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 the discovery of Mars, believed that this planet is the closest relative of the Earth. The first comparisons of Mars and Earth are associated with the system of channels seen through a telescope, which the red planet was girded with. 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 nearest 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 volume 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 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. Can't be ignored axial tilt... 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 the Earth, it is composed of nickel and metal, and the radius of its sphere 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 Earth's crust differs from the Martian one in 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 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 the ground average equal to +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 existence 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 is 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.
People have always been interested in the unexplored expanses of space. Exploration of other planets attracted many scientists, and the common man is interested in the question of what is there in space? First of all, scientists pay attention to the planets of the solar system. Since they are closest to Earth and are easier to study. The mysterious red planet - Mars is especially actively studied. Let's find out which planet is bigger - Mars or Earth, and try to understand why the red celestial body attracts us so much.
Brief characteristics of the planets of the solar system. Their sizes
From the Earth, all the planets of our system seem to us as small luminous points that are difficult to see with the naked eye. It differs from all Mars - it seems to us larger than the rest and sometimes, even without telescopic equipment, you can see its orange light.
Which planet is bigger: Mars or Earth? Do we see Mars so well because it is huge, or is it just closer to us? Let's take a look at this issue. To do this, we will sequentially consider the sizes of all planets belonging to the solar system. They were divided into two groups.
Terrestrial group of planets
Mercury is the smallest planet. In addition, it is the closest to the sun. Its diameter is 4878 km.
Venus is the planet next in distance from the Sun and closest to the Earth. Its surface temperature reaches +5000 degrees Celsius. The diameter of Venus is 12103 km.
The earth differs in that it has an atmosphere and water reserves, which made it possible for life to arise. Its size is slightly larger than Venus and is 12,765 km .
Mars is the fourth planet from the Sun. Earth and has a diameter at the equator of 6786 km. Its atmosphere is almost 96% composed of Mars has a more elongated rotation orbit than Earth.
Giant planets
Jupiter is the largest of the planets in the solar system. Its diameter is 143,000 km. It consists of gas, which is in a vortex motion. Jupiter rotates on its axis very quickly, in about 10 Earth hours it makes full turn... It is surrounded by 16 satellites.
Saturn is a planet that can justifiably be called unique. Its structure has the lowest density. Saturn is also known for its rings, which are 115,000 km wide and 5 km thick. It is the second largest planet in the solar system. Its size is 120,000 km.
Uranus is unusual in that it can be seen in blue-green with a telescope. This planet also consists of gases that move at a speed of 600 km / h. The diameter is just over 51,000 km.
Neptune is composed of a mixture of gases most of which is methane. It is because of this that the planet has acquired a blue color. The surface of Neptune is shrouded in clouds of ammonia and water. The size of the planet is 49,528 km.
The most distant planet from the Sun is Pluto, it does not belong to any of the groups of planets in the solar system. Its diameter is half that of Mercury and is 2320 km.
Characteristics of the planet Mars. Features of the Red Planet and comparison of its size with the size of the Earth
So we examined the sizes of all the planets in the solar system. Now you can answer the question of which planet is larger - Mars or Earth. A simple comparison of the planetary diameters can help in this. The sizes of Mars and Earth differ by half. The red planet is almost half the size of our Earth.
Mars is a very interesting space object to study. The mass of the planet is 11% of the Temperature on its surface varies throughout the day from +270 to -700 degrees C. The sharp drop is due to the fact that the atmosphere of Mars is not so dense and consists mainly of carbon dioxide.
The description of Mars begins with an emphasis on its deep red color. I wonder what caused this? The answer is simple - the composition of the soil is rich in iron oxides, and the increased concentration of carbon dioxide in its atmosphere. For such a specific color, the ancient people called the planet bloody and gave it a name in honor of the Roman god of war - Ares.
The planet's surface is mostly deserted, but there are also dark areas, the nature of which has not yet been studied. Mars is a plain, and the southern one is slightly elevated from the middle level and strewn with craters.
Many do not know, but there is the most high mountain in the entire solar system - Olympus. Its height from base to top is 21 km. The width of this hill is 500 km.
Is it possible
All the works of astronomers are aimed at finding signs of life in space. In order to study Mars for the presence of living cells and organisms on its surface, Mars rovers have repeatedly visited this planet.
Numerous expeditions have already proven that water was previously present on the Red Planet. It is there even now, only in the form of ice, and it is hidden under a thin layer of stony soil. The presence of water is also confirmed by photographs in which the channels of the Martian rivers are clearly visible.
Many scientists want to prove that humans can adapt to life on Mars. In support of this theory, the following facts are cited:
- Almost the same speed of movement of Mars and Earth.
- The similarity of gravitational fields.
- Carbon dioxide can be used to produce vital oxygen.
Perhaps, in the future, the development of technology will allow us to easily make interplanetary travel and even settle on Mars. But first of all, humanity must preserve and protect its home planet - the Earth, so that you never have to think about which planet is bigger - Mars or Earth, and whether the red planet will be able to accept all willing migrants.
Mars is the fourth in terms of distance from the Sun and the seventh largest planet in the solar system, 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 its surface given by iron oxide.
Mars is a planet terrestrial group with a rarefied atmosphere. 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 satellite, 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 and have an irregular shape. They may be asteroids captured by the gravitational field of Mars, similar to the asteroid (5261) Eureka from the Trojan group.
The relief of Mars has many unique features. Martian dormant 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 of the surface topography, Mars has a rotation period and change of 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 like continents and seas. The 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.
Because of low pressure water cannot exist in a liquid state on the surface of Mars, but it is likely that in the past conditions were different, 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 spacecraft NASA Phoenix.
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. Surface of Mars in currently explored 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 suggests 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. Some parts of Mars' south polar cap are gradually receding, according to observations from NASA's Mars Global Surveyor spacecraft.
Mars can be seen from Earth with the naked eye. Its visible 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 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.
Mars is nearly double in size less earth- its equatorial radius is 3396.9 km (53.2% of the earth's). The surface area of Mars is approximately 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). Acceleration of gravity at the equator is equal to 3.711 m / s² (0.378 Earth); the first space velocity is 3.6 km / s and the second - 5.027 km / s. Mars rotates around its axis, inclined to the perpendicular to the orbital plane at an angle of 24 ° 56 ′. The rotation period of the planet is 24 hours 37 minutes 22.7 seconds. Thus, the Martian year consists of 668.6 solar days (called sols). The tilt of the Mars axis of rotation ensures the change of seasons. In this case, the elongation of the orbit leads to large differences in their duration. So, the northern spring and summer, taken together, lasts 371 sol, that is, noticeably more than half of the Martian year. At the same time, they fall on the part of Mars' orbit, distant from the Sun. Therefore, on Mars, northern summers are long and cool, while southern summers are short and hot.
The planet's temperature ranges from −153 ° C at the pole in winter to over + 20 ° C at the equator at noon. The average temperature is -50 ° C.
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| The atmosphere of Mars. |
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 level of the surface. Due to the large difference in altitude on Mars, the pressure at the surface varies greatly. Maximum value reaches 10-12 mbar in the Hellas basin at a depth of 8 km. 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.
The atmosphere is 95% carbon dioxide; it also contains 2.7% nitrogen, 1.6% argon, 0.13% oxygen, 0.1% water vapor, 0.07% carbon monoxide. There are traces of methane.
The Martian ionosphere extends from 110 to 130 km above the planet's surface.
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. The orbiting probe Mars Odysseus has 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.
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 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.
The Opportunity rover has recorded numerous dust vortices. These are air vortices that arise at the surface of the planet and lift into the air a large number of sand and dust. They are often observed on Earth, but on Mars they can reach much larger sizes.
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 imagery shows that, in fact, dark patches are 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 terms of 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 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.
The large number of craters in the southern hemisphere suggests that the surface here is 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 a chaotic landscape near the hemispheric boundary, the surface experienced fractures and compression of large areas, sometimes followed by erosion (due to landslides or catastrophic release groundwater), as well as flooding with liquid lava. 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.
In the northern hemisphere, in addition to the vast volcanic plains, there are two areas of large volcanoes - Farsis 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.
The Tarsis Upland is also crossed by many tectonic faults, often very complex and lengthy. 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 km 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.
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. To a terrestrial observer, it seems that the darkening wave is spreading from the polar cap to the equator, although the orbiters do not record any significant changes.
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 Mars Odyssey spacecraft 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.
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 raises 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.
The 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. A glacier hundreds of meters thick covers an area of thousands square kilometers, and its further study can provide information about the history of the Martian climate.
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 long-term existence 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.
Data from NASA's Spirit and Opportunity rovers 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.
Several unusual deep wells have been discovered on the Tarsis volcanic upland. Judging by the image of the Mars Reconnaissance Satellite, taken 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.
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 also contains necessary elements for the emergence and maintenance of life both in the past and in the present and future. " “We were pleasantly surprised by the data we received. This type of soil is widely represented here on Earth - every villager deals with it every day in the garden. It has a high (much higher than expected) content of alkalis, and ice crystals are found. Such soil is quite suitable for growing various plants, such as asparagus. There is nothing here that makes life impossible. On the contrary: with each new study we find additional evidence in favor of the possibility of its existence, "said the lead research chemist of the project, Sam Cooneyves.
There is also significant amount water ice.
Unlike Earth, Mars has no movement lithospheric plates... As a result, volcanoes can exist for a much longer time and reach gigantic proportions.
Modern models internal structure Mars is assumed to consist of a crust with an average thickness of 50 km (and maximum 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 / cm³. 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 current 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. A significant part of the deeper layer consists of granular oxide dust to the glands.
Mars has a magnetic field, but it is weak and 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 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 strip magnetic anomalies in the oceans.
One theory, published in 1999 and retested in 2005 (using the Mars Global Surveyor unmanned station), shows that these stripes 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 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.
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 on Earth occur in the ionosphere and above, on Mars can be observed almost at its very surface.
The geological history of Mars includes the following three eras:
Noachian Era (named after the "Noachi Land", a 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.
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.
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 of the hypotheses, 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, personifying 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 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.
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| Phobos (above) and Deimos (below). |
Both satellites have a shape approaching a triaxial ellipsoid, Phobos (26.6 × 22.2 × 18.6 km) is slightly larger than Deimos (15 × 12.2 × 10.4 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 long time remained in orbit around the satellite, gradually settling and hiding the unevenness of the relief.
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, popularized the idea of a planet whose climate was getting drier, colder, 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 he had the idea that the interference could be artificially caused. Although he was unable to decipher their meaning, it was impossible for him that they arose entirely by accident. In his opinion, it was a greeting from one planet to another.
Tesla's theory caused warm support 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 terrestrial life.
The absence of a magnetosphere and the extremely thin atmosphere of Mars are also challenges for supporting 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 disputed by some scientists. This led to their lengthy dispute 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 on 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. Soil nutrients are sufficient 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 the 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.
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.
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 this difference from colors of the earth's sky - the properties of the thin, rarefied atmosphere of Mars containing suspended dust. On Mars, Rayleigh scattering of rays (which on Earth is the cause 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 sunset. Sometimes the color of the Martian sky takes on purple tint as a result of light scattering by water ice microparticles in clouds (the latter is a rather rare phenomenon).
Earth is an inner planet in relation to Mars, just like Venus is to Earth. Accordingly, from Mars, the Earth is observed as morning or evening Star that rises before dawn or seen 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 already 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 visible 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.
The angular size of the Sun, as observed from Mars, is smaller than that seen from Earth and amounts to 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 (there are four largest satellite can be observed without a telescope), on the third - the Earth.
Phobos, when viewed 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 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 11 hours later, thus crossing the Mars sky twice a day. The movement of this fast moon the sky will be easily noticeable during the night, as will the phase change. The naked eye will discern 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 disk of the Sun.
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 ′ and is not marked by a bright star: the closest to the pole is a faint sixth-magnitude star BD +52 2880 (others 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 northern part constellation Cetus before re-entering western part Pisces.
Due to the proximity of Mars to Earth, its colonization in the foreseeable future is important task for humanity. Relatively close to earthly natural conditions facilitate this task. In particular, there are places on Earth, explored by man, in which natural conditions are in many respects similar to those of Mars. Atmosphere pressure at an altitude of 34 668 meters - a record high point, which was reached balloon with crew on board (May 1961) - roughly equal to pressure on the surface of Mars. Extremely low temperatures in the Arctic and Antarctica are comparable to even the coldest temperatures on Mars, and in the summer months, the equator of Mars is also warm (+ 30 ° C) as on Earth. Also on Earth there are deserts similar in appearance to the Martian landscape.
However, there are several 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 atmosphere, this increases the amount of ionizing radiation reaching its surface. Radiation measurements carried out by the American unmanned spacecraft 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 will most likely be somewhat lower and can vary significantly depending on the terrain, altitude, and local magnetic fields.
Mars has some economic potential for colonization. In particular, the southern hemisphere of Mars did not undergo melting, unlike the entire surface of the Earth - therefore, the rocks of the southern hemisphere inherited the quantitative composition of the non-volatile component of the protoplanetary cloud. According to calculations, it should be enriched with those elements (relative to the Earth), which on Earth "drowned" in its core during the melting of the planet: metals of the copper, iron and platinum group, tungsten, rhenium, uranium. The export of rhenium, platinum metals, silver, gold and uranium to the Earth (in the event of a rise in prices for it to the level of prices for silver) has good prospects, but requires for its implementation the presence of a surface reservoir with liquid water for enrichment processes.
The flight time from Earth to Mars (with current technologies) is 259 days in semi-ellipse and 70 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 (the opposition of Mars, from an earthly point of view, which repeats every 780 days), and about 20 minutes. at the maximum distance of the planets (conjunction of Mars with the Sun); see Configuration (astronomy).
However, to date, no practical steps towards the colonization of Mars have been taken.
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, which coincides with the observed one.
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| Topographic map of Mars. |
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 surface details: 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. It is largely due to public interest and the famous scientific controversy surrounding 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, 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.
Orbital characteristics:
Perihelion
206.62 × 106 km
1.3812 a. e.
Aphelion
249.23 × 106 km
1.6660 a. e.
Semi-major axis (a)
227.92 × 106 km
1.5236 a. e.
Orbital eccentricity (e)
0,093315
Sidereal circulation period
686,971 days
1.8808 Earth Years
668.5991 sol
Synodic period of circulation
779.94 days
Orbital speed (v)
24.13 km / s (average)
Inclination (i)
1.85061 ° (relative to the plane of the ecliptic)
5.65 ° (relative to solar equator)
Ascending node longitude (Ω)
49.57854 °
Pericenter argument (ω)
286.46230 °
Satellites:
2 (Phobos and Deimos)
physical characteristics
Flatness
0,00589
Equatorial radius
3396.2 km
Polar radius
3376.2 km
Average radius
3386.2 km
Surface area (S)
144 798 465 km²
Volume (V)
1.6318 × 1011 km³
0.151 Earthly
Mass (m)
6.4185 × 1023 kg
0.107 Earthly
Average density (ρ)
3.9335 g / cm³
Acceleration of gravity at the equator (g)
3.711 m / s² (0.378 g)
Second space speed (v2)
5.027 km / s
Equatorial rotation rate
868.22 km / h
Rotation period (T)
24 hours 39 minutes and 36 seconds
Axis tilt
24.94 °
Right ascension of the North Pole (α)
21 h 10 min 44 s
317.68143 °
North Pole declination (δ)
52.88650 °
Albedo
0.250 (Bond)
0.150 (geom.albedo)
Temperature:
min. wednesday Max.
All over the planet 186 K 227 K 268 K
Atmosphere:
Atmosphere pressure
0.6-1.0 kPa (0.006-0.01 atm)
Composition:
95.32% Ang. gas
2.7% Nitrogen
1.6% Argon
0.2% Oxygen
0.07% Carbon monoxide
0.03% Water vapor
0.01% Nitrogen oxide
If you observe Earth and Mars from some distance, it becomes obvious that they exhibit some striking differences. In the first case, the predominant colors are white and blue, corresponding to clouds and oceans, with brown shades continents. Thus, the existence of water in its various conditions(solid in polar glaciers, liquid in oceans and seas and in gaseous state in the atmosphere) is obvious. And the presence of water presupposes the existence of life.
In fact, even from orbiting satellites, you can see the intense biological activity of the planet. This can be seen from the Antarctic sea ice or seasonal changes in forest colors.
Earth (first complete photograph of the planet from Apollo 17, with Antarctica at the top) and Mars (image captured by HST). Please note, the images are not shown in real scale, since Mars is much smaller than our planet (equatorial diameters 12,756.28 and 6,794.4 kilometers, respectively).
Red Planet
Mars is completely different. Its surface is dominated by various shades of orange, caused by the high content of iron oxide. Depending on the season and the position of the Red Planet relative to the Earth, one of the poles of Mars may be visible to astronomers, in which case dry ice (solid carbon dioxide) gives it a white color. However, several studies in recent years have made scientists understand that there is water and that the dynamics life cycle this compound on the planet is quite complex.
Mars has a thin atmosphere composed mainly of carbon dioxide (95.32%), nitrogen (2.7%), argon (1.4%), and traces of oxygen (0.13%). The Earth's atmosphere consists mainly of nitrogen (78.1%), oxygen (20.94%), argon (0.93%) and variable amounts of carbon dioxide (about 0.035% and growing rapidly). Average planetary temperatures vary widely: -55 degrees Celsius (ºC) in the case of Mars, with lows around -133 ºC and highs around +27 ºC; and an average of about +15 ºC for Earth with minima of -89.4 ºC (noted in Antarctica, although a temperature of -93.2 ºC was recently recorded by satellite measurements) and maximums of +58 ºC measured at El Aziz , Libya.
The average temperature of the Earth depends on greenhouse effect caused by gases in the atmosphere, mainly carbon dioxide, water vapor, ozone (oxygen molecules with three oxygen atoms instead of two that we breathe) and methane. Otherwise, the average temperature on Earth would be about 33 ºC lower, about -18 ºC, and therefore water would be solid throughout most of the planet.
Internal structure
In the case of Mars and Earth, their internal structure is divided into three well-differentiated regions: crust, mantle, and core. However, unlike Earth, Mars' core is solid and does not create its own magnetic field. Moreover, Mars has local magnetic fields, which are relict remnants of a global field that existed possibly when Mars possessed a partially liquid core. The virtual absence on the Red Planet of plate tectonics as we know it on Earth, causing strong volcanic activity and orogeny (mountain building), means that Martian soil is much older than the ocean floor and the Earth's continents. For example, the great lowland lowland of the southern hemisphere, the Plain of Hellas, was formed by the impact of a large celestial body about 3900 million years ago. In the case of Earth, evidence of an event of this age would have long since disappeared into her face.
Comparison of the elevation profiles of the two planets shows that they are very different: while most of the Earth's continental land mass is concentrated in the northern hemisphere, which also lacks a polar continent, the northern hemisphere on Mars is dominated by the great northern lowland lowland, located at the level of a thousand meters below the zero mark of the heights of Mars. It is located at a height where the atmospheric pressure is 6.1 millibars and there is a triple point of water, at which matter coexists in solid, liquid and gaseous at the same time. In the case of water, the exact value is 273.16 K (0.01 ° C) at a pressure of 6.1173 millibars. Therefore, below the reference point for the heights of Mars (for example, at the level of Hellas Planitia), liquid water could be found if the temperature there were high enough.
In contrast to what it looks like on Mars, the oceans and seas dominate in the southern hemisphere of the Earth, although several continental massifs stand out in the topographic profile of our planet, which rise to significant heights above sea level (for example, the Antarctic Plateau). The situation on Mars is more homogeneous. The biggest difference between the planets is that a large amount of solid water is concentrated on South Pole Earth. It covers an area of about 14 million square kilometers in summer, but, including sea ice, can increase to 30 million. The size reached by Martian Antarctica is much smaller - about 140,000 square kilometers, and its composition is very different from that of Earth. As mentioned earlier, it is dominated by dry ice.
Curiously, in our Antarctica we find some close similarities with Mars, namely the presence of low temperatures and low humidity. This refers to the McMurdo Valley system, which is very close to the coast, and may have geological equivalents on Mars.
Is there life on Mars?
Whether life exists on Mars or not, or whether there has ever been any biological activity, remains an open question. Some research suggests that Martian land is too salty for life to develop there. However, there are many examples of living things on our planet that develop in clearly hostile conditions. They are known as.
McMurdo Valley in Antarctica, off the coast. This system is generally snow-free and unusually dry. Therefore, it may be similar to some of the Martian regions. The comparative size of the planet
Planet Mars and Venus two celestial bodies most similar to Earth. Both are visible to the naked eye and are two of the brightest objects in the night sky.
Venus rotates at an average distance of only 108 million km from the Sun, and Mars 228 million km. Venus approaches the Earth at 38 million km, and Mars only 55.7 million km.
Size comparison
In terms of size, Venus is nearly the twin of planet Earth. Its diameter is 12104 km, which is equal to 95% of the Earth's diameter. It is much smaller, its diameter is only 6792 km. And again, in terms of mass, Venus is almost the twin of our planet. It has 81% of the mass of the Earth, and the red planet only 10% of the mass of the Earth.
Climate
The climate of the planets is very different, and very different from the Earth. The temperature on the surface of the second planet from the Sun averages 461 ° C over the entire surface. This is enough to melt the lead. While the average temperature on Mars is -46 ° C. This temperature difference is due to Venus being closer to the Sun and having a dense carbon dioxide atmosphere. Its atmosphere is almost 100 times thicker than that of the Earth, while the atmosphere on Mars is 1% of ours.
The study
Mars is the most studied planet in the solar system. Dozens of missions have been dispatched, including orbiters and rovers. Although many missions failed, there were several successful ones, including some that are still in operation. Many missions were launched to Venus, however, due to the aggressive conditions, we were able to obtain only a few photographs from the surface.
Mars has two satellites, Phobos and Deimos, while Venus does not have satellites, just as neither planet has rings.
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