By the beginning of the study of the radio emission of the Moon astronomers had one quite reliable characteristic of the Moon - the temperature of its surface. It was measured back in the 1930s by astrophysicists Petit and Nicholson by a simple, witty and so accurate method that so far no one has been able to exceed this accuracy. Based on the readings of infrared rays, scientists have established an amazing thing. The surface of our satellite heated at noon to plus 120 degrees Celsius at lunar night is bound by frost in minus 150 degrees Celsius. Moon temperature fluctuations are unheard of: 270 degrees! Nothing of the kind has ever been observed on Earth: not only from day to night, but also from winter to summer, from the tropics to the cold pole.
In 1939, Petite repeated his research, but during the lunar eclipse, when the Earth completely closed the Sun from the Moon. It turned out that in one hour the Moon's temperature fell from plus 120 degrees to minus 100 degrees Celsius.
Therefore, when radio astronomers Piddington and Minnet first sent their instruments to the Moon in 1949, they expected to detect no less change in its radio brightness. And what did the instruments show? As the moon's day changed on a moonlit night, radio emissions remained almost unchanged...
According to radio astronomers, the temperature of the moon did not change much! It excited scientists: how to explain the difference between infrared and radio-radio readings, how to connect such contradictory data?
The only correct conclusion was that radio waves are not emitted by the very surface of the Moon, whose temperature is subject to strong fluctuations, but by a deeper layer of soil, in which the temperature remains constant. This idea was supported by the fact that everyone knows that on Earth, winter and summer are actually felt only by the surface layer of soil, and at a depth of a few meters the temperature changes little.
But only the first question was solved, how did the following arise? What is the surface layer of the Moon, which, like a fur coat, covers the bowels of the Moon from sharp fluctuations in temperature?
Academician Fesenkov calculated that the thermal conductivity of the lunar soil should be almost a thousand times less than that of earthly rocks. Such a material is an old dream of builders, heat engineers and refrigeration specialists. But there is nothing like this on Earth. And scientists rightly doubt that such ideal insulation can exist in nature, even on the Moon, it is unlikely that such a huge difference between lunar and terrestrial rocks.
But soon it was possible to find a possible reason for this difference. When comparing earthly and lunar rocks, the skeptics did not take into account the fact that the substance on the Moon is in fact almost completely empty, in a vacuum. The atmosphere is not there. If the Earth's rocks on the Moon were empty, their pores would be empty, and they would sharply reduce their thermal conductivity. What kind of terrestrial material, as scientists have been guessing, can compete with the lunar material? Perhaps, only dust. By coming into contact with each other in a few points, the dust does not transfer heat well to each other. If you pump the air out of the gaps between the dust particles, the heat transfer through the dust layer becomes negligible.
Dust as a surface layer of the moon satisfied almost everyone. And supporters of the meteor hypothesis, which claims that the moon cover is created by a constant meteor bombardment. After all, billions of large and tiny meteors fall on the Moon with invisible rain at a speed several tens of times faster than the speed of a bullet or shell. Proponents of this hypothesis argue, by the way, that the same fate would have befallen the Earth if it had not been reliably wrapped in its atmosphere. Dust was also satisfying for the volcanic viewers. In their view, past lunar volcanoes could have produced enough dust and similar ashes.
There is no water on the Moon that would wash away these sediments. There is no wind that would scatter them. Over time, dust and ash could cover the entire surface of the moon.