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Subtitles
The study
The atmosphere of Mars was discovered even before the flights of automatic interplanetary stations to the planet. Thanks to spectral analysis and the oppositions of Mars with the Earth, which happen once every 3 years, astronomers already in the 19th century knew that it has a very homogeneous composition, more than 95% of which is carbon dioxide. Compared to 0.04% carbon dioxide in the Earth's atmosphere, it turns out that the mass of Martian atmospheric carbon dioxide exceeds the mass of the Earth's by almost 12 times, so that during the terraforming of Mars, the carbon dioxide contribution to the greenhouse effect can create a climate comfortable for humans somewhat earlier than a pressure of 1 atmosphere is reached, even taking into account the greater distance of Mars from the Sun.
Back in the early 1920s, the first measurements of the temperature of Mars were made using a thermometer placed at the focus of a reflecting telescope. Measurements by V. Lampland in 1922 gave an average surface temperature of Mars of 245 (−28 °C), E. Pettit and S. Nicholson in 1924 obtained 260 K (−13 °C). A lower value was obtained in 1960 by W. Sinton and J. Strong: 230 K (−43 ° C). The first estimates of pressure - averaged - were obtained only in the 60s using ground-based IR spectroscopes: a pressure of 25 ± 15 hPa obtained from the Lorentz broadening of carbon dioxide lines meant that it was the main component of the atmosphere.
The wind speed can be determined from the Doppler shift of the spectral lines. So, for this, the line shift was measured in the millimeter and submillimeter range, and measurements on the interferometer make it possible to obtain the distribution of velocities in the whole layer of great thickness.
The most detailed and accurate data on air and surface temperature, pressure, relative humidity and wind speed are continuously measured by the Rover Environmental Monitoring Station (REMS) instrumentation aboard the Curiosity rover, which has been operating in the Gale crater since 2012. And the MAVEN spacecraft, which has been orbiting Mars since 2014, is specifically designed to study the upper atmosphere in detail, their interaction with solar wind particles, and in particular the scattering dynamics.
A number of processes that are difficult or not yet possible for direct observation are subject only to theoretical modeling, but it is also important method research.
Atmospheric structure
In general, the atmosphere of Mars is divided into lower and upper; the latter is considered to be the region above 80 km above the surface, where the processes of ionization and dissociation play an active role. A section is devoted to its study, which is commonly called aeronomy. Usually, when people talk about the atmosphere of Mars, they mean the lower atmosphere.
Also, some researchers distinguish two large shells - the homosphere and the heterosphere. In the homosphere chemical composition does not depend on altitude, since the processes of heat and moisture transfer in the atmosphere and their vertical exchange are entirely determined by turbulent mixing. Since molecular diffusion in the atmosphere is inversely proportional to its density, then from a certain level this process becomes predominant and is the main feature of the upper shell - the heterosphere, where molecular diffuse separation occurs. The interface between these shells, which is located at altitudes from 120 to 140 km, is called the turbopause.
lower atmosphere
From the surface to a height of 20-30 km stretches troposphere where the temperature decreases with height. The upper limit of the troposphere varies depending on the time of year (the temperature gradient in the tropopause varies from 1 to 3 deg/km, with an average value of 2.5 deg/km).
Above the tropopause is an isothermal region of the atmosphere - stratomesosphere stretching up to a height of 100 km. The average temperature of the stratomesosphere is exceptionally low and amounts to -133°C. Unlike the Earth, where the stratosphere contains predominantly all atmospheric ozone, on Mars its concentration is negligible (it is distributed from altitudes of 50 - 60 km to the very surface, where it is maximum).
upper atmosphere
Above the stratomesosphere extends the upper layer of the atmosphere - thermosphere. It is characterized by an increase in temperature with height up to a maximum value (200-350 K), after which it remains constant up to the upper limit (200 km). The presence of atomic oxygen was registered in this layer; its density at a height of 200 km reaches 5-6⋅10 7 cm −3 . The presence of a layer dominated by atomic oxygen (as well as the fact that the main neutral component is carbon dioxide) combines the atmosphere of Mars with the atmosphere of Venus.
Ionosphere- area with a high degree ionization - is in the range of heights from about 80-100 to about 500-600 km. The content of ions is minimal at night and maximal during the day, when the main layer is formed at an altitude of 120-140 km due to the photoionization of carbon dioxide extreme ultraviolet solar radiation CO 2 + hν → CO 2 + + e -, as well as reactions between ions and neutral substances CO 2 + + O → O 2 + + CO and O + + CO 2 → O 2 + + CO. The concentration of ions, of which 90% O 2 + and 10% CO 2 +, reaches 10 5 per cubic centimeter (in other areas of the ionosphere it is 1-2 orders of magnitude lower). It is noteworthy that O 2 + ions predominate in the almost complete absence of molecular oxygen proper in the Martian atmosphere. The secondary layer is formed in the region of 110-115 km due to soft X-rays and knocked out fast electrons. At an altitude of 80-100 km, some researchers distinguish a third layer, sometimes manifested under the influence of particles space dust, bringing metal ions Fe + , Mg + , Na + into the atmosphere. However, later it was not only confirmed the appearance of the latter (moreover, over almost the entire volume of the upper atmosphere) due to the ablation of the substance of meteorites and other space bodies but also their constant presence in general. At the same time, due to the absence of Mars magnetic field their distribution and behavior are significantly different from what is observed in earth's atmosphere. Above the main maximum, other additional layers can also appear due to interaction with the solar wind. Thus, the layer of O+ ions is most pronounced at an altitude of 225 km. In addition to the three main types of ions (O 2 +, CO 2 and O +), relatively recently H 2 + , H 3 + , He + , C + , CH + , N + , NH + , OH + , H 2 O + , H 3 O + , N 2 + /CO + , HCO + /HOC + /N 2 H + , NO + , HNO + , HO 2 + , Ar + , ArH + , Ne + , CO 2 ++ and HCO2+. Above 400 km, some authors distinguish an "ionopause", but there is no consensus on this yet.
As for the plasma temperature, the ion temperature near the main maximum is 150 K, increasing to 210 K at an altitude of 175 km. Higher, the thermodynamic equilibrium of ions with a neutral gas is significantly disturbed, and their temperature rises sharply to 1000 K at an altitude of 250 km. The temperature of electrons can be several thousand kelvins, apparently due to the magnetic field in the ionosphere, and it grows with increasing solar zenith angle and is not the same in the northern and southern hemispheres, which may be due to the asymmetry of the residual magnetic field of the Martian crust. In general, one can even distinguish three populations of high-energy electrons with different temperature profiles. The magnetic field also affects the horizontal distribution of ions: streams of high-energy particles are formed above magnetic anomalies, swirling along the field lines, which increases the ionization intensity, and an increased ion density and local structures are observed.
At an altitude of 200-230 km, there is the upper boundary of the thermosphere - the exobase, above which the exosphere Mars. It consists of light substances - hydrogen, carbon, oxygen - which appear as a result of photochemical reactions in the underlying ionosphere, for example, dissociative recombination of O 2 + with electrons. The continuous supply of atomic hydrogen to the upper atmosphere of Mars occurs due to the photodissociation of water vapor near the Martian surface. Due to the very slow decrease in hydrogen concentration with height, this element is the main component of the outermost layers of the planet's atmosphere and forms a hydrogen corona that extends over a distance of about 20,000 km, although there is no strict boundary, and particles from this region simply gradually dissipate into the surrounding outer space.
In the atmosphere of Mars, it is also sometimes released chemosphere- the layer where photochemical reactions take place, and since, due to the lack of an ozone screen, like that of the Earth, ultraviolet radiation reaches the very surface of the planet, they are possible even there. The Martian chemosphere extends from the surface to an altitude of about 120 km.
Chemical composition of the lower atmosphere
Despite the strong rarefaction of the Martian atmosphere, the concentration of carbon dioxide in it is about 23 times greater than in the earth.
- Nitrogen (2.7%) is currently actively dissipating into space. In the form of a diatomic molecule, nitrogen is stably held by the attraction of the planet, but is split by solar radiation into single atoms, easily leaving the atmosphere.
- Argon (1.6%) is represented by the relatively dissipation-resistant heavy isotope argon-40. Light 36 Ar and 38 Ar are present only in parts per million
- Other noble gases: neon, krypton, xenon (ppm)
- Carbon monoxide (CO) - is a product of CO 2 photodissociation and is 7.5⋅10 -4 concentration of the latter - this is an inexplicably small value, since the reverse reaction CO + O + M → CO 2 + M is prohibited, and much more should have accumulated CO. Various theories have been proposed as carbon monoxide can still be oxidized to carbon dioxide, but they all have certain disadvantages.
- Molecular oxygen (O 2) - appears as a result of photodissociation of both CO 2 and H 2 O in the upper atmosphere of Mars. In this case, oxygen diffuses into the lower layers of the atmosphere, where its concentration reaches 1.3⋅10 -3 of the near-surface concentration of CO 2 . Like Ar, CO, and N 2 , it is a non-condensable substance on Mars, so its concentration also undergoes seasonal variations. In the upper atmosphere, at a height of 90-130 km, the content of O 2 (share relative to CO 2) is 3-4 times higher than the corresponding value for the lower atmosphere and averages 4⋅10 -3 , varying in the range from 3.1⋅10 -3 to 5.8⋅10 -3 . In ancient times, the atmosphere of Mars contained, however, a larger amount of oxygen, comparable to its share on the young Earth. Oxygen, even in the form of individual atoms, no longer dissipates as actively as nitrogen, due to its greater atomic weight, which allows it to accumulate.
- Ozone - its amount varies greatly depending on surface temperature: it is minimum at the time of the equinox at all latitudes and maximum at the pole, where winter is, moreover, inversely proportional to the concentration of water vapor. There is one pronounced ozone layer at about 30 km and another between 30 and 60 km.
- Water. The content of H 2 O in the atmosphere of Mars is about 100-200 times less than in the atmosphere of the driest regions of the Earth, and averages 10-20 microns of a precipitated water column. Water vapor concentration undergoes significant seasonal and diurnal variations. The degree of air saturation with water vapor is inversely proportional to the content of dust particles, which are centers of condensation, and in some areas (in winter, at an altitude of 20-50 km), steam was recorded, the pressure of which exceeds the saturated vapor pressure by 10 times - much more than in the earth's atmosphere .
- Methane. Since 2003, there have been reports of registration of methane emissions of an unknown nature, but none of them can be considered reliable due to certain shortcomings in the registration methods. In this case, we are talking about extremely small values - 0.7 ppbv (upper limit - 1.3 ppbv) as a background value and 7 ppbv for episodic bursts, which is on the verge of resolution. Since, along with this, information was also published about the absence of CH 4 confirmed by other studies, this may indicate some kind of intermittent source of methane, as well as the existence of some mechanism for its rapid destruction, while the duration of the photochemical destruction of this substance is estimated at 300 years. The discussion on this issue is currently open, and it is of particular interest in the context of astrobiology, in view of the fact that on Earth this substance has a biogenic origin.
- traces of some organic compounds. The most important are the upper limits on H 2 CO, HCl and SO 2, which indicate the absence, respectively, of reactions involving chlorine, as well as volcanic activity, in particular, the non-volcanic origin of methane, if its existence is confirmed.
The composition and pressure of the atmosphere of Mars make it impossible for humans and other terrestrial organisms to breathe. To work on the surface of the planet, a spacesuit is necessary, although not as bulky and protected as for the Moon and open space. The atmosphere of Mars itself is not poisonous and consists of chemically inert gases. The atmosphere somewhat slows down meteorite bodies, so there are fewer craters on Mars than on the Moon and they are less deep. And micrometeorites burn out completely, not reaching the surface.
Water, clouds and precipitation
Low density does not prevent the atmosphere from forming large-scale phenomena that affect climate.
Water vapor in the Martian atmosphere is no more than a thousandth of a percent, however, according to the results of recent (2013) studies, this is still more than previously thought, and more than in the upper layers of the Earth's atmosphere, and at low pressure and temperature, it is in a state close to saturation, so it often gathers in clouds. As a rule, water clouds form at altitudes of 10-30 km above the surface. They are concentrated mainly on the equator and are observed almost throughout the year. Clouds seen on high levels atmosphere (more than 20 km) are formed as a result of CO 2 condensation. The same process is responsible for the formation of low (at an altitude of less than 10 km) clouds in the polar regions in winter, when the atmospheric temperature drops below the freezing point of CO 2 (-126 ° C); in summer, similar thin formations are formed from ice H 2 O
One of the interesting and rare atmospheric phenomena on Mars was discovered ("Viking-1") when photographing the northern polar region in 1978. These are cyclonic structures that are clearly identified in photographs by vortex-like cloud systems with counterclockwise circulation. They were found in the latitudinal zone 65-80°N. sh. during the "warm" period of the year, from spring to early autumn, when the polar front is established here. Its occurrence is due to the sharp contrast in surface temperatures at this time of year between the edge of the ice cap and the surrounding plains. The wave movements of air masses associated with such a front lead to the appearance of cyclonic eddies so familiar to us on Earth. The systems of vortex clouds found on Mars vary in size from 200 to 500 km, their speed of movement is about 5 km/h, and the wind speed at the periphery of these systems is about 20 m/s. The duration of existence of an individual cyclonic eddy ranges from 3 to 6 days. The temperature values in the central part of the Martian cyclones indicate that the clouds are composed of water ice crystals.
Snow has indeed been observed more than once. So, in the winter of 1979, a thin layer of snow fell in the Viking-2 landing area, which lay for several months.
Dust storms and dust devils
A characteristic feature of the atmosphere of Mars is the constant presence of dust; according to spectral measurements, the size of dust particles is estimated at 1.5 µm. Low gravity allows even rarefied air flows to raise huge clouds of dust to a height of up to 50 km. And the winds, which are one of the manifestations of the temperature difference, often blow over the surface of the planet (especially in late spring - early summer in the southern hemisphere, when the temperature difference between the hemispheres is especially sharp), and their speed reaches 100 m / s. Thus, vast dust storms are formed, which have long been observed in the form of individual yellow clouds, and sometimes in the form of a continuous yellow veil covering the entire planet. Most often, dust storms occur near the polar caps, their duration can reach 50-100 days. Weak yellow haze in the atmosphere, as a rule, is observed after large dust storms and is easily detected by photometric and polarimetric methods.
Dust storms, which were well observed on images taken from orbiters, turned out to be barely visible when photographed from landers. The passage of dust storms at the landing sites of these space stations was recorded only by a sharp change in temperature, pressure, and a very slight darkening of the general sky background. The layer of dust that settled after the storm in the vicinity of the Viking landing sites amounted to only a few micrometers. All this indicates a rather low bearing capacity of the Martian atmosphere.
From September 1971 to January 1972, a global dust storm took place on Mars, which even prevented photographing the surface from the Mariner 9 probe. The mass of dust in the atmospheric column (with an optical thickness of 0.1 to 10) estimated during this period ranged from 7.8⋅10 -5 to 1.66⋅10 -3 g/cm 2 . Thus, the total weight of dust particles in the atmosphere of Mars during the period of global dust storms can reach up to 10 8 - 10 9 t, which is commensurate with total dust in the earth's atmosphere.
The aurora was first recorded by the SPICAM UV spectrometer aboard the Mars Express spacecraft. Then it was repeatedly observed by the MAVEN apparatus, for example, in March 2015, and in September 2017, a much more powerful event was recorded by the Radiation Assessment Detector (RAD) on the Curiosity rover. An analysis of the data from the MAVEN apparatus also revealed aurora of a fundamentally different type - diffuse, which occur at low latitudes, in areas that are not tied to magnetic field anomalies and are caused by the penetration of particles with very high energy, about 200 keV, into the atmosphere.
In addition, the extreme ultraviolet radiation of the Sun causes the so-called own glow of the atmosphere (eng. airglow).
The registration of optical transitions during auroras and intrinsic glow provides important information about the composition of the upper atmosphere, its temperature, and dynamics. Thus, the study of the γ- and δ-bands of nitric oxide emission during the night period helps to characterize the circulation between the illuminated and unilluminated regions. And registration of radiation at a frequency of 130.4 nm with its own glow helped to reveal the presence of high-temperature atomic oxygen, which was an important step in understanding the behavior of atmospheric exospheres and coronas in general.
Color
The dust particles that fill the Martian atmosphere are mostly iron oxide, and it gives it a reddish-orange tint.
According to measurements, the atmosphere has an optical thickness of 0.9, which means that only 40% of the incident solar radiation reaches the surface of Mars through its atmosphere, and the remaining 60% is absorbed by dust hanging in the air. Without it, the Martian skies would have approximately the same color as the earth's sky at an altitude of 35 kilometers. It should be noted that in this case the human eye would adapt to these colors, and the white balance would automatically be adjusted so that the sky would be seen the same as under terrestrial lighting conditions.
The color of the sky is very heterogeneous, and in the absence of clouds or dust storms from a relatively light on the horizon, it darkens sharply and in a gradient towards the zenith. In a relatively calm and windless season, when there is less dust, the sky can be completely black at the zenith.
Nevertheless, thanks to the images of the rovers, it became known that at sunset and sunrise around the Sun, the sky turns blue. The reason for this is Rayleigh scattering - light scatters on gas particles and colors the sky, but if on a Martian day the effect is weak and invisible to the naked eye due to rarefied atmosphere and dust, then at sunset the sun shines through a much thicker layer of air, due to which blue and violet begin to scatter components. The same mechanism is responsible for the blue sky on Earth during the day and yellow-orange at sunset. [ ]
A panorama of the Rocknest sand dunes, compiled from images from the Curiosity rover.
Changes
Changes in the upper layers of the atmosphere are quite complex, since they are connected with each other and with the underlying layers. Atmospheric waves and tides propagating upwards can have a significant effect on the structure and dynamics of the thermosphere and, as a consequence, the ionosphere, for example, the height of the upper boundary of the ionosphere. During dust storms in the lower atmosphere, its transparency decreases, it heats up and expands. Then the density of the thermosphere increases - it can vary even by an order of magnitude - and the height of the electron concentration maximum can rise by up to 30 km. Changes in the upper atmosphere caused by dust storms can be global, affecting areas up to 160 km above the planet's surface. The response of the upper atmosphere to these phenomena takes several days, and it returns to its previous state much longer - several months. Another manifestation of the relationship between the upper and lower atmosphere is that water vapor, which, as it turned out, is oversaturated with the lower atmosphere, can undergo photodissociation into lighter H and O components, which increase the density of the exosphere and the intensity of water loss by the Martian atmosphere. External factors causing changes in the upper atmosphere are extreme ultraviolet and soft x-rays Suns, solar wind particles, cosmic dust, and larger bodies such as meteorites. The task is complicated by the fact that their impact, as a rule, is random, and its intensity and duration cannot be predicted, moreover, episodic phenomena are superimposed by cyclical processes associated with changes in the time of day, season, and the solar cycle. At present, at best, there is accumulated statistics of events on the dynamics of atmospheric parameters, but a theoretical description of the regularities has not yet been completed. A direct proportionality between the concentration of plasma particles in the ionosphere and solar activity has been definitely established. This is confirmed by the fact that a similar regularity was actually recorded according to the results of observations in 2007-2009 for the Earth's ionosphere, despite the fundamental difference in the magnetic field of these planets, which directly affects the ionosphere. And particle emissions solar corona, causing a change in the pressure of the solar wind, also entail a characteristic compression of the magnetosphere and ionosphere: the maximum plasma density drops to 90 km.
Daily fluctuations
Despite its rarefaction, the atmosphere nevertheless reacts to changes in the flow. solar heat slower than the surface of the planet. So, in the morning period, the temperature varies greatly with height: a difference of 20 ° was recorded at a height of 25 cm to 1 m above the surface of the planet. With the rising of the Sun, cold air heats up from the surface and rises in the form of a characteristic swirl upwards, raising dust into the air - this is how dust devils are formed. In the near-surface layer (up to 500 m high) there is a temperature inversion. After the atmosphere has already warmed up by noon, this effect is no longer observed. The maximum is reached at about 2 o'clock in the afternoon. The surface then cools faster than the atmosphere and a reverse temperature gradient is observed. Before sunset, the temperature again decreases with height.
The change of day and night also affects the upper atmosphere. First of all, ionization by solar radiation stops at night, however, the plasma continues to be replenished for the first time after sunset due to the flux from the day side, and then is formed due to impacts of electrons moving downward along the magnetic field lines (the so-called intrusion of electrons) - then the maximum observed at an altitude of 130-170 km. Therefore, the density of electrons and ions on the night side is much lower and is characterized by a complex profile, which also depends on the local magnetic field and varies in a non-trivial way, the regularity of which is not yet fully understood and described theoretically. During the day, the state of the ionosphere also changes depending on the zenith angle of the Sun.
annual cycle
Like on Earth, on Mars there is a change of seasons due to the inclination of the axis of rotation to the plane of the orbit, so in winter the polar cap grows in the northern hemisphere, and almost disappears in the southern, and after six months the hemispheres change places. At the same time, due to the rather large eccentricity of the planet's orbit at perihelion (winter solstice in the northern hemisphere), it receives up to 40% more solar radiation than in aphelion, and in the northern hemisphere, winter is short and relatively moderate, and summer is long, but cool, in in the south, on the contrary, summers are short and relatively warm, and winters are long and cold. In this regard, the southern cap in winter grows up to half the pole-equator distance, and the northern cap only up to a third. When summer comes at one of the poles, carbon dioxide from the corresponding polar cap evaporates and enters the atmosphere; the winds carry it to the opposite cap, where it freezes again. In this way, the carbon dioxide cycle occurs, which, along with the different sizes of the polar caps, causes a change in the pressure of the Martian atmosphere as it orbits the Sun. Due to the fact that in winter up to 20-30% of the entire atmosphere freezes in the polar cap, the pressure in the corresponding area drops accordingly.
Seasonal variations (as well as daily ones) also undergo water vapor concentration - they are in the range of 1-100 microns. So, in winter the atmosphere is almost “dry”. Water vapor appears in it in the spring, and by mid-summer its amount reaches a maximum, following changes in surface temperature. During the summer-autumn period, water vapor is gradually redistributed, and its maximum content moves from the northern polar region to equatorial latitudes. At the same time, the total global vapor content in the atmosphere (according to Viking-1 data) remains approximately constant and is equivalent to 1.3 km 3 of ice. The maximum content of H 2 O (100 μm of precipitated water, equal to 0.2 vol%) was recorded in summer over the dark region surrounding the northern residual polar cap - at this time of the year the atmosphere above the ice of the polar cap is usually close to saturation.
In the spring-summer period in the southern hemisphere, when dust storms are most actively formed, diurnal or semi-diurnal atmospheric tides are observed - an increase in pressure near the surface and thermal expansion of the atmosphere in response to its heating.
The change of seasons also affects the upper atmosphere - both the neutral component (thermosphere) and the plasma (ionosphere), and this factor must be taken into account together with the solar cycle, and this complicates the task of describing the dynamics of the upper atmosphere.
Long term change
see also
Notes
- Williams, David R. Mars Fact Sheet (indefinite) . National Space Science Data Center. NASA (September 1, 2004). Retrieved 28 September 2017.
- N. Mangold, D. Baratoux, O. Witasse, T. Encrenaz, C. Sotin. Mars: a small terrestrial planet : [English] ]// The Astronomy and Astrophysics Review. - 2016. - V. 24, No. 1 (December 16). - P. 15. - DOI: 10.1007/s00159-016-0099-5 .
- Atmosphere of Mars (indefinite) . UNIVERSE-PLANET // PORTAL TO ANOTHER DIMENSION
- Mars is a red star. Description of the area. Atmosphere and climate (indefinite) . galspace.ru - Solar System Exploration Project. Retrieved 29 September 2017.
- (English) Out of Thin Martian Air Astrobiology Magazine, Michael Schirber, 22 August 2011.
- Maxim Zabolotsky. General information about atmosphere Mars (indefinite) . spacegid.com(21.09.2013). Retrieved 20 October 2017.
- Mars Pathfinder - Science Results - Atmospheric and Meteorological Properties (indefinite) . nasa.gov. Retrieved April 20, 2017.
- J. L. Fox, A. Dalgarno. Ionization, luminosity, and heating of the upper atmosphere of Mars: [English] ]// J Geophys Res. - 1979. - T. 84, issue. A12 (December 1). - S. 7315–7333. -
A common mistake that usually makes estimates of the climatic conditions of a particular planet is to confuse pressure with density. Although from a theoretical point of view we all know the difference between pressure and density, in reality it is taken to compare the atmospheric pressure on earth with the atmospheric pressure of a given planet without precaution.
In any terrestrial laboratory where gravity is about the same, this precaution is not necessary and often uses pressure as a "synonym" for density. Some phenomena are handled safely in terms of "pressure/temperature" cost, such as face diagrams (or State Diagrams), where it would actually be more correct to speak of "density and temperature coefficient" or "under pressure/temperature", in otherwise we do not understand the presence of liquid water in the absence of gravity (and then weightlessness) in spacecraft in orbit in space!
In fact, technically, atmospheric pressure is the "weight" that a certain amount of gas above our heads exerts on everything below. However, the real problem is that weight is due not only to density but obviously to gravity. If we for example decrease the Earth's gravity by 1/3, It is obvious that the same amount of gas that is above us will have one third of its original weight, Despite the amount of gas remains exactly the same. So, then, in comparison climatic conditions between two planets it would be more correct to speak of density rather than pressure.
We understand this principle very well by analyzing the functioning of the Torricelli barometer, the first instrument that measured the earth's atmospheric pressure. If we fill a closed tube of mercury on one side and set the vertically open end immersed in a tank filled with mercury also, you will notice the formation of a vacuum chamber at the top of the straw. Torricelli actually noted that the external pressure, present in the straw, It was to support the mercury column high by about 76 cm. By calculating the specific mercury product, the Earth's gravity and the height of the mercury column, one can calculate the weight above the atmosphere.
From Wikipedia at: http:///Wiki/Tubo_di_Torricelli it.wikipedia.org
This system, brilliant for its time, however, has strong limitations when used in "Earthlings". In fact, as real gravity in two of the three factors of the formula, Any difference in gravity produces a quadratic difference in the response of the barometer, then, the same column of air, on a planet with 1/3 of the original gravity, will produce, for the barometer, Torricelli , under pressure 1/9 of the original value.
Clearly, apart from instrumental artifacts, the fact remains: the same column of air will have a weight proportional to the gravity of the planets on which from time to time we will have it so just barometric pressure is not an absolute measure of density!
This effect is systematically ignored in analyzes of the Martian atmosphere. We speak easily of pressure in hPa and deal directly with the earth, completely ignoring the pressure of hPa, which is that gravity on Mars is about 1/3 that of earth (for an accuracy of 38%). The same mistakes you make when you look at the faces of water diagrams to demonstrate that on Mars, water cannot exist in liquid form. In particular, the triple point of water, on earth is 6.1 hPa, but on Mars, where gravity is 38% that of earth. If you do in hPa, it would be absolutely 6.1 but for 2.318 hPa (Although the barometer, Torricelli would mark 0.88 hPa). This analysis, however, is always, in my opinion fraudulently, systematically avoided, restoring the notation to the same ground values. The same indication of 5-7 hpa for Martian atmospheric pressure is not explicitly stated whether it means earth's gravity or Mars.
Actually 7 hPa on Mars should have a gas density on earth would measure about 18.4 hPa. It's absolutely avoidable at all modern research, Let's say in the second half of 60 Next, Whereas previously strictly stated that the pressure was one tenth of the earth but with a density of 1/3. From a purely scientific point of view, the real weight of a column of air was considered, which resulted in 1/3 of its actual weight on the ground, but that in fact the density was comparable to 1/3 of that of the earth. How come in recent studies there is this difference?
Maybe because it's easier to talk about the impossibility of keeping the liquid phase of water?
There are other clues to this thesis: Every atmosphere actually produces light scattering (scattering) predominantly in blue, which even in the case of Mars can be easily analyzed. Although the atmosphere of Mars is a bunch of dust to make it reddish, by separating the blue color component of the panoramic image of Mars, you can get an idea of the density of Mars' atmosphere. If we compare the earth's sky with images taken at different heights, and then with different degrees of density, we understand that the nominal size in which we must find 7 hPa, i.e. 35.000 m, the sky is completely black, the Salvo fair horizon is a band where in fact we can still see in the layers of our atmosphere.
Left: Footage of the Martian landscape taken by the Pathfinder probe on June 22, 1999. Source: http://photojournal.JPL. nasa.gov/catalog/PIA01546 right: Blue channel figure beside; Notice the intensity of the sky!
Left: Sydney - City of South East Australia, Capital of New South Wales, at 6 m. Right: Blue channel drawing near.
Left: Sydney, but always during a sandstorm. Right: Blue channel drawing near; as you can see, hanging dust reduce the brightness of the sky, not increase it, Contrary to what is claimed in the case of NASA Mars!
It is obvious that photographs of the Martian sky, filtered by the blue band, are much brighter, almost comparable to images taken on Mount Everest, a little less than 9.000 m, where to look if the atmospheric pressure is 1/3 normal sea level pressure.
Another evidence of a serious benefit of the Martian atmosphere density being higher than announced, was provided by the Devils dust phenomenon. These "mini tornadoes" are capable of lifting sand columns up to several kilometers; But how is this possible?
NASA, itself, tried to simulate them, in a vacuum chamber, Simulating a Martian pressure of 7 hPa, and they were unable to simulate the phenomena unless it raised the pressure at least 11 times! Initial pressure, even when using a very powerful fan, could not lift anything!
In fact, 7 GPa is really simple, Considering the fact that in addition to rising above sea level, it decreases quickly immediately for fractional values; but then all phenomena are observed near Mount Olympus, which means 17 km in height, How can it be?
It is known from telescopic observations that Mars has a very active atmosphere, especially in relation to the formation of clouds and fogs, not only sandstorms. Observations of Mars through a telescope in fact, inserting a blue light filter, you can highlight all these atmospheric phenomena is far from negligible. Morning and evening fog, orographic clouds, polar clouds were always observed in a telescope with medium media power. Anyone can for example, with an ordinary graphics program, separate three red levels, green, Blue colour images of Mars and check how it works. An image corresponding to the red channel will provide us with a good topographic map while the blue channel will show the polar ice caps and clouds. It is easy to do this both on images taken with small telescopes, both on images from a space telescope. Also, in the images taken from the space telescope, you notice a blue border caused by the atmosphere, which then appears blue and not red, as shown in the image location.
Typical images of Mars taken by the Hubble Space Telescope. Source: http://Science.NASA.gov/Science-News/Science-at-NASA/1999/ast23apr99_1/
Red channel (left), Green channel (center) and blue channel (right); Notice the equatorial cloud.
Another interesting point is the analysis of polar deposits; crossing altitude data and gravitometrici, It was impossible to determine that the polar deposits differ seasonally by approximately 1.5 meters at the North Pole and 2.5 meters at the South Pole, with an average population density at that time of a maximum height of approximately 0.5 g/cm 3 .
At the same time, the density of 1 mm of snow in CO 2 produces a pressure of 0.04903325 hPa; Now, even if we assume the most optimistic Martian pressure given above is 18.4 hPa, ignoring the fact that CO 2 represents 95% and not 100% of the Martian atmosphere, If we were to condensassimo all the atmosphere on earth would get a layer 37.5 cm thick!
On the other hand, 1.5 feet of carbon dioxide snow with a density of 0.5 g/cm 3 produces a pressure of 73.5 hPa and 2.5 meters instead of 122.6 hPa!
Time evolution of surface atmospheric pressure recorded two Viking Landers 1 and 2 (Viking Lander 1 He landed in Chris space at 22.48° n, 49.97° W, 1.5 km below mean. Viking Lander 2 He landed in Utopia space at 47.97° n , 225.74° W, 3 Km below mean) during the first three years of the Martian mission: year 1 (dots), year 2 (solid line) and year 3 (dashed line) fit in the same column. Tillman source and guest (1987) (See also Tillman 1989).
Consider also that, If the mass of seasonal dry ice was similar between the two hemispheres should not cause seasonal variations in global atmospheric pressure, Since the collapse of the polar cap will always be offset by condensation on the floor in the other hemisphere.
But we know that the flattening of the Martian orbit creates a difference of almost 20° C in the average temperature of the two hemispheres, from the top to 30° C favoring Latitude of -30° ~. Keep in mind that 7 GPa CO 2 ICES is 123 ° c (~ 150 ° K), while at 18.4 hPa ( correct value for Mars gravity) ICES down to ~-116°C (~157° K).
Comparison of data collected by the Mariner 9 mission during boreal spring (Ls = 43 – 54°). Shown by the solid line on the graph above the temperature (in Kelvin) detected by the IRIS experiment. The dashed-dotted curves show local winds (in m s-1) as derived from heat balance wind (Pollack et 1981). The middle graph shows the simulation temperature (K) for the same season, while the bottom graph represents the simulation winds (in m s-1). Source: "Meteorological Variability and Annual Surface Pressure Cycle on Mars" Frederic Hourdin, Le Van Foo, François Forget, Olivier Talagrand (1993)
According to Mariner 9, only at the South Pole we find the necessary weather conditions, Although according to damages the global surveyor (MGS) associated with the earth, Presence in both hemispheres is possible.
Minimum soil temperatures in degrees Celsius of Mars, taken from the Thermal Spectrometer (TES) aboard the Mars Global Surveyor (MGS). In horizontal and vertical Latitude Longitude of the sun (Ls). The blue part of the table shows the minimum temperature, the average annual maximum and always with reference to the daily minimum temperatures.
Then, debriefing, the atmosphere seems to reach a minimum temperature of -123 ° C zero -132 ° C; I note that at -132°2 the pressure must not exceed 1.4 GPa without ice!
Carbon dioxide vapor pressure graph; among other utilities of this graph, you can determine the maximum pressure CO2 can reach before condensing (in this case on ice) at a given temperature.
But back to seasonal polar deposits; as we have seen, at least at night, at 60° latitude, the conditions seem to exist for dry ice to form, but what really happens during the polar night?
Let's start with two completely different states: condensation from the surface to cool a mass of air, or "cold".
For the first case, suppose that the soil temperature falls below the freezing limit of carbon dioxide; the soil will begin to cover more and more with a layer of ice, until here the thermal insulation caused by the ice itself will be enough to stop the process. In the case of dry ice, being a good thermal insulator, it is simply very small, so this phenomenon itself is not effective enough to justify the observed ice accumulation! As proof of this, to the North Pole and South Pole belongs to the record -132°C, where the minimum is -130°C (According to TES MGS). I'm also interested in both reliable detection of -132°c from Martian orbit and the spectroscopic path, because at this temperature the soil itself must be veiled from the condensation process!
In the second case, If the air mass (in this case CO 2 almost pure) reaches the dew point, as soon as the temperature drops, its pressure does not exceed the limit set by the "vapor pressure" for that gas at that temperature, causing immediate ground condensation of the mass any excess gas! In fact, the effectiveness of this process is really dramatic; If we were to simulate a similar event on Mars, we would also need to consider the chain of events that would create.
We lower the temperature of the South Pole, for example to -130 ° C, the initial pressure is 7 hPa; arrival pressure should be ~ 2 GPa, causing snow precipitation of dry ice ~ 50 cm thick (0.1 Gy/cm 2) If compressed at 0.5 Gy/cm 2 match ~ 10 cm thick. Of course, such a pressure difference will be promptly air from the surrounding areas, with the effect of the lower (chain) pressure and temperature from the neighboring areas, but the condensation contribution is all in the snow. The process itself also tends to make thermal energy (then temperature rise) at the same, But if the temperature remains at -130 ° C, the condensation process will stop only when all the planets reach an equilibrium pressure of 2 hPa!
This small simulation is used to understand the relationship between minimum temperatures and barometric pressure changes, explaining why minimum temperature and pressure are related. From the presented barometric pressure graphs recorded by two Viking Landers we know that for Viking 1 the pressure varies from a minimum of 6.8 hPa to a maximum of 9.0 hPa, with an average value of 7.9 . For Vikings 2 Acceptable values are from 7.4 HPA at 10.1 GPa with an average of 8.75 hPa. We also know that VL 1 He landed 1.5 Km and VL 2 3 Km, both under average level Mars. Considering that the average level of Mars is 6.1 hPa (comes from the triple point of water!), if we scale the values above the average is 6.1 hPa, then both vary from less than 5.2 ± 0.05 hPa and a maximum of 7 ± 0.05 hPa. While the minimum value is 5.2 GPa, low temperature, we get ~-125°C (~148° K), already in clear disagreement with your data. Now, while the pressure drop from 7 HPA to 5.2 HPA is deposited 18.4 cm thick (0.1 Gy/cm 2) If compressed at 0.5 Gy/cm 2 match ~ 3.7 cm thick, and that the surface of the south polar cap is ~ 1/ 20 The total surface of Mars (definitely approaching the default!), 3.7 cm X 20 = 74 cm, This is a much smaller value within the polar deposits detected!
Therefore, there is an obvious contradiction between thermal data and weather data, If one does not support the other! Such a low temperature will result in strong pressure fluctuations (even between day and night!) or even lower overall pressure! On the other hand, however, 7 is absolutely insufficient to account for things like Devils Dust nominal HPA, gullies, skylight spreads, or the magnitude of transient polar deposits, which you explained better well above 7 hPa atmospheric pressure.
So far, only aspects related to carbon dioxide, considered to be a major component of the atmosphere (~95%); But if we introduce even water in this analysis, the designation 7 GPa becomes completely ridiculous!
For example, traces left by the flow of liquid water (see the Newton crater) where the water should only be a steam state, subject to very low pressure and temperatures down to about 27 ° C!
In such a situation, we can safely say that the pressure (in terrestrial conditions) cannot be less than 35 hPa!
Every planet is different from the rest in a number of ways. People compare other found planets with the one they know well, but not perfectly, - this is the planet Earth. After all, this is logical, life could appear on our planet, which means that if you look for a planet similar to ours, then it will also be possible to find life there. Because of these comparisons, the planets have their own distinctive features. For example, Saturn has beautiful rings, because of which Saturn is called the most beautiful planet solar system. Jupiter most big planet in solar system and this feature of Jupiter. So what are the features of Mars? This article is about this.
Mars, like many other planets in the solar system, has moons. Mars has two moons, Phobos and Deimos. The satellites got their names from the Greeks. Phobos and Deimos were the sons of Ares (Mars) and were always close to their father, just as these two satellites are always close to Mars. In translation, “Phobos” means “fear”, and “Deimos” means “horror”.
Phobos is a moon whose orbit is very close to the planet. It is the closest satellite to the planet in the entire solar system. The distance from the surface of Mars to Phobos is 9380 kilometers. The satellite revolves around Mars with a frequency of 7 hours 40 minutes. It turns out that Phobos manages to make three and a few revolutions around Mars, while Mars itself makes one revolution around its axis.
Deimos is the smallest moon in the solar system. The dimensions of the satellite are 15x12.4x10.8 km. And the distance from the satellite to the surface of the planet is 23,450 thousand km. The period of revolution of Deimos around Mars is 30 hours and 20 minutes, which is a little more than the time it takes the planet to rotate around its axis. If you are on Mars, then Phobos will rise in the west and set in the east, while making three revolutions per day, and Deimos, on the contrary, will rise in the east and set in the west, while making only one revolution around the planet.
Features of Mars and its Atmosphere
One of the main features of Mars is that it was created. The atmosphere on Mars is very interesting. Now the atmosphere on Mars is very rarefied, it is possible that in the future Mars will completely lose its atmosphere. The features of the atmosphere of Mars are that once upon a time Mars had the same atmosphere and air as on our home planet. But in the course of evolution, the Red Planet lost almost all of its atmosphere. Now the pressure of the atmosphere of the Red Planet is only 1% of the pressure of our planet. Features of the atmosphere of Mars is also that even with three times less gravity of the planet, relative to the Earth, Mars can raise huge dust storms, lifting tons of sand and soil into the air. Dust storms have already spoiled the nerves of our astronomers more than once, since dust storms are very extensive, then observation of Mars from the Earth becomes impossible. Sometimes such storms can even last for months, which greatly spoils the process of studying the planet. But exploration of the planet Mars doesn't stop there. There are robots on the surface of Mars that do not stop the process of exploring the planet.
The atmospheric features of the planet Mars are also in the fact that scientists' guesses about the color of the Martian sky have been refuted. Scientists thought that the sky on Mars should be black, but the pictures taken space station from the planet disproved this theory. The sky on Mars is not black at all, it is pink, thanks to the particles of sand and dust that are in the air and absorb 40% of the sunlight, thanks to which the effect of the pink sky on Mars is created.
Features of the temperature of Mars
Measurements of the temperature of Mars began relatively long ago. It all started with Lampland's measurements in 1922. Then the measurements indicated that the average temperature on Mars is -28º C. Later, in the 50s and 60s, some knowledge about the temperature regime of the planet was accumulated, which were carried out from the 20s to the 60s. From these measurements, it turns out that during the day at the equator of the planet the temperature can reach +27º C, but by evening it will drop to zero, and by morning it becomes -50º C. The temperature at the poles varies from +10º C, during the polar day, and to very low temperatures during the polar night.
Features of the relief of Mars
The surface of Mars, like other planets that do not have an atmosphere, is scarred by various impact craters. space objects. Craters are small in size (5 km in diameter) and large (from 50 to 70 km in diameter). Due to the absence of its atmosphere, Mars was subject to meteor showers. But the surface of the planet contains not only craters. Previously, people believed that there was never water on Mars, but observations of the surface of the planet tell a different story. The surface of Mars has channels and even small depressions, reminiscent of water deposits. This suggests that there was water on Mars, but for many reasons it disappeared. Now it is difficult to say what needs to be done so that the water on Mars reappears and we could observe the resurrection of the planet.
There are also volcanoes on the Red Planet. The most famous volcano is Mount Olympus. This volcano is known to all those who are interested in Mars. This volcano is the largest hill not only on Mars, but also in the solar system, this is another feature of this planet. If you stand at the foot of Mount Olympus, then it will be impossible to see the edge of this volcano. This volcano is so large that its edges go beyond the horizon and it seems that Olympus is endless.
Features of the magnetic field of Mars
This is probably the last interesting feature this planet. The magnetic field is the protector of the planet, which repels everything electric charges moving towards the planet and repels them from their original trajectory. The magnetic field is completely dependent on the core of the planet. The core on Mars is almost stationary and therefore the planet's magnetic field is very weak. The action of the Magnetic Field is very interesting, it is not global, as on our planet, but has zones in which it is more active, and in other zones it may not be at all.
Thus, the planet that seems so ordinary to us has a whole set of its own features, some of which are leading in our solar system. Mars is not as simple a planet as you might think at first glance.
The atmosphere of Mars is less than 1% of Earth's, so it does not protect the planet from solar radiation and does not retain heat on the surface. That's the shortest way to describe it, but let's take a closer look at it.
The atmosphere of Mars was discovered even before the flight of automatic interplanetary stations to the planet. Thanks to the oppositions of the planet, which occur every three years and spectral analysis, astronomers already in the 19th century knew that it has a very homogeneous composition, more than 95% of which is CO2.
The color of the Martian sky from the Viking Lander 1 lander. On sol 1742 (Martian day), a dust storm is visible.
In the 20th century, thanks to interplanetary probes, we learned that the atmosphere of Mars and its temperature are strongly interconnected, because due to the transfer of the smallest particles of iron oxide, huge dust storms arise that can cover half of the planet, raising its temperature along the way.
Approximate composition
The gas envelope of the planet consists of 95% carbon dioxide, 3% nitrogen, 1.6% argon, and trace amounts of oxygen, water vapor and other gases. In addition, it is very heavily filled with fine dust particles (mostly iron oxide), which give it a reddish hue. Thanks to the information about the particles of iron oxide, it is not at all difficult to answer the question of what color the atmosphere is.
Carbon dioxide
The dark dunes are the result of the sublimation of frozen carbon dioxide, which melted in the spring and escaped into the rarefied atmosphere, leaving behind such traces.
Why is the red planet's atmosphere made of carbon dioxide? The planet has not had plate tectonics for billions of years. The lack of plate movement allowed volcanic hotspots to spewing magma to the surface for millions of years on end. Carbon dioxide is also a product of an eruption and is the only gas that is constantly replenished by the atmosphere, in fact, this is actually the only reason why it exists. In addition, the planet lost its magnetic field, which contributed to the fact that lighter gases were carried away by the solar wind. Due to continuous eruptions, many large volcanic mountains have appeared. Mount Olympus is the largest mountain in the solar system.
Scientists believe that Mars lost its entire atmosphere due to the fact that it lost its magnetosphere about 4 billion years ago. Once upon a time, the gaseous envelope of the planet was denser and the magnetosphere protected the planet from the solar wind. The solar wind, atmosphere and magnetosphere are strongly interconnected. Solar particles interact with the ionosphere and carry away molecules from it, reducing the density. This is the key to the question of where the atmosphere has gone. These ionized particles have been detected by spacecraft in the space behind Mars. This results in an average pressure on the surface of 600 Pa, compared to an average pressure on Earth of 101,300 Pa.
Methane
A relatively large amount of methane has been discovered relatively recently. This unexpected finding showed that the atmosphere contains 30 parts per billion of methane. This gas comes from different regions of the planet. The data suggest that there are two main sources of methane.
The sunset, the blue color of the sky is due, in part, to the presence of methane
It is believed that Mars produces about 270 tons of methane per year. According to the conditions on the planet, methane is destroyed quickly, in about 6 months. For methane to exist in detectable quantities, there must be active sources below the surface. Volcanic activity and serpentinization are the most likely causes of methane formation.
By the way, methane is one of the reasons why the planet's atmosphere is blue at sunset. Methane diffuses blue better than other colors.
Methane is a by-product of life and is also the result of volcanism, geothermal processes, and hydrothermal activity. Methane is an unstable gas, so there must be a source on the planet that constantly replenishes it. It must be very active because studies have shown that methane is destroyed in less than a year.
Quantitative composition
The chemical composition of the atmosphere: it is made up of over 95% carbon dioxide, 95.32% to be exact. The gases are distributed as follows:
Carbon dioxide 95.32%
Nitrogen 2.7%
Argon 1.6%
Oxygen 0.13%
Carbon monoxide 0.07%
Water vapor 0.03%
Nitric oxide 0.0013%
Structure
The atmosphere is divided into four main layers: lower, middle, upper and exosphere. The lower layers are a warm region (temperature about 210 K). It is heated by dust in the air (dust 1.5 µm across) and thermal radiation from the surface.
It should be taken into account that, despite the very high rarefaction, the concentration of carbon dioxide in the gaseous envelope of the planet is approximately 23 times greater than in ours. Therefore, the atmosphere of Mars is not so friendly, not only people, but also other terrestrial organisms cannot breathe in it.
Medium - similar to the Earth. The upper layers of the atmosphere are heated by the solar wind and the temperature there is much higher than on the surface. This heat causes the gas to leave the gas envelope. The exosphere begins about 200 km from the surface and does not have a clear boundary. As you can see, the distribution of temperature in height is quite predictable for a terrestrial planet.
Weather on Mars
The prognosis on Mars is generally very poor. You can see the weather forecast on Mars. The weather changes every day and sometimes even every hour. This seems unusual for a planet that has an atmosphere only 1% of Earth's. Despite this, the climate of Mars and the general temperature of the planet influence each other as strongly as they do on Earth.
Temperature
In summer, daytime temperatures at the equator can reach up to 20 °C. At night, temperatures can drop as low as -90 C. A 110 degree difference in one day can create dust devils and dust storms that engulf the entire planet for several weeks. Winter temperatures are extremely low -140 C. Carbon dioxide freezes and turns into dry ice. The Martian North Pole has a meter of dry ice in winter, while the South Pole is covered permanently by eight meters of dry ice.
Clouds
Since radiation from the sun and solar wind are constantly bombarding the planet, liquid water cannot exist, so there is no rain on Mars. Sometimes, however, clouds appear and snow begins to fall. The clouds on Mars are very small and thin.
Scientists believe that some of them are composed of small particles of water. The atmosphere contains small amounts of water vapor. At first glance, it may seem that clouds cannot exist on the planet.
And yet on Mars, there are conditions for the formation of clouds. The planet is so cold that the water in these clouds never falls as rain, but as snow in the upper atmosphere. Scientists have observed this several times, and there is no evidence that the snow does not reach the surface.
Dust
It is quite easy to see how the atmosphere affects the temperature regime. The most revealing event is dust storms that heat the planet locally. They occur due to temperature differences on the planet, and the surface is covered with light dust, which is raised even by such a weak wind.
These storms dust the solar panels, making long-term exploration of the planet impossible. Luckily, the storms alternate with the wind blowing the accumulated dust off the panels. But the atmosphere of Curiosity is not able to interfere, the advanced American rover is equipped with a nuclear thermal generator and interruptions in sunlight are not terrible for it, unlike the other solar-powered Opportunity rover.
Such a rover is not afraid of any dust storms
Carbon dioxide
As already mentioned, the gaseous envelope of the red planet is 95% carbon dioxide. It can freeze and fall to the surface. Approximately 25% of atmospheric carbon dioxide condenses in the polar caps as solid ice(dry ice). This is due to the fact that the Martian poles are not exposed to sunlight during the winter period.
When sunlight hits the poles again, the ice turns into a gaseous form and evaporates back. Thus, there is a significant change in pressure over the year.
dust devils
Dust devil 12 kilometers high and 200 meters in diameter
If you've ever been to a desert area, you've seen tiny dust devils that seem to come out of nowhere. Dust devils on Mars are a bit more ominous than those on Earth. In comparison with ours, the atmosphere of the red planet has a density 100 times less. Therefore, tornadoes are more like tornadoes, towering several kilometers in the air and hundreds of meters across. This partly explains why, compared to our planet, the atmosphere is red - dust storms and fine iron oxide dust. Also, the color of the gas shell of the planet can change at sunset, when the Sun sets, methane scatters the blue part of the light more than the rest, so the sunset on the planet is blue.
Characteristics: The atmosphere of Mars is thinner than the atmosphere of the Earth. In composition, it resembles the atmosphere of Venus and consists of 95% carbon dioxide. About 4% is accounted for by nitrogen and argon. Oxygen and water vapor in the Martian atmosphere is less than 1% (See exact composition). The average pressure of the atmosphere at the surface level is about 6.1 mbar. This is 15,000 times less than on Venus, and 160 times less than at the surface of the Earth. In the deepest depressions, the pressure reaches 10 mbar.
The average temperature on Mars is much lower than on Earth - about -40 ° C. Under the most favorable conditions in the summer in the daytime half of the planet, the air warms up to 20 ° C - quite an acceptable temperature for the inhabitants of the Earth. But on a winter night, frost can reach up to -125 ° C. At winter temperatures, even carbon dioxide freezes, turning into dry ice. Such sharp temperature drops are caused by the fact that the rarefied atmosphere of Mars is not able to retain heat for a long time. The first measurements of the temperature of Mars using a thermometer placed at the focus of a reflecting telescope were carried out as early as the early 1920s. Measurements by W. Lampland in 1922 gave an average surface temperature of Mars of -28°C, E. Pettit and S. Nicholson in 1924 obtained -13°C. A lower value was obtained in 1960. W. Sinton and J. Strong: -43°C. Later, in the 50s and 60s. Numerous temperature measurements were accumulated and summarized at various points on the surface of Mars, in different seasons and times of the day. From these measurements, it followed that during the day at the equator the temperature can reach up to +27°C, but by morning it can reach -50°C.
There are also temperature oases on Mars, in the areas of the "lake" Phoenix (Sun Plateau) and the land of Noah, the temperature difference is from -53 ° C to + 22 ° C in summer and from -103 ° C to -43 ° C in winter. So, Mars is a very cold world, but the climate there is not much harsher than in Antarctica. When the first photographs of the surface of Mars taken by the Viking were transmitted to Earth, scientists were very surprised to see that the Martian sky was not black, as expected, but pink. It turned out that the dust hanging in the air absorbs 40% of the incoming sunlight, creating a color effect.
Dust storms: Winds are one of the manifestations of temperature difference. Over the surface of the planet often blow strong winds, whose speed reaches 100 m/s. Low gravity allows even rarefied air currents to raise huge clouds of dust. Sometimes quite vast areas on Mars are covered by grandiose dust storms. Most often they occur near the polar caps. A global dust storm on Mars prevented photographing the surface from the Mariner 9 probe. It raged from September 1971 to January 1972, raising about a billion tons of dust into the atmosphere at an altitude of more than 10 km. Dust storms most often occur during periods of great opposition, when summer in the southern hemisphere coincides with the passage of Mars through perihelion. Duration of storms can reach 50-100 days. (Previously, the changing color of the surface was explained by the growth of Martian plants).
Dust Devils: Dust devils are another example of temperature-related processes on Mars. Such tornadoes are very frequent manifestations on Mars. They raise dust into the atmosphere and arise due to temperature differences. Reason: during the day, the surface of Mars heats up enough (sometimes to positive temperatures), but at a height of up to 2 meters from the surface, the atmosphere remains just as cold. Such a drop causes instability, raising dust into the air - dust devils are formed.
Water vapor: There is very little water vapor in the Martian atmosphere, but at low pressure and temperature, it is in a state close to saturation, and often collects in clouds. Martian clouds are rather inexpressive compared to those on Earth. Only the largest of them are visible through a telescope, but observations from spacecraft have shown that on Mars there are clouds of a wide variety of shapes and types: cirrus, wavy, leeward (near large mountains and under the slopes of large craters, in places protected from the wind). Over the lowlands - canyons, valleys - and at the bottom of the craters in the cold time of the day there are often fogs. In the winter of 1979, a thin layer of snow fell in the Viking-2 landing area, which lay for several months.
Seasons: At the moment it is known that of all the planets of the solar system, Mars is the most similar to the Earth. It formed approximately 4.5 billion years ago. The axis of rotation of Mars is inclined to its orbital plane by approximately 23.9 °, which is comparable to the tilt of the Earth's axis, which is 23.4 °, and therefore there, as on Earth, there is a change of seasons. Seasonal changes are most pronounced in the polar regions. In winter, the polar caps occupy a significant area. The boundary of the northern polar cap can move away from the pole by a third of the distance to the equator, and the boundary of the southern cap overcomes half this distance. This difference is due to the fact that in the northern hemisphere winter occurs when Mars passes through the perihelion of its orbit, and in the southern hemisphere when it passes through aphelion. Because of this, winters in the southern hemisphere are colder than in the northern. And the duration of each of the four Martian seasons varies depending on its distance from the Sun. Therefore, in the Martian northern hemisphere, winters are short and relatively "moderate", and summers are long, but cool. In the south, on the contrary, summers are short and relatively warm, and winters are long and cold.
With the onset of spring, the polar cap begins to "shrink", leaving behind gradually disappearing islands of ice. At the same time, a so-called wave of darkening propagates from the poles to the equator. Modern theories explain it by the fact that spring winds carry large masses of soil along the meridians with different reflective properties.
Apparently, none of the caps disappear completely. Before the start of exploration of Mars with the help of interplanetary probes, it was assumed that its polar regions were covered with frozen water. More accurate modern ground and space measurements have also found frozen carbon dioxide in the composition of Martian ice. In summer, it evaporates and enters the atmosphere. The winds carry it to the opposite polar cap, where it freezes again. This cycle of carbon dioxide and the different sizes of the polar caps explain the variability in the pressure of the Martian atmosphere.
A Martian day, called a sol, is 24.6 hours long and its year is sol 669.
Climate influence: The first attempts to find direct evidence in the Martian soil of the presence of the basis for life - liquid water and elements such as nitrogen and sulfur, were not successful. An exobiological experiment conducted on Mars in 1976 after landing on the surface of the American interplanetary station Viking, which carried an automatic biological laboratory (ABL) on its board, did not provide evidence of the existence of life. Absence organic molecules on the studied surface could be caused by the intense ultraviolet radiation of the Sun, since Mars does not have a protective ozone layer, and the oxidizing composition of the soil. Therefore, the upper layer of the Martian surface (about a few centimeters thick) is barren, although there is an assumption that conditions that were billions of years ago have been preserved in deeper, subsurface layers. A certain confirmation of these assumptions was recently discovered on Earth at a depth of 200 m microorganisms - methanogens that feed on hydrogen and breathe carbon dioxide. A specially conducted experiment by scientists proved that such microorganisms could survive in the harsh Martian conditions. Warmer hypothesis ancient mars with open reservoirs - rivers, lakes, and maybe seas, as well as with a denser atmosphere - has been discussed for more than two decades, since it would be very difficult to “settle in” such an inhospitable planet, and even in the absence of water. In order for liquid water to exist on Mars, its atmosphere would have to be very different from the current one.
Variable Martian climate Modern Mars is a very inhospitable world. The rarefied atmosphere, which is also unsuitable for breathing, terrible dust storms, lack of water and sudden temperature changes during the day and year - all this indicates that it will not be so easy to populate Mars. But once upon a time, rivers flowed on it. Does this mean that Mars had a different climate in the past? |
