A group of paleontologists from NASA with the help of a satellite in near-Martian orbit, were able to determine why this planet turned into a lifeless desert. The researchers, after establishing the volumes of the catastrophe lost under the influence of the solar wind, came to the conclusion that this was quite enough for liquid water to disappear from the surface of Mars.
Mars is one of the planets closest to Earth. This planet is more comfortable for people who, quite likely, in the future will be able to walk on its surface in spacesuits, than Venus, whose hot and dense atmosphere even research vehicles cannot withstand. In addition, according to the results of new scientific research, rivers flowed on the Red Planet in the past, and the air was less rarefied. In particular, this is indicated by the traces of huge waves that could have caused the fall of the asteroid and which were recently discovered.
It is possible that sufficient oxygen and water created a habitable environment. Some scientists argue that about 3.5-2.5 billion years ago, a biosphere could exist on this planet. However, at present Mars is a desert devoid of water. According to paleontologists, the Red Planet almost completely lost its water several tens of millions of years ago. During the existence of dinosaurs on Earth on Mars, it is quite possible that some lakes could still be preserved. The planet's atmosphere is very rarefied, it consists mainly of carbon dioxide, therefore it is not able to protect possible microbes from ionizing radiation.
Researchers have been feeding for a long time to find the answer to the question of what triggered a global catastrophe that turned the water-rich planet into a dusty desert. According to scientists, it is extremely important to find the answer, it is not just idle curiosity. Thanks to this, it will be possible to understand the future of our planet, which, as some scientists believe, the Red Planet once looked like. According to paleontologists, the main reason is the abrupt changes in the global climate due to the loss of the atmosphere and a weak electromagnetic field.
At present, the atmosphere of Mars continues to dissolve into space. Scientists are studying this process, as well as trying to reconstruct the climatic changes of the past as part of NASA's Mars Scout space project. To observe the atmosphere of the Red Planet, the MAVEN satellite was sent to it. The main goal of the program is to find out the role that the loss of gases played in turning the planet into a desert.
The researchers determined the amount of losses by calculating the ratio of heavy and light isotopes, in particular argon. The gas that escapes into space carries away mainly the light nuclei of atoms, as a result of which heavy nuclei predominate in the atmosphere of Mars. In the atmosphere of this planet, their increased concentration was detected back in 2013 by NASA specialists. Thanks to the MAVEN satellite, which was launched into Mars orbit in 2014, scientists were able to reveal in more detail the processes that take place in the upper layers of the planet's gas envelope.
According to experts, the mechanism by which argon flies into space is quite simple. Due to the influence of the solar wind, ions are accelerated, which collide with argon atoms in the upper atmosphere, throwing them into space. This process is the same for Ar36 and Ar38. But differences do arise. The reason for this lies in the fact that the isotope Ar36 is lighter, so it penetrates into the upper atmosphere faster. As a result, it is he who is in great abundance at the exobase level. Above this level, particles are able to leave the planet without colliding with each other. Thus, the Ar36 isotope goes into space much faster than Ar38.
To determine the concentration of isotopes in the atmosphere, the scientists used an ion and neutral mass spectrometer built at the Goddard Space Center. The MAVEN satellite made measurements at various altitudes, in particular, at an altitude of about 150 kilometers from the surface of Mars. Thus, the researchers determined the level of the turbopause and ecobase. Turbopause is the layer of the atmosphere located above the homosphere, in which turbulent mixing of gases predominates, and also under the heterosphere, where molecular diffusion predominates.
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The turbopause height was determined as follows. Scientists took the N2 / Ar40 ratio at the surface of Mars obtained using the Curiosity rover. Due to the fact that gases mix well in the homosphere, this ratio should be the same up to the turbopause. The satellite measured this ratio many times at various altitudes, as a result of which a correlation was determined: the higher, the greater the ratio of nitrogen to argon. The researchers only had to transfer the results to the lower layers of the atmosphere, since the satellite could not get there - up to a value of 1.25. The altitude at which this happened was the turbopause.
After determining the level of the exobase and turbopause, scientists deduced the ratio between them of argon isotopes. As the researchers suggested, this layer was enriched with Ar38. This ratio was used as the basis for calculating the volume of gas loss. However, it was necessary to take into account the fact that some of the isotopes could enter the atmosphere due to volcanic activity, weathering of rocks and asteroid impacts. Thus, the final value of the fraction of argon that went into space in the total amount of gas present in the atmosphere for the entire period was 66 percent.
Paleontologists used the results to calculate the approximate losses of other gases. Thus, scientists came to the conclusion that as a result of collisions with ions from the atmosphere, about 10-20 percent of carbon dioxide could escape. The loss of oxygen was more catastrophic, and the consequences depended on which gas was the source of the loss of oxygen. In the event that it is carbon dioxide, the loss of carbon dioxide is about 30 times higher than the estimates of the researchers. The pressure could thus drop by more than one atmosphere. In the same case, if oxygen was in the composition of water vapor, water losses were large.
Scientists note that the early atmosphere of the Red Planet was dense enough and contained enough carbon dioxide so that liquid water could exist on the planet's surface due to the greenhouse effect. This study demonstrates that Mars has become a desert as a result of the loss of most of the gas envelope. And this does not take into account the fact that millions of years ago the Sun could have been more active. And this, according to experts, only increases the volume of the atmosphere blown into space.