Mars (planet)

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Mars  Astronomical symbol of Mars
Mars in natural colors, the data for the computer-generated image were recorded in April 1999 with the Mars Global Surveyor
Mars in natural colors, the data for the computer-generated image were recorded with the Mars Global Surveyor in 1999
Properties of the orbit
Major semi-axis 1.524  AU
(227.99 million km)
Perihelion - aphelion 1.381-1.666 AU
eccentricity 0.0934
Inclination of the plane of the orbit 1.8506 °
Sidereal period of rotation 686,980 d
Synodic period 779.94 d
Mean orbital velocity 24.07 km / s
Smallest - largest distance to earth 0.372-2.682 AU
Physical Properties
Equatorial diameter * 6,792.4 km
Pole diameter * 6,752.4 km
Dimensions ≈0.107 earth masses
6.417 · 10 23  kg
Medium density 3.933 g / cm 3
Gravitational acceleration * 3.69 m / s 2
Escape speed 5.03 km / s
Rotation period 24 h 37 min 22 s
Inclination of the axis of rotation 25.19 °
Geometric albedo 0.170
Max. Apparent brightness −2.94 m
Properties of the atmosphere
Pressure * 6 · 10 −3  bar
Temperature *
min. - average - max.
120 K  (-153  ° C )
210 K (-63 ° C)
293 K (+20 ° C)
Main ingredients
* based on the zero level of the planet
Moons Phobos , Deimos
Mars Earth Comparison 2.jpg
Size comparison between Earth (left) and Mars

The Mars is from the Sun counted out, the fourth planet in the solar system and the outer neighbor of the earth . It is one of the earth-like (terrestrial) planets .

At almost 6,800 kilometers, its diameter is about half that of the earth, and its volume is a good seventh of the earth's volume. This makes Mars the second smallest planet in the solar system after Mercury , but has a diverse geology and the highest volcanoes in the solar system. With an average distance of 228 million kilometers, it is around 1.5 times as far from the sun as the earth.

The mass of Mars is about a tenth that of the earth. The acceleration due to gravity on its surface is 3.69 m / s², which corresponds to about 38% of the earth's. With a density of 3.9 g / cm³, Mars has the lowest value of the terrestrial planets. Therefore, the gravity on it is even slightly lower than on the smaller, but denser Mercury.

Mars is also known as the Red Planet . This coloration is on iron oxide -Staub ( rust back) located on the surface and in the thin CO 2 - atmosphere has distributed. Its orange to blood red color and its fluctuations in brightness in the earthly night sky are also the reason for its name after the Roman god of war Mars .

The two polar caps and several dark plains that change color in spring are clearly visible in larger telescopes . Photos from space probes show a surface partially covered with craters and strong traces of earlier tectonics (deep canyons and a volcano over 20 km high ). Mars robots have already geologically examined several areas.

Mars has two small, irregularly shaped moons that were discovered in 1877: Phobos and Deimos (Greek for fear and terror ).

The astronomical symbol of Mars is .

Orbit and rotation


Mars moves at a distance of 206.62 to 249.23 million kilometers (1.38  AU to 1.67 AU) in just under 687 days (about 1.9 years ) in an elliptical orbit around the sun. The plane of the orbit is 1.85 ° inclined to the plane of the earth's orbit .

Its orbital speed fluctuates with the distance from the sun between 26.50 km / s and 21.97 km / s and averages 24.13 km / s. The orbital eccentricity is 0.0935. After the orbit of Mercury , this is the second largest deviation from the circular shape of all planetary orbits in the solar system.

In the past, Mars had a less eccentric orbit. 1.35 million years ago the eccentricity was only about 0.002, less than that of the earth today. The period of eccentricity of Mars is about 96,000 years, that of the earth about 100,000 years. However, Mars still has a longer cycle of eccentricity with a period of 2.2 million years superimposed on that with the period of 96,000 years. Over the past 35,000 years, the orbit has become slightly more eccentric due to the gravitational forces of the other planets. The minimum distance between Earth and Mars will get a little smaller over the next 25,000 years.

There are five numbered asteroids that share the same orbit with Mars ( Mars Trojans ). You are on the Lagrangian points L 4 and L 5 , that is, they hurry ahead of the planet by 60 ° or follow it by 60 °.


Rotation animation

Mars rotates around its own axis in 24 hours and 37.4 minutes ( sidereal day ). In relation to the sun, this results in a Martian day (also called a sol) of 24 hours, 39 minutes and 35 seconds. The equatorial plane of the planet is inclined by 25.19 ° to its orbit (that of the earth 23.44 °), so there are seasons similar to those on earth. However, these last almost twice as long, since the sidereal Martian year has 687 earth days. Since the orbit of Mars has a significantly greater eccentricity than that of Earth and Mars north tends to point in the direction of the major orbit ellipse axis, the seasons are of different lengths. Over the past 300,000 years the axis of rotation has varied between 22 ° and 26 °. Before that it was several times above 40 °, which resulted in strong climatic changes , there was also icing in the equatorial region and this explains the strong soil erosion .

The north pole of Mars points to the northern part of the constellation Swan , with which the direction differs by about 40 ° from that of the earth's axis. The Martian pole star is Deneb (with a slight deviation of the axis towards Alpha Cephei ).

The axis of rotation performs a precession movement , the period of which is 170,000 years (7 times slower than the earth). From this value, which was determined with the help of the Pathfinder mission, the scientists can infer the mass concentration inside the planet.

Atmosphere and climate

Above the Mars horizon, the atmosphere can be seen as a hazy veil. The Galle crater, which resembles a smiley face, can be seen on the left. ( Viking , 1976)

Mars has a very thin atmosphere. As a result, the atmospheric pressure is very low and water cannot exist in liquid form on the surface of Mars, except for a short time in the deepest areas.

Since the thin Martian atmosphere can only store little solar heat, the temperature differences on the surface are very large. The temperatures reached in Equator near about 20 ° C during the day and drop to -85 ° C at night. The mean temperature of the planet is around −63 ° C.

the atmosphere

The Martian atmosphere consists of 95.97% carbon dioxide . In addition there are 1.89% nitrogen , 1.93% argon , small amounts of oxygen (0.146%) and carbon monoxide (0.0557%) as well as traces of water vapor , methane , sulfur dioxide , ozone and other compounds of carbon, hydrogen and oxygen , Nitrogen, chlorine and sulfur.

The atmosphere is pretty dusty. It contains particles about 1.5  µm in diameter that make the sky over Mars appear in a pale yellow to orange-brown hue.

The average atmospheric pressure on the surface of Mars is only 6.36  hPa (hectopascal). Compared to an average of 1013 hPa on earth, this is only 0.63%, which corresponds to the air pressure of the earth's atmosphere at an altitude of 35 kilometers. The atmosphere was likely carried away by the solar wind over time and carried away into space. This was facilitated by the planet's low gravity and its weak magnetic field , which offers little protection from the high-energy particles of the sun.

Ice clouds over Mars ( Mars Pathfinder , Oct 1997)

Climate and Weather

Dynamic processes take place in the atmosphere, depending on the seasons and the intensity of solar radiation. The icy polar caps partially sublimate in summer, and condensed water vapor forms extensive cirrus clouds . The polar caps themselves are made of solid carbon dioxide and ice.

In 2008, the Mars Express spacecraft discovered clouds of frozen carbon dioxide. They are located at a height of up to 80 kilometers and have a horizontal extension of up to 100 km. They absorb up to 40% of the incoming sunlight and can thus reduce the temperature of the surface by up to 10 ° C.

With the help of the LIDAR laser from the Phoenix space probe , it was discovered in 2009 that in the second half of the night, fifty days after the solstice, tiny ice crystals fell from thin cirrus clouds onto the Martian floor.

Dust storm in the Syria region ( Mars Global Surveyor , May 2003)
Mars before and after / during the global dust storm in 2018


If Mars had an Earth-like orbit, the seasons would be similar to those of Earth due to the inclination of the axis. However, the comparatively large eccentricity of its orbit has a considerable effect on the seasons. Mars is located near the perihelion of its orbit during summer in the southern hemisphere and winter in the northern hemisphere . Near aphelion it is winter in the southern hemisphere and summer in the northern hemisphere.

As a result, the seasons in the southern hemisphere are much more pronounced than in the northern hemisphere, where the climate is more balanced than it would otherwise be the case. Summer temperatures in the south can be up to 30 ° C higher than comparable summer temperatures in the north. The seasons vary in length due to the eccentricity of the orbit of Mars. In the northern hemisphere spring 199.6, summer 181.7, autumn 145.6 and winter 160.1 earth days.

Wind and storms

Due to the strong day-night temperature fluctuations of the surface, there are daily morning and evening winds.

During the Martian spring, violent dust storms can occur in the vast plains , sometimes covering large parts of the Martian surface. The images of Mars probes also show whirlwinds that draw on the Martian plains and left on the ground dark tracks. Due to the very thin atmosphere, storms on Mars are much less powerful than storms on Earth. Even at high wind speeds, only small particles ( dust ) are blown. However, blown dust remains in the atmosphere much longer on Mars than on Earth, as there is no precipitation that cleans the air and gravity is lower.

Dust storms usually occur during the perihelion, as the planet receives 40 percent more sunlight at that time than during the aphelion. During the aphelion, clouds of water ice form in the atmosphere, which in turn interact with the dust particles and thus influence the temperature on the planet. The wind speeds in the upper atmosphere can reach up to 650 km / h, on the ground it can reach almost 400 km / h.


Heavy dust storms also seem to cause thunderstorms. In June 2006, researchers examined Mars with a radio telescope and found outbreaks of radiation in the microwave range, such as those that occur with lightning. In the region in which the radiation pulses were observed, there was a violent dust storm with high dust clouds at the time. Both the observed dust storm and the spectrum of radiation pulses indicate a dust storm with lightning or large discharges.


Typical boulders on the surface of Mars (Mars Pathfinder, 1997)

The surface of Mars is about a quarter of the earth's surface. With 144 million km² it corresponds to almost the total area of ​​all continents on earth (149 million km²) and is less than the total area of ​​the Pacific Ocean (166.24 million km²).

The planet owes the red color of its surface to the iron oxide dust that has spread over the surface and in the atmosphere. Thus the red planet is a "rusty planet".

Its two hemispheres are very different. The southern hemisphere represents a huge highland that is on average 2–3 km above the global zero level and has extensive shield volcanoes . The many impact craters prove its age of almost 4 billion years. This contrasts with the geologically young, almost craterless northern lowlands . It is 3–5 km below zero level and has lost its original structure due to geological processes that have not yet been clarified. It was possibly triggered by a massive collision in the early days of the planet.


Boulders , sandy soils and dunes are visible at the landing sites of the Mars probes . The Martian rocks have a bubble-like structure on the surface and are similar in their composition to terrestrial basalts , which was discovered decades ago from the Martian meteorites found on Earth (Antarctica) . The red soils are evidently the result of the weathering of ferrous, volcanic basalts.

In 1997, the Pathfinder probe found, in addition to a wide variety of basalts, also deep quartz rocks similar to the South American andesite , as well as olivine from the depths and round pebbles from conglomerates . Metamorphic regolith (similar to that on the moon ) and aeolian sediments , and occasionally blown sand made of sulfur-containing dust particles, are widespread .


The cartographic representation and description of the surface of Mars is the areography , from Ares (Άρης, Greek for Mars ) and graphein (γράφειν, Greek for describe ). Accordingly, the “ geology ” of Mars is sometimes referred to as the areology .

Areographic coordinates , which are defined as geographic longitude and latitude as on Earth , are used to determine positions on the surface of Mars .

Topographic map of Mars. The blue regions are below the specified zero level , the red regions above.
General map of Mars with the largest regions

Topographic hemispheres

The dichotomy , the “ dichotomy ”, of Mars is striking . The northern and southern hemisphere clearly differ, whereby one can speak of the low plains of the north and the highlands of the south. The central great circle that separates the topographical hemispheres is inclined around 40 ° to the equator. The center of mass of Mars is offset from the geometric center by about three kilometers in the direction of the northern lowlands.

In the northern hemisphere, sand and dust-covered plains are predominant, which have been given names such as Utopia Planitia or Amazonis Planitia . Dark surface features visible in telescopes were once mistaken for seas and given names like Mare Erythraeum , Mare Sirenum, or Aurorae Sinus . These names are no longer used today. The most extensive dark structure that can be seen from Earth is Syrtis Major , the "great Syrte".

The southern hemisphere is on average six kilometers higher than the northern hemisphere and consists of geologically older formations. The southern hemisphere is also more cratered, for example in the highland region of Arabia Terra . Among the numerous impact craters in the southern hemisphere is the largest Martian crater , Hellas Planitia , the Hellas lowland. The basin measures up to 2100 km in diameter. Inside, Mars Global Surveyor measured 8,180  m below  zero - below the average level of Mars - the lowest point on the planet. The second largest impact crater on Mars, Chryse Planitia , is located on the edge of the northern lowlands.

The clear differences in topography can be caused by internal processes or an impact event . In the latter case, a larger celestial body, such as an asteroid , could have struck the northern hemisphere in the early days of the formation of Mars and penetrated the silicate crust. Lava could have leaked from inside and filled the impact basin.

As has been shown, the Martian crust under the northern lowlands is about 40 km thick, which, in contrast to the step-like transition on the surface, increases only slowly to 70 km up to the South Pole. This could be an indication of internal causes of the dichotomy.

Surface structures

In the center of the picture is the system of the Mariner valleys . Far left the Tharsis volcanoes (picture mosaic from Viking 1 Orbiter, 1980)


To the south of the equator and almost parallel to it run the Valles Marineris (the Mariner valleys), the largest known rift system in the solar system. It extends over 4000 km and is up to 700 km wide and up to 7 km deep. It is a huge tectonic break . In its western part, the Noctis Labyrinthus , it branches into a chaotic-looking tangle of numerous gorges and valleys that are up to 20 km wide and up to 5 km deep.

Noctis Labyrinthus lies on the eastern flank of the Tharsis Ridge , a huge bulge of the Martian lithosphere across the equator with an extension of about 4,000 by 3,000 kilometers and a height of up to about 10 kilometers above the northern lowlands. The bulge is occupied by three very high, extinct shield volcanoes along what appears to be a central fault line : Ascraeus Mons , Pavonis Mons and Arsia Mons . The Tharsis Ridge and the Mariner Valleys are likely to have a causal connection. Volcanic forces probably pushed the surface of the planet up in this region, tearing open the crust in the area of ​​the rift system. One assumption is that this volcanic activity was triggered by an impact event, the impact point of which was the Hellas Basin on the opposite side of Mars. In 2007, seven deeper shafts with a diameter of 100 to 250 meters were discovered in the northeast of Arsia Mons.

Olympus Mons , the highest mountain in the solar system at 26 km
The complex caldera of Olympus Mons


Exactly opposite the Hellas Basin is the volcanic giant Alba Patera . It rises about 6 km over the surrounding lowlands directly on the northern edge of the Tharsis Ridge and, with a base diameter of over 1200 km, is the largest volcano in the solar system. Patera is the name for irregularly delimited volcanoes with flat relief. Alba Patera apparently collapsed once.

Immediately to the west of the Tharsis Ridge and southwest of Alba Patera, the highest volcano, Olympus Mons , rises 26.4 km over the area surrounding the northern lowlands. With a summit height of about 21.3 km above mean zero level, it is the highest known elevation in the solar system.

Another, albeit less extensive, volcanic area is the Elysium region north of the equator with the shield volcanoes Elysium Mons , Hecates Tholus, and Albor Tholus .

Volcanic activity could have occurred 210,000 years ago to just 53,000 years ago.

River valleys

Kasei Vallis , the largest river valley on Mars

River valleys that can be several hundred kilometers long and several kilometers wide run on the surface of Mars. Today's dry valleys begin quite abruptly and have no tributaries. Most of them arise at the ends of the Mariner valleys and converge north in the Chryse Basin . Streamlined islands sometimes rise up in the valleys. They point to a past flood period during which large amounts of water must have flowed over a relatively short geological period. It could have been water ice that was below the surface of Mars, after which it was melted by volcanic processes and then flowed off.

In addition, there are traces of erosion on slopes and crater edges , which may also have been caused by running water.

In 2006, NASA proclaimed a unique find : on some NASA photographs taken seven years apart from Mars, changes on the surface of Mars can be seen that are somewhat similar to changes caused by flowing water. NASA is now discussing whether there could be "liquid" water in addition to water ice.

Delta structures

In ancient Martian landscapes, e.g. Typical deposits of former river deltas can be found, for example, in the Eberswalde crater in the southern hemisphere or in the Xanthe Terra plateau near the equator .

Tharsis-tholus strip captured with the Hirise camera of the Mars Reconnaissance Orbiter . The stripe can be seen in the center left. On the right are the foothills of Tharsis Tholus .

It has long been assumed that the deeply cut valleys in Xanthe Terra were once formed by rivers. When such a river flowed into a larger basin, for example a crater, it deposited eroded rock material as sediments. The type of deposit depends on the nature of this basin: If it is filled with the water of a lake, a delta is formed. However, if the basin is dry, the river will lose speed and slowly seep away. A so-called alluvial cone forms , which is clearly different from the delta.

Recent analyzes of sediment bodies based on orbiter photos indicate deltas in numerous places in Xanthe Terra - rivers and lakes were therefore quite common in the early Martian period.

Dark Slope Streaks

Dark streaks on slopes are common on Mars. They appear on steep slopes of craters, hollows, and valleys and get lighter with age. Sometimes they start in a small point-like area and then get progressively wider. They were observed to move around obstacles such as hollows.

The color is believed to come from dark underlying layers exposed by avalanches of light dust. However, other hypotheses have also been made, such as water or even the growth of organisms. The most interesting thing about these dark slope streaks is that they are still forming today.

Chaotic areas

There are numerous regions on Mars with an accumulation of rocks of different sizes and table mountain-like elevations. They are also called “chaotic areas”. Ariadnes Colles is such an area with an area of ​​about 29,000 km². It is located in the Terra Sirenum , a southern highlands of Mars. The blocks have dimensions of one to ten kilometers. The larger blocks resemble table mountains with elevations of up to 300 meters.

There occur here cried like structures and "Runzelrücken" (English. Wrinkle ridges ) on. The reasons for this are volcanic-tectonic movements.

Rock layers and deposits

Salt store

With the help of the Mars Odyssey probe , NASA found extensive salt deposits in the plateaus of the southern hemisphere of Mars. These deposits were probably formed by surface water around 3.5 to 3.9 billion years ago.

Carbonate deposits

With the help of the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on board NASA's Mars Reconnaissance Orbiter, scientists were able to detect carbonate compounds in rock layers around the almost 1,500-kilometer Isidis impact basin . According to this, the water that existed here more than 3.6 billion years ago would not have been acidic, but rather alkaline or neutral.

Carbonate rock is formed when water and carbon dioxide react with calcium , iron or magnesium in volcanic rock. During this process, carbon dioxide from the atmosphere is stored in the rock. This could mean that Mars used to have a dense carbon dioxide-rich atmosphere, which made a warmer climate possible, in which there was also water in a liquid state.

With the help of data from the MRO, rocks were discovered in 2010 that had been carried to the surface by cosmic impacts from the depths. Based on their specific spectroscopic fingerprints, it could be determined that they were changed hydrothermally (under the action of water). In addition to these carbonate minerals, silicates have also been detected, which are believed to have been formed in the same way. This new find proves that these are not localized occurrences, but that carbonates formed in a very large region of early Mars.

Hematite spheres on the rock "Berry Bowl"

Hematite globules

The Mars probe Opportunity found millimeter-sized spheres of the iron mineral hematite in the area of ​​the Meridiani Planum . These could have deposited billions of years ago under the action of water. In addition, minerals were found that are composed of sulfur , iron or bromine compounds , such as jarosite . On the opposite hemisphere of Mars, the Spirit probe found the mineral goethite in the "Columbia Hills" , which can only be formed under the influence of water.


In 2010, researchers used MRO to discover deposits on a volcanic cone caused by water. They were able to identify the mineral as silicic acid hydrate, which can only have formed in connection with water. The scientists believe that if there was life on Mars, it could have lasted the longest there in the hydrothermal environment.

Polar caps

The North Pole Region (Mars Global Surveyor, 1999)

Mars has two conspicuous polar caps, which are mainly composed of frozen carbon dioxide ( dry ice ) and a small amount of water ice. The northern polar cap has a diameter of around 1000 kilometers during the northern Martian summer. Their thickness is estimated at 5 km. With a diameter of 350 km and a thickness of 1½ km, the southern polar cap is less extensive. The polar caps show spiral incisions, the origin of which has not yet been clarified.

When the respective polar ice caps partially melt in summer, layered deposits become visible underneath, which may be composed of alternating dust and ice. In the Martian winter, the diameter of the polar cap, which is then turned away from the sun, increases again due to freezing out carbon dioxide.

In the absence of a larger, stabilizing moon, Mars wobbles with a period of about 5 million years. The polar regions are therefore repeatedly heated so much that the water ice melts. The straps and strips on the polar ice caps are created by the water running off.

Water resources

What Mars might have looked like billions of years ago

Mars appears today as a dry desert planet. However, the results of the Mars missions available so far allow the conclusion that the Martian atmosphere was much denser in the past (billions of years ago) and that there was abundant liquid water on the surface of the planet.

The South Pole Region ( Viking Orbiter, Dec 2008)

Ice deposits at the poles

Radar measurements with the Mars Express probe revealed layers of deposits with embedded water ice in the southern polar region, the Planum Australe , which are far larger and deeper than the southern polar cap, which consists mainly of carbon dioxide ice. The water ice layers cover an area almost the size of Europe and reach a depth of up to 3.7 kilometers. The volume of water stored in them is estimated to be up to 1.6 million cubic kilometers - around two thirds of the Earth's Greenland ice cream - which, according to the European Space Agency (ESA), would be enough to cover the surface of Mars with a layer of water around 11 meters thick.

More ice deposits

Observed changes could be signs of running water within the last few years.

The long-held assumption that there might be water ice beneath the surface of Mars was proven correct in 2005 by discoveries made by ESA's Mars Express probe .

Geologists assume recurring periods of ice on Mars, similar to terrestrial ice ages. In the process, glaciers are said to have advanced into subtropical latitudes. The researchers conclude this from orbiter photos that show traces of former glaciers in these equatorial areas. In addition, radar measurements from orbit also support the existence of considerable amounts of ground ice in these same areas. These ground ice deposits are interpreted as remnants of such “Mars ice ages”.

On the European Planetologenkonferenz EPSC in September 2008 in Muenster high resolution images of were Mars Reconnaissance Orbiter of NASA presented, showing the recent impact craters. Because of the very thin atmosphere, the meteorites crash onto the surface of Mars with practically no glowing up. The five new craters, which are only three to six meters in diameter and 30 to 60 cm deep, were found in mid- northern latitudes . They show a glistening white material on their bottom. A few months later the white spots had disappeared due to sublimation. This corroborates the evidence that water ice is buried close to the Martian surface even far outside the polar regions.

Liquid water

Large amounts of liquid water are believed to be beneath the Martian cryosphere . Close to or on the surface it is too cold for liquid water, and ice would slowly evaporate because the partial pressure of water in the Martian atmosphere is too low.

However, there is evidence that the Phoenix spacecraft detected water droplets on the surface. Perchlorates could act as frost protection. These salts have the property of attracting water. This can also be water vapor from the atmosphere. With a sufficient concentration of the salts, water could even remain liquid down to −70 ° C. By mixing with perchlorates, water could also be present under the surface in a liquid state. In 2010, researchers at the University of Münster found evidence that at least in spring and in craters such as the Russell crater, liquid water exists on the surface of Mars. In photos taken by the Mars Reconnaissance Orbiter, they discovered erosion channels on steep slopes that had lengthened between November 2006 and May 2009. The researchers interpret the fact that the gutters are getting thinner downwards as seepage, others as evaporation.

Scientists at NASA proposed an alternative explanation for the erosion channels in 2010: carbon dioxide , which in the Martian winter collects from the atmosphere on the mountain slopes as dry ice at temperatures below −100 ° C , "flows" down the slopes as a sublimated gas when the planet warms dust eroded in the process.

With the imaging spectrometer (CRISM) of the Mars Reconnaissance Orbiter spectra were active (seasonal darker) channels are obtained, published their analysis, in 2015, magnesium perchlorate , magnesium perchlorate and sodium perchlorate revealed.

In July 2018, researchers from the National Institute for Astrophysics in Bologna announced that they had found evidence of a 20 km wide and 1.5 km deep lake under the ice of the southern Martian pole using radar technology. They suspect that the water in this subglacial lake remains liquid despite a temperature of about −75 ° C due to dissolved perchlorates .

Disappearance of the water

Scientists reported in 2020 that the current loss of atomic hydrogen from water on Mars is largely driven by seasonal warming and dust storms that transport water directly into the upper atmosphere. This has played a significant role in the planet's climate and water loss over the past 1 billion years.

internal structure

Illustration of the presumed structure of Mars

Little is known about the internal structure of Mars, as so far only limited seismic measurements have been made.

Mars has a shell structure similar to that of the earth. It is divided into a crust, a rock mantle and a core.

The core consists mainly of iron . However, it contains around twice as many light elements as the earth's core, including around 14 to 17 percent sulfur . It has a correspondingly lower density . Measurements by the Mars Global Surveyor showed a core temperature of 1500 degrees Celsius and a pressure of 23 gigapascals. Simulations showed that the core of Mars, unlike the Earth's core, presumably does not have an internal solid area, but is completely liquid. This is also proven by the analysis of the orbital data of the Mars Global Surveyor. It could be proven that Mars has a liquid core with a radius between 1520 and 1840 km and thus has a higher temperature than previously assumed.

The core is surrounded by a mantle of silicates that shaped many of the tectonic and volcanic features of the planet but now appears to be inactive. The average thickness of the planet's crust is about 50 km, with a maximum of 125 km. In comparison, the earth's crust, with an average thickness of 40 km, is only about a third as thick if one takes into account the relative size of the two planets.

Magnetic field

Magnetization of Mars: red and blue indicate opposite directions of the magnetic field, a third of the southern hemisphere

Unlike Earth and Mercury , Mars no longer has a global magnetic field since it lost it around 500 million years after its formation. It probably went out when the decay of radioactive elements no longer produced enough thermal energy to drive convection currents in the liquid core. Because Mars does not have a solid inner core, it could not create the dynamo effect in the same way as Earth.

Nevertheless, measurements showed individual and very weak local magnetic fields. The measurement of the magnetic field is made more difficult by the magnetization of the crust with field strengths of up to 220 nanotesla and by external magnetic fields with strengths between a few nanotesla and up to 100 nanotesla, which arise from the interaction of the solar wind with the Martian atmosphere and which vary greatly over time. After analyzing the data from the Mars Global Surveyor, the strength of the magnetic field could still be determined very precisely - it is less than 0.5 nanotesla compared to 30 to 60 microtesla of the earth's magnetic field . Modeling of the magnetic field by means of spherical surface functions made it possible to calculate the remanent crustal field e.g. B. on the surface of the planet. It was found that the vector components of the crustal magnetization, especially in the southern hemisphere of the planet, had values ​​of almost 12 microtesla. This is about sixty times the Earth's maximum crustal magnetization.

Measurements of magnetic field lines by Mars Global Surveyor showed that parts of the planetary crust are strongly magnetized by the former magnetic field, but with different orientations, with rectified bands around 1000 km long and 150 km wide. Their size and distribution are reminiscent of the striped magnetic anomalies on the Earth's ocean floors. They supported the theory of plate tectonics , which is why a similar theory was developed for Mars. In contrast to the Earth, this theory is not supported by observable movements of the crust or by topographical markers for plate tectonics ( mid-ocean ridges , transform faults , etc.).

Another special feature of the Field of Mars is the fact that it correlates almost perfectly with the Mars dichotomy. The northern hemisphere is largely unmagnetized, while strong crustal magnetizations can be found in the southern hemisphere.

It is possible that the inevitable cooling of the Martian core over time due to the crystallization of the iron and the released heat of crystallization will set in again convections that are sufficient for the planet to have a global magnetic field at its old strength again in a few billion years. It is likely that the potential field in the far-field approximation corresponds to a dipole field similar to that of Earth.

It is also believed that Mars' original magnetic field corresponded to a dipole field. On the basis of this assumption, magnetic pole reconstructions were carried out, which came to the conclusion that Mars underwent at least one pole reversal in its past.


Phobos and Deimos orbits
Phobos (above) and Deimos (below) in size comparison

Two small moons, Phobos and Deimos (Greek for fear and terror), orbit Mars. They were discovered in 1877 by the American astronomer Asaph Hall and named after the two companions handed down in the Iliad who pull the chariot of the god of war Ares (Latin: Mars).

Phobos (diameter 26.8 km × 22.4 km × 18.4 km) and Deimos (diameter 15.0 km × 12.2 km × 10.4 km) are two irregularly shaped boulders. They may be asteroids captured by Mars. Phobos' major semi-axis is 9376 km, that of Deimos 23459 km. Phobos is hardly more than 6000 km away from the surface of Mars, the distance is less than the diameter of the planet.

The periodic orbital motions of the two moons are 0.31891 (Phobos) and 1.262 days (Deimos) in a 1: 4 orbital resonance to each other .

The orbital time of Phobos is shorter than the rotation time of Mars. The moon slowly comes closer and closer to the planet through the tidal interaction on a spiral path and will eventually crash on it or be torn apart by the tidal forces, so that it becomes a ring of Mars for a short time . DLR researchers calculated for him , based on more recent data from the European space probe Mars Express , that this will happen in around 50 million years. Deimos, on the other hand, will escape Mars in an even more distant future. Due to the interaction of the tides, it drifts slowly outwards, like all moons that orbit more slowly (and not retrograde ) around a planet than it rotates.

Their existence had long been described in literary terms several times, most recently by Voltaire , who wrote about two Martian moons in his story Micromégas , published in 1750 . It is likely that Voltaire adopted this idea from Jonathan Swift , whose book Gulliver's Travels was published in 1726. It is described in the third part that the astronomers of the land of Laputa had "also discovered two smaller stars or satellites orbiting Mars, the inner one of which is exactly three of its diameters away from the center of the main planet and the outer five." It is assumed that Swift had heard of Johannes Kepler's misinterpretation . He understood the anagram that Galileo Galilei sent to him in 1609 to inform him of the discovery of the phases of Venus as the discovery of two Martian moons.

History of origin

History of the origins of Mars
Animation showing the topography of Mars. Olympus Mons → Mariner Valleys → Mars South Pole → Hellas Basin → Mars North Pole

A large part of the planet's history can be deduced from the diversity of astrogeological formations and the distribution of impact craters. Like the other planets in the solar system , Mars was formed around 4.5 billion years ago through the agglomeration of smaller bodies, so-called planetesimals , within the protoplanetary disk to form a protoplanet . 4 billion years ago the still glowing liquid planetary body formed a solid rock crust that was subjected to a violent bombardment by asteroids and comets .

Noachian period

The oldest of the formations still existing today, such as the Hellas Basin, and the cratered highlands, such as Noachis Terra , were formed 3.8 to 3.5 billion years ago, in the so-called Noachian period . During this period, the surface of Mars began to be divided into two, with the formation of the northern lowlands. Strong volcanic eruptions covered large parts of the planet with deposits of volcanic lava and ash . These were removed again in many places by wind and water, leaving a network of valleys behind.

Hesperian period

The geological "Middle Ages" of Mars is known as the Hesperian period . It covers the period from 3.5 to 1.8 billion years ago. During this period, huge amounts of lava poured from extensive fissures in the Martian crust and formed wide plains like Hesperia Planum . The oldest volcanoes of the Tharsis and Elysium regions were also formed, with the rock crust being severely deformed and the rift system of the Mariner valleys opening up. The huge river valleys formed, in which large amounts of water flowed and in places dammed up.

A water cycle developed on Mars. In contrast to Earth, however, there was no weather cycle with evaporation, cloud formation and subsequent precipitation. The water seeped underground and was later driven back to the surface by hydrothermal processes. However, as the planet continued to cool, this process ended about 1.5 billion years ago and only glaciers remained on the surface. Signs of this activity are the recently discovered moraines on Olympus Mons.

Amazonian period

The most recent geological age of Mars is known as the Amazonian Period and began 1.8 billion years ago. During this phase the younger volcanoes of the Tharsis and Elysium regions were formed, from which large volumes of lava flowed. This is how vast plains formed, such as the Amazonis Planitia .

In 2008, researchers found evidence of geysers on Mars that may have been active a few million years ago. They would have shot fountains of carbonated water a few kilometers high. This is also indicated by the forms of deposits that British researchers discovered in the vicinity of two extensive systems of rifts. These eruptions were likely caused by bubbles of carbon dioxide . As a result, the water was pushed to the surface from a depth of up to four kilometers through crevices in the Martian soil. The fountains must have been pressed out with such a high pressure that the muddy water only rained on the ground several kilometers away from the outlet or, due to the low temperatures, fell as hail.

Currently, the surface of Mars is shaped mainly by wind erosion and landslides .


Due to its high brightness, Mars was known as a planet even in ancient times. Because of its long planetary loops (which occur every 2 years in opposition ), its movements were considered unpredictable by the Egyptians. The Babylonians succeeded in predicting them approximately, but attributed the orbital anomalies to the whims and violence of the god Nergal .

Before the space age

Mars surface according to Schiaparelli (1888)
Mars on a 19th century astronomical drawing ( Trouvelot , 1881)


  • Tycho Brahe (1546–1601) measured the planetary positions of Mars with previously unknown accuracy and made it possible for Johannes Kepler (1571–1630) to calculate the elliptical orbit of the planet and to derive Kepler's three laws .
  • Christiaan Huygens discovered a dark, triangular zone ( Syrtis Major ) on the surface of Mars in 1659 . From their changes in position, he calculated Mars' own rotation to be 24.5 hours (today's value: 24.623 hours).
  • Giovanni Domenico Cassini described the white polar caps of Mars in 1666 .
  • In 1784 Wilhelm Herschel determined the inclination of the axis of rotation in relation to the orbit to be 25 ° (today's value 25.19 °).
  • Wilhelm Beer made the first map of Mars in 1830 , Angelo Secchi in 1863 in color.
  • Richard Proctor published a detailed map of Mars in 1869, which he created from drawings by William Rutter Dawes .
  • In 1877 Giovanni Schiaparelli noticed delicate line structures on the surface of Mars , which he called “Canali” (Italian for “channels” or “ trenches ”) and entered them on a detailed map. At first he did not give any information about the origin of the Canali (which he estimated to be wider than 100 km), but they were incorrectly translated as "Channel" in the English media and soon interpreted as the work of intelligent Martians. Many of these lines were given names on older Martian maps. While some astronomers confirmed Schiaparelli's observations, the existence of the Canali has been questioned by others, claiming it to be the result of optical illusions. It was only when the American Mariner probes flew by that speculation ended, because photos of the Martian surface did not show such wide gullies. However, three canals correspond to the huge canyons of Valles Marineris , others trace terrain levels and shadow lines, some also longer crater chains .
  • Asaph Hall discovered the two Martian moons Phobos and Deimos in the favorable opposition in 1877 .
  • Percival Lowell founded the Lowell Observatory in Arizona in 1894 to study the Martian canals, their seasonal discoloration and any signs of life . Biological molecules were found spectroscopically, but later turned out to be terrestrial. Spectral lines of oxygen have been discovered in the atmosphere, but the proportion of its volume is overestimated.
  • The first photographs of Mars were known in 1905.
  • Eugène Antoniadi initially confirmed the Martian channels, but in 1909 , using the Meudon giant telescope , came to the conclusion that they would only appear as such in smaller telescopes. In his detailed Mars cards - up to the first Mars probes were hardly exceeded - he drew them a diffuse spots as a result.
  • Gerard Kuiper detected carbon dioxide in the Martian atmosphere in the 1950s and believed in the possible existence of mosses or lichens until the first Mars probes .

In the space age

The first close-up of Mars taken by Mariner 4

Many unmanned space probes have already been sent to Mars, some of which have been successful. About half of the missions ended in failure, most of which were Soviet probes. In contrast to the exploration of the Earth's moon, there are still no rock samples that were taken from Mars, so Martian meteorites are the only way to research material from Mars in terrestrial laboratories. So far there has not been a manned mission to Mars either. According to all, partly contradicting, partly unreliable information, the Mars One project is far from being realized, the shares of the sponsoring company have fallen to zero. From the medical side, considerable doubts are expressed about the possibility of longer manned space flights.


The two Soviet probes Marsnik 1 and 2 were launched in October 1960 to fly past Mars, but did not even reach Earth orbit . In 1962 three more Soviet probes (Sputnik 22, Mars 1 and Sputnik 24) failed, two of them remained in Earth orbit, and the third lost contact with Earth on the way to Mars. Another attempt in 1964 also failed.

Between 1962 and 1973, ten were Mariner -Raumsonden from the Jet Propulsion Laboratory of NASA designed and built to explore the inner solar system. They were relatively small probes that mostly weighed less than half a ton.

Mariner 3 and Mariner 4 were identical spacecraft that were supposed to fly past Mars. Mariner 3 was launched on November 5, 1964, but the shipping fairing did not come off properly and the probe did not reach Mars.

Three weeks later, on November 28, 1964, Mariner 4 was successfully sent on an eight-month voyage to the Red Planet. On July 15, 1965, the probe flew past Mars and provided the first close-ups - a total of 22 photos - of the planet. The images showed moon-like craters, some of which appear to be covered in frost .

In 1969 Mariner 6 and Mariner 7 followed and delivered a total of 200 photos.


In 1971 the launch of Mariner 8 failed , but NASA received several thousand images from Mariner 9 in the same year .

Also in 1971, the Soviet Mars 3, the first probe landed softly on Mars, after Mars 2 had failed a few days earlier. However, radio contact broke off 20 seconds after landing. The possible cause was a raging global dust storm that could have knocked over the lander. The Soviet Union attempted two more landings on Mars in 1973, but failed.

Picture by Viking 1. The large rock to the left of center is about two meters wide. He was named Big Joe .

In the 1970s, the Viking probes landed on Mars and provided the first color images and data from soil samples: on July 20, 1976, Viking 1 was the first US probe to make a soft landing.


The only space probes that flew to Mars in the 1980s were the two Soviet Fobos probes. They were launched from Baikonur in 1988 and were intended to study Mars and its moon Phobos . For this purpose, as part of an international cooperation, they were equipped with numerous Western instruments as well as Soviet ones. However, contact with Fobos 1 broke off on the way to Mars due to an incorrect control command. Fobos 2 entered Mars orbit and some data and images from Mars were transmitted to Earth. Then the probe was directed to Phobos. However, shortly before the rendezvous, contact with Fobos 2 also broke off.


In 1992 the US Mars Observer probe was launched. It was lost in 1993 shortly before it entered orbit.

On November 16, 1996, Mars 96 was launched , the first Russian spacecraft since the collapse of the Soviet Union. But the Proton launcher failed , so Mars 96 re-entered the earth's atmosphere and burned up.

The Mars rover Sojourner

In 1997, the Mars Pathfinder attracted particular attention , when a small Martian mobile, the Rover Sojourner, was used for the first time . It landed on July 4th, American Independence Day , with great public appeal , and provided many recordings of the area around the landing site, which NASA published immediately on the Internet for the first time.

Another successful mission in 1997 was that of the Mars Global Surveyor , during which the surface of Mars was mapped in high resolution. On November 2, 2006 - five days before the 10th anniversary of its launch - contact with the satellite was lost.

The failure of the Mars probe Mars Climate Orbiter , which was lost due to a programming error in the navigation, and Mars Polar Lander , which probably crashed due to a faulty sensor when landing from a great height, represented a major setback for Mars research in 1999.

The Japanese space probe Nozomi , launched in 1998, was also unable to reach Mars.


Since October 24, 2001, in addition to the Global Surveyor, Mars Odyssey has been orbiting the red planet in 2001 , which has special instruments for remote sensing of water resources on board.

Of the 33 missions to Mars up to 2002, only eight were successful, all of them American.

Mars Rover Opportunity (MER-B)

On June 2, 2003 as part launched the first European Mars mission, the ESA - space probe Mars Express with the lander Beagle 2 successfully to Mars. Beagle 2 landed on the surface of Mars on December 25, 2003, but radio contact could never be established. In 2014 he was discovered in images of the MRO . However, the orbiter Mars Express works successfully in orbit around Mars and was able to take, among other things, many recordings of formations that are believed to be dry or frozen river valleys. He maps the planet, among other things. by means of radar and a stereo camera in visible light, as well as spectroscopically in infrared. On November 30, 2005, the probe found an ice field 250 km in diameter under the Chryse Planitia plain .

On June 10, 2003, the US Mars probe Spirit (MER-A) was launched to Mars. There was a rover on board that was supposed to take rock samples for three months after landing and look for traces of previously existing water. The landing took place on January 4, 2004 in Gusev crater , into which the Ma'adim Vallis empties. In April 2009, the rover got stuck in a pile of sand and has not been able to be contacted since March 22, 2010 (as of March 2011).

On July 8, 2003, the identical probe Opportunity (MER-B) was launched with a Delta II rocket. It landed on January 25, 2004 in the Meridiani Planum plain near the Martian equator, almost exactly across from Spirit. The evidence gathered by the rover that Mars was once warm and humid was recognized in the annual review of the journal Science with the choice of "Breakthrough of the Year 2004". Opportunity was active until June 10, 2018.

Detail of a panorama image of the Victoria crater from Cap Verde : assembled from hundreds of individual images ( Opportunity , October 6th to November 6th, 2006)

On August 12, 2005, the US probe Mars Reconnaissance Orbiter was sent on its journey with an Atlas V rocket and reached Mars on March 10, 2006. It should map it with high-resolution cameras and also look for suitable landing sites for later rover missions. In addition, it should serve for high-speed communication between future space probes on the surface of Mars and the earth.

Sunset on Mars at Gusev Crater ( Spirit on May 19, 2005)
The locations of the ten successful Mars landings

In 2007 Mars Reconnaissance photographed seven almost circular black and structureless spots in the northeast of the Martian volcano Arsia Mons . The largest, called Jeanne , is about 150 meters in diameter. An oblique photograph of the sunlit side wall in August 2007 showed that it must be a vertical shaft at least 78 meters deep. These structures are very likely of volcanic nature and were created by the collapse of a no longer load-bearing surface layer.

On December 26, 2007, the Mars Express High Resolution Stereo Camera took pictures of Eumenides Dorsum , a ridge west of the Tharsis region. The recordings show kilometer-long linear structures interrupted by canals. These are yardangs ( wind humps or sand walls) created by wind erosion .

With the Mars Odyssey probe , NASA demonstrated an extensive salt deposit in the plateaus of the southern hemisphere in March 2008 . The scientists at JPL in Pasadena believe that it formed between 3.5 and 3.9 billion years ago. Presumably, the salts were created by mineral-rich groundwater that came to the surface and evaporated there. The images from "Mars Odyssey" show canal-like structures that end in the salt basin. A total of over 200 areas with salt deposits were identified, which are between 1 and 25 km² in size. The discovery suggests that Mars long ago had a warmer and significantly more humid climate. Such climatic fluctuations are likely to result from aperiodic changes in the axis of rotation , the inclination of which (currently 25 °) varies between 14 and 50 °.

On May 26, 2008, the Phoenix probe landed in the northern polar region of the planet. Up until November 2008, she looked for water ice and “habitable zones” in the soil , that is, environments that are habitable for primitive organisms. Her robotic arm was able to collect samples from a depth of around 50 cm and then analyze them in a mini-laboratory. During an excavation, Phoenix discovered white lumps that disappeared after a few days. It was suspected that it was water ice, which was confirmed on July 31 - when a rock sample was heated, water vapor was released. With the wet chemical laboratory MECA , which determined the water-soluble ions in the Martian soil, considerable amounts of perchlorates could be detected. On earth, perchlorates occur in the arid desert areas. Sodium perchlorate is created by the oxidation of sodium chloride in the atmosphere and then deposited with the dust. In 2009, the first pure communications satellite, Mars Telecommunications Orbiter, was supposed to enter Mars orbit and serve to transmit scientific data from other missions to Earth for about ten years, but in 2005 NASA canceled the project for cost reasons.


Curiosity on Mars

On November 26, 2011 at 15:02  UTC , NASA's Mars Science Laboratory (Curiosity) rover mission started with an Atlas V (541) from Cape Canaveral and landed on Mars on August 6, 2012. The rover can travel long distances and perform extensive surveys of a large area. The most important project goal is geological analysis of the Martian soil.

On November 18, 2013, another NASA probe launched for Mars. The mission with the project name " Mars Atmosphere and Volatile Evolution " (MAVEN) aims to solve the mystery of the lost atmosphere. The orbiter has been orbiting the planet since September 22, 2014 and is expected to approach in five low-level flights. Furthermore, an Indian mission to Mars was launched on November 5, 2013 . It will also investigate the atmosphere and various surface phenomena.

On May 5, 2018, NASA's InSight probe launched an Atlas V (401) rocket from Vandenberg Air Force Base on the California coast. It is the first probe that did not take off from the Kennedy Space Center . InSight landed on November 26, 2018 as scheduled on the extensive Elysium Planitia plain north of the Mars equator to investigate the geological structure of the planet.


With the Al-Amal space probe , launched by Japan on July 19, 2020, the United Arab Emirates became the first Arab state to send a probe to Mars. It entered orbit around the planet in February 2021. The mission's task is to capture the first complete picture of Mars' climate over a full Mars year. The space probe has three scientific instruments on board for this purpose.

With the Tianwen-1 mission , the People's Republic of China sent a combination of orbiter, lander and rover to Mars on July 23, 2020. One day after al-Amal, this probe also entered orbit around the planet. On May 14, 2021, the rover Zhurong landed in the Utopia Planitia , the main task of the mission is to study the morphology, geology, mineralogy and space environment , as well as the distribution of water ice on the planet. Of the total of 13 scientific instruments, seven are on board the orbiter, and six are part of the rover.

On July 30, 2020, NASA launched the Perseverance rover mission (Mars 2020). On February 18, 2021, the rover landed successfully in the 250-meter-deep Jezero Mars crater . One of the aims of the project is to search for clues about potential microbial life in the planet's past. In addition to seven scientific instruments, the rover's equipment also includes a 1.8 kilogram autonomous helicopter called Ingenuity (roughly translated: ingenuity). The mini helicopter powered by lithium-ion batteries successfully completed a demonstration flight on April 19, 2021 without a scientific task.

Scheduled missions

Other NASA and ESA plans for Mars research include the launching of smaller drones in the atmosphere and - 2026 at the earliest - the return of Mars samples from the rover Perseverance to Earth ( Mars Sample Return mission ). This will take samples by means of a core hole drilling and deposit them on its route in a contamination-proof manner. The Fetch Rover is supposed to collect these samples and take them to a return module. This would be the first return of Martian samples back to Earth.

Panoramic image of the surface of Mars taken by the Pathfinder probe

ExoMars Rover is a European rover that is scheduled to launch in 2022. He is specifically supposed to look for traces of life.

Possibility of life

The ecosphere (or habitable zone ) of the solar system is subject to the results of various model calculations and assumed boundary conditions. For a long time, a distance to the sun of 0.95 to 1.37 AU was considered a good estimate. Currently, however, the models allow habitable zones for earth-like planets of up to 0.94–1.72 AU, with the outer limit being defined by a dense CO 2 atmosphere , caused by an extreme greenhouse effect . Other models come to significantly smaller solar habitable zones for earth-like planets. In all models in the solar system, only the earth is constantly within this belt around the sun, Mars lies in its orbit, sometimes inside, sometimes outside.

There is no higher or even intelligent life on Mars, but scientists consider primitive life forms ( microbes ) deeper in the ground to be protected from UV rays to be conceivable. In fact, the fungus species Cryomyces antarcticus and Cryomyces minteri, which live inside rocks in the Antarctic, withstood simulated Mars environmental conditions relatively well: after 18 months on the International Space Station , almost 10% of the samples still contained cells capable of reproduction. The lichen Xanthoria elegans also survived the simulated Martian conditions during the experiment.

Pre-space age conjectures

Mars surface according to Oswald Lohse (1888). The Schiaparelli canal system is not shown on the map. The names chosen by Lohse for “lakes” and “oceans” are no longer in use today

The thought of the possibility of life on Mars often fired people's imaginations. In the 18th century, it was observed that the dark spots on the surface of Mars changed their color and grew or shrunk. They were believed to be extensive vegetation zones , the extent of which changed with the seasons.

Schiaparelli's “discovery” of the Martian canals fueled speculation about intelligent life on Mars.

This is how numerous legends arose about supposed civilizations on Mars. The discussions about the “ Martians ” lasted for about a century. The American Percival Lowell , one of the strongest proponents of the Martian canals theory, even founded his own observatory to study the Martians. For him, the canals were the product of extraterrestrial engineers created to save the Martian civilization from a great drought. Lowell described his ideas about the Martian world in numerous publications that were widely distributed.

Although not all astronomers could see the channels and no photos existed, the theory held up, accompanied by heated debate. The idea of extraterrestrial life still exerts a fascination on people today, which often cannot be explained with scientific interest alone. Only the results of the unmanned Mars missions ended the dispute over the canals.

Investigations by Viking

When orbiter 1 of the Viking mission took pictures of the Cydonia region in July 1976 and sent them to Earth, Mars became a topic of public conversation again. One of the recordings showed a formation on the surface of Mars that resembled a human face looking up at the sky. Structures that resemble pyramids on earth and rectangular structures (called “Inca City” by scientists) have also been discovered in the immediate vicinity . It was not until NASA's Mars Global Surveyor mission in April 1998 that many were disillusioned: all the structures discovered were the result of natural erosion . New images with a much higher resolution made it clear that no artificial structures of extraterrestrial intelligence are visible on Mars.

The face of Mars in the Cydonia region; Image of the orbiter from Viking 1, 1976

Viking  1 and 2 had, among other things, the task of investigating the question of life on Mars. One chemical and three biological experiments were carried out. In the chemical experiment an attempt was made to detect organic substances in the Martian soil. A GC / MS unit developed at MIT (coupling of a gas chromatograph with a mass spectrometer ) was used for this purpose. However, no organic substances based on carbon could be detected.

The first biological experiment was based on the metabolic activities of organisms. A soil sample was wetted with a nutrient solution and the gases produced were recorded. The Martian soil reacted to the experiment by releasing large amounts of oxygen . In the second experiment, a nutrient solution was provided with radioactive carbon atoms and applied to a sample. As a result of a metabolism, they should have been detected among the excreted gases. In fact, radioactive carbon atoms were detected. The third experiment was a photosynthesis experiment. Radiolabelled carbon dioxide was added to the Martian soil. This carbon dioxide should have been assimilated and later detected. This result was also positive. Although the results of the biological experiments were positive, due to the negative result of the GC / MS experiment, they did not provide conclusive evidence of the existence or non-existence of life on Mars.

1990s and 2000s

Mars Face ( Mars Global Surveyor , 2001)

In 1996, David S. McKay and his colleagues found structures in the Martian meteorite ALH 84001 , which they interpreted as traces of fossil bacteria. The chain-like magnetite found in this meteorite is morphologically similar to the bacterial magnetite from Magnetospirillum magnetotacticum . However, the evidential value of the structures found is questioned by many scientists, as these could also be created purely chemically.

On January 23, 2004, the European Mars Express probe discovered large amounts of frozen water at the South Pole of Mars, and at the end of July 2005 also in a crater near the North Pole.

At the end of March 2004 it became known that researchers from NASA and ESA had independently detected methane in the Martian atmosphere. Further investigations should show whether the methane is of geological origin or whether it was formed by the metabolism of microorganisms.

Also in early 2004, the Opportunity Mars probe discovered rocks that must have been deposited in open water and contain many regularly distributed spherical hematite concretions up to 1 cm in size . Such concretions also occur on earth. Under terrestrial conditions, bacteria are likely to be involved in their formation . Only laboratory tests on Earth could show whether this also applies to Mars.

Further microstructures, which the rovers Spirit and Opportunity had discovered in 2004 and in which part of the interested public wanted to see evidence of life, turned out to be abiotic or artificial on closer examination, for example grinding marks on rock surfaces or filaments processed by the instruments , which turned out to be the textile fibers of the landing airbags .

Research on earth confirms that life can exist even in extreme conditions. When drilling in the Greenland ice in 2005 , researchers from the University of California, Berkeley discovered a striking amount of methane at a depth of three kilometers. This gas is produced by methanogenic bacteria that survive in the ice despite inhospitable living conditions such as cold, darkness and lack of nutrients. In doing so, they only keep themselves alive with great difficulty - they repair genetic damage, but do not significantly increase their population. Methanogenic microbes are a subgroup of archaebacteria that specialize in extreme locations. In 2002, for example, microbes were found in a 15,000 year old hot spring in Idaho . As the name suggests, bacteria are among the oldest microorganisms on earth. The scientists estimate the age of the bacterial colony discovered in Greenland to be 100,000 years and suspect that the methane detected in the atmosphere of the Red Planet could not only come from chemical processes, but also from such microbes.

Current research

The Mars Science Laboratory is trying to provide new information about possible life on Mars. It is questionable whether the Mars rover can drill deep enough to find life, or at least the remains of life. But an isotope analysis of methane can already provide further information. Life, as it is known on Earth, prefers lighter isotopes of hydrogen.


Position to the earth and orbital properties

Mars opposition from 2003 to 2018, relative movement of Mars to Earth, with Earth in the center; View of the plane of the ecliptic
Planetary loop of Mars in the constellation Aquarius in 2003

Due to the orbital properties of the planets, the earth “overtakes” Mars on its inner orbit on average every 779 days. This period, which fluctuates between 764 and 811 days, is called the synodic period . If the sun, earth and Mars are aligned in this arrangement, Mars is in opposition to the sun when viewed from earth . At this point in time, Mars can be observed particularly well, as a reddish “star” it is strikingly bright in the night sky. If you observe Mars regularly, you can see that it loops in the sky before and after an opposition. This planetary loop (opposition loop) results from the viewing angles that Mars offers as it is overtaken by Earth.

Since the planets do not move on ideal circular orbits, but rather on more or less pronounced elliptical orbits, Earth and Mars are at different distances from each other at the time of the oppositions. These can be between 55.6 and 101.3 million kilometers or 0.37 and 0.68 AU. If the distance to the opposition is short, it is called a perihelion opposition, if it is large, it is called an aphle opposition.

The perihelion operations, which take place every 15 to 17 years, offer the best opportunities to observe Mars from Earth using a telescope . The planet will then have an apparent diameter of up to 25.8 arc seconds . At 14.1 arc seconds, it is only about half as large for an apheloposition. Particularly near-Earth oppositions took place every 79 years, for example in 1766, 1845, 1924 and 2003. On August 28, 2003, the distance between Earth and Mars was 55.76 million kilometers. This was the closest distance in about 60,000 years. Only in the year 2287 will Mars come even closer to Earth, the distance will then be 55.69 million kilometers.

In the telescope, Mars initially appears as a reddish disc. At a higher magnification, the polar ice caps and dark surface features such as the Great Syrte can be made out. If major dust storms occur on Mars, the features fade as the surface is enveloped by a reddish layer of haze that can sometimes last for weeks. By using CCD cameras, even amateur astronomers are now able to obtain detailed images of the Martian surface that could only be made by the most powerful large telescopes about ten years ago.

Events (beginning of the season applies to the northern hemisphere):

occurrence 2018 / '19 2020 / '21 2022 / '23
Beginning of autumn May 22, 2018 April 8, 2020 February 24, 2022
opposition July 27, 2018 October 14, 2020 December 8, 2022
Perihelion 16th September 2018 August 3, 2020 June 21, 2022
Start of winter October 16, 2018 September 2, 2020 July 21, 2022
Beginning of spring 23 March 2019 February 7, 2021 December 26, 2022
Aphelion 26th August 2019 July 13, 2021 May 30, 2023
conjunction 2nd September 2019 October 8, 2021 November 18, 2023
Beginning of summer October 8, 2019 August 25, 2021 July 12, 2023
Fluctuation of the minimum distance between Earth and Mars in the event of oppositions. The points represent the actual distances, the gray curve the corridor of these points.


Because of the eccentricity of the orbit of Mars, the closest point to the earth can be reached up to a week before or after opposition, and the apparent brightness during opposition as well as the distance and diameter during proximity to the earth can vary considerably.

An opposition takes place roughly every two years (779.94 days). With a perihelion, the maximum apparent brightness can reach up to −2.91 m . At this point only the sun , the earth's moon , Venus and in rare cases Jupiter (up to −2.94 m ) are still brighter. In conjunction, on the other hand, Mars only appears with a brightness of +1.8 m .

Cultural history

Occupation with Mars from antiquity to modern times

Allegorical representation of Mars as ruler of the zodiac signs Aries and Scorpio, by Hans Sebald Beham , 16th century

Mars has particularly moved mankind from ancient times. In ancient Egypt , Mars was known as "Horus the Red". Since the planet temporarily moves retrograde during its opposition loop (planetary loop), the Egyptians spoke of Mars moving backwards. The name of the Egyptian capital " Cairo " is derived from "Al Qahira", the old Arabic name for the planet Mars.

In Indian Sanskrit , Mars is referred to as “Mangal” (full of promise), “Angaraka” (glowing coal) and “Kuja” (the blonde). It represents powerful action, trust and confidence.

Due to its red color, Mars has been associated with the deities of war in various cultures. The Babylonians saw in him Nergal , the god of the underworld, of death and of war. For the ancient Greeks and Romans , he represented their gods of war Ares and Mars, respectively . In Norse mythology he stands for Tyr , the god of law and war. The Aztecs called him Huitzilopochtli , the destroyer of people and cities. For the Chinese he was Huoxing (Chin. Huŏxīng, 火星), star of fire.

In astrology , Mars is, among other things, the symbol of the driving force. It is assigned to the element fire, the planetary metal iron , the zodiac signs Aries and Scorpio and the 1st house.

Reception in literature, film, video games and music

Mars and its fictional inhabitants are also the subject of numerous novels and film adaptations.

An example of the 18th century is Carl Ignaz Geiger's novel Journey of an Earthling to Mars from 1790.

In 1880, Percy Greg published his novel Across the Zodiac , in which he described a journey to Mars in a spaceship called the Astronaut .

The classic figure of the little green man with antennae on his head first appeared in a comic in 1913 and has been a cliché ever since .

When the astronomer Percival Lowell developed the idea at the end of the 19th century that the Martian canals that can be perceived with a telescope were artificially created water channels, this idea was taken up and further developed in science fiction literature. There, Mars was often imagined as a dying world, in whose cold desert regions ancient and well-developed civilizations struggled to survive.

In 1897, Kurd Laßwitz published his very extensive novel On two planets about a visit to the Martians.

Attack of the Martians in War of the Worlds by H. G. Wells. Book illustration of the French edition by Alvim Corréa from 1906

In H. G. Wells ' famous novel War of the Worlds , published in 1898, the Martians leave their homeworld to conquer the more livable earth. The human race, hopelessly inferior to the high-tech martial Martians, only escapes its extinction when the invaders are carried away by earthly microbes that are harmless to humans. Orson Welles used the material in a radio play in 1938 , where he landed the Martians in New Jersey . The radio play was broadcast in the style of a realistic report. Listeners who tuned in later believed the Martian invasion was a reality.

Wells' novel was made into a film in 1952, with the plot again being relocated to the United States of the present. The film received an Oscar for the special effects that were groundbreaking at the time .

The red star from 1907 is a utopian novel by the Russian writer Alexander Bogdanow , which describes an ideal social order of socialist / communist character on Mars.

In 1923 Alexei Tolstoy published his novel Aelita , which is about the love of a Soviet engineer for the Mars princess and the downfall of civilization on the planet. This work was filmed in 1924 .

In 1978 the film company Capricorn was made . He took up the subject of the conspiracy theories about the moon landing by transferring it in a very pointed form to a Martian expedition faked in the film studio.

The 1996 film Mars Attacks! ironically deals with the subject of Martian invasion, with the Martians being doomed by American music from the 1950s.

Directed by Brian De Palma , the 2000 film Mission to Mars dramatically addressed the speculation about the Martian face of the Cydonia region as a building left behind.

Steven Spielberg's 2005 remake of War of the Worlds took up the topic again and showed the invasion of aliens on Earth from the perspective of a family man from the USA.

Other well-known science fiction films set on Mars are Red Planet (2000) and Total Recall (1990).

Edgar Rice Burroughs , the author of Tarzan , wrote the 11-volume saga John Carter von Mars from 1917 to 1943 , in which the earthly hero falls in love with Martian princesses and fights against air pirates, green-skinned fiends, giant white monkeys and other beasts.

The Mars Chronicles (1950), an atmospheric collection of stories by the writer Ray Bradbury , are also set on Mars.

The Martian trilogy , a series of novels about the colonization of Mars written by Kim Stanley Robinson from 1993 to 1996, received great attention . The special approach of these stories lies in the predominantly technical description, completely dispensing with fantastic elements.

Mark Watney's route in a simulated topographical map by the DLR Institute for Planetary Research

Probably the most prominent appearance of Mars in music is probably the first movement of Gustav Holst's orchestral suite The Planets (1914–1916), the first movement of which Mars, the Bringer of War, with its menacingly martial character, impressively portrays the mythological figure Mars.

From 2001 to 2008, bestselling author Andreas Eschbach wrote the pentalogy The Mars Project .

In 2011 Andy Weir published the science fiction novel The Martian , in which an astronaut is left behind on Mars after an accident and has to fight for his survival from now on. A film adaptation of this bestseller was released in 2015 with Der Martianer - Rettet Mark Watney .

Helga Abret and Lucian Boa give in their book Das Jahrhundert der Martianer (1984) a literary overview of stories and novels about Mars and its fictional inhabitants. From the description of an "ecstatic trip" to Mars ( itinerary exstaticum coeleste, 1656) of the Jesuit Father Athanasius Kircher to science fiction stories of the 20th century the range of annotated works with which to demonstrate the authors attempt enough that " a modern myth ”developed from the interaction of natural sciences, astronomy and literature.

See also

Portal: Mars  - Overview of Wikipedia content on Mars


(In chronological order)

  • Robert Henseling : Mars. Its riddles and its history. Cosmos Society of Friends of Nature. Franckh'sche Verlagsbuchhandlung, Stuttgart 1925 (the book is of historical interest)
  • Alexander Niklitschek: Excursion into the solar system , chapter “The riddles of Mars” (pp. 135–148). Gottlieb Gistel & Cie., Vienna 1948 (deals with the Canali and earlier ideas of life forms)
  • Roland Wielen: Planets and their moons. Spectrum Academic Publishing House, Heidelberg-Berlin-Oxford 1988, ISBN 3-922508-46-4
  • David Morrison: Planetary Worlds. Spectrum Academic Publishing House, Heidelberg-Berlin-Oxford 1995, ISBN 3-86025-127-9
  • Rolf Sauermost, Arthur Baumann: Lexicon of Astronomy - the great encyclopedia of space research. 2 volumes. Spectrum Academic Publishing House, Heidelberg-Berlin-Oxford 1995, ISBN 3-86150-145-7
  • William Sheehan: The Planet Mars - A History of Observation and Discovery. Univercity of Arizona Press, Tucson 1996, 1997, ISBN 0-8165-1641-3
  • Holger Heuseler, Ralf Jaumann , Gerhard Neukum : The Mars Mission. BLV Verlagsgesellschaft, Munich 1998, ISBN 3-405-15461-8
  • David McNab, James Younger: The Planets. C. Bertelsmann, Munich 1999, ISBN 3-570-00350-7
  • Paul Raeburn: Mars - The secrets of the red planet. Steiger, Augsburg 2000, ISBN 3-89652-168-3
  • Ronald Greeley: The NASA Atlas of the Solar System. Knaur, Munich 2002, ISBN 3-426-66454-2
  • Hans-Ulrich Keller: Das Kosmos Himmelsjahr 2003. Franckh-Kosmos Verlags-GmbH, Stuttgart 2002, ISBN 3-440-09094-9
  • Dirk Lorenzen : Mission: Mars. Franckh-Kosmos Verlags-GmbH, Edition: 1 (2004), ISBN 978-3-440-09840-0
  • Robert Markley: Dying Planet: Mars in Science and the Imagination. Duke University Press 2005, ISBN 0-8223-3638-3
  • Thorsten Dambeck: Water-rich early days of Mars. Spectrum of Science , May 2006, pp. 14-16, ISSN  0170-2971
  • Ernst Hauber: Water on Mars. Physics in our time , 38 (1), pp. 12-20 (2007), ISSN  0031-9252
  • Jim Bell: The Martian surface - composition, mineralogy and physical properties. Cambridge Univ. Press, Cambridge 2008, ISBN 978-0-521-86698-9
  • Nadine Barlow: Mars - an introduction to its interior, surface and atmosphere. Cambridge Univ. Press, Cambridge 2008, ISBN 978-0-521-85226-5
  • Donald Rapp: Human missions to Mars - enabling technologies for exploring the red planet. Springer, Berlin 2008, ISBN 978-3-540-72938-9
  • Ulf von Rauchhaupt : The ninth continent - The scientific conquest of Mars. S. Fischer, Frankfurt am Main 2009, ISBN 978-3-10-062938-8
  • Maria D. Lane: Geographies of Mars. Seeing and Knowing the Red Planet , University of Chicago Press, Chicago 2010, ISBN 978-0-226-47078-8
  • Jesco von Puttkamer : Project Mars. Human dream and future vision. , FA Herbig Verlagsbuchhandlung GmbH, Munich 2012, ISBN 978-3-7766-2685-8
  • Ralf Jaumann , Ulrich Köhler: Mars. A planet full of puzzles. Published by DLR . Ed. Torch bearer, Cologne 2013, ISBN 978-3-7716-4502-1
  • Giles Sparrow: Mars. The red planet within reach. Kosmos, Stuttgart 2015, ISBN 978-3-440-14615-6
  • Ann Bagaley, Owen P. Jones et al .: The Planets (Chapter Mars). Dorling Kindersley Verlag, Munich 2015, ISBN 978-3-8310-2830-6 , pp. 110-138.
  • Paul Thomas: Paleopole investigation of Martian magnetic field anomalies . Center for Astronomy and Astrophysics of the TU-Berlin, Berlin 2019, doi: 10.14279 / depositonce-8724 .
  • Thorsten Dambeck, Rüdiger Vaas: Departure to Mars. Bild der Wissenschaft , July 2020, pp. 12–33, ISSN  0006-2375

Web links


Commons : Mars  - album with pictures, videos and audio files
Wiktionary: Mars  - explanations of meanings, word origins, synonyms, translations
Wikibooks: Mars  - learning and teaching materials
Wikiquote: Mars  Quotes


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