Mars has always been a topic of interest for scientists and ordinary people. The atmosphere of Mars was discovered long before the flight of automatic interplanetary stations to the planet. Due its confrontations that happen every three years according to the spectral analysis, astronomers in the XXI century know that Mars has a rather homogeneous composition, as CO2 constitutes more than 95% of its atmosphere. In the article NASA Plans to Make Oxygen from Atmosphere on Mars, it is stated that “Mars’s atmosphere contains just 0.13% oxygen, compared with 21% on Earth” (Wilford 2017). Many scientific studies are being dedicated to the research of this planet these days. It is connected with the fact that people want to know whether life on Mars is possible. There are many studies concerning the atmosphere of Mars as the favorable atmosphere is considered the major factor for the possibility of life on a particular planet.
History of the Atmosphere
Scientists think that the atmosphere of Mars changed during the life of the planet. Some scientists argue that several billion years ago, this planet comprised vast oceans (Brandenburg 2011). Nevertheless, at present, water on Mars can exist only in the form of ice or steam. The atmospheric pressure can primarily retain water in the liquid form only at the lowest points of the planet. Besides, the average surface temperature on Mars is -63 Celsius and, thus, water there can exist only in the solid state (Brandenburg 2011). Still, Mars had more advantageous conditions for the inception of life at the beginning of its history. In 2013, it was declared that the atmosphere of Mars contained oxygen in the past (Haberle, et al. 2017). Researchers calculated the density of the atmosphere that could be on the planet four billion years ago. The calculations were based on the isotope composition of the current atmosphere on Mars.
The results showed that the pressure of the gas shell of the planet was equal to half of the current pressure on Earth (Haberle, et al. 2017). Today, it is about 100 times lower. This new data explained the fact of how oceans and seas could exist on Mars many years ago (Haberle, et al. 2017). Scientists analyzed the ratio of argon-38 to argon-36 and nitrogen-15 to nitrogen-14 both in the microcavities of the meteorite ALH 84001 and the current Martian atmosphere (Haberle, et al. 2017). It was previously discovered in Antarctica and had the same isotopic and chemical composition that showed its Martian origin. Because the initial age of the Martian meteorite material amounts to approximately four billion years, researchers compared the content of bubbles from the ancient Martian atmosphere with various isotopes in the microcavities. In such a way, it made it possible to calculate the total density in that epoch. It comprised a considerable amount and the atmospheric pressure on the Mars’ surface was not more than 0.5 compared to the terrestrial (Haberle, et al. 2017). Nowadays, it is 150 times lower than that of Earth at the Martian poles (Haberle, et al. 2017). Scientists distinguished several possible reasons of such changes. They include low gravity of Mars that did not allow retaining the atmosphere, collision with a vast comet or meteorite that had destructive consequences for the planet, and slow destruction of the atmosphere by the solar wind (Haberle, et al. 2017). Such a high atmospheric pressure signifies that the planet had a stronger greenhouse effect than nowadays. It also means that it could keep heat better. This fact explains the existence of traces of a network of river channels and former oceans on the surface of Mars.
The Structure of the Atmosphere
Due to the lower gravity on Mars compared with that of Earth, Mars is characterized by smaller gradients of pressure and atmospheric density. In such a way, the Martian atmosphere is more extended than the one on Earth (Brandenburg 2011). The height of the homogeneous atmosphere on Mars is greater than on the Earth and is spread over nearly 11 km. In spite of strong sparseness of the Martian atmosphere, it has similar concentric layers compared to the terrestrial ones. As Mars has little concentration of ozone, there is no ozone screen on the planet (Brandenburg 2011). It leads to the fact that ultraviolet radiation reaches the very surface of the planet. In such a way, photochemical reactions are extremely active even on the surface of Mars (Brandenburg 2011). Therefore, it is possible to note that despite insignificant similarities, the atmosphere of Mars is completely different from that of the Earth.
The Chemical Composition
A great difference also exists in the chemical composition of Mars’ atmosphere. Carbon dioxide is the major component in the Martian atmosphere. Its quantity in the atmosphere undergoes seasonal fluctuations due to evaporation in summer and condensation in polar caps in winter (Miller 2014). It is widely known that nitrogen is the major component of the Earth’s atmosphere. However, it amounts to only a few percent in the atmosphere of Mars. Apart from nitrogen, there are water, ozone, oxygen, and carbon monoxide in the atmosphere of the planet but their amount is insignificant. Carbon monoxide represents a product of photodissociation. Molecular oxygen emerges due to photodissociation of H2O and CO2 in the upper atmosphere of the planet (Miller 2014). Moreover, oxygen diffuses into the lower layers of the atmosphere. The quantity of ozone may vary significantly depending on the temperature of Mars’ surface. The content of H2O is approximately 200 times less than in the atmosphere of the driest regions of the Earth. In winter, the atmosphere is practically dry (Miller 2014). In spring, water vapor can be observed, and its amount reaches a maximum level in the middle of summer after the fluctuations in temperature of the surface. During a summer-autumn period, water vapor is redistributed and a maximum of its content shifts from the northern polar region to the equatorial latitudes (Miller 2014). The total global content of vapor in the atmosphere remains unchanged. Scientists constantly monitor and record the amount of various chemical components in Mars’ atmosphere and these records show that this planet is currently not suitable for life.
Dust Storms and Tornadoes
Winds represent one of the manifestations of the temperature fluctuations on Mars. In this regard, strong winds frequently blow above the surface of the planet and their speed reaches 100 m / s (Miller 2014). Because of small gravity, even sparse airflows lift huge clouds of dust. A particular characteristic of the atmosphere of Mars is the permanent existence of dust that gives the atmosphere a yellow shade (Miller 2014). Therefore, dust storms are extremely frequent on the planet. Scientists have long noticed them in the form of a single yellow cloud or a permanent yellow shroud that cover the whole planet. Spectral measurements show the size of the dust particles that is measured at 1 μm (Miller 2014). The speed of dust cloud’s movement can reach more than 40 km/h (Miller, 2014). As a rule, weak yellow fog in the atmosphere can be observed after strong dust storms. Moreover, astronauts can easily detect it with the help of polarimetric and photometric methods. Grandiose dust storms sometimes cover large areas on the planet. Most often, they originate near the polar caps. The global dust storm on the planet prevented taking photos of the planet’s surface from the side of the probe Mariner 9. The storm lasted from September 1971 till January 1972 (Miller 2014). It released approximately one billion tons of dust to the atmosphere at an altitude of about 10 km (Miller 2014). Thus, strong dust storms can last upt to 100 days and prevent making photographs of the planet.
In addition to dust storms, such phenomenon as dusty tornadoes is one more example of the on-going processes on Mars associated with temperature fluctuations. Tornadoes occur rather frequently on the Red Planet (Miller 2014). They release dust into the atmosphere and are caused by temperature differences. During the day, the surface of Mars is heated. However, the atmosphere is cold at an altitude of up to two meters from the surface (Miller 2014). Such a difference becomes a reason of instability in the atmosphere releasing dust into the air and causing tornadoes.
Condensation is another phenomenon that characterizes Mars. Formations of the condensation nature that sometimes occur in the atmosphere of Mars are represented by polar haze, fogs, and white clouds. The latter were discovered in the course of telescopic observations while polar haze and fogs were witnessed with the help of a spacecraft (Miller 2014). The condensation of CO2 leads to the formation of clouds that are usually observed at high levels of the atmosphere. Infrared spectra of white clouds received by spacecraft show that ice crystals are the major component of the cloud formations. In turn, water clouds are formed above the Martian surface at altitudes of less than 20 km (Miller 2014). Scientists have noticed that many of such clouds are formed when air masses are raised along the wide relief forms of windward slopes (Miller 2014). Fogs and clouds are rather widespread for the territories near winter polar caps, where the atmospheric temperature is reduced to the freezing point of CO2 (-126 ° C) (Miller 2014). Polar clouds are located low above the surface and represent thin formations of ice H2O in summer and CO2 in winter.
In 1978, in the process of photographing the northern polar region, one of the rare and interesting atmospheric phenomena was discovered on Mars. These were cyclonic structures distinctly identifiable in photographs by vortical systems of clouds circulating counterclockwise (Miller 2014). They were observed during a warm time of the year, from spring to early autumn, when the polar front on the planet is set. Its appearance is associated with the harsh differences in surface temperatures between the edge of the ice cap and the surrounding plains occurring at this time of year. The wave motions of air masses connected with this front result in the appearance of cyclonic vortices similarly to the ones on Earth. The systems of vortex clouds found on Mars stretch across 500 km (Miller 2014). The speed of their movement is approximately 5 km/h and the speed of winds on the periphery of these systems can reach more than 20 m/s (Miller 2014). The duration of the existence of a single cyclonic vortex ranges from 3 to 6 days (Miller 2014). The temperature values in the central part of the Martian cyclones show that clouds consist of ice crystals of water.
Seasons on Mars
Nowadays, scientists know that Mars is the most similar planet to the Earth of all other planets in the solar system. This planed originated approximately 4.5 billion years ago (Haberle, et al. 2017). The axis of rotation of Mars is inclined to its orbital plane by approximately 23.9° (Haberle, et al. 2017). It can be compared with the inclination of the Earth’s axis, which is 23.4° (Haberle, et al. 2017). It indicates that just like on Earth, there is a change of seasons on Mars. Polar regions have the most vivid manifestations of various seasonal changes. For example, in winter, the polar caps occupy a considerable area (Haberle, et al. 2017). The border of the northern polar cap can withdraw from the pole to the third of the distance to the equator and the border of the southern cap crosses half of this distance. This difference is explained by the fact that in the northern hemisphere, winter comes when the planet passes through the perihelion of its orbit and in the southern hemisphere, winter starts when the planet passes through the aphelion. It explains why winters in the southern hemisphere are colder than in the northern one (Haberle, et al. 2017). The duration of every Martian season is different. It depends on the distance between the planet and the Sun. Thus, winter is relatively mild and short in the northern hemisphere while summer is cold and long (Haberle, et al. 2017). In contrast, summer is rather warm and short in the south and winter is cold and long in this region. This data was obtained based on the observations of scientists.
Potential for Humans
The question of how people can use the atmosphere of Mars is frequently asked, as the colonization of Mars does not look like an inapproachable fantastic dream. These days, it is possible to use carbon dioxide from the atmosphere of Mars for various purposes. For example, it can be used for the creation of rocket fuel for the return flight to the Earth. There are several options in applying a rich volume of CO2 and one of them is the Sabatier process (Haberle, et al. 2017). This chemical process includes the reaction of carbon dioxide with hydrogen with the use of a nickel catalyst. As a result, it produces methane and oxygen. This reaction is already applied by NASA scientists for the conversion of carbon dioxide on the International Space Station that remains after the breath of the astronauts (Haberle, et al. 2017). In such a way, people perhaps will not need oxygen in the atmosphere of Mars and scientists will be able to produce it themselves.
People have always strived for flying to Mars. Therefore, there are many researches devoted to the study of the atmosphere of this planet. Such study can help find out whether there is a favorable environment for a person to exist on this planet and whether the atmosphere of Mars serves as sufficient protection against harmful radiations that penetrate the interplanetary space. However, it is known that it will be extremely difficult for a man to visit Mars, as the environment of the planet is extremely different from the one on Earth. The atmosphere of Mars consists mostly of carbon dioxide. It was also found that it contains almost no ozone, which absorbs the ultraviolet rays of the Sun because of which they penetrate the surface of the planet and pose a great danger to the living beings. In such a way, this planet proves to be unsuitable for life.
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