Mars, the fourth planet from the sun, is one of the smallest planets in the solar system - it is second only to the very tiny Mercury in this respect. If we compare Mars with the Earth, then the comparison at first glance will clearly not be in favor of the first:
- the diameter of Mars is 53% of the diameter of the Earth (6739.8 km versus 12742 km).
- The mass of Mars is only 10.7% of the Earth's.
- the total surface area of Mars is only slightly smaller than the land area of the Earth (144,371,391 km² versus 148,940,000 km²).
However, the answer to a simple question - how big Mars is, is not so simple, because we are talking about a whole planet, albeit not a very impressive size. It all depends on what you compare and how you think!
Diameter and circumference of Mars
Despite the apparent regularity of the form, Mars is not a sphere, but a spheroid oblate from the poles (however, like the Earth). What does it mean? It's simple - any planet rotates around its axis, and, although we do not notice this from the surface, for an outside observer this rotation is extremely fast. Mars, for example, makes a complete rotation around its axis in 24.6 hours (respectively, this number is the duration of the Martian day). The planet rotates and under the action of centrifugal forces its mass is distributed unevenly, as a result of which the planet “compresses” at the poles, and “bursts” it at the equator.
Due to this, the diameter of Mars along the equator is 6,794 km, but the diameter from pole to pole is 6,752 km. Thus, the circumference of Mars along the equator will be equal to 21343 km, and along the poles - 21244 km.
Mass and gravity on Mars
The mass of Mars is 6.42 x 10 23 kg, that is, about 10 times less than that of the Earth. Of course, this also affects the force of gravity. The force of gravity on Mars is 38% of Earth's gravity, so a 100-kilogram person on Earth would weigh 38 kilograms on Mars.
This, by the way, explains the nature of the "Martian meteorites" that are also found on Earth - it is much easier here for a stone knocked out by a powerful blow from the surface of the planet to leave a planet with low gravity.
Mars records
Despite its modest size, there is something on Mars that can surprise anyone with its parameters. There are at least two such things here: the Mariner Valley and Mount Olympus.
Mariner Valley Discovered in 1971 by the Mariner 9 probe, it is a gigantic canyon system that stretches 4,000 kilometers from east to west and is up to 10 kilometers deep. If this hulk were on Earth, it would cross the whole of Australia from north to south, or, say, the territory of the United States from west to east! What to say about Mars - here the Mariner Valley stretches for 1/5 of the planet's surface and looks like a monstrous scar left in time immemorial by a huge cosmic body that hit Mars tangentially.
Mount Olympus really worthy of its name - a giant extinct volcano rises 27 kilometers above the surface of Mars - just think, these are three Mount Everest stacked one on top of the other! Mount Olympus is so large that it has no analogues in the solar system - such a huge volcano is only on Mars. The diameter of Olympus is 600 kilometers. In order to cover such a distance in a straight line, driving a car at a speed of 90 km / h, you would need to drive 7 hours.
Mars is the fourth largest planet from the Sun and the seventh (penultimate) largest planet in the solar system; the mass of the planet is 10.7% of the mass of the Earth. Named after Mars - the ancient Roman god of war, corresponding to the ancient Greek Ares. Mars is sometimes referred to as the "red planet" because of the reddish hue of the surface given to it by iron oxide.
Mars is a terrestrial planet with a rarefied atmosphere (the pressure at the surface is 160 times less than the earth's). The features of the surface relief of Mars can be considered impact craters like those of the moon, as well as volcanoes, valleys, deserts and polar ice caps like those of the earth.
Mars has two natural satellites - Phobos and Deimos (translated from ancient Greek - "fear" and "horror" - the names of the two sons of Ares who accompanied him in battle), which are relatively small (Phobos - 26x21 km, Deimos - 13 km across ) and have an irregular shape.
The great oppositions of Mars, 1830-2035
| Year | the date | Distance a. e. |
|---|---|---|
| 1830 | September 19 | 0,388 |
| 1845 | August 18 | 0,373 |
| 1860 | July 17th | 0,393 |
| 1877 | September 5 | 0,377 |
| 1892 | August 4 | 0,378 |
| 1909 | September 24 | 0,392 |
| 1924 | August 23 | 0,373 |
| 1939 | July 23 | 0,390 |
| 1956 | 10 September | 0,379 |
| 1971 | August 10 | 0,378 |
| 1988 | September 22nd | 0,394 |
| 2003 | August 28 | 0,373 |
| 2018 | July 27 | 0,386 |
| 2035 | September 15th | 0,382 |
Mars is the fourth largest planet from the Sun (after Mercury, Venus and Earth) and the seventh largest (surpasses only Mercury in mass and diameter) planet of the solar system. The mass of Mars is 10.7% of the mass of the Earth (6.423 1023 kg versus 5.9736 1024 kg for the Earth), the volume is 0.15 of the volume of the Earth, and the average linear diameter is 0.53 of the diameter of the Earth (6800 km).
The relief of Mars has many unique features. The Martian extinct volcano Mount Olympus is the highest mountain in the solar system, and the Mariner Valley is the largest canyon. In addition, in June 2008, three papers published in the journal Nature presented evidence for the existence of the largest known impact crater in the solar system in the northern hemisphere of Mars. It is 10,600 km long and 8,500 km wide, about four times larger than the largest impact crater previously discovered on Mars, near its south pole.
In addition to similar surface topography, Mars has a rotation period and seasons similar to Earth's, but its climate is much colder and drier than Earth's.
Until the first flyby of Mars by the Mariner 4 spacecraft in 1965, many researchers believed that there was liquid water on its surface. This opinion was based on observations of periodic changes in light and dark areas, especially in polar latitudes, which were similar to continents and seas. Dark furrows on the surface of Mars have been interpreted by some observers as irrigation channels for liquid water. It was later proven that these furrows were an optical illusion.
Due to the low pressure, water cannot exist in a liquid state on the surface of Mars, but it is likely that conditions were different in the past, and therefore the presence of primitive life on the planet cannot be ruled out. On July 31, 2008, water in the state of ice was discovered on Mars by NASA's Phoenix spacecraft.
In February 2009, the orbital research constellation in Mars orbit had three functioning spacecraft: Mars Odyssey, Mars Express and Mars Reconnaissance Satellite, more than around any other planet besides Earth.
The surface of Mars is currently explored by two rovers: "Spirit" and "Opportunity". There are also several inactive landers and rovers on the surface of Mars that have completed research.
The geological data they collected suggests that most of the surface of Mars was previously covered with water. Observations over the past decade have made it possible to detect weak geyser activity in some places on the surface of Mars. According to observations from the Mars Global Surveyor spacecraft, some parts of the south polar cap of Mars are gradually receding.
Mars can be seen from Earth with the naked eye. Its apparent stellar magnitude reaches 2.91m (at the closest approach to the Earth), yielding in brightness only to Jupiter (and even then not always during the great confrontation) and Venus (but only in the morning or evening). As a rule, during a great opposition, orange Mars is the brightest object in the earth's night sky, but this happens only once every 15-17 years for one to two weeks.
Orbital characteristics
The minimum distance from Mars to Earth is 55.76 million km (when the Earth is exactly between the Sun and Mars), the maximum is about 401 million km (when the Sun is exactly between the Earth and Mars).
The average distance from Mars to the Sun is 228 million km (1.52 AU), the period of revolution around the Sun is 687 Earth days. The orbit of Mars has a rather noticeable eccentricity (0.0934), so the distance to the Sun varies from 206.6 to 249.2 million km. The orbital inclination of Mars is 1.85°.
Mars is closest to Earth during opposition, when the planet is in the opposite direction from the Sun. Oppositions are repeated every 26 months at different points in the orbit of Mars and the Earth. But once every 15-17 years, the opposition occurs at a time when Mars is near its perihelion; in these so-called great oppositions (the last was in August 2003), the distance to the planet is minimal, and Mars reaches its largest angular size of 25.1" and brightness of 2.88m.
physical characteristics
Size comparison of Earth (average radius 6371 km) and Mars (average radius 3386.2 km)
In terms of linear size, Mars is almost half the size of the Earth - its equatorial radius is 3396.9 km (53.2% of the Earth's). The surface area of Mars is roughly equal to the land area of Earth.
The polar radius of Mars is about 20 km less than the equatorial one, although the period of rotation of the planet is longer than that of the Earth, which gives reason to assume a change in the rate of rotation of Mars with time.
The mass of the planet is 6.418 1023 kg (11% of the mass of the Earth). The free fall acceleration at the equator is 3.711 m/s (0.378 Earth); the first escape velocity is 3.6 km/s and the second is 5.027 km/s.
The planet's rotation period is 24 hours 37 minutes 22.7 seconds. Thus, a Martian year consists of 668.6 Martian solar days (called sols).
Mars rotates around its axis, which is inclined to the perpendicular plane of the orbit at an angle of 24°56?. The tilt of the axis of rotation of Mars causes the change of seasons. At the same time, the elongation of the orbit leads to large differences in their duration - for example, the northern spring and summer, taken together, last 371 sols, that is, noticeably more than half of the Martian year. At the same time, they fall on the part of Mars' orbit that is farthest from the Sun. Therefore, on Mars, northern summers are long and cool, while southern summers are short and hot.
Atmosphere and climate
Atmosphere of Mars, photo of the Viking orbiter, 1976. Halle's "smiley crater" is visible on the left
The temperature on the planet ranges from -153 at the pole in winter to over +20 °C at the equator at noon. The average temperature is -50°C.
The atmosphere of Mars, which consists mainly of carbon dioxide, is very rarefied. The pressure at the surface of Mars is 160 times less than the earth's - 6.1 mbar at the average surface level. Due to the large elevation difference on Mars, the pressure near the surface varies greatly. The approximate thickness of the atmosphere is 110 km.
According to NASA (2004), the atmosphere of Mars consists of 95.32% carbon dioxide; it also contains 2.7% nitrogen, 1.6% argon, 0.13% oxygen, 210 ppm water vapor, 0.08% carbon monoxide, nitric oxide (NO) - 100 ppm, neon (Ne) - 2, 5 ppm, semi-heavy water hydrogen-deuterium-oxygen (HDO) 0.85 ppm, krypton (Kr) 0.3 ppm, xenon (Xe) - 0.08 ppm.
According to the data of the AMS Viking descent vehicle (1976), about 1-2% argon, 2-3% nitrogen, and 95% carbon dioxide were determined in the Martian atmosphere. According to the data of AMS "Mars-2" and "Mars-3", the lower boundary of the ionosphere is at an altitude of 80 km, the maximum electron density of 1.7 105 electrons / cm3 is located at an altitude of 138 km, the other two maxima are at altitudes of 85 and 107 km.
Radio translucence of the atmosphere at radio waves of 8 and 32 cm by the AMS "Mars-4" on February 10, 1974 showed the presence of the nighttime ionosphere of Mars with the main ionization maximum at an altitude of 110 km and an electron density of 4.6 103 electrons / cm3, as well as secondary maxima at an altitude 65 and 185 km.
Atmosphere pressure
According to NASA data for 2004, the pressure of the atmosphere at the middle radius is 6.36 mb. The density at the surface is ~0.020 kg/m3, the total mass of the atmosphere is ~2.5 1016 kg.
The change in atmospheric pressure on Mars depending on the time of day, recorded by the Mars Pathfinder lander in 1997.
Unlike the Earth, the mass of the Martian atmosphere varies greatly during the year due to the melting and freezing of the polar caps containing carbon dioxide. During winter, 20-30 percent of the entire atmosphere is frozen on the polar cap, which consists of carbon dioxide. Seasonal pressure drops, according to various sources, are the following values:
According to NASA (2004): from 4.0 to 8.7 mbar at the average radius;
According to Encarta (2000): 6 to 10 mbar;
According to Zubrin and Wagner (1996): 7 to 10 mbar;
According to the Viking-1 lander: from 6.9 to 9 mbar;
According to the Mars Pathfinder lander: from 6.7 mbar.
The Hellas Impact Basin is the deepest place to find the highest atmospheric pressure on Mars
At the landing site of the AMC Mars-6 probe in the Eritrean Sea, a surface pressure of 6.1 millibars was recorded, which at that time was considered the average pressure on the planet, and from this level it was agreed to count the heights and depths on Mars. According to the data of this device, obtained during the descent, the tropopause is located at an altitude of about 30 km, where the pressure is 5·10-7 g/cm3 (as on Earth at an altitude of 57 km).
The Hellas (Mars) region is so deep that atmospheric pressure reaches about 12.4 millibars, which is above the triple point of water (~6.1 mb) and below the boiling point. At a sufficiently high temperature, water could exist there in a liquid state; at this pressure, however, water boils and turns into steam already at +10 °C.
At the top of the highest 27 km volcano Olympus, the pressure can be between 0.5 and 1 mbar (Zurek 1992).
Before landing on the surface of Mars, the pressure was measured by attenuating radio signals from the AMS Mariner-4, Mariner-6 and Mariner-7 when they entered the Martian disk - 6.5 ± 2.0 mb at the average surface level, which is 160 times less than the earthly; the same result was shown by the spectral observations of AMS Mars-3. At the same time, in areas located below the average level (for example, in the Martian Amazon), the pressure, according to these measurements, reaches 12 mb.
Since the 1930s Soviet astronomers tried to determine the pressure of the atmosphere using photographic photometry - by the distribution of brightness along the diameter of the disk in different ranges of light waves. For this purpose, the French scientists B. Lyo and O. Dollfus made observations of the polarization of the light scattered by the Martian atmosphere. A summary of optical observations was published by the American astronomer J. de Vaucouleurs in 1951, and they obtained a pressure of 85 mb, overestimated by almost 15 times due to interference from atmospheric dust.
Climate
Microscopic photo of a 1.3 cm hematite nodule taken by the Opportunity rover on March 2, 2004 shows the presence of liquid water in the past
The climate, like on Earth, is seasonal. In the cold season, even outside the polar caps, light frost can form on the surface. The Phoenix device recorded snowfall, but the snowflakes evaporated before reaching the surface.
According to NASA (2004), the average temperature is ~210 K (-63 °C). According to Viking landers, the daily temperature range is from 184 K to 242 K (from -89 to -31 °C) (Viking-1), and wind speed: 2-7 m/s (summer), 5-10 m /s (autumn), 17-30 m/s (dust storm).
According to the Mars-6 landing probe, the average temperature of the Mars troposphere is 228 K, in the troposphere the temperature decreases by an average of 2.5 degrees per kilometer, and the stratosphere above the tropopause (30 km) has an almost constant temperature of 144 K.
According to researchers from the Carl Sagan Center, the process of warming has been going on on Mars in recent decades. Other experts believe that it is too early to draw such conclusions.
There is evidence that in the past the atmosphere could have been denser, and the climate could have been warm and humid, and liquid water existed on the surface of Mars and it rained. The proof of this hypothesis is the analysis of the ALH 84001 meteorite, which showed that about 4 billion years ago the temperature of Mars was 18 ± 4 °C.
dust whirlwinds
Dust swirls photographed by the Opportunity rover on May 15, 2005. The numbers in the lower left corner indicate the time in seconds since the first frame
Since the 1970s as part of the Viking program, as well as the Opportunity rover and other vehicles, numerous dust whirlwinds were recorded. These are air turbulences that occur near the surface of the planet and raise a large amount of sand and dust into the air. Vortices are often observed on Earth (in English-speaking countries they are called dust demons - dust devil), but on Mars they can reach much larger sizes: 10 times higher and 50 times wider than the earth. In March 2005, a vortex cleared the solar panels off the Spirit rover.
Surface
Two-thirds of the surface of Mars is occupied by light areas, called the continents, about a third - by dark areas, called seas. The seas are concentrated mainly in the southern hemisphere of the planet, between 10 and 40 ° latitude. There are only two large seas in the northern hemisphere - the Acidalian and the Great Syrt.
The nature of the dark areas is still a matter of controversy. They persist despite the fact that dust storms rage on Mars. At one time, this served as an argument in favor of the assumption that the dark areas are covered with vegetation. Now it is believed that these are just areas from which, due to their relief, dust is easily blown out. Large-scale images show that in fact, the dark areas consist of groups of dark bands and spots associated with craters, hills and other obstacles in the path of the winds. Seasonal and long-term changes in their size and shape are apparently associated with a change in the ratio of surface areas covered with light and dark matter.
The hemispheres of Mars are quite different in the nature of the surface. In the southern hemisphere, the surface is 1-2 km above the mean level and is densely dotted with craters. This part of Mars resembles the lunar continents. In the north, most of the surface is below average, there are few craters, and the main part is occupied by relatively smooth plains, probably formed as a result of lava flooding and erosion. This difference between the hemispheres remains a matter of debate. The boundary between the hemispheres follows roughly a great circle inclined 30° to the equator. The boundary is wide and irregular and forms a slope towards the north. Along it there are the most eroded areas of the Martian surface.
Two alternative hypotheses have been put forward to explain the asymmetry of the hemispheres. According to one of them, at an early geological stage, the lithospheric plates "came together" (perhaps by accident) into one hemisphere, like the Pangea continent on Earth, and then "frozen" in this position. Another hypothesis involves the collision of Mars with a space body the size of Pluto.
Topographic map of Mars, from Mars Global Surveyor, 1999
A large number of craters in the southern hemisphere suggests that the surface here is ancient - 3-4 billion years. There are several types of craters: large craters with a flat bottom, smaller and younger cup-shaped craters similar to the moon, craters surrounded by a rampart, and elevated craters. The latter two types are unique to Mars - rimmed craters formed where liquid ejecta flowed over the surface, and elevated craters formed where a crater ejecta blanket protected the surface from wind erosion. The largest feature of impact origin is the Hellas Plain (about 2100 km across).
In a region of chaotic landscape near the hemispheric boundary, the surface experienced large areas of fracture and compression, sometimes followed by erosion (due to landslides or catastrophic release of groundwater) and flooding with liquid lava. Chaotic landscapes are often found at the head of large channels cut by water. The most acceptable hypothesis for their joint formation is the sudden melting of subsurface ice.
Mariner Valleys on Mars
In the northern hemisphere, in addition to vast volcanic plains, there are two areas of large volcanoes - Tharsis and Elysium. Tharsis is a vast volcanic plain with a length of 2000 km, reaching a height of 10 km above the average level. There are three large shield volcanoes on it - Mount Arsia, Mount Pavlina and Mount Askriyskaya. On the edge of Tharsis is the highest mountain on Mars and in the solar system, Mount Olympus. Olympus reaches 27 km in height in relation to its base and 25 km in relation to the average level of the surface of Mars, and covers an area of 550 km in diameter, surrounded by cliffs, in places reaching 7 km in height. The volume of Mount Olympus is 10 times the volume of the largest volcano on Earth, Mauna Kea. Several smaller volcanoes are also located here. Elysium - a hill up to six kilometers above the average level, with three volcanoes - the dome of Hecate, Mount Elysius and the dome of Albor.
According to others (Faure and Mensing, 2007), the height of Olympus is 21,287 meters above zero and 18 kilometers above the surrounding area, and the diameter of the base is approximately 600 km. The base covers an area of 282,600 km2. The caldera (depression in the center of the volcano) is 70 km wide and 3 km deep.
The Tharsis Upland is also crossed by many tectonic faults, often very complex and extended. The largest of them - the Mariner valleys - stretches in the latitudinal direction for almost 4000 km (a quarter of the circumference of the planet), reaching a width of 600 and a depth of 7-10 km; this fault is comparable in size to the East African Rift on Earth. On its steep slopes, the largest landslides in the solar system occur. The Mariner Valleys are the largest known canyon in the solar system. The canyon, which was discovered by the Mariner 9 spacecraft in 1971, could cover the entire territory of the United States, from ocean to ocean.
A panorama of Victoria Crater taken by the Opportunity rover. It was filmed over three weeks, between October 16 and November 6, 2006.
Panorama of the surface of Mars in the Husband Hill region, taken by the Spirit rover November 23-28, 2005.
Ice and polar ice caps
North polar cap in summer, photo by Mars Global Surveyor. A long wide fault that cuts through the cap on the left - Northern Fault
The appearance of Mars varies greatly depending on the time of year. First of all, changes in the polar caps are striking. They grow and shrink, creating seasonal phenomena in the atmosphere and on the surface of Mars. The southern polar cap can reach a latitude of 50°, the northern one also 50°. The diameter of the permanent part of the northern polar cap is 1000 km. As the polar cap in one of the hemispheres recedes in spring, details of the planet's surface begin to darken.
The polar caps consist of two components: seasonal - carbon dioxide and secular - water ice. According to the Mars Express satellite, the thickness of the caps can range from 1 m to 3.7 km. The Mars Odyssey spacecraft has discovered active geysers on the south polar cap of Mars. As NASA experts believe, jets of carbon dioxide with spring warming break up to a great height, taking dust and sand with them.
Photographs of Mars showing a dust storm. June - September 2001
The spring melting of the polar caps leads to a sharp increase in atmospheric pressure and the movement of large masses of gas to the opposite hemisphere. The speed of the winds blowing at the same time is 10-40 m/s, sometimes up to 100 m/s. The wind raises a large amount of dust from the surface, which leads to dust storms. Strong dust storms almost completely hide the surface of the planet. Dust storms have a noticeable effect on the temperature distribution in the Martian atmosphere.
In 1784, astronomer W. Herschel drew attention to seasonal changes in the size of the polar caps, by analogy with the melting and freezing of ice in the earth's polar regions. In the 1860s the French astronomer E. Lie observed a wave of darkening around the melting spring polar cap, which was then interpreted by the hypothesis of the spreading of melt water and the growth of vegetation. Spectrometric measurements that were carried out at the beginning of the 20th century. at the Lovell Observatory in Flagstaff, W. Slifer, however, did not show the presence of a line of chlorophyll, the green pigment of terrestrial plants.
From photographs of Mariner-7, it was possible to determine that the polar caps are several meters thick, and the measured temperature of 115 K (-158 ° C) confirmed the possibility that it consists of frozen carbon dioxide - “dry ice”.
The hill, which was called the Mitchell Mountains, located near the south pole of Mars, looks like a white island when the polar cap melts, since glaciers melt later in the mountains, including on Earth.
Data from the Martian Reconnaissance Satellite made it possible to detect a significant layer of ice under the scree at the foot of the mountains. The glacier hundreds of meters thick covers an area of thousands of square kilometers, and its further study can provide information about the history of the Martian climate.
Channels of "rivers" and other features
On Mars, there are many geological formations that resemble water erosion, in particular, dried up river beds. According to one hypothesis, these channels could have formed as a result of short-term catastrophic events and are not proof of the long-term existence of the river system. However, recent evidence suggests that the rivers have flowed for geologically significant periods of time. In particular, inverted channels (that is, channels elevated above the surrounding area) have been found. On Earth, such formations are formed due to the long-term accumulation of dense bottom sediments, followed by drying and weathering of the surrounding rocks. In addition, there is evidence of channel shifting in the river delta as the surface gradually rises.
In the southwestern hemisphere, in the Eberswalde crater, a river delta with an area of about 115 km2 was discovered. The river that washed over the delta was more than 60 km long.
Data from NASA's Spirit and Opportunity rovers also testify to the presence of water in the past (minerals have been found that could only form as a result of prolonged exposure to water). The device "Phoenix" discovered deposits of ice directly in the ground.
In addition, dark stripes have been found on the slopes of hills, indicating the appearance of liquid salt water on the surface in our time. They appear shortly after the onset of the summer period and disappear by winter, “flow around” various obstacles, merge and diverge. "It's hard to imagine that such structures could form not from fluid flows, but from something else," said NASA employee Richard Zurek.
Several unusual deep wells have been found on the Tharsis volcanic upland. Judging by the image of the Martian Reconnaissance Satellite, taken in 2007, one of them has a diameter of 150 meters, and the illuminated part of the wall goes no less than 178 meters deep. A hypothesis about the volcanic origin of these formations has been put forward.
Priming
The elemental composition of the surface layer of the Martian soil, according to the data of the landers, is not the same in different places. The main component of the soil is silica (20-25%), containing an admixture of iron oxide hydrates (up to 15%), which give the soil a reddish color. There are significant impurities of sulfur compounds, calcium, aluminum, magnesium, sodium (a few percent for each).
According to data from NASA's Phoenix probe (landing on Mars on May 25, 2008), the pH ratio and some other parameters of Martian soils are close to Earth's, and plants could theoretically be grown on them. "In fact, we found that the soil on Mars meets the requirements, and also contains the necessary elements for the emergence and maintenance of life both in the past, in the present and in the future," said Sam Kunaves, lead research chemist of the project. Also, according to him, many people can find this alkaline type of soil in “their backyard”, and it is quite suitable for growing asparagus.
There is also a significant amount of water ice in the ground at the landing site of the apparatus. The Mars Odyssey orbiter also discovered that there are deposits of water ice under the surface of the red planet. Later, this assumption was confirmed by other devices, but the question of the presence of water on Mars was finally resolved in 2008, when the Phoenix probe, which landed near the planet's north pole, received water from the Martian soil.
Geology and internal structure
In the past, on Mars, as on Earth, there was a movement of lithospheric plates. This is confirmed by the features of the magnetic field of Mars, the locations of some volcanoes, for example, in the province of Tharsis, as well as the shape of the Mariner Valley. The current state of affairs, when volcanoes can exist for a much longer time than on Earth and reach gigantic sizes, suggests that now this movement is rather absent. This is supported by the fact that shield volcanoes grow as a result of repeated eruptions from the same vent over a long period of time. On Earth, due to the movement of lithospheric plates, volcanic points constantly changed their position, which limited the growth of shield volcanoes, and possibly did not allow them to reach heights, as on Mars. On the other hand, the difference in the maximum height of volcanoes can be explained by the fact that, due to the lower gravity on Mars, it is possible to build higher structures that would not collapse under their own weight.
Comparison of the structure of Mars and other terrestrial planets
Modern models of the internal structure of Mars suggest that Mars consists of a crust with an average thickness of 50 km (and a maximum thickness of up to 130 km), a silicate mantle 1800 km thick, and a core with a radius of 1480 km. The density in the center of the planet should reach 8.5 g/cm2. The core is partially liquid and consists mainly of iron with an admixture of 14-17% (by mass) of sulfur, and the content of light elements is twice as high as in the core of the Earth. According to modern estimates, the formation of the core coincided with the period of early volcanism and lasted about a billion years. The partial melting of mantle silicates took approximately the same time. Due to the lower gravity on Mars, the pressure range in the mantle of Mars is much smaller than on Earth, which means that it has fewer phase transitions. It is assumed that the phase transition of olivine to spinel modification begins at fairly large depths - 800 km (400 km on Earth). The nature of the relief and other features suggest the presence of an asthenosphere consisting of zones of partially molten matter. For some regions of Mars, a detailed geological map has been compiled.
According to observations from orbit and analysis of the collection of Martian meteorites, the surface of Mars consists mainly of basalt. There is some evidence to suggest that, on part of the Martian surface, the material is more quartz-bearing than normal basalt and may be similar to andesitic rocks on Earth. However, these same observations can be interpreted in favor of the presence of quartz glass. A significant part of the deeper layer consists of granular iron oxide dust.
Mars magnetic field
Mars has a weak magnetic field.
According to the readings of the magnetometers of the Mars-2 and Mars-3 stations, the magnetic field strength at the equator is about 60 gammas, at the pole 120 gammas, which is 500 times weaker than the earth's. According to AMS Mars-5, the magnetic field strength at the equator was 64 gamma, and the magnetic moment was 2.4 1022 oersted cm2.
The magnetic field of Mars is extremely unstable, at different points on the planet its strength can differ from 1.5 to 2 times, and the magnetic poles do not coincide with the physical ones. This suggests that the iron core of Mars is relatively immobile in relation to its crust, that is, the planetary dynamo mechanism responsible for the Earth's magnetic field does not work on Mars. Although Mars does not have a stable planetary magnetic field, observations have shown that parts of the planet's crust are magnetized and that there has been a reversal of the magnetic poles of these parts in the past. The magnetization of these parts turned out to be similar to strip magnetic anomalies in the oceans.
One theory published in 1999 and retested in 2005 (using the unmanned Mars Global Surveyor) suggests that these bands show plate tectonics 4 billion years ago before the planet's dynamo ceased to function, causing a sharp weakening magnetic field. The reasons for this sharp decline are unclear. There is an assumption that the functioning of the dynamo 4 billion. years ago is explained by the presence of an asteroid that rotated at a distance of 50-75 thousand kilometers around Mars and caused instability in its core. The asteroid then dropped to its Roche limit and collapsed. However, this explanation itself contains ambiguities, and is disputed in the scientific community.
Geological history
Global mosaic of 102 Viking 1 orbiter images from February 22, 1980.
Perhaps, in the distant past, as a result of a collision with a large celestial body, the rotation of the core stopped, as well as the loss of the main volume of the atmosphere. It is believed that the loss of the magnetic field occurred about 4 billion years ago. Due to the weakness of the magnetic field, the solar wind penetrates the atmosphere of Mars almost unhindered, and many of the photochemical reactions under the influence of solar radiation that occur on Earth in the ionosphere and above can be observed on Mars almost at its very surface.
The geological history of Mars includes the following three epochs:
Noachian Epoch (named after "Noachian Land", a region of Mars): formation of the oldest extant surface of Mars. It continued in the period 4.5 billion - 3.5 billion years ago. During this epoch, the surface was scarred by numerous impact craters. The plateau of the province of Tharsis was probably formed during this period with intense water flow later.
Hesperian era: from 3.5 billion years ago to 2.9 - 3.3 billion years ago. This era is marked by the formation of huge lava fields.
Amazonian era (named after the "Amazonian plain" on Mars): 2.9-3.3 billion years ago to the present day. The regions formed during this epoch have very few meteorite craters, but otherwise they are completely different. Mount Olympus was formed during this period. At this time, lava flows were pouring in other parts of Mars.
Moons of Mars
The natural satellites of Mars are Phobos and Deimos. Both were discovered by the American astronomer Asaph Hall in 1877. Phobos and Deimos are irregularly shaped and very small. According to one hypothesis, they may represent asteroids like (5261) Eureka from the Trojan group of asteroids captured by the gravitational field of Mars. The satellites are named after the characters accompanying the god Ares (that is, Mars) - Phobos and Deimos, personifying fear and horror, who helped the god of war in battles.
Both satellites rotate around their axes with the same period as around Mars, therefore they are always turned to the planet by the same side. The tidal influence of Mars gradually slows down the movement of Phobos, and eventually will lead to the fall of the satellite to Mars (while maintaining the current trend), or to its disintegration. On the contrary, Deimos is moving away from Mars.
Both satellites have a shape approaching a triaxial ellipsoid, Phobos (26.6x22.2x18.6 km) is somewhat larger than Deimos (15x12.2x10.4 km). The surface of Deimos looks much smoother due to the fact that most of the craters are covered with fine-grained matter. Obviously, on Phobos, which is closer to the planet and more massive, the substance ejected during meteorite impacts either hit the surface again or fell on Mars, while on Deimos it remained in orbit around the satellite for a long time, gradually settling and hiding uneven terrain.
Life on Mars
The popular idea that Mars was inhabited by intelligent Martians became widespread in the late 19th century.
Schiaparelli's observations of the so-called canals, combined with Percival Lowell's book on the same subject, popularized the idea of a planet that was getting drier, colder, dying, and had an ancient civilization doing irrigation work.
Numerous other sightings and announcements by famous people gave rise to the so-called "Mars Fever" around this topic. In 1899, while studying atmospheric interference in a radio signal using receivers at the Colorado Observatory, inventor Nikola Tesla observed a repeating signal. He then speculated that it might be a radio signal from other planets such as Mars. In a 1901 interview, Tesla said that the idea came to him that interference could be caused artificially. Although he could not decipher their meaning, it was impossible for him that they arose completely by chance. In his opinion, it was a greeting from one planet to another.
Tesla's theory was strongly supported by the famous British physicist William Thomson (Lord Kelvin), who, visiting the United States in 1902, said that in his opinion Tesla had picked up the Martian signal sent to the United States. However, Kelvin then vehemently denied this statement before he left America: "In fact, I said that the inhabitants of Mars, if they exist, can certainly see New York, in particular the light from electricity."
Today, the presence of liquid water on its surface is considered a condition for the development and maintenance of life on the planet. There is also a requirement that the planet's orbit be in the so-called habitable zone, which for the solar system begins behind Venus and ends with the semi-major axis of the orbit of Mars. During perihelion, Mars is within this zone, but a thin atmosphere with low pressure prevents the appearance of liquid water over a large area for a long period. Recent evidence suggests that any water on the surface of Mars is too salty and acidic to support permanent terrestrial life.
The lack of a magnetosphere and the extremely thin atmosphere of Mars are also a problem for sustaining life. There is a very weak movement of heat flows on the surface of the planet, it is poorly isolated from bombardment by solar wind particles, in addition, when heated, water instantly evaporates, bypassing the liquid state due to low pressure. Mars is also on the threshold of the so-called. "geological death". The end of volcanic activity apparently stopped the circulation of minerals and chemical elements between the surface and the interior of the planet.
Evidence suggests that the planet was previously much more prone to life than it is now. However, to date, the remains of organisms have not been found on it. Under the Viking program, carried out in the mid-1970s, a series of experiments were conducted to detect microorganisms in the Martian soil. It has shown positive results, such as a temporary increase in CO2 release when soil particles are placed in water and nutrient media. However, then this evidence of life on Mars was disputed by some scientists [by whom?]. This led to their lengthy dispute with NASA scientist Gilbert Lewin, who claimed that the Viking had discovered life. After re-evaluating the Viking data in the light of current scientific knowledge about extremophiles, it was determined that the experiments carried out were not perfect enough to detect these life forms. Moreover, these tests could even kill the organisms, even if they were contained in the samples. Tests conducted by the Phoenix Program have shown that the soil has a very alkaline pH and contains magnesium, sodium, potassium and chloride. The nutrients in the soil are sufficient to support life, but life forms must be protected from intense ultraviolet light.
Interestingly, in some meteorites of Martian origin, formations were found that resemble the simplest bacteria in shape, although they are inferior to the smallest terrestrial organisms in size. One of these meteorites is ALH 84001, found in Antarctica in 1984.
According to the results of observations from the Earth and data from the Mars Express spacecraft, methane was detected in the atmosphere of Mars. Under the conditions of Mars, this gas decomposes rather quickly, so there must be a constant source of replenishment. Such a source can be either geological activity (but no active volcanoes have been found on Mars), or the vital activity of bacteria.
Astronomical observations from the surface of Mars
After the landings of automatic vehicles on the surface of Mars, it became possible to conduct astronomical observations directly from the surface of the planet. Due to the astronomical position of Mars in the solar system, the characteristics of the atmosphere, the period of revolution of Mars and its satellites, the picture of the night sky of Mars (and astronomical phenomena observed from the planet) differs from the earth's and in many ways seems unusual and interesting.
Sky color on Mars
During sunrise and sunset, the Martian sky at the zenith has a reddish-pink color, and in close proximity to the disk of the Sun - from blue to purple, which is completely opposite to the picture of earthly dawns.
At noon, the sky of Mars is yellow-orange. The reason for such differences from the color scheme of the earth's sky is the properties of the thin, rarefied atmosphere of Mars containing suspended dust. On Mars, Rayleigh scattering of rays (which on Earth is the cause of the blue color of the sky) plays an insignificant role, its effect is weak. Presumably, the yellow-orange coloration of the sky is also caused by the presence of 1% magnetite in dust particles constantly suspended in the Martian atmosphere and raised by seasonal dust storms. Twilight begins long before sunrise and lasts long after sunset. Sometimes the color of the Martian sky takes on a purple hue as a result of light scattering on microparticles of water ice in clouds (the latter is a rather rare phenomenon).
sun and planets
The angular size of the Sun, observed from Mars, is less than that visible from the Earth and is 2/3 of the latter. Mercury from Mars will be practically inaccessible to observation with the naked eye due to its extreme proximity to the Sun. The brightest planet in the sky of Mars is Venus, in second place is Jupiter (its four largest satellites can be observed without a telescope), in third is Earth.
Earth is an inner planet to Mars, just like Venus is to Earth. Accordingly, from Mars, the Earth is observed as a morning or evening star, rising before dawn or visible in the evening sky after sunset.
The maximum elongation of the Earth in the sky of Mars will be 38 degrees. To the naked eye, the Earth will be visible as a bright (maximum visible stellar magnitude of about -2.5) greenish star, next to which the yellowish and dimmer (about 0.9) star of the Moon will be easily distinguishable. In a telescope, both objects will show the same phases. The revolution of the Moon around the Earth will be observed from Mars as follows: at the maximum angular distance of the Moon from the Earth, the naked eye will easily separate the Moon and the Earth: in a week the “stars” of the Moon and the Earth will merge into a single star inseparable by the eye, in another week the Moon will again be visible at maximum distance, but on the other side of the Earth. Periodically, an observer on Mars will be able to see the passage (transit) of the Moon across the Earth's disk or, conversely, the covering of the Moon by the Earth's disk. The maximum apparent distance of the Moon from the Earth (and their apparent brightness) when viewed from Mars will vary significantly depending on the relative position of the Earth and Mars, and, accordingly, the distance between the planets. During the epoch of oppositions, it will be about 17 minutes of arc, at the maximum distance of Earth and Mars - 3.5 minutes of arc. Earth, like other planets, will be observed in the constellation band of the Zodiac. An astronomer on Mars will also be able to observe the passage of the Earth across the disk of the Sun, the next one will occur on November 10, 2084.
Moons - Phobos and Deimos
Passage of Phobos across the disk of the Sun. Pictures of Opportunity
Phobos, when observed from the surface of Mars, has an apparent diameter of about 1/3 of the disk of the Moon in the earth's sky and an apparent magnitude of about -9 (approximately like the Moon in the phase of the first quarter). Phobos rises in the west and sets in the east, only to rise again 11 hours later, thus crossing the sky of Mars twice a day. The movement of this fast moon across the sky will be easily seen during the night, as will the changing phases. The naked eye can distinguish the largest feature of the relief of Phobos - the crater Stickney. Deimos rises in the east and sets in the west, looks like a bright star without a noticeable visible disk, about magnitude -5 (slightly brighter than Venus in the earth's sky), slowly crossing the sky for 2.7 Martian days. Both satellites can be observed in the night sky at the same time, in which case Phobos will move towards Deimos.
The brightness of both Phobos and Deimos is sufficient for objects on the surface of Mars to cast sharp shadows at night. Both satellites have a relatively small inclination of the orbit to the equator of Mars, which excludes their observation in the high northern and southern latitudes of the planet: for example, Phobos never rises above the horizon north of 70.4 ° N. sh. or south of 70.4°S sh.; for Deimos these values are 82.7°N. sh. and 82.7°S sh. On Mars, an eclipse of Phobos and Deimos can be observed when they enter the shadow of Mars, as well as an eclipse of the Sun, which is only annular due to the small angular size of Phobos compared to the solar disk.
Celestial sphere
The north pole on Mars, due to the tilt of the planet's axis, is in the constellation Cygnus (equatorial coordinates: right ascension 21h 10m 42s, declination +52 ° 53.0? and is not marked by a bright star: the closest to the pole is a dim star of the sixth magnitude BD +52 2880 (other its designations are HR 8106, HD 201834, SAO 33185. The south celestial pole (coordinates 9h 10m 42s and -52° 53.0) is a couple of degrees from the star Kappa Parusov (apparent magnitude 2.5) - it, in principle , can be considered the South Pole Star of Mars.
The zodiac constellations of the Martian ecliptic are similar to those observed from Earth, with one difference: when observing the annual movement of the Sun among the constellations, it (like other planets, including the Earth), leaving the eastern part of the constellation Pisces, will pass for 6 days through the northern part of the constellation Cetus before how to re-enter the western part of Pisces.
History of the study of Mars
The exploration of Mars began a long time ago, even 3.5 thousand years ago, in ancient Egypt. The first detailed accounts of the position of Mars were made by Babylonian astronomers, who developed a number of mathematical methods to predict the position of the planet. Using the data of the Egyptians and Babylonians, ancient Greek (Hellenistic) philosophers and astronomers developed a detailed geocentric model to explain the movement of the planets. A few centuries later, Indian and Islamic astronomers estimated the size of Mars and its distance from Earth. In the 16th century, Nicolaus Copernicus proposed a heliocentric model to describe the solar system with circular planetary orbits. His results were revised by Johannes Kepler, who introduced a more accurate elliptical orbit for Mars, coinciding with the observed one.
In 1659, Francesco Fontana, looking at Mars through a telescope, made the first drawing of the planet. He depicted a black spot in the center of a clearly defined sphere.
In 1660, two polar caps were added to the black spot, added by Jean Dominique Cassini.
In 1888, Giovanni Schiaparelli, who studied in Russia, gave the first names to individual surface details: the seas of Aphrodite, Eritrean, Adriatic, Cimmerian; lakes of the Sun, Lunar and Phoenix.
The heyday of telescopic observations of Mars came at the end of the 19th - the middle of the 20th century. It is largely due to public interest and well-known scientific disputes around the observed Martian channels. Among the astronomers of the pre-space era who made telescopic observations of Mars during this period, the most famous are Schiaparelli, Percival Lovell, Slifer, Antoniadi, Barnard, Jarry-Deloge, L. Eddy, Tikhov, Vaucouleurs. It was they who laid the foundations of areography and compiled the first detailed maps of the surface of Mars - although they turned out to be almost completely incorrect after flights of automatic probes to Mars.
Mars colonization
Estimated view of Mars after terraforming
Relatively close to terrestrial natural conditions make this task somewhat easier. In particular, there are places on Earth where natural conditions are similar to those on Mars. Extremely low temperatures in the Arctic and Antarctica are comparable to even the lowest temperatures on Mars, and the equator of Mars during the summer months is as warm (+20 °C) as on Earth. Also on Earth there are deserts similar in appearance to the Martian landscape.
But there are significant differences between Earth and Mars. In particular, the magnetic field of Mars is weaker than the earth's by about 800 times. Together with a rarefied (hundreds of times in comparison with the Earth) atmosphere, this increases the amount of ionizing radiation reaching its surface. Measurements carried out by the American unmanned vehicle The Mars Odyssey showed that the radiation background in the orbit of Mars is 2.2 times higher than the radiation background at the International Space Station. The average dose was approximately 220 millirads per day (2.2 milligrays per day or 0.8 grays per year). The amount of radiation received as a result of staying in such a background for three years is approaching the established safety limits for astronauts. On the surface of Mars, the radiation background is somewhat lower and the dose is 0.2-0.3 Gy per year, varying significantly depending on the terrain, altitude and local magnetic fields.
The chemical composition of the minerals common on Mars is more diverse than that of other celestial bodies near the Earth. According to the 4Frontiers corporation, they are enough to supply not only Mars itself, but also the Moon, the Earth and the asteroid belt.
The flight time from Earth to Mars (with current technologies) is 259 days in a semi-ellipse and 70 days in a parabola. To communicate with potential colonies, radio communication can be used, which has a delay of 3-4 minutes in each direction during the closest approach of the planets (which repeats every 780 days) and about 20 minutes. at the maximum distance of the planets; see Configuration (astronomy).
To date, no practical steps have been taken for the colonization of Mars, however, colonization is being developed, for example, the Centenary Spacecraft project, the development of a habitation module for staying on the Deep Space Habitat planet.
» Features of Mars
Mars is the fourth planet from the Sun in the solar system. Sometimes Mars is also called the red planet because of the characteristic reddish-brown coating that covers the entire celestial body.
The radius of Mars is approximately half the radius of the Earth, and in terms of mass it is about ten times inferior to our planet.
When iron comes into contact with air, a reddish-brown rust coating forms on it. And since the surface of Mars contains a large amount of such dust, the planet itself looks red. What's more, due to rusty dust, Mars' atmosphere also has a slight pink-red tint. According to scientists, this dust appeared as a result of volcanic eruptions.
A Martian year is the period it takes for Mars to revolve around the sun. It lasts a little more than two Earth years and is 687 Earth days.
The climate on Mars is colder than on Earth. This is due to the fact that the Red Planet is further from the Sun. The average winter temperature is -70 °C, and sometimes the thermometer can drop to -125 °C. In summer the temperature rises to +20 °С. The atmosphere on Mars is 80% carbon dioxide and is very thin.
Moreover, a rarefied atmosphere cannot perform a protective function and retain heat, as the Earth's atmosphere does. Therefore, large temperature differences are observed on Mars in winter and summer.
Atmospheric pressure on the planet's surface is about 150 times less than the earth's.
Mars has the strongest dust storms of any planet in the solar system. They last for months throughout the planet. A very unstable and extremely weak magnetic field has been recorded on Mars. This indicates the absence of a liquid metal core, as, for example, the Earth.
The relief of the planet
On the surface of Mars there are both high-mountainous and flat areas. At the same time, mountains and hills are located in the southern part of the planet, and plains are in the northern part. Scientists still cannot explain this feature of the planet's relief.
Mount Olympus is located near the equator of Mars. It is known that the diameter of its base is 600 km, and the height is approximately 22 km. Olympus is considered the highest mountain not only on Mars, but also on all the planets of the solar system. It is so big that astronomers could see it through a telescope already in the 19th century!
Another mystery of Mars has worried scientists for quite some time. These are the so-called Martian channels, which were noticed by one of the astronomers at the end of the 19th century. Upon closer examination, it turned out that this is actually an optical illusion. Thousands of years ago, the climate on Mars was much different from the modern one: it is known that rivers flowed on the surface of this planet. Then they dried up, and in the pictures taken from space, the dried up riverbeds are still visible.
The structure of the planet
In terms of internal structure, Mars is not much different from other terrestrial planets. The surface of the Red Planet is covered with crust, the thickness of which ranges from 50 to 125 km. Under the crust is a silicate mantle, inside it is a partially liquid core.
Moons of Mars
In the middle of the XIX century. Astronomers have discovered that Mars has two moons. The celestial bodies of an irregular oblong shape were named Phobos and Deimos, which in ancient Greek means “fear” and “horror”. However, the sizes of the satellites do not at all correspond to their names. Both satellites are quite small: Phobos is no more than 30 km across, and Deimos is even smaller.
Mars belongs to the terrestrial planets (4th in terms of distance from the Sun). The atmosphere is rarefied, and the relief is a complex of impact craters, volcanic mountains, deserts, valleys, and polar ice caps. The main color of the planet is red-orange due to iron oxide, which is why it is called the red planet. Other colors also come across: golden, brown, greenish-brown. Such a variety of shades is given by the minerals present in the soil.
The density of the soil cover is lower than on Earth. It is equal to 3.933 g / cm³, and for the Earth this indicator corresponds to 5.518 g / cm³. The size of Mars relative to the Earth is not in favor of the first. The red planet is about half the diameter of Earth, with a surface area slightly smaller than Earth's land area. In numbers it looks like this:
Equatorial radius: 3396.2 km (0.52 Earth);
Polar radius: 3376.2 km (0.51 Earth);
Average radius: 3389.5 km (0.53 Earth);
Surface area: 144,371,391 sq. km (0.25 Earth).
For comparison, the land area of the blue planet Earth is 148,939,063 square meters. km. This is only 29.2% of the total area of the Earth. Everything else is occupied by the seas and oceans.
You should also know that the volume of Mars is 15% of the volume of the blue planet, and its mass reaches 11% of the earth. Accordingly, gravity is only 38% of the earth's. In numbers, the mass of the red planet is: 6.423 × 10 23 kg, against the earth's 5.974 × 10 24 kg.
The relief of Mars has many unique features. On the red planet is the highest mountain in the solar system - Mount Olympus (27 km in height). As well as the largest canyon Mariner. This is no longer on any planet in the solar system. However, on Pluto's moon Charone, the canyon is large.
The southern and right hemispheres are fundamentally different in their relief. There is a hypothesis that almost the entire northern hemisphere is an impact crater. In terms of area, it occupies almost 40% of the planet's surface, and if this is really a crater, then it is the largest in the solar system.
This hypothetical crater is called the North Pole Basin. Some experts believe that it was formed 4 billion years ago from the impact of a cosmic body with a diameter of 1900 km and a mass of 2% of the mass of Mars. But at present, this basin is not recognized as an impact crater.
The outer dimensions of Mars are not very impressive. The red planet noticeably loses to the Earth in all respects. In addition, it has a weak magnetic field, which is directly related to the bowels of the cosmic body. The semi-liquid core has a radius of about 1800 km. It consists of iron, nickel and 17% sulfur. It contains 2 times more light elements than the Earth. The mantle is located around the core. Volcanic and tectonic processes depend on it, but at present it is inactive.
The bowels of the red planet are "packed" in the Martian crust. It is dominated by such elements as iron, potassium, magnesium, calcium, aluminum. The average thickness of the crust is 50 km, and the maximum is 125 km. The thickness of the earth's crust is on average 40 km, so that according to this indicator, Mars outperforms the blue planet. But in general, it is a small cosmic body, which is the second most important neighbor of the Earth after the Moon.
Vladislav Ivanov
RED PLANET MARS
Mars is the first planet in the solar system after the Earth, to which for some time people began to show special interest, caused by the hope that there is developed extraterrestrial life.
The planet is named Mars in honor of the ancient Roman god of war (the same as Ares in ancient Greek mythology) forits blood-red color, due to the presence of iron oxide in the soil of Mars.
Main characteristics
Mars is the fourth largest planet from the Sun and the seventh largest planet in the solar system.It can be seen from Earth with the naked eye. It is second in brightness only to Venus, the Moon and the Sun.
Mars is almost half the size of Earth - its equatorial radius is3,396.9 kilometers (53.2% of the earth). The surface area of Mars is roughly equal to the land area of Earth.
The average distance from Mars to the Sun is 228 million kilometers, the period of revolution around the Sun is 687 Earth days.
The minimum distance from Mars to Earth is 55.75 million kilometers, the maximum is about 401 million kilometers.
Mars is closest to Earth during opposition, when the planet is in the opposite direction from the Sun.The distances between the Earth and Mars at the moments of confrontation vary from 55 to 102 million kilometers. A great opposition is called when the distance between two planets becomes less than 60 million kilometers. The great opposition of Earth and Mars is repeated every 15-17 years (the last was in August 2003).And the usual ones - every 26 months at different points in the orbit of Mars and the Earth.
Mars has a rotation period and seasons similar to Earth's, but its climate is much colder and drier than Earth's.
The planet's rotation period is 24 hours 37 minutes 22.7 seconds.
On Mars, as on Earth, there are two poles, North and South. Mars rotates fast enough that it has a slightly flattened shape at both poles. At the same time, the polar radius of the planet is about 21 kilometers less than the equatorial one.
The Martian year consists of 668.6 Martian solar days, called sols.
The mass of the planet Mars is 6.418 × 1023 kilograms (11% of the mass of the Earth).
Mars has two natural satellites, Phobos and Deimos, and three artificial satellites.
As of February 2009, there are three operational spacecraft orbiting Mars: Mars Odyssey, Mars Express, and Mars Reconnaissance Orbiter, more than any other planet except Earth.
There are several inactive landers and rovers on the surface of Mars that have completed their missions.
Climate of Mars
The climate on Mars, like on Earth, is seasonal. The change of seasons on Mars occurs in much the same way as on Earth, but the climate there is colder and drier than ours. In the cold season, even outside the polar caps, light frost can form on the surface. A picture of frost was once taken by the Viking 2 aircraft..
Mars rover "Phoenix" at some point succeededto fix falling snow on Mars during"Martian winter". Snowfall on Mars was recorded using a laser, which is equipped with a rover. The rover managed to fix the snow with the help of a special laser with which it was equipped. Snow fell from a height of about 4000 meters, but it did not reach the surface of the planet, dissolving in the air.
The change of seasons on Mars is provided bytilt of its axis of rotation. In this case, the elongation of the orbit leads to large differences in the duration of the seasons. Unlike earthly ones, which have the same duration of 3 months. Mars has northern spring and summer, which fall on the part of the orbit that is farthest from the Sun. These seasons together last 371 sols, that is, noticeably more than half of the Martian year. Therefore, on Mars, northern summers are long and cool, while southern summers are short and hot.
Mars is characterized by a sharp temperature drop. Temperatures at the planet's equator range from +30°C at noon to -80°C at midnight. Near the poles, the temperature sometimes drops to −143°C, at which temperature carbon dioxide condenses. Mars is a very cold world, but the climate there is not much harsher than in Antarctica.
There is currently no liquid water on Mars. However, most likely, the white polar caps, discovered in 1704, consist of water ice mixed with solid carbon dioxide. In winter, they extend a third (the south polar cap - half) of the distance to the equator. In the spring, this ice partially melts, and a wave of darkening spreads from the poles to the equator, which was previously mistaken for Martian plants.
The appearance of Mars varies greatly depending on the time of year. First of all, changes in the polar caps are striking. They grow and shrink, creating seasonal phenomena in the atmosphere and on the surface of Mars.The polar caps consist of two components: seasonal - carbon dioxide and secular - water ice. The thickness of the caps can range from 1 meter to 3.7 kilometers.
Previously, many researchers seriously believed that there is still water in a liquid state on the surface of Mars. This opinion was based on observations of periodic changes in light and dark areas, especially in polar latitudes, which were similar to continents and seas.
Dark grooves on the surface of Mars have been explained by some observers as channels for liquid water.
Later it was proved that these furrows did not actually exist, but were just an optical illusion.
Research conducted by the Mariner 4 spacecraft in 1965 showed that there is currently no liquid water on Mars.
Due to the low pressure, water cannot exist in a liquid state on the surface of Mars. With such a small pressure that is currently acting on the planet, it boils at very low temperatures, but it is likely that conditions were different in the past, and therefore the presence of primitive life on the planet cannot be ruled out.
On July 31, 2008, water in the state of ice was discovered on Mars at the landing site of NASA's Phoenix spacecraft. The device found ice deposits directly in the ground.
Data from NASA's Spirit and Opportunity rovers also provide evidence for the presence of water in the past (minerals found that could only form as a result of prolonged exposure to water).
The glacier hundreds of meters thick covers an area of thousands of square kilometers, and its further study can provide information about the history of the Martian climate.
According to modern concepts, the total volume of ice enclosed in the polar cap of the northern hemisphere is approximately 1.5 million kilometers, therefore, in the melted form, this ice could not form a giant ocean, which, according to many researchers, once covered almost the entire northern hemisphere. hemisphere of Mars. Thus, it remains a mystery where the water that once abounded on the now arid planet has gone.
Presumablyin the past, the climate of Mars may have been warmer and wetter, and liquid water was present on the surface, and it even rained.
Magnetic field and atmosphere of Mars
Mars has a magnetic field, but it is weak and extremely unstable. In different parts of the planet, it can differ from 1.5 to 2 times. At the same time, the magnetic poles of the planet do not coincide with the physical ones. This suggests that the iron core of Mars is more or less motionless relative to its crust, that is, the mechanism responsible for the Earth's magnetic field does not work on Mars.
Modern models of the internal structure of Mars suggest that Mars consists of a crust with an average thickness of 50 kilometers (and a maximum thickness of up to 130 kilometers), a silicate mantle (mantle enriched in iron) with a thickness of 1800 kilometers and a core with a radius of 1480 kilometers.
According to calculations, the core of Mars has a mass of up to 9% of the mass of the planet. It consists of iron and its alloys, while the core is in a liquid state.
Perhaps, in the distant past, as a result of a collision with a large celestial body, the rotation of the core stopped, as well as the loss of the main volume of the atmosphere.It is believed that the loss of the magnetic field occurred about 4 billion years ago.
Because the magnetic field of Mars is so weak, the solar wind freely penetrates its atmosphere. Because of this, many reactions under the influence of solar radiation on Mars occur almost at its very surface.On Earth, a strong magnetic field does not transmit solar radiation, so all these reactions occur in the ionosphere and above.
The Martian ionosphere extends over the surface of the planet from 110 to 130 kilometers.
The atmosphere of Mars is 95% carbon dioxide. The atmosphere also contains 2.5-2.7% nitrogen, 1.5-2% argon, 0.13% oxygen, 0.1% water vapor, 0.07% carbon monoxide.
In addition, the atmosphere of Mars is very rarefied. The pressure at the surface of Mars is 160 times less than the Earth's at the average surface level. Due to the large elevation difference on Mars, the surface pressure varies greatly.
Unlike Earth, the mass of the Martian atmosphere varies greatly during the year due to the melting and freezing of the polar caps containing carbon dioxide.
There is evidence that the atmosphere may have been denser in the past.
Topography of Mars
Studies have shown that two-thirds of the surface of Mars is occupied by light areas, called continents, and the remaining third is dark areas, called seas. The nature of the dark areas is still a matter of controversy.But in fact, no water has been found in the Martian seas.
The seas are concentrated mainly in the southern hemisphere of the planet. There are only two large seas in the northern hemisphere - the Acidalian and the Great Syrt.
Large-scale images show that the dark areas are actually made up of groups of dark streaks and patches associated with craters, hills, and other obstructions in the path of the winds. Seasonal and long-term changes in their size and shape are apparently associated with a change in the ratio of surface areas covered with light and dark matter.
The hemispheres of Mars are quite different in the nature of the surface. The surface of Mars has a reddish color due to large impurities of iron oxides.
Everywhere on the surface of Mars lie boulders - pieces of volcanic rocks that have broken off during marsquakes or meteorite falls.
From time to time come across craters - the remains of meteorite impacts.
In some places, the surface is covered with multi-layered rocks, similar to terrestrial sedimentary rocks left after the retreat of the sea.
In the southern hemisphere, the surface is 1-2 kilometers above the mean level and is densely dotted with craters. This part of Mars resembles the lunar continents.
A large number of craters in the southern hemisphere may indicate that the surface here is ancient - 3-4 billion years.
The rovers exploring the planet left their marks on the untouched surface.
In the north, the surface is mostly below average, with few craters and mostly relatively smooth plains, probably formed by lava flooding and soil erosion.
In the northern hemisphere there are two areas of large volcanoes - Tarsis and Elysium.
Tharsis is a vast volcanic plain 2000 kilometers long, reaching a height of 10 kilometers above the average level. It has three large volcanoes.
On the edge of Tarsis is the highest mountain on Mars and on the planets in the solar system - the Martian extinct volcano Olympus.
Olympus reaches 27 kilometers in height and 550 kilometers in diameter. The cliffs that surround the volcano, in some places reach a height of 7 kilometers.
Currently, all Martian volcanoes are not active. Traces of volcanic ash found on the slopes of other mountains suggest that Mars was once volcanically active.
A typical landscape of Mars is the Martian desert.
Sand dunes, giant canyons and fissures, as well as meteorite craters have been photographed on Mars. The most grandiose canyon system - the Mariner Valley - stretches for almost 4,500 kilometers (a quarter of the planet's circumference), reaching a width of 600 kilometers in width and 7-10 kilometers in depth.
Soil of Mars
The composition of the surface layer of the Martian soil, according to the data of the landers, is different in different places.
The soil mainly consists of silica (20-25%), containing an admixture of iron oxide hydrates (up to 15%), giving the soil a reddish color. The soil contains significant impurities of sulfur, calcium, aluminum, magnesium, and sodium compounds. The ratio of acidity and some other parameters of Martian soils are close to those of the Earth, and it would theoretically be possible to grow plants on them.
From reports by lead research chemist Sam Kunaves:
“In fact, we found that the soil on Mars meets the requirements, and also contains the necessary elements for the emergence and maintenance of life, both in the past and in the present, and in the future ... .. Such soil is quite suitable for growing various plants, such as asparagus. There is nothing here to make life impossible. On the contrary, with each new study, we find additional evidence in favor of the possibility of its existence.”
Interesting phenomena on Mars
The Mars Odyssey spacecraft has detected active geysers at the south polar cap of Mars. Jets of carbon dioxide with spring warming break up to a great height, carrying dust and sand with them. The spring melting of the polar caps leads to a sharp increase in atmospheric pressure and the movement of large masses of gas to the opposite hemisphere.
The speed of the winds blowing at the same time is 10-40 m/s, sometimes up to 100 m/s. The wind raises a large amount of dust from the surface, which leads to dust storms. Strong dust storms almost completely hide the surface of the planet. Dust storms have a noticeable effect on the temperature distribution in the Martian atmosphere.
After the landings of automatic vehicles on the surface of Mars, it became possible to conduct astronomical observations directly from the surface of the planet.
The picture of the night sky of Mars (and astronomical phenomena observed from the planet) differs from the earth's and in many ways seems unusual and interesting.
For example, at noon the sky of Mars is yellow-orange. The reason for such differences from the color scheme of the earth's sky is the properties of the thin, rarefied atmosphere of Mars containing suspended dust.
Presumably, the yellow-orange coloration of the sky is caused by the presence of 1% magnetite in dust particles that are constantly suspended in the Martian atmosphere and raised by seasonal dust storms. Duration of storms can reach 50-100 days.
Evening dawn on Mars turns the sky a fiery red or deep orange.
