Flickering in the days of confrontation with an ominous blood-red color and causing primitive mystical fear, the mysterious and mysterious star, which the ancient Romans named in honor of the god of war Mars (Ares among the Greeks), would hardly fit a female name. The Greeks also called it Phaeton for its "radiant and brilliant" appearance, which the surface of Mars owes to the bright color and "lunar" relief with volcanic craters, dents from giant meteorite impacts, valleys and deserts.
Orbital characteristics
The eccentricity of the elliptical orbit of Mars is 0.0934, thus causing the difference between the maximum (249 million km) and minimum (207 million km) distances to the Sun, due to which the amount of solar energy entering the planet varies within 20-30%.
The average orbital speed is 24.13 km/s. Marscompletely goes around the Sun in 686.98 Earth days, which exceeds the Earth's period twice, and turns around its own axis in almost the same way as the Earth (in 24 hours 37 minutes). The angle of inclination of the orbit to the plane of the ecliptic, according to various estimates, is determined from 1.51 ° to 1.85 °, and the inclination of the orbit to the equator is 1.093 °. Relative to the equator of the Sun, the orbit of Mars is inclined at an angle of 5.65 ° (and the Earth is about 7 °). A significant inclination of the planet's equator to the plane of the orbit (25.2°) leads to significant seasonal climate changes.
Physical parameters of the planet
Mars among the planets of the solar system is in seventh place in terms of size, and in terms of distance from the Sun it occupies the fourth position. The volume of the planet is 1.638×1011 km³, and the weight is 0.105-0.108 Earth masses (6.441023 kg), yielding to it in density about 30% (3.95 g/cm3). Free fall acceleration in the equatorial region of Mars is determined in the range from 3.711 to 3.76 m/s². The surface area is estimated at 144,800,000 km². Atmospheric pressure fluctuates within 0.7-0.9 kPa. The speed required to overcome gravity (second space) is 5,072 m/s. In the southern hemisphere, the average surface of Mars is 3–4 km higher than in the northern hemisphere.
Climatic conditions
The total mass of the atmosphere of Mars is about 2.51016 kg, but during the year it varies greatly due to the melting or "freezing" of the carbon dioxide-containing polar caps. The average pressure at the surface level (about 6.1 mbar) is almost 160 times less than near the surface of our planet, but in deep depressionsreaches 10 mbar. According to various sources, seasonal pressure drops range from 4.0 to 10 mbar.
95.32% of the atmosphere of Mars consists of carbon dioxide, approximately 4% is argon and nitrogen, and oxygen together with water vapor is less than 0.2%.
A highly rarefied atmosphere cannot retain heat for long. Despite the "hot color" that distinguishes the planet Mars from others, the temperature on the surface drops to -160°C at the pole in winter, and at the equator in summer, the surface can only warm up to +30°C in the daytime.
The climate is seasonal, just like on Earth, but the elongation of the orbit of Mars leads to significant differences in the duration and temperature regime of the seasons. The cool spring and summer of the northern hemisphere together last significantly more than half of the Martian year (371 Mart. days), and winter and autumn are short and moderate. Southern summers are hot and short, while winters are cold and long.
Seasonal climate changes are most clearly manifested in the behavior of the polar caps, composed of ice with an admixture of fine, dust-like particles of rocks. The front of the northern polar cap can move away from the pole by almost a third of the distance to the equator, and the boundary of the southern cap reaches half this distance.
The temperature on the surface of the planet was determined already in the early 20s of the last century by a thermometer located exactly in the focus of a reflecting telescope aimed at Mars. The first measurements (until 1924) showed values from -13 to -28 ° C, and in 1976 the lower and upper temperature limits were specifiedlanded on Mars by the Viking spacecraft.
Martian dust storms
"Revealing" dust storms, their scale and behavior has revealed a secret that Mars has long kept. The surface of the planet mysteriously changes color, captivating observers since ancient times. Dust storms turned out to be the cause of the "chameleonism".
Sudden temperature changes on the Red Planet cause rampant violent winds, the speed of which reaches 100 m / s, and low gravity, despite the thinness of the air, allows the winds to raise huge masses of dust to a height of more than 10 km.
Dust storms are also fueled by a sharp increase in atmospheric pressure caused by the evaporation of frozen carbon dioxide from the winter polar caps.
Dust storms, as shown by images of the surface of Mars, spatially gravitate towards the polar caps and can cover enormous areas, lasting up to 100 days.
Another dusty sight, which Mars owes to anomalous temperature changes, are tornadoes, which, unlike earthly "colleagues", roam not only in desert areas, but also host on the slopes of volcano craters and impact funnels, being understood upward up to 8 km. Their traces turned out to be giant branched-striped drawings that remained mysterious for a long time.
Dust storms and tornadoes occur mainly during the great oppositions, when in the southern hemisphere summer falls on the period of the passage of Mars through the point of the orbit closest to the Sunplanets (perihelion).
The images of the surface of Mars, taken by the Mars Global Surveyor spacecraft, , which has been orbiting the planet since 1997, turned out to be very fruitful for tornadoes.
Some tornadoes leave traces, sweeping away or sucking in a loose surface layer of fine soil particles, others do not even leave "fingerprints", others, furiously, draw intricate figures, for which they were called dust devils. Whirlwinds work, as a rule, alone, but they do not refuse group "representations" either.
Relief features
Probably, everyone who, armed with a powerful telescope, looked at Mars for the first time, the surface of the planet immediately resembled the lunar landscape, and in many areas this is true, but still the geomorphology of Mars is peculiar and unique.
Regional features of the planet's relief are due to the asymmetry of its surface. The predominant flat surfaces of the northern hemisphere are 2–3 km below the conditionally zero level, and in the southern hemisphere, the surface complicated by craters, valleys, canyons, depressions, and hills is 3–4 km above the base level. The transition zone between the two hemispheres, 100–500 km wide, is morphologically expressed by a strongly eroded giant scarp, almost 2 km high, covering almost 2/3 of the planet in circumference and traced by a system of faults.
The predominant landforms that characterize the surface of Mars are presenteddotted with craters of various genesis, uplands and depressions, impact structures of circular depressions (multi-ring basins), linearly elongated uplands (ridges) and irregularly shaped steep basins.
Flat-topped uplifts with steep edges (mesas), extensive flat craters (shield volcanoes) with eroded slopes, meandering valleys with tributaries and branches, leveled uplands (plateaus) and areas of randomly alternating canyon-like valleys (mazes) are widespread.
Characteristic of Mars are sinking depressions with a chaotic and shapeless relief, extended, complexly constructed steps (faults), a series of subparallel ridges and furrows, as well as vast plains of a completely "terrestrial" appearance.
Annular crater basins and large (over 15 km across) craters are the defining morphological features of much of the southern hemisphere.
The highest regions of the planet with the names of Tharsis and Elysium are located in the northern hemisphere and represent huge volcanic highlands. The Tharsis Plateau, rising above the plain surroundings by almost 6 km, stretches in longitude for 4000 km and extends for 3000 km in latitude. On the plateau there are 4 giant volcanoes with a height of 6.8 km (Mount Alba) to 21.2 km (Mount Olympus, diameter 540 km). The peaks of the mountains (volcanoes) Pavlina / Pavonis (Pavonis), Askrian (Ascraeus) and Arsia (Arsia) are at an altitude of 14, 18 and 19 km, respectively. Mount Alba stands alone to the northwest of the strict row of other volcanoes andIt is a shield volcanic structure with a diameter of about 1500 km. Volcano Olympus (Olympus) - the highest mountain not only on Mars, but in the entire solar system.
Two vast meridional lowlands adjoin the province of Tharsis from the east and west. The surface marks of the western plain with the name Amazonia are close to the zero level of the planet, and the lowest parts of the eastern depression (Chris Plain) are 2-3 km below the zero level.
In the equatorial region of Mars is the second largest volcanic highlands of Elysium, about 1500 km across. The plateau rises 4–5 km above the base and bears three volcanoes (Mount Elysium proper, Albor Dome, and Mount Hekate). The highest Mount Elysium has grown to 14 km.
To the east of the Tharsis plateau in the equatorial region, a giant rift-like system of valleys (canyons) Mariner stretches along the scale of Mars (almost 5 km), exceeding the length of one of the largest Grand Canyons on earth by almost 10 times, and times wider and deeper. The average width of the valleys is 100 km, and almost sheer ledges of their sides reach a height of 2 km. The linearity of the structures indicates their tectonic origin.
Within the heights of the southern hemisphere, where the surface of Mars is simply littered with craters, there are the largest circular shock depressions on the planet with the names of Argir (about 1500 km) and Hellas (2300 km).
The Hellas Plain is deeper than all the depressions on the planet (almost 7000 m below the average level), and the excess of the Argir Plain isin relation to the level of the surrounding hill is 5.2 km. A similar rounded lowland, the Isis Plain (1100 km across), is located in the equatorial region of the planet's eastern hemisphere and adjoins the Elysian Plain in the north.
On Mars, about 40 more such multi-ring basins are known, but smaller in size.
In the northern hemisphere is the largest lowland on the planet (Northern Plain), bordering the polar region. Plain markers are below the zero level of the planet's surface.
Eolian landscapes
It would be difficult to describe the surface of the Earth in a few words, referring to the planet as a whole, but to get an idea of what kind of surface Mars has, if you simply call it lifeless and dry, reddish-brown, rocky sandy desert, because the dissected relief of the planet is smoothed out by loose alluvial deposits.
Eolian landscapes, composed of sandy-fine silty material with dust and formed as a result of wind activity, cover almost the entire planet. These are ordinary (as on earth) dunes (transverse, longitudinal and diagonal) ranging in size from a few hundred meters to 10 km, as well as layered eolian-glacial deposits of the polar caps. The special relief "created by Aeolus" is confined to closed structures - the bottoms of large canyons and craters.
The morphological activity of the wind, which determines the peculiar features of the surface of Mars, manifested itself in intenseerosion (deflation), which resulted in the formation of characteristic, "engraved" surfaces with cellular and linear structures.
Laminated eolian-glacial formations, composed of ice mixed with precipitation, cover the polar caps of the planet. Their power is estimated at several kilometers.
Geological characteristics of the surface
According to one of the existing hypotheses of the modern composition and geological structure of Mars, the inner core of a small size, consisting mainly of iron, nickel and sulfur, first melted from the primary substance of the planet. Then, around the core, a homogeneous lithosphere with a thickness of about 1000 km, along with the crust, formed, in which, probably, active volcanic activity continues today with the ejection of ever new portions of magma to the surface. The thickness of the Martian crust is estimated at 50-100 km.
Since man began to look at the brightest stars, scientists, like all people who are not indifferent to the universal neighbors, among other mysteries, were primarily interested in what surface Mars has.
Almost the entire planet is covered with a layer of brownish-yellowish-red dust with an admixture of fine silty and sandy material. The main components of loose soil are silicates with a large admixture of iron oxides, giving the surface a reddish tint.
According to the results of numerous studies carried out by spacecraft, fluctuations in the elemental composition of loose deposits of the surface layer of the planet are not so significant as to suggest a wide variety of mineral composition of mountainsrocks that make up the Martian crust.
Established in soil average content of silicon (21%), iron (12.7%), magnesium (5%), calcium (4%), aluminum (3%), sulfur (3.1%), as well as potassium and chlorine (<1%) indicated that the basis of loose deposits of the surface are the products of the destruction of igneous and volcanic rocks of the basic composition, close to the bas alts of the earth. At first, scientists doubted the significant differentiation of the stone shell of the planet in terms of mineral composition, but studies of the bedrocks of Mars carried out as part of the Mars Exploration Rover (USA) project led to the sensational discovery of analogues of terrestrial andesites (rocks of intermediate composition).
This discovery, later confirmed by numerous finds of similar rocks, made it possible to judge that Mars, like the Earth, may have a differentiated crust, as evidenced by the significant contents of aluminum, silicon and potassium.
Based on a huge number of images taken by spacecraft and made it possible to judge what the surface of Mars consists of, in addition to igneous and volcanic rocks, the presence of volcanic-sedimentary rocks and sedimentary deposits is obvious on the planet, which are recognized by the characteristic platy separation and layering fragments of outcrops.
The nature of the layering of rocks may indicate their formation in the seas and lakes. Areas of sedimentary rocks have been recorded in many places on the planet and are most often found in vast craters.
Scientists do not exclude the "dry" formation of precipitation of their Martian dust with their furtherlithification (petrification).
Permafrost formations
A special place in the morphology of the surface of Mars is occupied by permafrost formations, most of which appeared at different stages of the geological history of the planet as a result of tectonic movements and the influence of exogenous factors.
Based on the study of a large number of space images, scientists unanimously concluded that water plays a significant role in shaping the appearance of Mars along with volcanic activity. Volcanic eruptions led to the melting of the ice cover, which, in turn, served to develop water erosion, traces of which are still visible today.
The fact that the permafrost on Mars was formed already at the earliest stages of the geological history of the planet is evidenced not only by the polar caps, but also by specific landforms similar to the landscape in permafrost zones on Earth.
Vortex-like formations, which look like layered deposits in the polar regions of the planet on satellite images, close up are a system of terraces, ledges and depressions that form a variety of forms.
Polar cap deposits several kilometers thick consist of layers of carbon dioxide and water ice mixed with silty and fine silty material.
Dip-subsidence landforms characteristic of the equatorial zone of Mars are associated with the process of destruction of cryogenic strata.
Water on Mars
On most of the surface of Mars, water cannot exist in liquidstate due to low pressure, but in some regions with a total area of \u200b\u200babout 30% of the planet's area, NASA experts admit the presence of liquid water.
Reliably established water reserves on the Red Planet are concentrated mainly in the near-surface layer of permafrost (cryosphere) with a thickness of up to many hundreds of meters.
Scientists do not exclude the existence of relict lakes of liquid water and under the layers of the polar caps. Based on the estimated volume of the Martian cryolithosphere, water (ice) reserves are estimated at about 77 million km³, and if we take into account the likely volume of thawed rocks, this figure could decrease to 54 million km³.
In addition, there is an opinion that under the cryolithosphere there may be layers with colossal reserves of s alt water.
Many facts indicate the presence of water on the surface of the planet in the past. The main witnesses are minerals, the formation of which implies the participation of water. First of all, it is hematite, clay minerals and sulfates.
Martian clouds
The total amount of water in the atmosphere of the "desiccated" planet is more than 100 million times less than on Earth, and yet the surface of Mars is covered, albeit rare and inconspicuous, but real and even bluish clouds, however, consisting of ice dust. Cloudiness is formed in a wide range of altitudes from 10 to 100 km and is concentrated mainly in the equatorial belt, rarely rising above 30 km.
Ice fogs and clouds are also common near the polar caps in winter (polar haze), but here they can"fall" below 10 km.
Clouds can turn a pale pinkish color when ice particles mix with dust raised from the surface.
Clouds of a wide variety of shapes have been recorded, including wavy, striped and cirrus.
Martian landscape from human height
For the first time to see what the surface of Mars looks like from the height of a tall man (2.1 m) allowed the "arm" of the curiosity rover armed with a camera in 2012. Before the astonished gaze of the robot, a "sandy", gravel-gravelly plain, dotted with small cobblestones, with rare flat outcrops, possibly bedrock, volcanic rocks, appeared.
A dull and monotonous picture on one side was enlivened by the hilly ridge of the edge of the Gale crater, and on the other side by the gently sloping mass of Mount Sharp, 5.5 km high, which was the object of the spacecraft's hunt.
When planning the route along the bottom of the crater, the authors of the project, apparently, did not even suspect that the surface of Mars, taken by the Curiosity rover, would be so diverse and heterogeneous, contrary to the expectation to see only a dull and monotonous desert.
On the way to Mount Sharp, the robot had to overcome fractured, platy flat surfaces, gentle stepped slopes of volcanic-sedimentary (judging by the layered texture on the chips) rocks, as well as block collapses of dark bluish volcanic rocks with a cellular surface.
The apparatus along the way fired at "indicated from above" targets (cobblestones) with laser pulses and drilled small wells (up to 7 cm deep) to study the material composition of the samples. The analysis of the obtained material, in addition to the contents of rock-forming elements characteristic of rocks of basic composition (bas alts), showed the presence of compounds of sulfur, nitrogen, carbon, chlorine, methane, hydrogen and phosphorus, that is, "components of life".
In addition, clay minerals were found, formed in the presence of water with a neutral acidity and low s alt concentration.
Based on this information, in conjunction with previously obtained information, scientists were inclined to conclude that billions of years ago there was liquid water on the surface of Mars, and the density of the atmosphere is much higher than today.
Morning Star of Mars
Ever since the Mars Global Surveyor spacecraft orbited the Red Planet at a distance of 139 million km around the world in May 2003, this is what the Earth looks like from the surface of Mars.
But in fact, our planet looks from there approximately the way we see Venus in the morning and evening hours, only glowing in the brownish blackness of the Martian sky, a lonely (except for the faintly distinguishable Moon) small dot is slightly brighter than Venus.
The first picture of the Earth from the surface wasmade in the wee hour from the Spirit rover in March 2004, and the Earth posed "hand in hand with the Moon" for the Curiosity spacecraft in 2012 and it turned out even "more beautiful" than the first time.
