Russian scientists, together with their American colleagues, have found out where the dust-plasma cloud that surrounds the Moon and stretches several hundred kilometers above it comes from. After checking the theoretical calculations and experimental data, the scientists concluded that it is most likely made up of matter that rose from the surface of the Moon as a result of the fall of mini-asteroids - meteoroids. Article presented in the Journal of Physics: Conference Series.
The interplanetary space of the Solar System is filled with dust particles, they are present in the plasma of the ionospheres and magnetospheres of planets, in the vicinity of cosmic bodies that do not have their own atmosphere. There is no dust only on the Sun and in its immediate vicinity due to high temperatures.
“During the space missions of the Surveyor and Apollo spacecraft to the Moon, scientists noticed that sunlight is scattered in the terminator region (the border between the illuminated and dark halves of the celestial body), and this, in turn, leads to the formation of lunar dawns and streamers (elongated bright helmet-like structures with an open top, forming above the surface of a celestial body, - approx. Indicator. Ru) above the surface, even though there is no atmosphere, - says one of the authors of the study Sergey Popel from the Higher School of Economics and IKI. - Light scattering most likely occurs on charged dust particles, the source of which is the surface of the Moon. Indirect evidence of the existence of a lunar plasma-dust cloud was obtained during the Soviet expeditions Luna-19 and Luna-22."
In their work, the authors consider, as far as possible, the fact that a plasma-dust cloud above the Moon was formed due to the fact that meteoroids hit the lunar surface, that is, bodies are significantly smaller than asteroids, but much more dust. The data obtained on the basis of this theory correspond to the results of experimental studies carried out in the framework of the American LADEE mission (Lunar Atmosphere and Dust Environment Explorer, a researcher of the lunar atmosphere and dusty environment, - approx. Indicator. Ru).
Around the Moon in a radius of several hundred kilometers there is a dust cloud of submicron size. The astronomers carried out the characteristics of the dust using the LDEX impact ionization dust sensor, which allows the direct detection of dust particles in orbit of the spacecraft. The purpose of the experiment was to determine the distribution of dust particles in height, size and concentration over various parts of the lunar surface. The data obtained during the LADEE experiment gave impetus to continue the previously started theoretical studies. The specialists were able to compare their calculations with experimental data. It turned out that they agree, in particular, this concerns the speed of movement of particles and their concentration.
“The concentration of particles of a dusty plasma cloud in our calculations does not contradict the experimental data. A continuous stream of meteoroids falls on the surface of the Moon: micron, millimeter sizes, explains Sergey Popel. - Therefore, a substance is practically continuously ejected from the surface, part of it is in a molten state. Rising above the surface of the Moon, liquid melt drops solidify and, as a result of interaction, in particular, with electrons and ions of the solar wind, as well as with solar radiation, acquire electric charges. Some particles leave the moon and fly into space. And those particles above the lunar surface, which did not have enough speed, constitute a plasma-dust cloud."
During the LADEE experiments, astronomers found that the concentration of dust increases abruptly when some of the annual meteor showers interact with the Moon. This effect was especially evident during the high-speed Geminid meteor shower. All this confirms the connection between the processes of formation of a dust cloud and collisions of meteoroids with the surface of the Moon. Theories that say that dust particles rise above the lunar surface due to electrostatic processes, for example, the so-called fountain model, cannot explain why dust rises to great heights and, accordingly, why a dust-plasma cloud is formed.
The authors of the work add that more research will be required, so far a simple model is presented, which requires improvement. In particular, it is necessary to make calculations taking into account the surface relief, because of which the particles rise at different angles. In the near future, it is planned to launch lunar missions in Russia, these are Luna-25 and Luna-27, which will be equipped with equipment that will examine dust near the lunar surface. Possibly, theoretical calculations will be supplemented taking into account new experimental data.
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