There are "unusual" comets, the properties of which do not fit into the "reasonable", from the point of view of modern science, framework. One of these comets was discovered in 1956 and named after its discoverers comet Arenda-Roland.
Soviet scientists, doctors of technical sciences VP Burdakov and Yu. I. Danilov in their book "Rockets of the Future" suggested that such objects could be probes of extraterrestrial civilizations.
Here are their arguments:
Comet Arenda-Roland's tail appeared after April 22, 1957 and disappeared at the very beginning of May. Previously, such tails were not observed in comets! Together with the "normal" tail directed away from the Sun, the comet had a very narrow, like a spear, anomalous tail, which was directed towards the Sun.
At first, they tried to explain this phenomenon by a natural cause: the anomalous tail was supposedly the products of the comet's destruction, which were concentrated in the form of a trace in its orbit, therefore, at the time the comet was between the Sun and the Earth, both tails directed from the comet were located as if on opposite sides of the comet's nucleus. But the comet continued to move, and the anomalous tail, as the plane of the cometary orbit rotated relative to the terrestrial observer, did not turn, as expected, into a sector connected to the main tail, but took the form of a well-outlined diverging ray! In addition, the spectrum of the anomalous tail was not continuous, as is usually the case with dust tails. It is also unusual that the anomalous tail appeared and disappeared suddenly.
Now about the "normal" tail. It consisted of two tails: a tail of the first type (according to the classification of F. A. Bredikhin), which was associated with an inner head, very blurred and resembling a bulb in shape, and a tail of the second type, which was associated with an outer head, which had clear parabolic outlines. …
According to the theory of comet tails, developed on the basis of numerous observations of comets, everything should be just the opposite. In addition, the inner tail had a continuous spectrum, which was not observed at all in the tails of the first type.
Promotional video:
In order to somehow combine the observational data with the theory of cometary tails, one would have to make the assumption that the initial velocity of the outflowing particles was higher than three thousand meters per second. But for the artificial achievement of such speeds, equal to the speed of the outflow of jets from modern liquid-propellant rocket engines, it is necessary to use special accelerators - expanding nozzles, the profile of which is carefully calculated and matched with the chemical composition and temperature of the outgoing gas.
In other words, the assumption about the occurrence of such high flow rates is hardly legitimate. But that's not all. On March 10, 1957, a station at the University of Ohio (USA) registered radio emission from the comet at a wavelength of 11 meters (27.6 MHz). The radiation intensity varied within ± 30%, and its source was located in the main tail at a considerable distance from the head. Starting from April 20-21, that is, before the appearance of the anomalous tail, this source began to move away from the Sun, approximately in the radial direction.
On April 9, 1957, radio emission from a comet was detected in Belgium at a wavelength of 0.5 meters (600 MHz). The high stability of this radio emission, both in amplitude and in frequency, contradicts the suggestive assumption of natural sporadic radiation in the plasma of cometary tails. Radiation at a wavelength of II meters was observed for more than a month. It was strongest from March 16 to April 19, that is, on the eve of the appearance of the anomalous tail. Moreover, the intensity of the signals sent increased daily.
Thus, an exhaustive explanation of comet Arenda - Roland only by natural causes is associated with a number of contradictions.
There is also no sufficient reason to say that an artificial celestial body was observed, although there are projects of future space ramjet engines, the observation of the operation of which from the side would remarkably resemble all anomalies of the comet Arenda - Roland without exception.
Scientists cite data on other amazing comets. So, in the spectrum of comet 188211, iron, chromium and nickel were found - elements that are in the spectra of jet jets of liquid fuel rocket engines due to insignificant erosion of jet nozzles containing these metals. The difference between the spectra of the head and tail of comet 1907IV was also puzzling.
In comet 1926III, there was no influence of the Sun on the position of the tail, which turned in space, seemingly completely arbitrarily, and the comet did not adhere to the trajectory calculated for it, but deviated significantly from it. This deviation can only be explained by the significant thrust developed during the outflow of mass from the comet's nucleus.
It is possible that our solar system has already been visited by alien probes. For example, the unusual behavior of comet 188IV, which was discovered in 1881 by the Bristol astronomer Dennig. The comet did not come close to the Sun, practically did not have a tail - the main feature of almost all comets, but came very close to the Earth.
The minimum distance from a comet to Earth was 6 million kilometers. In addition, it also approached Mars at a distance of 9 million kilometers. The comet passed close enough from the orbit of Venus (at a distance of 3 million kilometers) and from the orbit of Jupiter (at a distance of 24 million kilometers). The comet was observed as a hazy disc-shaped speck with luminous dots in its center.
There are moments in the solar system, although it is quite rare that its planets are located in such a way that an interplanetary ship, moving along an elliptical passive trajectory, can come close enough to three planets. Maybe a certain civilization took advantage of this moment to get the maximum information about the planets of the solar system? Moreover, the Earth was given more attention than Mars. And this is natural: the Earth has an atmosphere.
“Thus,” scientists believe, “among a large number of observed comets, very rarely (with a period of 20-30 years) appeared unique, promising in the sense of detecting in their behavior and appearance traces of intelligent activity of extraterrestrial civilizations. Apparently, one should prepare very carefully for the possible appearance of such comets in the future."