Want to get a closer look at Mars and its physical characteristics?
To make it easier to analyze the difference between the planets, all general parameters, features and main characteristics will be presented in comparison with the Earth.


Physical characteristics of Mars

Mars in many ways, but in size and gravitational attraction, it is very different. Thanks to all the accumulated knowledge, it is safe to say that it is much smaller than the Earth, its mass is also significantly inferior to that of the Earth. It is 0.17 of the mass of the Earth, and its gravity is about 62 percent less. Therefore, there you will feel three times easier than on Earth.

A Martian day is slightly longer than a day on Earth. It takes 24 hours and 40 minutes to complete a complete revolution around its axis. The angle of inclination of the axis of rotation for both planets is approximately equal. It is 23.26 degrees for Earth and 25.2 degrees for Mars. This slope triggers the seasons. The Martian span of the year is also longer than the terrestrial one. This is because it takes 687 days to complete one revolution around the Sun, as opposed to the 365.25 day year of the Earth.

The mass of Mars is 6.4169 X 10 23 kg. This is ten times less than the mass of the Earth. In our solar system, it is the second largest planet in the solar system. Its volume is 1.63116 X 10 11 km 3. The volume of Mars is equal to 15% of the earth. If we imagine the Earth as a hollow sphere, then it could fit 6.7 planets like Mars.

Mars' lower density makes it about 10% as massive as Earth. In fact, in terms of density, it is closer to that of the Earth than to the other three inner planets. Its average density is about four times that of water.

Geographic dimensions of Mars

Mars is the second smallest planet in the solar system, after Mercury, and the first in terms of study after Earth.

The size of Mars is difficult to express in one number. Scientists view and evaluate planets from different angles, taking into account various factors. The first dimensions of Mars were made by Galileo Galilei in 1610, even before the invention of the telescope. Nowadays, when the latest technologies come to the rescue, it is not difficult to obtain such information about any planet in the solar system (and sometimes beyond).

The radius of Mars is 3,389.5 km. Its circumference is 21,344 km. By comparison, Mars has 53% of the Earth's diameter. Its diameter at the equator is 6,792 kilometers, while the diameter of the Earth is 12,756 kilometers. It turns out that Mars is only slightly more than half the size of the Earth. If you measure the diameter from pole to pole, you can see that both planets are not an ideal sphere, but have a flattened shape at the poles. So the diameter of Mars between the poles is 6,752 kilometers, and the diameter of the Earth is 12,720 kilometers. This slight flattening is due to the fact that the planets rotate on their axis.

In terms of area, Mars occupies 38% of the Earth's surface area. It seems like a small area, but it is comparable to the territory that all land on Earth occupies.
Scientists believe Mars was a larger planet? when the solar system was just formed. But under external influence, it was thrown out of its former orbit, lost part of its mass and magnetic field.

As you can see, the size of Mars is not the main characteristic of this planet, which can provide answers to many questions. And this is a good incentive for further intensified work in this direction. The luggage of knowledge about the red planet, which we have accumulated over a long time, arouses considerable interest not only of the scientific community, but also of ordinary inhabitants of our planet. Science and research allow us to look at the real planet, estimate its small size in relation to other planets of the solar system, its harsh climate and rocky lifeless relief.

Mars is the fourth in terms of distance from the Sun and the seventh (penultimate) planet in the solar system in size; 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 tinge of the surface given by iron oxide.

Mars is a terrestrial planet with a rarefied atmosphere (surface pressure is 160 times less than that of the Earth). The features of the surface relief of Mars can be considered impact craters like lunar ones, as well as volcanoes, valleys, deserts and polar ice caps like earthly ones.

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.

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 5th 0,377
1892 4 august 0,378
1909 24 september 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 in terms of distance from the Sun (after Mercury, Venus and Earth) and the seventh in size (surpasses only Mercury in mass and diameter) planet in 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 Earth's volume, and the average linear diameter is 0.53 of the Earth's diameter (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 articles published in the journal Nature provided evidence for 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 the largest impact crater previously also found on Mars, near its south pole.

In addition to the similarity in surface relief, Mars has a rotation period and seasons similar to those on Earth, but its climate is much colder and drier than Earth.

Until the first flyby of 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 grooves on the surface of Mars have been interpreted by some observers as irrigation channels for liquid water. It was later proven that these grooves were an optical illusion.

Due to 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 Mars Orbiting Research Orbiter consisted of three functioning spacecraft: Mars Odysseus, Mars Express, and Mars Reconnaissance Satellite, more than around any planet other than Earth.

The surface of Mars is currently being explored by two rovers: Spirit and Opportunity. There are also several inactive landing modules and rovers on the surface of Mars that have completed their studies.

The geological data they have collected suggest that most of the surface of Mars was previously covered by water. Observations over the past decade have revealed weak geyser activity in some places on the surface of Mars. According to observations from the Mars Global Surveyor spacecraft, parts of Mars' south polar cap 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), second in brightness only to Jupiter (and even then not always during the great opposition) and Venus (but only in the morning or evening). Typically, during the 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 inclination of Mars' orbit is 1.85 °.

Mars is closest to Earth during opposition, when the planet is in the opposite direction to the Sun. Confrontations repeat every 26 months at different points in the orbits of Mars and Earth. But once every 15-17 years, opposition falls on 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 maximum angular size of 25.1 "and a brightness of 2.88m.

physical characteristics

Comparison of the sizes of Earth (average radius 6371 km) and Mars (average radius 3386.2 km)

In linear size, Mars is almost half the size of 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 on Earth.

The polar radius of Mars is about 20 km less than the equatorial one, although the rotation period of the planet is longer than that of the Earth, which suggests a change in the rate of rotation of Mars over time.

The mass of the planet is 6.418 1023 kg (11% of the Earth's mass). The acceleration of gravity at the equator is 3.711 m / s (0.378 Earth); the first space velocity is 3.6 km / s and the second - 5.027 km / s.

The rotation period of the planet is 24 hours 37 minutes 22.7 seconds. Thus, the Martian year consists of 668.6 Martian solar days (called sols).

Mars rotates around its axis, inclined to the perpendicular to the orbital plane at an angle of 24 ° 56 °. The tilt of the Mars axis of rotation ensures 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 sol, that is, noticeably more than half of the Martian year. At the same time, they fall on the part of the Mars orbit, which is distant 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 planet's temperature ranges from -153 at the pole in winter and up to more than +20 ° C at the equator at noon. The average temperature is -50 ° C.

The atmosphere of Mars, which is mainly composed of carbon dioxide, is very rarefied. The pressure near the surface of Mars is 160 times less than that of the Earth - 6.1 mbar at the average surface level. Due to the large difference in altitude on Mars, the pressure at the surface varies greatly. The approximate thickness of the atmosphere is 110 km.

According to NASA (2004), the atmosphere of Mars is 95.32% carbon dioxide; it also contains 2.7% nitrogen, 1.6% argon, 0.13% oxygen, 210 ppm water vapor, 0.08% carbon monoxide, nitrogen oxide (NO) - 100 ppm, neon (Ne) - 2, 5 ppm, light water hydrogen-deuterium-oxygen (HDO) 0.85 ppm, krypton (Kr) 0.3 ppm, xenon (Xe) - 0.08 ppm.

According to the data of the 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 the Mars-2 and Mars-3 AMS, the lower boundary of the ionosphere is at an altitude of 80 km, the maximum electron concentration of 1.7 105 electron / cm3 is located at an altitude of 138 km, the other two maxima are at heights of 85 and 107 km.

Radio scanning of the atmosphere at radio waves of 8 and 32 cm by the Mars-4 AMS on February 10, 1974 showed the presence of a nighttime ionosphere of Mars with a main ionization maximum at an altitude of 110 km and an electron concentration of 4.6 × 103 electron / cm3, as well as secondary maxima at an altitude 65 and 185 km.

Atmosphere pressure

According to NASA data for 2004, the atmospheric pressure at the average 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 Earth, the mass of the Martian atmosphere varies greatly throughout the year due to the melting and freezing of polar caps containing carbon dioxide. During the winter, 20-30 percent of the entire atmosphere is frozen on the polar cap, which is made up of carbon dioxide. Seasonal pressure drops, according to various sources, are as follows:

NASA (2004): 4.0 to 8.7 mbar at mid-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.

Hellas Impact Basin - the deepest place to find the highest atmospheric pressure on Mars

At the landing site of the AMS Mars-6 probe in the Eritrean Sea, a pressure at the surface 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 measure the heights and depths on Mars. According to the data of this apparatus, 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 region of Hellas (Mars) 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 high enough temperature, water could exist there in a liquid state; at this pressure, however, the water boils and turns into steam already at + 10 ° C.

At the summit of the tallest 27 km volcano, Olympus, the pressure can range from 0.5 to 1 mbar (Zurek 1992).

Before the landing modules landed on the surface of Mars, the pressure was measured due to the weakening of radio signals from the AMS Mariner-4, Mariner-6 and Mariner-7 when they went behind the Martian disk - 6.5 ± 2.0 mb at the average surface level, which is 160 times less than earthly; the same result was shown by spectral observations of the Mars-3 AMS. 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 methods - from the distribution of brightness along the diameter of the disk in different ranges of light waves. For this purpose, the French scientists B. Lyot and O. Dolphus made observations of the polarization of light scattered by the atmosphere of Mars. A summary of optical observations was published by the American astronomer J.-de Vaucouleurs in 1951, and they obtained a pressure of 85 mb, which was overestimated by almost 15 times due to interference from atmospheric dust.

Climate

A 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 spacecraft recorded snowfall, but the snowflakes evaporated before reaching the surface.

According to NASA (2004), the average temperature is ~ 210 K (-63 ° C). According to the Viking lander, the daily temperature range is from 184 K to 242 K (-89 to -31 ° C) (Viking-1), and the wind speed is 2-7 m / s (summer), 5-10 m / s (autumn), 17-30 m / s (dust storm).

According to the Mars 6 lander, the average temperature of the Mars troposphere is 228 K, the temperature in the troposphere 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, Mars has been warming 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 warm and humid, and liquid water existed on the surface of Mars and it rained. Evidence of this hypothesis is the analysis of the meteorite ALH 84001, which showed that about 4 billion years ago, the temperature of Mars was 18 ± 4 ° C.

Dust whirlwinds

Dust whirlwinds photographed by the Opportunity rover on May 15, 2005. The numbers in the lower left corner represent the time in seconds since the first frame.

Since the 1970s. within the framework of the Viking program, as well as the Opportunity rover and other vehicles, numerous dust vortices were recorded. These are air turbulences that arise at the surface of the planet and lift large amounts of sand and dust into the air. Vortexes 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 Earth. In March 2005, a vortex cleared the solar panels of the Spirit rover.

Surface

Two-thirds of the surface of Mars is occupied by light areas, called 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. In the northern hemisphere there are only two large seas - the Acidali and Bolshoi Syrt.

The nature of the dark areas is still a matter of controversy. They persist despite dust storms raging on Mars. At one time, this served as an argument in favor of the assumption that dark areas are covered with vegetation. Now it is believed that these are simply areas from which, due to their relief, dust is easily blown out. Large-scale images show that, in fact, dark areas are made up of groups of dark streaks 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 terms of the nature of the surface. In the southern hemisphere, the surface is 1–2 km above average and is densely cratered. This part of Mars resembles lunar continents. In the north, most of the surface is below average, there are few craters, and the bulk is relatively smooth plains, likely from lava flooding and erosion. This hemispheric difference remains a matter of debate. The border between the hemispheres follows an approximately large circle inclined 30 ° to the equator. The boundary is wide and irregular and slopes towards the north. The most eroded areas of the Martian surface are found along it.

Two alternative hypotheses have been put forward to explain the asymmetry of the hemispheres. According to one of them, at an early geological stage, lithospheric plates "collapsed" (possibly by accident) into one hemisphere, like the continent of Pangea on Earth, and then "froze" in this position. Another hypothesis suggests a collision of Mars with a space body the size of Pluto.
Topographic map of Mars, according to the Mars Global Surveyor, 1999.

The large number of craters in the southern hemisphere suggests that the surface is ancient - 3-4 billion years old. There are several types of craters: large flat-bottomed craters, smaller and younger lunar-like bowl-shaped craters, rampart craters, and elevated craters. The latter two types are unique to Mars - rim craters formed where liquid ejections flowed across the surface, and elevated craters formed where a crater ejection blanket protected the surface from wind erosion. The largest detail of impact origin is the Hellas Plain (approximately 2,100 km across).

In an area 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 liquid lava flooding. Chaotic landscapes are often found at the source of large canals cut by water. The most acceptable hypothesis for their joint formation is the sudden melting of subsurface ice.

Mariner Valley on Mars

In the northern hemisphere, in addition to the vast volcanic plains, there are two areas of large volcanoes - Tharsis and Elysium. Farsis is a vast volcanic plain with a length of 2000 km, reaching an altitude of 10 km above average. There are three large shield volcanoes on it - Mount Arsia, Mount Peacock and Mount Askriyskaya. At the edge of Tarsis 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 Olympus is 10 times the volume of the largest volcano on Earth, Mauna Kea. Several smaller volcanoes are also located here. Elysium is an elevation up to six kilometers above the average level, with three volcanoes - the dome of Hecate, Mount Elysium and the dome of Albor.

According to other sources (Faure and Mensing, 2007), Olympus is 21,287 meters above ground level and 18 kilometers above the surrounding terrain, and the base diameter is approximately 600 km. The base covers an area of ​​282,600 km2. The caldera (a depression in the center of the volcano) is 70 km wide and 3 km deep.

The Tarsis Upland is also crossed by many tectonic faults, often very complex and extended. The largest of them - the Mariner Valley - stretches in the latitudinal direction for almost 4000 km (a quarter of the planet's circumference), 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. The largest landslides in the solar system occur on its steep slopes. The Mariner Valley is the largest known canyon in the solar system. The canyon, which was discovered by the Mariner 9 spacecraft in 1971, could cover the entire US territory, from ocean to ocean.

A panorama of Victoria Crater taken by the Opportunity rover. It was filmed in three weeks, from October 16 to November 6, 2006.

A panorama of the surface of Mars in the Husband Hill region, captured by the Spirit rover November 23-28, 2005.

Ice and polar caps

North polar cap in summer, photo Mars Global Surveyor. Long wide rift cutting through the cap on the left - Severny rift

The appearance of Mars varies greatly with the seasons. First of all, the 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 latitude 50 °, and the northern one also 50 °. The diameter of the permanent part of the northern polar cap is 1000 km. As the polar cap recedes in one of the hemispheres in spring, the details of the planet's surface begin to darken.

The polar caps are composed of two components: seasonal - carbon dioxide and secular - water ice. According to data from the Mars Express satellite, the thickness of the caps can range from 1 m to 3.7 km. The device "Mars Odysseus" discovered active geysers on the south polar cap of Mars. According to NASA experts, jets of carbon dioxide with spring warming burst upward to great heights, taking with them dust and sand.

Photos 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 in this case is 10-40 m / s, sometimes up to 100 m / s. The wind picks up large amounts of dust from the surface, resulting in 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 atmosphere of Mars.

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. French astronomer E. Lee observed a wave of darkening around the melting spring polar cap, which was then interpreted by the hypothesis about the spreading of melt water and the growth of vegetation. Spectrometric measurements, which were carried out at the beginning of the XX century. at the Lovell Observatory in Flagstaff by W. Slipher, however, they did not show the presence of a line of chlorophyll, the green pigment of terrestrial plants.

From the 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 is called the Mitchell Mountains, located near the south pole of Mars, when the polar cap melts, looks like a white island, since glaciers melt later in the mountains, including on Earth.

Data from the Mars Reconnaissance Satellite made it possible to find 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.

River channels and other features

Mars has 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 evidence of the long-term existence of the river system. However, recent evidence suggests that rivers flowed for geologically significant periods of time. In particular, inverted channels were found (that is, channels raised above the surrounding terrain). 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 a displacement of channels in the river delta with a gradual uplift of the surface.

In the southwestern hemisphere, in the Eberswalde crater, a river delta with an area of ​​about 115 km2 was discovered. The river that washed out the delta was more than 60 km long.

Data from NASA's Mars rovers Spirit and Opportunity also indicate the presence of water in the past (minerals found that could only have formed as a result of prolonged exposure to water). The Phoenix spacecraft found ice deposits directly in the ground.

In addition, dark stripes have been found on the slopes of the hills, indicating the appearance of liquid salt water on the surface in modern times. 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 have formed not from liquid streams, but from something else,” said NASA employee Richard Zurek.

Several unusual deep wells have been discovered in the Tarsis volcanic upland. Judging by the image of the Mars Reconnaissance Satellite, made in 2007, one of them has a diameter of 150 meters, and the illuminated part of the wall goes to a depth of no less than 178 meters. A hypothesis was put forward about the volcanic origin of these formations.

Priming

The elemental composition of the surface layer of the Martian soil, according to the data of the lander, is not the same in different places. The main constituent of the soil is silica (20-25%), containing an admixture of iron oxide hydrates (up to 15%), which gives the soil a reddish color. There are significant impurities of compounds of sulfur, calcium, aluminum, magnesium, sodium (units of percent for each).

According to 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 theoretically it would be possible to grow plants on them. “In fact, we have found that the soil on Mars meets the requirements and contains the necessary elements to create and sustain life in the past, present and future,” said project lead chemist Sam Coonaves. Also, according to him, many 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. The Mars Odysseus orbiting probe also discovered that there are deposits of water ice beneath 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 north pole of the planet, received water from the Martian soil.

Geology and internal structure

In the past, on Mars, as well as on Earth, the movement of lithospheric plates took place. This is confirmed by the peculiarities of the magnetic field of Mars, the locations of some volcanoes, for example, in the province of Farsis, 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 proportions, 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 for a long 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 height, as on Mars. On the other hand, the difference in the maximum heights 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 maximum up to 130 km), a silicate mantle with a thickness of 1800 km 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) 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 for about a billion years. The partial melting of mantle silicates took about the same time. Due to the lower gravity on Mars, the range of pressures in the mantle of Mars is much smaller than on Earth, which means there are fewer phase transitions in it. It is assumed that the phase transition of olivine to the spinel modification begins at rather large depths - 800 km (400 km on Earth). The nature of the relief and other signs 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 is composed mainly of basalt. There is some reason to believe that on part of the Martian surface, the material is more quartz-containing than normal basalt and may be similar to andesite rocks on Earth. However, these same observations can be interpreted in favor of the presence of quartz glass. Much of the deeper layer consists of iron oxide grainy dust.

Mars magnetic field

Mars had 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 gamma, at the pole 120 gamma, which is 500 times weaker than the earth's. According to the data of 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 of 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 in relative immobility 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 stripe magnetic anomalies in the oceans.

One theory, published in 1999 and retested in 2005 (with the help of an unmanned Mars Global Surveyor station), these stripes show plate tectonics 4 billion years ago before the planet's dynamo ceased to function, which caused a sharp weakening magnetic field. The reasons for this sharp decline are unclear. There is an assumption that the functioning of the dynamo is 4 mldr. years ago is explained by the presence of an asteroid that orbited at a distance of 50-75 thousand kilometers around Mars and caused instability in its core. Then the asteroid descended to the Roche limit and collapsed. However, this explanation itself contains ambiguities, and is disputed in the scientific community.

Geological history

A global mosaic of 102 images of the Viking 1 orbiter from 22 February 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 almost unhindered into the atmosphere of Mars, and many of the photochemical reactions under the influence of solar radiation, which occur on Earth in the ionosphere and higher, on Mars can be observed practically at its very surface.

The geological history of Mars includes the following three eras:

Noachian era (named after the "Noachi land", the region of Mars): the formation of the oldest surviving surface of Mars. It continued in the period 4.5 billion - 3.5 billion years ago. During this era, the surface was scarred by numerous impact craters. The plateau of the Tarsis province was probably formed during this period with intense water flow later.

The 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 era have very few meteorite craters, but otherwise they are completely different. Mount Olympus was formed during this period. At this time, lava flows were poured in other parts of Mars.

Satellites of Mars

Natural satellites of Mars are Phobos and Deimos. Both of them were discovered by the American astronomer Asaf Hall in 1877. Phobos and Deimos are irregular in shape and very small in size. According to one hypothesis, they may be asteroids captured by the gravitational field of Mars, like (5261) Eureka from the Trojan group of asteroids. The companions are named after the characters accompanying the god Ares (that is, Mars) - Phobos and Deimos, who personify fear and horror who helped the god of war in battles.

Both satellites revolve around their axes with the same period as around Mars, therefore they are always turned to the planet by the same side. The tidal effect of Mars gradually slows down the movement of Phobos, and ultimately 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 slightly 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 by meteorite impacts either inflicted repeated impacts on the surface or fell on Mars, while on Deimos it remained in orbit around the satellite for a long time, gradually precipitating and hiding the unevenness of the relief.

Life on Mars

The popular idea that Mars is inhabited by intelligent Martians spread widely in the late 19th century.

Schiaparelli's observations of the so-called canals, combined with Percival Lowell's book on the same topic, made popular the idea of ​​a planet whose climate was getting drier, colder, which was dying and in which there was an ancient civilization producing irrigation works.

Numerous other sightings and announcements of famous people have spawned 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. Then he suggested that it could be a radio signal from other planets, such as Mars. In a 1901 interview, Tesla said that the idea occurred to him that the interference could be caused artificially. Although he could not decipher their meaning, it was impossible for him that they arose completely by accident. In his opinion, it was a greeting from one planet to another.

Tesla's theory was warmly supported by the famous British physicist William Thomson (Lord Kelvin), who, visiting the United States in 1902, said that he believed Tesla had caught a signal from the Martians sent to the United States. However, then Kelvin strongly denied this statement before leaving 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 inside this zone, however, 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 sustain permanent Earth-like life.

The absence of a magnetosphere and the extremely thin atmosphere of Mars are also problems for the maintenance of life. On the surface of the planet there is a very weak movement of heat flows, it is poorly insulated from the bombardment by particles of the solar wind, in addition, when heated, water instantly evaporates, bypassing the liquid state due to low pressure. Mars is also on the doorstep of the so-called. "Geological death". The end of volcanic activity appears to have stopped the circulation of minerals and chemical elements between the surface and the interior of the planet.

The evidence suggests that the planet was previously significantly more predisposed to the presence of life than it is now. However, to date, no organisms have been found on it. Under the Viking program in the mid-1970s, a series of experiments were carried out to detect microorganisms in Martian soil. It has shown positive results, such as a temporary increase in CO2 emission when soil particles are placed in water and growth media. However, then this evidence of life on Mars was challenged by some scientists [by whom?]. This led to their lengthy disputes with NASA scientist Gilbert Levin, who claimed that the Viking had discovered life. After reevaluating the Viking data in the light of modern scientific knowledge about extremophiles, it was found that the experiments carried out were not perfect enough to detect these life forms. Moreover, these tests could even kill organisms, even if they were contained in the samples. Tests carried out under the Phoenix program have shown that the soil has a very alkaline pH and contains magnesium, sodium, potassium and chloride. There are enough nutrients in the soil to sustain life, but life forms must be protected from intense ultraviolet light.

It is interesting that 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 such meteorite is ALH 84001, found in Antarctica in 1984.

According to the results of observations from Earth and data from the Mars Express spacecraft, methane was found in the atmosphere of Mars. Under Mars conditions, this gas decomposes rather quickly, so there must be a constant source of its replenishment. Such a source can be either geological activity (but active volcanoes on Mars have not been found), or the vital activity of bacteria.

Astronomical observations from the surface of Mars

After the landing 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 orbital period of Mars and its satellites, the picture of the night sky of Mars (and astronomical phenomena observed from the planet) differs from the terrestrial one and is in many ways unusual and interesting.

The color of the sky on Mars

During sunrise and sunset, the Martian sky at its zenith has a reddish-pink color, and in the immediate vicinity of the Sun's disk - from blue to purple, which is completely opposite to the picture of the earth's dawn.

At noon, the sky of Mars is yellow-orange. The reason for such differences from the color scale 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 sky) plays an insignificant role, its effect is weak. Presumably, the yellow-orange color 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 the sun rises and lasts long after it sets. Sometimes the color of the Martian sky takes on a purple hue as a result of light scattering by microparticles of water ice in the clouds (the latter is a rather rare phenomenon).

Sun and planets

The angular size of the Sun observed from Mars is smaller than that seen from Earth and is 2/3 of the latter. Mercury from Mars will be practically inaccessible for observations 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 - Earth.

Earth is an inner planet in relation 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 apparent magnitude of about -2.5) greenish star, next to which a yellowish and dimmer (about 0.9) star of the Moon will be easily distinguishable. Through the telescope, both objects will show the same phase. The rotation 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, and in a week the Moon will be visible again 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 over 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. In 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. The Earth, like other planets, will be observed in the constellation strip 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 nearest one will happen on November 10, 2084.

Satellites - Phobos and Deimos


The passage of Phobos across the disk of the Sun. Opportunity Pictures

Phobos, when viewed from the surface of Mars, has an apparent diameter of about 1/3 of the Moon's disk in the earth's sky and an apparent magnitude of the order of -9 (approximately like the Moon in the first quarter phase). Phobos rises in the west and sets in the east, only to ascend again in 11 hours, thus crossing the Mars sky twice a day. The movement of this fast moon across the sky will be easily noticeable during the night, as will the phase change. The naked eye will distinguish the largest detail of the Phobos relief - Stickney Crater. Deimos rises in the east and sets in the west, looks like a bright star without a noticeable visible disk, with a magnitude of about -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 this case Phobos will move towards Deimos.

The brightness of both Phobos and Deimos is sufficient for objects on the surface of Mars to cast clear shadows at night. Both satellites have a relatively small orbital inclination 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. NS. or south of 70.4 ° S. NS.; for Deimos, these values ​​are 82.7 ° N. NS. and 82.7 ° S. NS. 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 located in the constellation Cygnus (equatorial coordinates: right ascension 21h 10m 42s, declination + 52 ° 53.0 its designations are HR 8106, HD 201834, SAO 33185) The South Pole of the world (coordinates 9h 10m 42s and -52 ° 53.0) is located a couple of degrees from the star Kappa Parusov (apparent magnitude 2.5) - it is, in principle , can be considered the South Pole Star of Mars.

The zodiacal 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 in front of how to re-enter the western part of Pisces.

History of Mars exploration

The exploration of Mars began a long time ago, 3.5 thousand years ago, in Ancient Egypt. The first detailed reports on the position of Mars were compiled by Babylonian astronomers, who developed a number of mathematical methods for predicting the position of the planet. Using data from the Egyptians and Babylonians, ancient Greek (Hellenistic) philosophers and astronomers developed a detailed geocentric model to explain the motion of the planets. Several centuries later, Indian and Islamic astronomers estimated the size of Mars and the distance to it 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 of Mars, coinciding with the observed one.

In 1659, Francesco Fontana, examining Mars through a telescope, made the first drawing of the planet. He depicted a black spot in the center of a well-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 details of the surface: the Aphrodite, Eritrean, Adriatic, Cimmerian seas; lakes of the Sun, Lunnoye and Phoenix.

The heyday of telescopic observations of Mars came in the late 19th - mid-20th centuries. Much of this is due to public interest and the well-known scientific controversy around the observed Martian channels. Among the astronomers of the pre-space era who conducted telescopic observations of Mars during this period, the most famous are Schiaparelli, Percival Lovell, Slipher, Antoniadi, Barnard, Jarry-Delozh, L. Eddy, Tychov, Vaucouleur. 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 to Mars of automatic probes.

Colonization of Mars

Estimated view of Mars after terraforming

Relatively close to terrestrial natural conditions somewhat facilitate the implementation of this task. In particular, there are places on Earth in which natural conditions are similar to those of Mars. Extremely low temperatures in the Arctic and Antarctica are comparable to even the coldest temperatures on Mars, and the equator of Mars in 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 about 800 times weaker than that of the Earth. 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 aerial vehicle The Mars Odyssey showed that the background radiation in Mars orbit is 2.2 times higher than the background radiation at the International Space Station. The average dose was approximately 220 milligrams per day (2.2 milligrams per day or 0.8 warms per year). The amount of radiation received as a result of being in such a background for three years is approaching the established safety limits for astronauts. On the surface of Mars, the background radiation is slightly lower and the dose is 0.2-0.3 Gy per year, significantly changing depending on the terrain, altitude and local magnetic fields.

The chemical composition of 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, Earth and the asteroid belt.

The flight time from Earth to Mars (with current technologies) is 259 days in semi-ellipse and 70 days in 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 to colonize Mars, but the development of colonization is underway, for example, the Centennial Spacecraft project, the development of a living module for staying on the planet Deep Space Habitat.

A wide variety of space bodies are located within our home solar system. We call them planets, but each of them has its own properties, unique. So, the first four, located closest to the star, are included in the category of "terrestrial planets". They have a core, mantle, hard surface, and atmosphere. The next four are gas giants, which have only a core that is clothed with a wide variety of gases. But on the agenda we have Mars and Earth. Comparing these two planets will be fascinating and exciting, especially considering the fact that both of them are representatives of the "terrestrial category".

Introduction

Astronomers of the past, after they discovered Mars, believed that this planet is the closest relative of the Earth. The first comparisons between Mars and Earth are related to the system of channels seen through a telescope, which was girded with the red planet. Many were convinced that there was water and, as a result, organic life. It is likely that millions of years ago, this object within the solar system had conditions similar to those of today. However, now it has been more than possible to establish more than accurately: Mars is a red desert. Nevertheless, comparisons between Earth and Mars are a favorite topic of astronomers to this day. Studying the features of the structure and rotation of our closest neighbor, they believe that soon this planet will be able to colonize. But there are nuances that still prevent humanity from taking this step. We learn about what they are and what they are, drawing an analogy on all points between our native Earth and the mysterious neighboring Mars.

Weight, size

These indicators are the most important, so we'll start with Mars and Earth. Even in children's books on astronomy, we all noticed that the red planet is slightly smaller than ours, about one and a half times. Let's look at this difference in specific numbers.

  • The average radius of the Earth is 6371 km, while for Mars this figure is 3396 km.
  • The volume of our home planet is 1.08321 x 10 12 km 3, while the Martian is equal to 1.6318 × 10¹¹ km³, that is, it is 0.151 of the Earth's volume.

The mass of Mars in comparison with the Earth is also less, and this indicator differs radically, in contrast to the previous one. The earth weighs 5.97 × 10 24 kg, and the red planet is content with only 15 percent of this indicator, namely - 6.4185 x 10 23 kg.

Orbital features

From the same children's astronomical textbooks, we know that Mars, due to the fact that it is farther from the Sun than the Earth, is forced to walk in a larger orbit. It is about twice as large as the Earth, in fact, and the year on the red planet is twice as long. From this we can conclude that this cosmic body rotates at a speed comparable to that of the Earth. But it is important to know these data in exact numbers. The remoteness of the Earth from the Sun is 149,598,261 km, but Mars is at a distance of 249,200,000,000 km from our star, which is almost twice as much. The orbital year in the kingdom of the dusty and red desert is 687 days (we remember that on earth a year lasts 365 days).

It is important to note that the sidereal rotation of the two planets is practically the same. A day on Earth is 23 hours and 56 minutes, and on Mars - 24 hours and 40 minutes. Axial tilt cannot be ignored. For Earth, the characteristic indicator is 23 degrees, and for Mars - 25.19 degrees. It is likely that there may be seasonality on the planet.

Composition and structure

Comparison of Mars and Earth would be incomplete if the structure and density of these two planets are ignored. Their structure is identical, since both belong to the terrestrial group. In the very center is the core. In Earth, it consists of nickel and metal, and its sphere radius is 3500 km. The Martian core has the same composition, but its spherical radius is 1800 km. Then, on both planets, a silicate mantle is located, followed by a dense crust. But the Earth's crust differs from the Martian one by the presence of a unique element - granite, which is not present anywhere else in space. It is important to note that the depth is on average 40 km, while the Martian crust reaches a depth of up to 125 km. The average is 5.514 grams per cubic meter, and Mars - 3.93 grams per cubic meter.

Temperature and atmosphere

At this point, we are faced with fundamental differences between two neighboring planets. And the thing is that in the solar system, only one Earth is equipped with a very dense air shell, which maintains a unique microclimate on the planet. So, the comparison of the atmosphere of the Earth and Mars should start with the fact that the first air layer has a complex, five-stage structure. We all learned in school terms such as stratosphere, exosphere, etc. The Earth's atmosphere is 78 percent nitrogen and 21 percent oxygen. On Mars, there is only one layer, very thin, which consists of 96 percent carbon dioxide, 1.93% argon and 1.89% nitrogen.

This was also the reason for the difference in temperature. On Earth, the average is +14 degrees. It rises to a maximum of +70 degrees, and drops to -89.2. It's much cooler on Mars. The average temperature is -46 degrees, while the minimum is 146 below zero, and the maximum is 35 with a + mark.

Gravity

This word is the whole essence of our being on the blue planet. It is she who is the only one in the solar system that can provide gravity, acceptable for the life of people, animals and plants. We mistakenly believed that gravity is absent on other planets, but it's worth saying that it is there, just not as strong as ours. The attraction on Mars in comparison with the Earth is almost three times less. If we have such an indicator as G - that is, the acceleration of gravity is 9.8 m / s squared, then on the red desert planet it equates to 3.711 m / s squared. Yes, it is possible to walk on Mars, but, alas, it will not work without a special suit with weights.

Satellites

The only satellite of the Earth is the Moon. She not only accompanies our planet on its mysterious cosmic path, but is also responsible for many natural processes in life, for example, tides. The moon is also the most studied space body at the moment, as it is closest to us. Escort Mars - Satellites were discovered in 1877 and named after the sons of the god of war Ares (translated as "fear" and "horror"). It is most likely that they were pulled by the gravity of the red planet from the asteroid ring, since their composition is identical to all other stones orbiting between Mars and Jupiter.

Among all the planets, Mars is the closest to Earth in terms of its climatic conditions. Despite the negative results of the first experiments to search for life on Mars, this problem is still considered open. In the XIX and XX centuries. astronomers have intensively studied Mars using ground-based telescopes, believing that there is at least plant life on its surface. Over the past 40 years, Mars has been intensively explored with the help of interplanetary vehicles, without stopping its observation by ground-based and space telescopes. There is no doubt that Mars will be the first planet to be visited by manned expeditions.

Table: Basic data about Mars
Table 1. BASIC DATA ABOUT MARS
Average distance from the Sun AU 1.524
Orbital eccentricity 0,093
Equator tilt to orbit 25.2 °
Equatorial radius 3394 km
Weight 0.107 Earth masses
Medium density 3.94 g / cm 3
Gravity 0.38 Earth Gravity
Rotation period 24 hours 37 minutes 23 sec.
Duration of sunny days 24 hours 39 minutes 35 sec.
Length of the year 1.88 Earth Years
Atmosphere rarefied (95% carbon dioxide, 2.5% nitrogen, 1.6% argon)
A magnetic field very weak
Satellites Phobos and Deimos.

Mars movement.

From the point of view of the terrestrial observer, Mars belongs to the "upper" planets: together with the giant planets (Jupiter, Saturn, Uranus and Neptune), as well as the dwarf "double planet" Pluto, Mars moves beyond the Earth's orbit. Inside the earth's orbit, closer to the Sun, two "internal" planets move - Mercury and Venus. However, according to its physical properties, Mars is included in the group of terrestrial planets (Mercury, Venus, Earth and Mars). The terrestrial planets are similar in that they are small, rocky and rather dense bodies. They rotate relatively slowly around their axes, are devoid of rings and have few or no satellites: the four planets of this group have only three satellites in total - the Earth's Moon and the Martian Phobos and Deimos.

In the history of astronomy, the study of the motion of Mars played a special role: using Tycho Brahe's long-term observations of the movement of Mars relative to the stars, Johannes Kepler was able to correctly determine the shape of planetary orbits for the first time. He proved that the orbit of Mars is an ellipse. Kepler succeeded only because the ellipticity of the Martian orbit is relatively high, noticeably higher than that of all planets available for detailed observation in the pre-telescopic epoch.

The orbital period of Mars is about 687 Earth days, or about 670 Martian days, which are only slightly longer than Earth ( cm... tab. one). The same mutual position of Mars, Earth and the Sun repeats on average every 780 days. - this is the synodic period of the revolution of Mars. In particular, oppositions of Mars occur with such periodicity, in which it is observed from the Earth approximately at a point opposite to the Sun; hence the term - the opposition of Mars and the Sun in the earthly firmament. During these periods, Mars is especially convenient for studying its surface with a telescope.

Depending on the season, i.e. from the position of the Earth in orbit, at the moment of opposition, the distance to Mars can be from 56 to 101 million km. If the confrontation takes place in July-September, then the distance is 56-60 million km; such close confrontations are called great ( cm... THE GREAT CONFRONTATIONS OF MARS). At these moments, the diameter of the Mars disk, visible from Earth, reaches 25І, and the brightness rises to 2.5 magnitude, comparing with the brightness of Jupiter and second only to Venus.

Seasonal changes on Mars occur throughout the year similar to those on Earth: the inclination of the equator to the orbital plane for Mars is 25.2 °, for Earth, 23.4 °. The year of Mars is divided into four seasons by the moments of equinoxes and solstices: from the vernal equinox to the summer solstice - spring, etc. Since the period of Mars' revolution around the Sun is twice that of the Earth, the length of the seasons is also twice as long. In addition, the duration of the Martian seasons is more different from each other than the terrestrial ones. The reason for this is the significant ellipticity of the Martian orbit, which is why Mars moves at different speeds at different points of its orbit. For example, in the southern hemisphere of Mars, spring lasts 146 Earth days, summer 160 days, autumn 199 days, and winter 182 days.

During the northern spring, Mars is at a greater distance from the Sun (in the aphelion of the orbit), and therefore the solar radiation reaching the planet during this period is only 70% of the radiation in the period closest to the Sun (at perihelion). When Mars passes perihelion, the average surface temperature in the daytime hemisphere of the planet is 25-30 degrees higher than in aphelion. For this reason, autumn and winter in the northern hemisphere of Mars are less severe than in the southern one, and the southern summer, unlike the northern one, is hotter.

The nature of Mars.

Mars is twice the size of the Moon and half the size of the Earth. The force of gravity on the surface of Mars is exactly between the earth and the lunar. The average density of Mars is also between the density of the Moon and the Earth, although closer to the lunar density. And one more quality unites the Moon and Mars: these are the most studied (after the Earth) objects of the solar system.

However, even during the period of great opposition, Mars is 150 times farther from us than the Moon, so its study by traditional astronomical methods is a difficult problem. Nevertheless, before the beginning of the space age, astronomers accurately measured the length of the Martian day, made a rough map of the surface of Mars, and found an atmosphere in it, mainly consisting of carbon dioxide. The temperature of the surface of Mars was measured quite accurately, which, as expected, turned out to be lower than on Earth, and equal to about –30 ° C (the average temperature on Earth is about + 15 ° C).

Measurements from onboard automatic stations - artificial satellites of Mars - significantly improved these data. The average temperature turned out to be even lower, about –60 ° С. In summer at the equator, it rises to zero, but in winter in the polar regions it drops to –150 ° С. Due to the rarefied atmosphere, the daily fluctuations in surface temperature are very large: up to 70 degrees. However, already at a shallow depth of soil, about 25 cm, the temperature changes little during the day or even the year; in the tropics it is close to –60 ° С.

The bright white spots located in the polar regions of Mars have always attracted much attention of astronomers. If you start observing the polar cap on any of the hemispheres of Mars at the end of winter, you will notice that at first it occupies a very large space, about 10 million km 2, but over time it begins to decrease, slowly at first, and then faster and faster. By mid-spring, dark stripes appear, cutting the polar cap into a number of separate areas of varying brightness. Small areas are separated from the main massif at the edges, which gradually disappear after a while. During the summer, the polar cap continues to decrease and becomes very small. By the end of summer, whitish blurred spots appear over the polar region, which rapidly increase and soon spread to the entire polar region and partially even to temperate latitudes. This light mobile haze persists throughout autumn and winter and dissipates only towards the end of winter. After that, the large polar cap becomes visible again, at first a little dim, and then taking on a bright white color and covering, as at the end of the previous year, a significant area.

The nature of the northern and southern polar caps is not the same. The northern cap is larger and consists mainly of water ice, while the southern cap is mainly composed of frozen carbon dioxide. The reason for this is the difference in average temperature and length of seasons in the northern and southern hemispheres. The thickness of the snow cover on most of the surface of the polar caps does not exceed a few centimeters.

In mid-latitudes, the snowless surface of Mars is fairly light and mostly has a reddish-orange hue. These areas are called "deserts"; their color is determined by the presence of iron oxide hydrates, which form a layer of red powder on the grains of silicate sand - the main component of the surface. Closer to the equator, there are greenish-gray spots ("seas"), generally occupying about a third of the surface; they darken with the onset of spring. In the past, it has been argued that these are swampy plains, but now it is clear that there are no vast open bodies of water on Mars.

The surface of Mars is very uneven, the height difference on it reaches 30 km. On Earth, it is noticeably smaller: from the bottom of the Mariana Trench to the summit of Everest about 20 km. An equipotential surface with an atmospheric pressure of 6.1 mbar is usually taken as the reference level for altitude on Mars. This pressure on the diagram of the state of water corresponds to the "triple point": at a higher pressure, water can be in three states of aggregation (depending on temperature) - solid, liquid and gaseous. But if the pressure is lower, then when heated, the ice immediately turns into steam, bypassing the liquid phase. At the most significant elevations of Mars, the atmospheric pressure is about 3 mbar, and at the bottom of the canyons - about 10 mbar; there water can be in a liquid state.

On average, the pressure at the surface of Mars is almost 200 times less than the normal atmospheric pressure at the surface of the Earth at sea level and is close to the pressure at an altitude of 40 km, where airplanes and balloons do not rise on Earth. The atmosphere of Mars is very dry. The thickness of the conditionally deposited layer of water in it is only about 0.05 mm, even near the melting polar cap at the height of summer (in the earth's atmosphere, the water layer is hundreds of times larger). With distance from the melting polar cap, the amount of vapor in the atmosphere decreases to several micrometers.

Nevertheless, even the first images of automatic stations showed that some of the details of the Martian relief owe their origin to the currents of water. For example, the winding bed of the ancient Martian river Nergal with tributaries. Its length reaches 400 km. There has been no water in the Nergal valley for a long time. Apparently, the river flowed into a huge reservoir formed by a wide lowland in the area of ​​Uzboy Canyon and the Holden Hale crater chain. The sinuous shape of Nergal resembles the channels of earthly rivers. Other valleys of this nature have been discovered, indicating that water currents once raged on the dry planet Mars.

However, it is possible that in our time on Mars sometimes "streams run." This is indicated by high-resolution images transmitted from Mars orbit in recent years by the Mars Global Surveyor and Mars Odyssey spacecraft (USA). On the slopes of some valleys and craters, objects of a new type have been discovered; perhaps these are water or water-mud streams that arise today, literally before our eyes. The presence of liquid water on Mars greatly increases its chances of being a haven for life.

Table: The most important expeditions of automatic stations to Mars
Table 2. THE MOST IMPORTANT EXPEDITIONS OF AUTOMATIC STATIONS TO MARS
Launch date Machine name Country Expedition content
November 28, 1964 Mariner-4 USA First successful flyby near Mars (July 15, 1965). 21 photographs of the surface have been submitted.
May 29, 1971 Mars-3 USSR First soft landing on Mars (December 2, 1971). Data was transmitted from the surface for 20 seconds.
30.05.1971 Mariner 9 USA The first artificial satellite of Mars. Exploration from orbit of the surface of Mars (since November 14, 1971) and its satellites - Phobos and Deimos.
August 20, 1975
September 9, 1975		 Viking 1
Viking-2		 USA First successful landing on Mars (July 20, 1976 and September 3, 1976). The search for life and many years of surface and climate research.
November 7, 1996 Mars GlobalServeyor USA Long-term exploration of Mars from orbit (since September 12, 1997).
December 4, 1996 Mars Passfinder USA Soft landing on Mars (July 4, 1997); the first automatic self-propelled vehicle "Sojourner" was delivered to study the composition of the surface.

Search for life on Mars.

In the middle of the 20th century. Exobiologists pinned great hopes on Mars, and not only because some astronomers saw on its surface many thin straight lines - "channels" - which gave science fiction writers and dreamers a reason to talk about artificial irrigation structures on the surface of Mars. This planet is really more similar to the Earth than others and, probably, could become a refuge for the most unpretentious forms of earthly life.

Several automatic expeditions to Mars, and especially landings on its surface, made it possible to get closely acquainted with the landscape and climate of the planet ( cm... tab. 2). The findings disappointed exobiologists. Even on a summer day, the temperature on Mars rarely rises above 0 ° C, and at night it can drop to -120 ° C. Mars' poor atmosphere contains almost no water vapor and is devoid of oxygen. The surface of Mars is significantly more intensely bombarded by meteorites than the surface of the Earth. It is possible that in the past, the fall of large meteorites (asteroids) caused strong climatic changes, dangerous for the biosphere of Mars, of course, if it existed.

Analyzing the conditions for life on Mars, one should also take into account that this planet is practically devoid of a magnetosphere that protects against cosmic rays. The magnetic field of Mars is very weak, probably due to the total effect of paleomagnetic fields in certain areas of the surface. Its intensity at the equator ranges from 0.07 to 0.8 μT (on Earth, about 30 μT).

It is safe to say that in the current era, conditions on Mars are unfavorable for the emergence of life: it is cold, dry, very rarefied and deprived of oxygen, the air, which is not able to retain the strong ultraviolet radiation of the Sun, sterilizing the surface of the planet. Several special instruments delivered to Mars in 1976 by the Viking 1 and 2 landing blocks (USA) did not detect organic matter in the planet's soil.

Now there is practically no hope of finding active life on Mars. However, the history of Mars may have known more favorable periods for life. There are indications that the climate of Mars has changed significantly: in the distant past, water flowed along its surface. As already noted, in the detailed images of the planet, transmitted by artificial satellites of Mars, traces of water erosion are visible - ravines and empty river beds. The Mars Passfinder probe (USA), which made a soft landing on Mars in 1997 and delivered the first automated Mars rover Sojourner, discovered in the geological structure of the surface signs of powerful water currents that took place in distant eras.

Long-term variations in the Martian climate may be associated with a change in the inclination of its polar axis. With a slight increase in the planet's temperature, its rarefied atmosphere can become 100 times denser due to the evaporation of ice from the polar caps and a possible layer of permafrost. Therefore, it is possible that life on Mars once existed. An accurate answer to this question will be possible only after studying the samples of the Martian soil. But getting them to Earth is a daunting task.

Fortunately, nature sometimes gives scientists unexpected luck: of the thousands of meteorites found on Earth, some may have come from Mars: microscopic gas bubbles in them have the same composition as the atmosphere of Mars. Such finds are called "Shergottites" or SNC-meteorites, since the first such "stones" were found near the settlements of Shergotti (India), Nakla (Egypt) and Chassigny (France). The ALH 84001 meteorite found in Antarctica belongs to the same group; it is much older than the others and contains polycyclic aromatic hydrocarbons, possibly of biological origin. Since the mid-1990s, a heated scientific debate has been going on about this meteorite: astronomers are sure that the flight of matter from planet to planet is possible - its release can occur under the influence of a powerful asteroid impact; however, not all biologists agree that ALH 84001 does indeed contain traces of Martian life.

It is clear that staying on Earth will not be able to solve the problem of life on Mars. Studies of the ALH 84001 meteorite stimulated public interest in this problem, so in 1999 the British government approved a plan to create an interplanetary station "Beagle 2", which went to Mars on June 2, 2003 and will again try to find traces of life there. The station is named after the ship on which Charles Darwin made a research voyage in 1830. Scientists view the new expedition as a continuation of the research into the origin of life begun by Darwin a century and a half ago.

The weight of Mars is about 6.4169 x 10 23 kg, which is about 10 times less than the earth's mass.

The planet Mars bears the name of the ancient Roman god of war Mars - according to legends, precisely because of its reddish "bloody" color. In relation to the Sun, Mars is in fourth place - between its closest neighbors Earth and Jupiter. The length of the "path" between Mars and the Sun is about 228 million kilometers. In terms of its dimensions, this red planet is the seventh number among other planets. Today we will find out how much Mars weighs in comparison with the rest of the planets, as well as other interesting facts "from the life" of this celestial body.

A little about Mars

Since ancient times, Mars has been of great interest to world scientists, since its "temperament" is very similar to that of the earth. Indeed, the Martian surface is covered with a layer of loose rocks (regoliths), which contain a lot of iron, mineral dust and stones. The composition of the earth's soil is almost the same, except that it contains much more organic matter.

Mars weighs 6.4169 x 1023 kg

According to research, in the past, Mars had rivers, lakes and even entire oceans. However, over time, the water completely evaporated, and today the liquid on the Red Planet remains only underground and on the polar "caps" - in the form of ice.

The atmosphere of Mars contains 95% carbon dioxide and is highly discharged. In addition, the Martian "air" is filled with fine dust particles that give it a reddish tint. Dust storms are characteristic of the Martian climate. There is a theory that these hazardous weather events are caused by the absorption of sunlight by fine dust particles. As a result, the atmosphere of Mars heats up and a global storm rises over the planet.

Mars and Earth - comparative characteristics and parameters

  • The size... The diameter of the Red Planet is 6792 km (along the equator), which is two times less than the Earth's - this figure for the Earth is 12756 km. So, Earth is about 1.877539 times larger than Mars. If we compare the entire area of ​​the earth's land and the surface of Mars, then these figures will turn out to be almost equal to each other.
  • Weight... Mars has a relatively low mass, accounting for about 10 percent of the earth's mass. For comparison: Mars weighs 6.4169 x 10 23 kg, and the weight of the Earth is 5.9722 x 10 24 kg. In addition, the force of gravity on the Martian surface is less than that of the earth by about 38%. Therefore, all objects on Mars will weigh less than on Earth. For example, if a child on a "native" planet weighs 32 kg, then on Mars his weight will be only 12 kg.
  • Volume and density... It is known that the average density of Mars is 3.94 g / cm 3, and that of the Earth is about 5.52 g / cm 3. As you can see, in comparison with the Earth, the Red Planet has a rather low density. After all, this indicator directly depends on the mass, and the mass of Mars is only 10% of the earth. As for the volume of Mars, it is equal to only 15% of the earth's volume. If we imagine the Earth as a hollow sphere, then six such small “balls” as Mars are needed to fill it.
  • Orbital length and speed of movement of planets in orbit... The earth's orbit is 939,120,000 km, and Mars is 1,432,461,000 km. The orbital speed of Mars is 107,218 km / h, and the Earth's speed is 86,676 km / h. So the duration of one complete revolution of Mars is about 687 Earth days.
  • Seasons... It is scientifically proven that a Martian day lasts 40 minutes longer than an Earth day. The number of seasons on the two planets is the same, since the tilt of the axis is almost the same (Earth - 23.5˚, Mars - 25˚). However, the length of the year on Mars is about twice as long as on Earth, so the seasons are also longer.

Mass of Mars and other planets of the solar system - a comparative analysis

As can be seen from the table, in the solar system Mars is a fairly small planet in mass, less than which only Mercury.

Is there life on Mars?

This question worried many generations of earthlings. After all, Mars contains all the necessary components for the origin of life - chemical elements (carbon, hydrogen, oxygen, nitrogen), a source of energy and water.

In addition, back in 1996, scientists found evidence of life on Mars at the level of microorganisms, including various complex organic molecules, grains of the mineral magnetite and microscopic compounds that resemble fossilized microbes. Of course, the opinions of scientists on this issue differ, but so far no evidence has been found of the complete absence of life on Mars.

So, now we know how much Mars weighs, its comparative characteristics with the rest of the celestial "inhabitants" of the solar system, as well as other entertaining facts.