidence for landscapes carved by glacial erosions, for example, U-shaped valleys, coral hills and tail, cedar, drumlins. Such features are abundant in the glacial regions of Earth, so their absence on Mars has proven to be confusing. The lack of this landscape is thought to be linked to the cold nature of ice in the most recent glacier on Mars. Because the solar insulation reaches the planet, the temperature and density of the atmosphere, and the geothermal heat flux are all lower on Mars than on Earth, modeling shows the interface temperature between the glaciers and the beds remain below freezing and the ice is completely frozen to the ground. This prevents it from sliding over the bed, which is thought to inhibit the ability of the ice to erode the surface.
Development of Mars water inventory
Variations in the surface water content of Mars are closely related to the evolution of the atmosphere and may have been characterized by several key stages.
The early era of Noachian (4.6 Ga to 4.1 Ga)
Loss of atmosphere into space from heavy meteorite bombardment and hydrodynamic flight. Ejection by meteorites may have removed ~ 60% of the initial atmosphere. Significant amounts of phyllosilicates may have formed during this period requiring a sufficiently dense atmosphere to maintain surface water, since the spectralally dominant phyllosilicate group, smectite, exhibits moderate water-to-stone ratios. However, the pH-pCO 2 between smectite and carbonate indicates that smectite precipitation will limit pCO 2 to a value of no more than 1 ÃÆ' - 10 -2 Ã, atm (1.0 kPa). As a result, the dominant component of the solid atmosphere at the beginning of Mars becomes uncertain, if the clays are formed in contact with the Martian atmosphere, especially given the lack of evidence for carbonate deposits. An additional complication is that a ~ 25% lower brightness than young Sun will require an ancient atmosphere with a significant greenhouse effect to raise the surface temperature to maintain liquid water. A higher CO 2 content alone would not be enough, as CO 2 precipitates at a partial pressure exceeding 1.5Ã, atm (1,500 hPa), reducing its effectiveness as a greenhouse gas.
Middle to late Noachian times (4.1 Ga to 3.8 Ga)
The potential for secondary atmospheric formation by outgassing is dominated by Tharsis volcanoes, including large numbers of H 2 O, CO 2 , and SO 2 . The Martani valley network dates from this period, showing a large and temporal surface water globally as opposed to a flood disaster. The end of this period coincides with the cessation of the internal magnetic field and the surge of meteoritic bombing. The termination of the internal magnetic field and subsequent attenuation of any local magnetic field allows the atmospheric stripping unimpeded by the solar wind. For example, when compared to their terrestrial counterparts, 38 Ar/ 36 Ar, 15 N/ 14 N , and 13 C/ 12 The C ratio of Mars atmosphere is consistent with ~ 60% losses Ar, N 2 , and CO 2 by the release of solar wind from the enriched upper atmosphere in the lighter isotope through Rayleigh fractionation. Completing the solar wind activity, the impact will release large amounts of atmospheric components without the isotope fraction. However, the impact of comets in particular may have contributed volatile to the planet.
Hesperian into the Amazonian era (present) (~ 3.8 Ga to present)
Increased atmosphere by sporadic outgassing events is denied by the atmospheric sun-stripping wind, though less intense than by young Sun. Flood disaster dates to this period, supporting volatile sudden ground release, as opposed to sustainable surface flow. While the earlier part of this era may have been characterized by the aqueous acidic environment and the Tharsis-centric groundwater discharge dating to the late Noachian, many processes of surface change during the latter part are characterized by oxidative processes including the formation of Fe 3 oxide gives a reddish hue to the surface of Mars. Oxidation such as primary mineral phase can be achieved by low pH (and possibly high temperature) processes associated with the formation of tephra palagonite, by the action of H 2 O 2 that forms photochemistry in the atmosphere of Mars , and by the action of water, no one requires O 2 . Action H 2 O 2 may have been a temporary dominance due to the drastic decrease in aqueous and frozen activity in the recent era, making Fe observed 3 oxide volumetrically small, although pervasive and spectral dominant. However, aquifers may have encouraged sustainable surface water, but are highly localized in recent geological history, as evidenced in the geomorphology of craters such as Mojave. In addition, the Lafayette Martian meteorite shows evidence of recent aqueous changes as 650 Ma.
Ice age
Mars has experienced about 40 large-scale changes in the number and distribution of ice on its surface over the past five million years, with the most recently occurring around 2.1-0.4 Myr last, during the late Amazon glaciation at the dichotomy boundary. This change is known as the ice age. The ice age on Mars is very different from that experienced by Earth. The ice age is driven by changes in the orbit and slope of Mars - also known as obliquity. Orbital calculations show that Mars vibrates on its axis far more than Earth. The earth is stabilized by its large proportional moon, so it only swayes a few degrees. Mars can change its tilt with dozens of degrees. When the slope is high, the poles get more direct sunlight and heat; this causes the ice cap to warm up and become smaller as ice sublimes. Adding climate variability, the eccentricity of the orbits of Mars is twofold from Earth's eccentricity. As the pole is sublime, ice is positioned closer to the equator, which receives a slightly less solar insolation on high obliquities. Computer simulations show that a 45 ° slope of Mar axis will result in ice accumulation in areas that feature glacial landscapes.
The moisture from the ice layer moves to the lower latitudes in the form of ice or snow deposits mixed with dust. The atmosphere of Mars contains many fine dust particles, moisture condenses on these particles which then fall to the ground due to the additional weight of the water layer. When the ice above the mantle layer returns to the atmosphere, it leaves the dust that serves to isolate the rest of the ice. The total volume of water discharged is a few percent of the ice cap, or enough to cover the entire surface of the planet under one meter of water. Most of this moisture from the ice cap produces a thick coat thick with a mixture of ice and dust. This ice-rich coat, which can be as thick as 100 meters in mid-latitudes, smooths the land at lower latitudes, but in places it displays a wavy texture or pattern that gives the presence of ice water underneath.
Evidence for current stream
Pure liquid water can not exist in stable form on the surface of Mars with low atmospheric pressure and low temperature, except at the lowest elevation for several hours. Thus, a geological mystery began in 2006 when the observations of the NASA Mars Reconnaissance Orbiter revealed the dug precipitate that had not existed ten years earlier, possibly due to the flow of brine liquid during the hottest months on Mars. The images consist of two craters called Terra Sirenum and Centauri Montes that appear to indicate the presence of a (wet or dry) stream on Mars at a point between 1999 and 2001.
There is disagreement in the scientific community about whether sewers are formed by liquid water or not. It is also possible that the streams that engrave the trenches are dry granules, or may be lubricated by carbon dioxide. Several studies have shown that trenches formed in the southern highlands can not be formed by water because of improper conditions. The cooler, non-geothermal, cooler regions will not give way to liquid water at any point of the year but will be ideal for solid carbon dioxide. Carbon dioxide that melts in warmer summers produces liquid carbon dioxide which will then form trenches. Even if the trenches are carved with water flowing on the surface, the precise water source and the mechanism behind the movement are not understood.
Dry sewers are deep grooves engraved on existing slopes throughout the year. There are many other features on Mars, and some of them change seasonally.
In August 2011, NASA announced the discovery by the American undergraduate student Nepal Lujendra Ojha about the current seasonal changes on a steep slope under a rocky outcrop near the crater rim in the Southern Hemisphere. These dark lines, now called recurrent slope lineae, appear to grow down the slopes during the warmest parts of the Martian summer, then gradually fade throughout the remainder of the year, repeating cycles between the years. The researchers suggest these signs are consistent with saltwater (salt water) that flows down the slopes and then evaporates, possibly leaving some sort of residue. The CRISM spectroscopic instrument has since made a direct observation of the hydro-salts that appear at the same time as this recurrent slope form, which confirms by 2015 that the lineae is produced by the flow of liquid saline water through shallow soil. Lineae contains hydrate chlorate and perchlorate salt ( ClO
4 - ), which contains liquid water molecules. Lineae flow decreases in the summer of Mars, when the temperature is above -23 ° C (-9 ° F, 250 ° K). However, the source of the water is still unknown. However, the neutron spectrometer data by Mars Odyssey orbiter more than a decade, published in December 2017, and show no evidence of water (hydrogenated regolith) in the active site, so the authors also support the hypothesis of both deliquesence short-lived atmospheric water vapor, or dry flowing granular. They conclude that liquid water on Mars today may be limited to traces of dissolved moisture from the atmosphere and thin film, which is a challenging environment for life as we know it.
Opportunity assessment
Liquid water is a necessary condition but not sufficient for life as we know it, because feasibility is a function of many environmental parameters. Today's life on Mars can occur miles beneath the surface in a hypothetical hydrosphere, or under sub geothermal heat, or may occur near the surface. The permafrost layer on Mars is just a few centimeters below the surface. Salty salty water can melt a few centimeters below but not far down. Most of the proposed surface habitats are within centimeters of the surface. Any life deeper than that may be inactive. Water is close to its boiling point even at the deepest point in the Hellas basin, so it can not remain long molten on the surface of Mars in its present state, except when it is ice-covered or after a sudden water release. Current liquid water on Mars may be limited to the trace of dissolved moisture from the atmosphere and thin film, which is a challenging environment for life as we know it.
So far, NASA has been pursuing a "water-following" strategy on Mars and has not been looking for biosignatures to live there directly since the Viking landings in July 1976. Observations by Phoenix in landing 2008 from the potential of molten salt water drops formed on its feet causes a renewed interest in the feasibility of the Martian surface potential. Since then, experiments have generated many suggestions for potential habitats on the surface of Mars. However, although liquid water is now confirmed to occur in the brine layer, it is unknown if anything is inhabitable. It depends on factors such as salt mix, temperature, energy source, and radiation environment on Mars.
Propose a surface habitat for Earth microorganisms
Source of the article : Wikipedia
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