Mars Express - summary of findings

The original work plan consisted of observing and exploring Mars for one Mars year, but the mission has been extended 3 times to date. The spacecraft is still active

introduction

The Mars Express spacecraft is a European spacecraft twinned to the Venus Express spacecraft, but its goal, as you can understand from its name, is Mars. The spacecraft was launched from Russia on June 2.6.2003, 3 and entered orbit around it in December of that year. The original work plan consisted of observing and exploring Mars for one Mars year, but the mission has been extended 96 times to date. The spacecraft is still active and the duration of its future activity depends on the amount of fuel in its tanks. The spacecraft engineers and Mars explorers took advantage of its orbit and also photographed the moon Phobos from a distance of XNUMX km.

Methods of geological dating

The accepted method for geological dating of planets differs from the geological dating methods of the Earth. Planetary geological periods are based on counting craters. The basic premise is that surfaces that are more exposed in terms of time to space have suffered more impacts from meteorites and therefore have more craters. According to this method, 3 periods were distinguished on the surface of Mars and they are (1):

The Noachian Period - from the formation of Mars until 3.5-3.8 billion years ago. The name of the period is derived from the name of a high plateau in the southern hemisphere Noach Terra. The many impacts on Mars created many craters. But many evidences of water erosion gave a basis for the assessment that the surface at that time was warm and humid.

The Hesperian Period - This period began when the impact rate on Mars weakened and probably lasted 1.8 billion years. The name of this period is derived from the name of a high plateau also in the southern hemisphere - Hesperian Planum. In this area there was intense volcanic activity that covered many craters from the Noahic period.

The Amazonian Period - from the end of the Hesperian period to the present day. The name of the period is derived from the name of a low plain in the southern hemisphere - Amazonian Planitia. This period was too cold for the presence of liquid water at least on the surface.

The European researchers propose a different dating model based on the mineralogical content of the surface. The names are given based on phyllosilicate minerals. The European researchers also divided the geology of Mars into 3 periods, partially overlapping with the accepted chronological division, although it should be noted that one of the American Martian researchers, Michael Carr, disagrees with this method. According to the European system, the periods are:

The Phyllosian period is characterized by the presence of phyllosilicates-clays that have a lot of iron.

The Thiikian period is characterized by the presence of sulfates, evidence of volcanic activity, formed by reaction with water.

The Siderikian period is characterized by iron oxides without the presence of water and there is no liquid water in this period.

It is possible that with the beginning of manned activity on Mars, the dating method will change. Stratigraphic dating will be used as is customary on Earth. This assessment is based on high-resolution photographs, based on which it will be possible to make stratigraphic sections in different places, especially in the cliffs.

atmosphere

The impression obtained from the study of the atmosphere of Mars is that in the past the amount of carbon in it was greater, it was in the first stages of the planet's existence as it was in the corresponding period on Earth. The source of the carbon is from inside the planet itself from the mantle and from external sources (carbonate meteorites, micrometeorites and comets). Today the carbon molecules are more volatile and are destroyed by oxidation and ionization on the surface. These processes did not occur in the past when the atmosphere was denser, with a greater content of
CO2 and a magnetic field that protected the planet (2). Although Mars and Earth were formed from the same materials, each evolved separately. The water during this period broke up and only after the first billion years did Mars apparently become a cold and dry planet. A possible clue to the loss of water from the atmosphere comes from the way in which the interaction between the atmosphere and the solar wind occurs. This interaction shows that Mars loses 100 tons of its atmosphere every day (3) . The obvious question is how does Mars still have an atmosphere. The sources of the renewal of the atmosphere are comet impacts, the CO2 ice at the poles and the intrusion of water from the earth's condensate that turns into gas (4). The researchers identified a type of double whammy solar supper wave that causes the depletion of the Martian atmosphere. These waves are created when one current of the solar wind reverses and is lifted by another wave and accelerates the speed of particles from the sun. This creates a stream of particles moving towards Mars, hitting it in one blow and spraying particles from the atmosphere into space (4).

The ionosphere of Mars rises to a height of 110-130 km. At this altitude, solar radiation is very powerful, and particles from the solar wind break apart atoms and molecules in the upper atmosphere and release electrons. The global mapping of the ionosphere made it possible for the first time to examine its behavior even at night. The mapping of the atmosphere indicated changes in the geographical space during the hours of darkness. During the nocturnal mapping, a complex web of areas with high electron density was discovered. One of the interesting discoveries was the large correlation between the number of electrons in the ionosphere at night and the direction of the local magnetic field. The areas with the greatest electron density are associated with areas with high magnetism, especially south of the equator, near the places where the magnetic field lines are perpendicular to the ground. On Earth, such a situation is only possible at the magnetic poles. The solar wind enveloping Mars probably allows the formation of an ionosphere on the night side. The interaction with the solar wind energizes the atmosphere and creates a population of free electrons (5).

Aurora

Polar aurora phenomena were also discovered on Mars. Their discovery was made in 2004 using the spacecraft's infrared and ultraviolet spectrometer. This equipment makes it possible to study the structure and composition of the Martian atmosphere. It turned out that this caution occurs near places where there are remnants of a magnetic field in the rocks of the crust. 9 new emissions of this zahira were discovered, which made it possible to map the Martian zahira. On the other planets where the phenomenon was detected, their geographic location, like on Earth, is delimited to the polar region. On Mars the phenomenon occurs in pockets of magnetism, places where the crustal rocks are themselves magnetic and their distribution is over the entire planet. They are caused by the collision of charged particles with molecules in the atmosphere. The origin of the particles is from the sun. It is still not clear how the electrons are accelerated to high speeds to the point of creating a cautionary phenomenon on Mars (6). On Earth, the molecules that cause visible light are oxygen and nitrogen, which are not common enough on Mars.

climate change

In terms of the long-term climate change, the researchers use the photographs of the glaciers and these raise the possibility that such a climate change occurred 4.6 billion years ago. According to the same approach, Mars is currently in a transitional period between ice ages. Due to the tilt of the axis, Mars is now closer to the sun, ice deposits in low latitudes evaporate and change the surface of the land (7). Two groups of researchers concluded that the axis of Mars oscillates periodically on its axis. According to the calculations of one group, the axis changes between 40°-15° and according to the calculations of the other group, the axis changes at an angle of 45° (8,9). In any case, these are very strong fluctuations and the reason for this is that Mars does not have a large moon like that of the Earth which stabilizes this fluctuation. The result is strong climatic fluctuations over millions of years. It is estimated that 5 million years ago Mars underwent a strong angular change. Moisture that was trapped at the poles was transported by winds to the equatorial region and deposited as snow there. Thanks to this, it created a frozen sea and patterns of glacial activity in this area, ancient strips of ice. These are probably remnants of ice along the equator (8). Other places rich in ice were found in the valleys east of the Hellas region and on the western flanks of the equator the mighty volcanoes called Tharsis Montes. This is a similar process to the cyclic snow cover of the Rockies in the USA and the glaciers on Kilimanjaro in Africa and the Andes in South America (9).

clouds

On Mars there are clouds of water ice and CO2 ice crystals. The clouds of water ice are found, for example, on the flanks of the mighty volcanoes and the clouds of methane were found at a height of 80 km above the ground. Some of the methane clouds are dense and some are hundreds of kilometers long. Due to their size and density, the methane clouds cast an extensive shadow on the ground. They are similar to high conventional clouds that grow due to warm air rising up. The size of the particles that make up these clouds is more than a micron and their density is so high that it dims the sunlight by 40%. From this you can understand the size of the cloud's shadow cast on the ground. Usually particles of this size are not formed at high altitude and do not stay there for long until they fall to the ground. The temperature in the shadow area is 10 ° lower than its surroundings and this changes the local weather especially the winds. Since the CO2 clouds are mainly found in equatorial regions, it is estimated that the shape of the clouds and the size of the ice crystals can be explained through extreme changes in the daily temperatures that occur near the equator.

The low night temperatures and the relatively high daytime temperatures during the day create long daily waves in the atmosphere and thus the potential for large convection currents in particular during the time when the morning sun's rays warm the ground. Bubbles of hot gas rise above the surface and when they reach heights they become cold and the CO2 condenses. This process releases latent heat which causes the gas and ice crystals to rise to greater heights. A fundamental question is what the particles around which the CO2 condenses are made of. On Earth these kernels are made of dust or salt particles. Regarding Mars, 3 options were proposed. One possibility is dust carried to these heights, a second possibility particles left by micrometeorites penetrating the atmosphere and a third possibility very small particles of water ice brought to these heights by hot air currents. Finding the right option will help in understanding the climate of Mars in the past. It seems that billions of years ago Mars was warmer and according to one estimate the planet was once covered in CO2 clouds (10). This calls for another conclusion - it is possible that in the distant past, the greenhouse effect worked on the surface of Mars.

Makhteshim

In this review of craters, several craters will be noted, each with its own characteristics:

1. The Hellas crater - the largest crater not only on Mars, but also in the solar system. Its diameter is 2400 km and its depth is 9 km. In winter, its bottom is covered with frost, its rim is crossed by sunken and elliptical formations in the northwest-southeast direction. There are several small craters (11) in it.

2. Nicholson Crater - The location of this crater is E ° 195.5 - ° 0 at the southern end of Amazonis Planitia and its diameter is 100 km. In its center there is a semi-domed and elongated structure. The length of this formation is 55 km, its width is 37 km and its maximum height is 3.5 km. It is not clear how it was created, but it is safe to say that it was shaped by winds or water. On its slopes are elongated and narrow depressions, perhaps evidence of water activity (12).

3. Mounder Crater, located E °2 - S ° 50. Its diameter is 90 km and its depth is 900 meters. Since its formation it has been partially filled with large amounts of material. In its western part there are internal rockslides (to the crater) towards the east. In the transition area from the western rim of the Great Crater to its smooth floor on the eastern side, there are many cliffs and they were formed by rockfalls on the eastern side. The floor of the crater in the east is bordered by a depression 700 meters deep. It is possible to distinguish several channels (gulleies) that originate from the eruption of water. The small dark formations that are 500-2500 meters long on the floor of the crater are Barachan dunes (barachan dunes) similar to those found on Earth in the arid regions of the Namibian desert (13).

4. In Meridiani Planum, a crater with a diameter of 50 km, the floor of which is covered with a dark substance similar to volcanic ash, probably from the minerals pyroxene and olivine. In the dark material there are small hills that are probably made of a material resistant to the material around it. The soft material underwent processes of erosion and was blown out of the crater by winds in a northeast direction and created dark stripes around it. Near this crater there is a smaller crater with a diameter of 15 km whose floor is also made of dark material. The same material that was blown out of the great crater (14).

5. Spiral crater (Schiaparelli) - location E °17 - S ° 3 in Terra meridiani. Its diameter is 460 km. On the floor of the crater there is a sedimentation of a dark material similar to the material deposited in lakes that evaporated on Earth. The interior of the crater was shaped by geological processes such as the impact of material that was blown out due to a meteorite impact that created it and lava flows that created the smooth surface and material that was deposited by water sedimentation (15).

6. An elongated crater - found south of the Huygens basin. Its length is 78 km. At one end it is 10 km wide, at the other end it is 25 km wide and 2 km deep. It is probably two hits next to each other that created the configuration, or a body that had not yet been hit was broken into two parts. What supports the possibility of the double injury is the material thrown from both injuries, from each injury separately. Within the configuration itself you notice 3 areas each with its own depth. This in itself can indicate the possibility of more than two hits to the ground (16).

7. Buried Craters - Beneath the smooth plains in the Northern Hemisphere are 10 underground craters whose diameter ranges from 130-470 km. Only one of them can be seen with great difficulty with a normal eye observation. It turned out that the rim of the craters was removed by erosive processes, which made it difficult to view them (17,18).

sockets

Unique formations of fragments were also found on Mars. We will present several examples:

1. A series of depressions with a diameter of 200 km and a depth of 1 km in relation to their surroundings (19) were discovered in high street lines.

2. Arcus Patera- location E °177 – N ° 14 between the volcanoes Elysium Mons and Olympus Monts. Its direction is north northeast-south southwest. Its dimensions are 380 X 140 km. Its rim is 1800 meters high above its surroundings and its floor is 600 meters deep. The width of the socket is not symmetrical along its entire length. At one end it is wide and at the other end it is narrow. Its floor is smooth and mostly bright. In its center there is a slightly darker strip. The number of craters in the floor is few. Grabens are found on its rim, which indicates that tectonic forces acted here after the formation of the depression. It is possible that there are also graben on the floor of the socket, but it is impossible to know. Perhaps they were previously covered with material that was transported to the place by spirits and filled them (20).

3. Sink in Phoenicis Lacus. It is 3 km deep and was created due to land subsidence. Its shape is the shape of the letter V and on its slopes you can probably distinguish the sand (21).

tectonics

As on Earth, tectonic forces operate on Mars as well, and quite a few grabens have been found on it. Here are some examples:

1. In the Acheron mountain range there is a system of fractures that reach a depth of 1.7 km and were created as a result of uplift processes. The cracks were formed when hot material rose from deep within the Martian mantle and lifted the lithosphere or layers of rock. As pressures increase, the brittle crust at the top of the lithosphere breaks along zones of weakness. The Acheron Fossae is similar to places like the rift valley in East Africa, a place where continental plates split and moved away from each other (22).

2. Nili Fossea - a system of grabens northeast of the Syritis Major area. The grabens are arranged concentrically around Isidis Crater. It is estimated that the flooding of the lava crater floor after its formation is a result of the subsidence of the basin floor, which increased the pressure in the crust and was released by the creation of the fissures. The depth of some of the graben is 500 meters. This area has aroused great interest among astronomers because in the observations of telescopic observations from the Earth a significant increase in the amount of methane in the atmosphere was observed there (23).

Volcanic activity

Calderas in the 5 largest volcanoes on Mars were active at least 2 million years ago and may still be active today (7). According to one estimate, the volcanic activity affected the activity of glaciers since the volcanic eruptions also cause water movement (24).

Massif

The fiber is mostly a geological or topographical structure, usually built of harder rocks than those found in its surroundings and in most cases they are trending or those that have undergone metamorphosis. One such on Mars is Ausonia Mensa found in Hesperian Planum and located E ° 97.8 -S ° 30.3. Its height above its surroundings is 3.7 km and its dimensions are 98 X 48 km. As a result of the erosion, several ravines were formed in it running from the summit to the plains. On the western side there is a crater with a diameter of 6 km surrounded by materials that were blown out of secondary craters. Formations that are the product of wind activity are found 50 km southeast of Masib and it is possible to learn from this according to the direction of wind movement. In the north of the massif there is a crater with a diameter of 6 km which has undergone strong erosion and inside it are several small craters. Another crater with a diameter of 7.5 km is partially filled with sedimentary materials (25).

The Mendusae Fossae Formation

This configuration is found along the equator in the place that separates the high areas from the low areas and contains deposits that represent some of the young investment materials on the surface of Mars. There are no craters in this area. The thickness of the deposits in several places is 2.5 km. Several hypotheses have been put forward as to the origin of these materials. One possibility is volcanic ash that came from vents or nearby volcanoes. A second possibility is material transported by winds as a result of erosive processes on the Martian rocks. A third possibility, sediments made of ice similar to layers of ice deposited near the poles, but they were formed at a time when the axis of Mars was tilted at a greater angle than today, so that the equatorial region was colder (26).

Poles

Today the largest reservoir of water on Mars is in the poles. The thickness of the ice layer at each of the poles is 3.5 km. The ice layer is covered with a thin layer of CO2 ice a few centimeters to tens of centimeters thick. In the summer months, most of the CO2 evaporates directly into the atmosphere. Dark matter is mostly dust carried by the winds. Snow and ice are deposited during colder periods by snow and ice. The balance between the sedimentation and the ice creates the stratification of the layers visible in the photographs. At the edges of the ice caps you can see grooves that are 100 km long. One of them is Chasma Borealis. Why they are created is not clear (27) .

A series of photographs of the poles solved one of the mysteries of Mars. During the summer in the southern hemisphere a large part of the water ice evaporates. Of which only a small part remains in the summer. It is mostly made of CO2 ice. The ice cap in winter has a symmetrical structure, while part of the residual cold is deflected by 4-3°. The accepted assessment was that during the winter in the Western Hemisphere at the Pole it rains more and for this reason there will be residual material in it. The latest findings indicate that in practice the mechanism is different. In fact, it is a strange interaction between wind, snow and the sun. During the observations, the temperatures and other conditions of the atmosphere above the South Pole were measured at the same time as the CO2 accumulation in the polar dome was measured. It turned out that the drifting of the residual ice cap begins with strong easterly winds in the mid-latitudes that blow straight into the massive Las Crater. The steep sides of the crater deflect the winds and create huge waves in the atmosphere. These waves change the direction of winds at high altitudes and drive weather systems towards the South Pole. The result is that a strong low pressure system forms in the Western Hemisphere near the South Pole and a high pressure system in the Eastern Hemisphere also near the Pole, the low pressure system in the Western Hemisphere lowers the temperatures. These temperatures contribute to condense the CO2 into snow. This means that snow and frost form in the western hemisphere of the South Pole. In the high pressure system in the Eastern Hemisphere the temperatures are too high for snow to form, so only frost covers the ground. The areas where there is extensive snow cover reflect more sunlight into space than the rest of the surface. Frost grains tend to be larger than ice grains and have a rougher surface. Such texture of the surface stores more sunlight, which accelerates sublimation. Due to this combination of factors, the western region of the Southern Hemisphere has a large amount of CO2 ice deposits whose sublimation is slower during the summer (28).

A strange phenomenon that was discovered during the 70s by the Viking spacecraft, takes place in the South Pole in a place called the "cryptic region". During the spring, large areas become dark compared to the Arctic Circle. The obvious question was why this area is darkening. Observations made in 1990 deepened the mystery, when it became clear that the prevailing temperature in the mysterious area is -135 C, a temperature at which CO2 ice should exist. The model proposed to solve the problem claims that a 2 meter thick layer of CO1 ice covers this area and that the dark surface can be seen. The Mars Express observations disproved this hypothesis. Examining the amount of reflection of visible and infrared radiation from the surface, a weak absorption of infrared radiation was found, which indicates that the amount of CO2 ice in the mysterious area is small. The only way so far to solve the problem is to accept the assumption that there is indeed an ice surface in the area, but it is covered by a large amount of dust, so that only a little of the sunlight can penetrate through the ice and return. If so, another question arises and that is how the dust gets to the place. The answer may lie in strange formations found in the area such as spots, "spiders" and "fans" discovered between 1998-1999 by the American Mars Global Surveyor spacecraft. It may be that the sunlight penetrating through the ice heats the surface from below. As a result, a strong pressure is created in the bubbles of the CO2 until they burst out as geysers that blow the dust off the surface and this and their flow to the ground create these formations. Another question can be asked here, why do these formations only appear in small sections of the mysterious area? (29).

rivers

Photographs from Lybia Montes, located south of Isidis Planitia, show a 400 km long valley cutting through the land, which is estimated to have formed 3.5 billion years ago. In the center of the valley there are traces of an inner valley with clear signs of water flow during periods when the Martian climate was humid. The rate of water flow was like in the central part of the Mississippi River in the USA. Based on the explosions of the craters and their size on the floor of the valley and its surroundings, it is estimated that this valley where the water flowed was formed 350 million years ago. Examining the rate of erosion activity raises the possibility that the active periods were short and in which there was an intense flow of water (30).

Similar to the Earth, also on Mars some of the rivers that have been identified have delta formations and at the bottom of them material that has been deposited over time. One of the places where a delta was detected is Xanthe Terra near the equator. There are places where you can see layers of material that has been layered. These places are found in valleys that penetrate into craters. River water naturally carries with it material that has been eroded downstream. When the transport rate is low, the water does not have enough power to move it and because of this the material sinks and accumulates on the river bed. Since this process occurs in places where a river flows into a large basin and in places where the flow rate tends to zero, sedimentary sediments are formed there. The type of material deposited depends on the nature of the basin. If the lake is full of water, a lake or a sea, a delta is obtained. If the basin is dry like a desert, the river slows down, the water seeps into the ground and a formation called playas is obtained. The material deposited in these places is called an alluvial fan. The plateaus in Xanthe Terra are crossed by deep valleys. In a crater with a diameter of 5 km. There is a delta, the river Numedi entering the crater from its south. The crater is almost full of material that was carried to it by the water. The thickness of the deposited material is 50 meters and the size of the area covered as a whole is 23 km.

Counting craters shows that water flowed in the valleys 3.8-4 billion years ago. In the period between 3.5-3.8 billion years the amount of rainfall was less and the valleys dried up. The erosion since then has been minimal, which has contributed to the fact that it is still possible to distinguish the deposited materials (31).

lakes

A slab-like area south of Elysium Planitia located near the equator looks like an ice pack on Earth. The dimensions of this place "the frozen lake" are 900 X 800 km, its depth is 45 meters and similar in size to the North Sea of ​​a ball in Israel. It is believed that these are the remains of an ocean formed from subterranean ice that melted due to volcanic activity and burst out along the entire length of the Cerberus Fossae. The water froze and was covered by a layer of volcanic ash. This layer acted like an insulating layer and slowed the rate of water evaporation into the thin Martian atmosphere. According to one estimate, this reservoir was created 3-7 million years ago (32).

Another place where there was a water reservoir is Meridiani Plains. It is estimated that this place is actually the bottom of a lake because of it there is a large amount of hematite, a mineral rich in iron, which is formed in the presence of water (33). Inside a crater found in Vastitas Borealis is a block of ice. The location E°103 – N° 70.5. The diameter of the crater is 35 km and its depth is 2 km. The block of ice is a remnant of liquid water. The temperatures in the place are too low to allow the water to evaporate (34).

Dunes with water

Other places where frozen water is found in the Northern Hemisphere are dunes that contain 50-40% water. One of these dunes is the Kaiser Dune which is 6.5 km long and 475 meters high. There are such dunes on Earth, but it is still unclear how they were formed. Their place is in the polar regions. These dunes are found above jagged ridges and are the product of ice and snow binding sand grains that have developed resistance against erosion. A phenomenon identical to this was observed on Mars. In places where the ice melts and seeps through the sand in the dunes, cracks and fractures form in the form of fans. These characteristics were also found in the dunes of Mars. One of the fan formations that is over 400 meters long has lost a large part of its water mass.. Kaiser Dune has 500 cubic meters of water. Since there are no craters in these places, it is estimated that they were created recently, probably 100,000 years ago (35).

Frost, snow, ice, glaciers

In one of the most impressive photographs inside the Valles Marineras, the massive canyon of Mars shows frost rising from the floor of the canyon to close to its rim (36). In Rupes Tenuis, located at E ° 297 – N °81, a large area is visible covered with snow (27). Other places besides the poles where ice is found are in the equatorial region. The thickness of the ice layer is several centimeters (37). Snow is the source of the glaciers at the base of the large volcanoes and probably also in the mountainous areas in middle latitudes in the tropics. On the eastern side of the Las crater are probably the remains of huge glaciers that existed 5 million years ago on Mars. The origin of the glaciers is the snow that was transported from the poles several million years ago. The axis of Mars was tilted so that the poles were closer to the sun. The sun's heat melted the polar ice caps, large amounts of water vapor were released into the atmosphere and mons-like winds carried them towards the Tharsis Monts and Olympus Monts. In these places the water vapor condensed and fell to the ground as snow. Over the years the snow turned into ice and it turned into glaciers (9).

Mapping and characterization of the water ice deposits in combination with a computer model of the global climate allowed a better understanding of the formation of the ice. The structure of these deposits at the pole became clear. A distinction must be made between 3 types of sediments. Water ice mixed with CO2, extensive patches of tens of kilometers of water ice and sediment covered by a thin layer of CO2. The detection of the first type confirms the assumption that the CO2 acts as a trap for the water ice. The obvious question is how did the other types accumulate? It is estimated that the water ice deposits move between the poles in cycles of 51,000 years depending on the length of the tilt of the Martian axis. Water in the North Pole in an unstable state was easily transported to the South Pole in the form of water vapor, condensed (condensed) again and froze on the ground. The rate of land subsidence at the South Pole was 1 mm per year. After Mars was for 10,000 years in this climatic event, this accumulation of water ice formed a layer 6 meters thick. At that time, the leap year changed and returned to the format known today. The water ice at the South Pole became unstable and began to sink back. in the north pole At that time, the erosion of the water ice deposits in the South Pole was stopped by ice layers of CO2 that were deposited there and trapped the water ice within them (38).

minerals

Mars Express observations up to the end of 2005 discovered minerals that require the massive presence of liquid water. In the observations that lasted for 18 months, two groups of minerals were discovered, phyllosilicate hydrous minerals and hydrous sulfates. Both types of minerals are a product of chemical exchange with the rocks, although these are different processes for each group of minerals, they point to periods of different environmental conditions in the history of Mars. The phyllosilicates are a product of basic rocks (minerals of trend origin) that have long-term contact with water. A familiar example of a silicate mineral is clay. The minerals were discovered in Arabia Terra, Syritis Major, Terra Meridiani, Nili Fossae and Maurth Valis. Sulfate minerals are a product of salt deposition. The formation of sulfate minerals is a product of salt deposition. The formation of most sulfate minerals requires the presence of acidic water. They have been identified in the geological layers in Valles Marineris, Terra Meridiani and within dark dunes in the Arctic Dome. The fundamental questions are when did the chemical alteration of the soil occur that led to the formation of hydric minerals and at what point in the history of Mars was there large amounts of liquid water?

Combining all the findings led to the development of the following model: the clay-rich phyllosilicates were formed in the very early history of Mars. The replaced material was probably buried by lava flows. This material was then exposed by erosive processes in certain places or was exposed following a meteorite impact. All this happened at the right time. The long-term contact with liquid water that resulted in the formation of the phyllosilicates must have been stable, only if the area was warm enough. Another possibility is that the phyllosilicates were formed by the contact of the water with a thin, hot crust. The philolitic deposits were formed afterwards (39,40) .

A crater where sulfates and iron oxides were discovered is Aran Chaos, which is connected to Ares Valles through a channel 15 km long and 2.5 km deep (41). Mars Express and the American spacecraft MRO (Mars Reconnaissance Orbiter) discovered silicate hydrates in the northern low regions of Mars, conclusive evidence that water once flowed there. The phyllosilites or other hydrous silicates have been discovered in the northern hemisphere in at least 9 large craters. These minerals are the same as those found in the southern hemisphere. The massive presence of water is estimated to have been 4 billion years ago. The liquid aqueous presence lasted only tens to hundreds of millions of years (42).

Sources

1. Tenenbaum D. - "Is it time for a new Martian chronology" 17.10.2006
http://www.marsdaily.com/reports/ Is_ It _Time_ For _A_ New_ Martian _Chronology
_999.html

2. "Questioning Martian Life" 22.11.2007
http://www.marsdaily.com/reports/ Questioning _ Martian_ Life_999.html

3. "Wading Martian water" 3.5. 2005
http://www.spacedaily.com/news/mars-water-science-05jhtml

4. O'lanlon L. - "Martian air blown away by solar super wave" 16.3.2010
http://news.discovery.com/space/mars-solar-wind-atmosphere.html

5. "Mars Express creates first global map of Martian ionosphere" 19.112007
http://www.marsdaily.com/reports/ Mars- Express _Creates_ First_ Global _Map_Of _Martian_ ionosphere_999.html

6. "Mars Express observes aurora on the red planet" 21.11.2008
http://www.esa.int/SPECIALS/Mars_Express/SEMY1B5DHNE_0.html

7. "Martian fire and ice" 23.3.2005
http://www.spacedaily.com/news/marsexpress-05ihtml

8. Rincon P. - "Ice belt encircled Mars equator" 9.9.2005
http://news.bbc.es. uk/1/hi/sci/tech/4226236.stm

9. "Martian snow source of tropical glaciers research team reports" 20.1.2006
http://www.spacedaily/reports/ Martian _Snow_ Source_ Of_Tropical_ Glaciers _ Research_ Team_ Rreports.html

10. "Ice clouds put Mars in the shade" 17.1.2008
http://www.marsdaily.con/reports/ Ice_ Clouds_ Put _Mars_In _The_ Shade_999.html

11. "Northern rim of Hellas Basin" 29.7.2007
http://www.spacedaily.com/news/news-mars-04zzzzj.html

12. Cain N.-"Nicholson crater on Mars" 15.7.2005
http://universetoday.com/10701/ nicholson- crater- on- mars/

13. Hummocky and shallow Mounder Crater" 17.10.2007
http://www.marsdaily.con/reports/ Hummocky_ And_ Shallow _Mounder _Crater_999.html

14. "Volcanic ash in Meridiani Alanum" 12.5.2010
http://www.esa.int/SPECIALS/Mars-Express/SEMO5A/ay86_2.html

15. "Wind and water have shaped Schiaparelli on Mars" 13.12. 2010
http://www.marsdaily.com/reports/ Wind _And_ Water_ Have_ Shaped _Schiaparelli_ On_ Mars_999.html

16. "The scars of impacts on Mars" 4.3.2011
http://www.esa.int/SPECIALS/Mars-Express/SEMTK5VTLKG_2.html

17. "Mars Express scientist find a different Mars underneath" 13.12.2006
http://www.esa.int/SPECIALS/Mars-Express/SEMQ4NPJNVE_2.html

18. Mckee M. - "Big new reservoir of water ice suspected under Mars" 16.3.2006
http://newscientistspace.com/article/dn8857- big- new- reservoir- of –water- ice- suspected-under- mars.html

19. "MARSIS radar estimates the volume of water in the south pole of mars" 5.4.2007
http://www.marsdaily.com/reports/ MARSIS_ Radar_ Estimates_ The_ Volume_ Of_ Water_ In_ The_ South_ Pole _Of_ Mars_999.html

20. "Mars's mysteries elongated crater" 27.10.2010
http://www.esa.int/SPECIALS/Mars-Express/SEMDV9B0310G_3.html

21. "Light and dark in the Phoenix lake" 15.11.2010
http://www.marsdaily.com/reports/ Light_ And _Dark_ In _The_ Phoenix_ lake_999.html

22. "Image reveals Mars' active past" 10.5.2004
http://news/bbc/co.uk/2/hi/science/nature/3700111.stm

23. "Mars Express sees deep fractures on Mars" 9.5.2011
http://www.marsdaily.com/reports/ Mars_ Express_ Sees_ Deep_ Fractures _On _Mars_999.html

24. Rincon P. – “Martian volcanoes may be active” 7.9.2005
http://newa.bbc.co.uk/1/hi/scientists/4219858.stm

25. "Ausonia Mensa remnant massif by Mars Express" 27.2.2006
http://www.marsdaily.com/reports/ Ausonia_ Mensa _Remmanent _ Massif_ By_ Mars _Express_999.html

26. "Mars Express probes planet's unusual deposits'" 1.11.2007
http://mars.jpl.nasa.gov/express/newsroom/pressreleases/200711.01a.html

27. "Ice-covered martian north pole" 6.3. 2009
http://www.esa.int/SPECIALS/Mars-Express/SEMMQQCDNRF_2.html

28. Bryner J.- "Wind and snow do strange things on Mars" 29.9.2008
http://www.space.com/scienceastronomy/080929-mm-mars-ice.html

29. "Decoding the Cryptic region of Mars" 20.10.2006
http://www.marsdaily.com/reports/ Decoding_ The _Cryptic_ Region_ Of_ Mars_999.html

30. "Mars Express images huge ancient valley" 28.5.2008
http://www.marsdaily.com/reports/ Mars_ Express_ Images_ Huge_ Ancient _Valley_999.html

31. "The ancient rains of Mars" 29.9.2008
http://www.marsdaily.com/reports/ The _Ancient _Rains _Of _Mars_999.html

32. "Frozen lake found on mars, May have preserved primitive life: scientist" 16.3.2005

http://www.spacedaily.com/news/mars-life.05e.html

33. "Warming up to a Martian carcass" 23.2.2005
http://www.spacedaily.com/news/mars-atmosphere-05bhtml

34. "Water ice in crater at Martian north pole" 29.7.2005
http://www.spacedaily.com/news/marsexpress-05y.html

35. Johnson O.- "Martian dunes hide water secret" 5.9.2005
http://news.bbc.co.uk/1/hi/sci/tech/4217528.stm

36. Images
http://www.cyberspaceorbit.com/Marinarsfogs.jpg

37. Zurbin R. - "Evidence for large water resources found near Mars equator" 24.2.2005
http://www.marsdaily.com/news/mars-water-science-05c.html

38. "The origin of perennial water ice at the south pole of Mars" 16.62007
http://www.marsdaily.com/reports/ The _Origin _Of _Perennial _Water_ Ice_ At _The_ South _Pole_ Of_ Mars_999.html

39. "Spacecraft finds evidence for large aquifers on early Mars" 1.12.2005
http://www.spacedaily.com/news/n0512/01marsexpress/

40. "Five years of Mars Express" 3.6.2008
http://www.marsdaily.com/reports/Five_ Years_ Of_ Mars_ Express_999.html

41. "Ferric oxides and sulfates in equatorial regions of Mars" 22.12.2008
http://www.marsdaily.com/reports/ Ferric _Oxides_And _Sulfates_ In_ Equatorial_ Regions _Of _Mars_999.html

42. "Wet era on early Mars was global" 28.6.2010
http://www.marsdaily.com/reports/ Wet_ Era_ On_ Early_ Mars_ Was_ Global_999.html