Good day. I decided to start publishing my book about Venus exploration in web format. This is the first part published (first chapter). If all goes well, I'll try to put the whole book out. If here they decide that this is not a format, I am ready to delete everything. Go!
Several mysterious lines
Over the twentieth century, our ideas about Venus have changed dramatically. Thanks to the joint efforts of scientists from many countries, an aura of obscurity was broken from our closest companion. The story of the study of the Morning Star is reminiscent of a good detective story.
It has a plot, a tangled tangle of secrets, a climax and a denouement. Eyewitnesses who pointed in the wrong direction and facts that were not initially taken seriously. What was the first step towards solving the secrets of our neighbor?
If you look at the big picture, the modern history of the study of Venus - the story that started understanding what the planet is - began in April 1932, on a clear and clear night. In the southwest of California there is a beautiful mountain range - San Gabriel. One of its attractions is the Mount Wilson Alpine Astronomical Observatory. It is located at an altitude of about 1740 meters above sea level. At the time of the events described, a brand new infrared spectrograph was mounted on its main telescope, and the observatory employees spent sleepless nights, obtaining the spectral characteristics of celestial bodies. Another experiment, staged by astronomers Theodore Dunham and Walter Adams, was aimed at finding water in the atmosphere of Venus.To increase the accuracy, we decided to limit ourselves to studying a small spectral band in the near infrared region.
By that time, spectrometric theory was well developed and successfully applied both on Earth and to study bright astronomical objects like the Sun. Moreover, back in the 19th century, it was possible to identify the absorption bands of ammonia near Jupiter and other giant planets. But in determining the composition of the atmospheres of Venus or Mars closest to us, she could not help yet. The signal from other planets was too weak, it was too easy to confuse it with the lines that appeared in the sun's coronosphere or the Earth's atmosphere. But on this clean and clear spring night, success finally came. However, here too it was not without chance, good luck. Knowing about the experiment, Kenneth Meese, head of Kodak Research Laboratories, gave the experimenters a set of specially made photographic plates. One batch of sensitized contrast plates was particularly successfulfeaturing high sensitivity, high contrast and excellent resolution. There were no other emulsions of this type that met these parameters at least half. It was thanks to them that the discovery was made.
After the development of the plate, traces of water absorption could not be found, but the absorption lines of some gas appeared quite clearly (Fig. 21). Unknown gas. There were no such lines in reference books. No one has seen it in terrestrial experiments, but this gas clearly appeared in the atmosphere of Venus.
Fortunately, spectral analysis is based not only on comparing the obtained bands with those already known. It is based on the fundamental properties of matter, and even from the arrangement of the lines, you can tell a lot about the molecule that caused the absorption. The unknown gas turned out to be similar in its characteristics to ordinary carbon dioxide.
A new question arose - why were these lines not visible in ordinary experiments? One of the answers was that the absorption lines in this range are very weak and poorly visible at the CO2 concentrations with which they usually work. To test this hypothesis, the Mount Wilson Observatory fabricated a sealed tube 21 meters long. The air from the pipe was pumped out, and carbon dioxide was pumped into it under pressure.
Up to 10 atmospheres, no absorption was observed in the studied range. With an even greater increase in pressure, a very weak and diffuse line appeared, extremely close to the line observed in the spectrum of Venus. The hypothesis was confirmed - the absorption was caused by carbon dioxide. Now it was necessary to determine his concentration. It should be noted that the spectrometric method cannot directly estimate the percentage of gas in the atmosphere. It is relatively easy to estimate the so-called reduced thickness of the gas layer. This fully conventional value was introduced to simplify calculations. Suppose that the gas suddenly stopped expanding and at all points has a constant pressure of 1 atmosphere. What is the height of the gas layer providing this absorption? Or such an example: if we take the experiment with the pipe as a basis, but assume thatIf the pipe cannot withstand pressures of more than one atmosphere, how long will the pipe need to be to ensure the specified absorption? The length of this pipe would be numerically equal to the reduced thickness of the gas layer. The experiment with the pipe made it possible to determine the minimum value - not less than 400 meters. Refined estimates made from this spectrogram showed an even more spectacular result - 3.2 km. This is a very large value. For comparison: the entire air ocean of the Earth corresponds to the reduced thickness of 8.5 km, and the reduced thickness of carbon dioxide in the earth's atmosphere is only 220 cm.The experiment with the pipe made it possible to determine the minimum value - not less than 400 meters. Refined estimates made from this spectrogram showed an even more spectacular result - 3.2 km. This is a very large value. For comparison: the entire air ocean of the Earth corresponds to the reduced thickness of 8.5 km, and the reduced thickness of carbon dioxide in the earth's atmosphere is only 220 cm.The experiment with the pipe made it possible to determine the minimum value - not less than 400 meters. Refined estimates made from this spectrogram showed an even more spectacular result - 3.2 km. This is a very large value. For comparison: the entire air ocean of the Earth corresponds to the reduced thickness of 8.5 km, and the reduced thickness of carbon dioxide in the earth's atmosphere is only 220 cm.
In 1940, astronomer Rupert Wildt took it one step further. He examined the windows of absorption and emission of CO2 and, knowing the reflection coefficient of Venus from telescopic observations, he obtained that the temperature on the surface can reach 135 ° C. In fact, it is he who is the author of the theory of the greenhouse effect, but in those years his article went almost unnoticed ... She got a second life in 1952, when Gerard Kuiper was preparing for the reprint of his book "Atmospheres of the Earth and Planets". Having found this article, he revised the calculations again and, using more modern data on Venus, deduced that the temperature should be about 77 ° C.
In 1956, the first observations of Venus's own radio emission were carried out by McClough, Mayer and Slonaker in the 3.15 cm range at the 15-meter radio telescope of the US Marine Research Laboratory. The result amazed everyone. According to the result obtained, the temperature of Venus turned out to be about 287 ° for the shadow side of the planet, which significantly exceeded any other calculations and measurements. We decided to change the length of the radio wave by 9.4 cm.
Two observations were carried out and indicators were obtained - 157 ° and 467 ° , respectively. The next experiment, conducted by Gibson and McIwan in January 1958, at a wavelength of 8.6 mm gave a temperature of 137 ° C 160 ° C. But when in September 1959 Kuzmin and Salomonovich decided to conduct a similar experiment on the newly launched Soviet 22- meter radio telescope, for 8 mm we got a noticeably "colder" result - 42 ° C.
The radar data came quite in time. By the end of the 1950s, spectroscopic methods for studying Venus were in crisis. By that time, several dozen absorption lines were known in the atmosphere of Venus, but they all belonged to carbon dioxide. It was not possible to identify any other gases for a long time.
Reports of the discovery of new gases in the Venusian atmosphere sometimes flashed like sparks, but quickly burned out. For example, the Soviet astronomer Kozyrev in 1954, when studying the ash light of Venus, received a large number of new absorption lines, the American astronomer Newkirk confirmed his data. Some of the lines Kozyrev identified with the lines of highly ionized nitrogen, and if this turned out to be true, it would be the first discovery of nitrogen in the atmosphere of another planet. Then they tried to explain some of the lines with ionized oxygen. As a result, it turned out that it was ionized carbon dioxide.
The most unpleasant thing is that it was not possible to confidently prove the presence of water in the atmosphere of Venus. All observations aimed at this showed either a negative result or a concentration that could have been produced by traces of moisture in the earth's atmosphere. Moreover, it could not be detected even by indirect methods. For example, under the influence of ultraviolet radiation from the Sun, water and carbon dioxide could form formaldehyde, but formaldehyde in the atmosphere of Venus could not be detected either. Or such a fact: the high content of carbon dioxide indicated that the so-called Yuri equilibrium was disturbed in the atmosphere of Venus. Under the conditions of the Earth, carbon dioxide is actively bound by the world's oceans, transforming into sedimentary rocks. Moreover, water serves as a catalyst in this process. And if there is water on the planet, then there should be much less carbon and sour gas.Nevertheless, the clouds over Venus with a good telescope were perfectly visible, and if they did not consist of water, then of what? Maybe it is still from water, but it cannot be accurately identified due to moisture in the Earth's atmosphere affecting the readings of the spectrograph?
It was necessary to do something about this situation. Say, try to set up an experiment in such a way that water from the earth's atmosphere cannot influence the result. In 1959, a very interesting attempt was made. In the 1950s, the US Navy Research Center conducted an extensive program to launch manned stratospheric balloons (Fig. 22). Initially, the flight was carried out to study the Earth's atmosphere, but a group of scientists from Johns Hopkins University proposed a project to obtain infrared spectra of Mars and Venus - to search for water on them. The proposal was accepted and work began. A specially modified telescope with a spectrograph was installed on the stratospheric balloon. The preliminary aiming was to be carried out by a person, then the telescope aiming at the planet was controlled by a special automatic tracking system. The first attempt took place in 1958,her target was Mars. Due to a faulty stratospheric balloon shell, the flight had to be postponed, and the opportunity to study Mars this year was lost. In 1959, it was Venus's turn.
At the end of November 1959, the stratospheric balloon with pilot Ross and observer Moore reached an altitude of 24 km. At this altitude, the amount of water vapor in the Earth's atmosphere did not exceed 0.1% of the total value. Ross and Moore aimed the telescope at a target and were able to capture several infrared spectra of Venus. The task was not easy. The oscillations of the nacelle were sometimes so sharp that it was necessary to completely stop working. According to the directors of the experiment, even the fact that they managed to get at least some results was amazing in itself. But there was a result: it turned out to identify several lines of water absorption. Unfortunately, the range of values turned out to be too large, which raised doubts about the obtained data.
Also in 1959, another significant event took place, thanks to which another piece appeared in the Venusian mosaic: the so-called covering (eclipse) by Venus of one of the brightest stars in the sky - Regula (Alpha Leo). Such eclipses are extremely rare. In the 20th century, at that time, only three such events were recorded. Venus's coverage of Regulus was calculated in advance, and large observatories were preparing for it. It was a great success that the weather was good at many observation points. As you know, when a star approaches the very edge of the planetary disk, its light begins to weaken. In this case, the attenuation is caused not by scattering, but by refraction of light. Passing through the atmosphere of Venus, light deviates from a straight path. Knowing the physical foundations of refraction, one can very accurately calculate the parameters of the planet's upper atmosphere. Truth,there is one "but": these data can only give a certain coefficient (absolute density of the atmosphere) associated with both the temperature and the molecular weight of the gas causing refraction. And only knowing the exact composition of the atmosphere, you can easily calculate its temperature and density at the altitude at which the coating took place.
Nitrogen was taken as the main gas in the Venusian atmosphere; taking its molar mass, we obtained the density and temperature distribution in the upper layers. These data were included in the first models of the atmosphere of Venus.
Automated interplanetary vehicles could, when used correctly, provide answers to many riddles. To assess current knowledge and analyze experiments, the Space Research Council of the US National Academy of Sciences decided on July 24, 1960 to hold a special conference to discuss the parameters of the atmospheres of Mars and Venus. It was to these planets that the terrestrial vehicles were to be sent in the first place. In view of the importance of the issue, it was also decided to hold an additional conference in Pasadena in late December 1960 - early February 1961. This conference, which was attended by all the color of American planetary scientists, is interesting because, according to the reports delivered at it, ideas about the planets at the beginning of the space era are clearly visible. There were no particular doubts about Mars, which cannot be said about Venus. The conference clearly revealed:there is no consistent theory describing the structure of the Venusian atmosphere! Each planetary scientist defended his own version, and not a single hypothesis was free from internal problems. Among the scientific assumptions, there were sometimes very amusing ones. In particular, I would like to mention the very extravagant theory of Dr. Hoyle. On it, Venus was covered by the ocean, in which the water was under a huge layer of oil.
And this hypothesis was also well developed and did a good job of explaining some of the available data.
At that time, three theories of the structure of the atmosphere of Venus can be considered the main ones. All of them were developed to explain the high brightness temperature received by radio astronomers. Here you need to clearly understand what was being discussed. Until then, there were only eight points on the graph of the radio emission from Venus, depending on the wavelength. The accuracy of these measurements, unfortunately, was low due to the intrinsic noise of the receiver; the experiments were carried out at the sensitivity limit of the instruments. But they generally showed that the emission of Venus at different frequencies of radio emission is different.
In the millimeter range, the temperature was relatively low, 50–70 degrees Celsius, but could significantly exceed 300 ° C in the centimeter range. It was necessary to understand where this radiation is coming from. To explain the emerging picture, two types of hypotheses were developed: a hot bottom and a cold top and, accordingly, a hot top and a cold bottom (Fig. 23).
The hot bottom meant the surface of the planet. And it was she, according to the theory of the first type, that was red-hot to monstrous temperatures; cold radiation came from higher layers of the atmosphere - for example, from clouds. The greenhouse hypothesis was the classic representative of the first type. Carl Sagan worked it out very carefully. Carbon dioxide by itself, it would seem, could not cause such heating, this came out of the calculations of Wildt and Kuiper. Carl Sagan carefully repeated the calculations and showed that absorption in carbon dioxide alone could not explain the experimental data in any way. But if you add even a little water vapor to the atmosphere of Venus, everything changed. Water vapor is a very good greenhouse gas. He could delay radiation in the infrared range, which caused strong heating of the surface.
The greenhouse hypothesis painted a very boring world. The surface temperature is more than 300 ° C, the pressure could reach several atmospheres. Venus should be dry, calm, dark and hot. The sun could only be seen as a reddish disc. The greenhouse hypothesis left little hope for a Venusian life. At the beginning of the 1960s, it was she who was worked out better than any other, although she also had several drawbacks.
For example, the fact that Venus had problems with water. Ernst Epik criticized the greenhouse hypothesis and proposed his own. He named it Eolospheric, in honor of Aeolus, the ancient Greek god of the wind. The fact is that the polarimetric curve of the clouds was much more like the curve of dust than water. According to this hypothesis, the clouds that everyone observed were not clouds, but a grand dust storm that swept the entire planet. It covered the surface of Venus with a giant mantle, and due to the friction of grains of sand on the surface, the temperature increased.
However, when calculating data on pressure and temperature on the surface of Venus, they turned out to be similar to the results obtained under the greenhouse hypothesis. Just as in the greenhouse hypothesis, it turned out that the surface temperature is more than 300 ° C, the pressure is up to 4 atmospheres. Dry, but very dusty and windy. Alas, both of these theories did not leave hopes for the existence of life on Venus.
However, there was also the "hot top" theory - the ionospheric one. According to it, the lower temperature belonged to the surface, and the higher one was caused by the radiation of the planet's ionosphere. In this case, Venus would indeed have a perfectly tolerable temperature - about 27 degrees Celsius. And it is quite possible, and life. In many ways, this hypothesis was based on an earlier assumption built on the theory of the origin of planets in the solar system.
Venus appeared to be a cloudy twin of the Earth, in the situation that developed on our planet millions of years ago, in the Carboniferous period. Warm and humid climate with an abundance of moisture, cloudy skies and an organic world similar to that of the end of the Paleozoic era. There, romantically minded scientists thought, tropical gardens grow and the ancestors of dinosaurs walk. A lost world that awaits its Challenger professors. After all, it was a whole unknown planet! Writers and artists portrayed the world that excites the imagination in all its full color.
In 1961, the Soviet Union released the feature film "Planet of Storms" directed by Pavel Klushantsev (Fig. 24). Klushantsev was a very successful documentary filmmaker with a meticulous scientific approach. This was his only feature film based on the story of the same name by Alexander Kazantsev. At the beginning of the film, he honestly warned the audience: “Scientific information about the planet Venus is scarce and contradictory. Only fantasy is able to look into the undiscovered world. It may not be the same as in our film. But we believe in the coming feat of the Soviet people, who will see the planet of storms with their own eyes. "
In the film, viewers saw alien landscapes, underwater travel, aggressive flora and fauna. They traveled and escaped with the heroes from the volcano ... And then there was no person on our planet who could confidently prove that this was not so. Three assumptions. Three different worlds. No hypothesis could contain all the available data. Each of them explained well some facts and was completely refuted by others. More detailed data were needed to understand which hypothesis was correct.
This is a fragment of my book “Venus. Indomitable planet ". Also, now there is a collection for my new book. It can be supported here .