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CHILDREN'S SCIENTIFIC LABORATORY
About the Moon, mercury and earthquakes. Children's Science Lab
Directory / Children's Science Lab Stakheev's simple trick worked flawlessly. To his question - with what I associate the word "mercury" in the first place - I, as Yuri Ivanovich suggested in advance, honestly answered: with a "thermometer". It is always a shame when you are caught in stereotyped thinking. Of course, if you strain your memory, you could recall mercury fluorescent lamps, that "liquid silver" was one of the favorite substances of alchemists, that mercury is a metal that was known even in prehistoric times ... And yet a thermometer.
Why did I start with this seemingly ordinary fact? Because in the thousand-year history of mercury, Soviet scientists have recently written a completely new page, amazing in originality. And one more thing - we will just talk about non-stereotypical thinking, which combines unusual associations and a harmonious research logic, perseverance and patience on the way to the goal. Perhaps that is why this story, told by a senior researcher at the Laboratory of Space Chemistry of the Institute of Geochemistry and Analytical Chemistry of the USSR Academy of Sciences, is like a kind of scientific detective story. It began several years ago, when the Luna-13 automatic station delivered samples of lunar soil to Earth. Scientists had to clarify the structure of the lunar crust - at least that part of it, to which the sampler reached. And the first step was to arrange the samples in the same order in which the station took them. Prior to this, all samples remained, so to speak, anonymous - they were all mixed in one container. So the lunar rocks ended up in the laboratory of space chemistry. To find out from what depth this or that sample was taken, it was necessary to find differences in their chemical composition. Spectral studies have shown that on the Moon there are practically all the same elements as on Earth - molybdenum, lead, iron, mercury ... Mercury interested scientists most of all. She, according to the researchers, could serve as the most reliable guide in their work. The idea was as follows. The temperature on the surface of the moon varies greatly during the day. It is cold there at night - minus 150 °. And in the daytime - plus 150 ° C. And mercury is a liquid, volatile substance. During the day, the mercury contained in the upper layers actively evaporates. Deeper layers heat up less, therefore, more mercury should remain in them. It was these differences that had to be caught with the help of a device specially created for this purpose. The device in this story plays a special role, so let's dwell on it in more detail. First, it had to be invented. True, there were devices for sanitary control of the atmosphere, but their sensitivity, according to spectral studies of the moon, turned out to be about a thousand times lower than was necessary to determine the concentration of mercury in the lunar soil. And other devices, more sensitive, are associated with radioactivity and cannot work continuously for a long time. The main part of the new appliance was purchased ... at a household electrical store. This is a portable cosmetic device for artificial tanning "Photon" in which a mercury lamp is installed, which gives ultraviolet light. Mercury vapor is known to glow in the ultraviolet. Moreover, the intensity of the glow is proportional to the concentration of mercury. They took the "Photon" lamp, carved a metal cylinder with two holes at an angle of 90 °. From one end, a lamp shines into such a cylinder, from the opposite end, a photocell looks. If air containing mercury vapor is pumped through the cylinder, the photocell "sees" the glow and converts it into an electric current. The stronger the glow, the stronger the current. But this is just a schematic diagram. The most difficult thing in a real device was to find a suitable dimming. The rays of the lamp are repeatedly reflected from the inner walls of the cylinder and fall on the photocell. And the glow of the vapors is so weak that even a beam reflected a thousand times can be stronger. Whatever they smoked inside the cylinder - with a candle, gas, coal ... Finally, they found the blackest coating for ultraviolet rays. He was given soot from birch bark. The device started working with hitherto unknown sensitivity. The results of the first measurements suddenly showed that mercury in the lunar soil is almost half as much as expected. We decided to double-check these results. Now mercury has become ... more. Another series of verification experiments, literally an hour later. The concentration of mercury is increasing... What's the matter? Faulty device? It was re-calibrated, verified... Alas, new experiments gave the same picture. It turned out that at first mercury from the soil disappeared somewhere, and then slowly returned. Why is mercury disappearing? Samples for experiments were crushed in air. Maybe that's when the mercury evaporates? But at the same time, the soil was not heated at all, there was no imitation of a lunar day and night here. And yet we decided to check it out. The next portion of the soil was not crushed, but, having been isolated from the atmosphere, it was dissolved in acid. Everything fell into place - the experiment proved that almost half of the mercury is lost under pressure. But how can this be explained? Put forward such a hypothesis. The destruction of the sample under pressure is preceded by microshears in the rock. Mercury inside a piece of rock is located on the faces of the grains-crystals that make up this piece. Now let's use a distant, but, according to the researchers, a fairly accurate analogy. Imagine a butter sandwich topped with another piece of bread. If one piece is moved relative to the other, the oil will squeeze out. The same can be said for mercury. It is exposed during the destruction of the rock and begins to evaporate intensively. Now it was necessary to somehow answer the second question: where does mercury then come from? Then they remembered the so-called "mercury paradox". In meteorites, a huge, thousands of times greater than in terrestrial rocks, mercury content was found many times. Moreover, they noticed: the longer the meteorite lay in the museum collection, the more mercury it turned out to be. Samples of lunar soil, when they were removed from under a sealed glass cap, were also exposed to the open air for some time before the verification experiment. An idea was born - what if we compare the rate of accumulation of mercury by meteorites that have lain for a certain time in the museum, and lunar soil? It turned out that the speeds are approximately the same! So, the second question has been answered. Samples of lunar rock, like a sponge, absorb mercury from the earth's atmosphere. But, as always happens in scientific research, when one riddle is solved, new ones arise. Why is there so much mercury in the earth's atmosphere? Why don't terrestrial rocks accumulate it? How does mercury enter the atmosphere? Employees of the laboratory of space chemistry went on long, distant, but quite terrestrial expeditions, armed with their device. Their result was a new understanding of the role of mercury in terrestrial processes. We learn at school about the cycle in nature of water, carbon, nitrogen ... Now this list has been supplemented by mercury. Moreover, without knowledge of the regularities of the mercury cycle, as it became clear, it is impossible to form a complete picture of the complex geochemical, biological, and physical processes occurring in the biosphere. During the expeditions, scientists found out that from the depths of the planet, mercury rises through rocks along with the so-called gas breathing of the earth. The mercury released into the atmosphere is then washed away by rain to find itself back in the ground. The measurements made during the expeditions also brought new mysteries. When the measurements began, at first the concentration of mercury in the air grew. This went on for about a week. Then the concentration began to decrease. And a week later it started growing again. How does this biweekly periodicity come about? Scientists have suggested that the moon is to blame. It raises meter-long waves of ocean tides, makes the earth's crust rise and fall with exactly the same frequency. At the same time, stresses and cracks appear in the depths of the earth. Mercury at this time most intensively evaporates from the bowels. Thinking about this fact, the researchers also remembered the riddle with the press, which “stealed” mercury from the lunar soil. In fact, in both cases, the reason for the intensive evaporation of mercury was the same ... But after all, during earthquakes, as geophysicists had found out by that time, exactly the same conditions arise! Shortly before the catastrophe, stresses increase underground, the number of cracks in rocks increases. This means that before an earthquake near its source, the concentration of mercury must also increase! The device was taken to areas of high seismicity. The studies were carried out in Turkmenistan, Tajikistan, Kyrgyzstan. There were no major earthquakes in these areas at that time. But there were many small underground strikes. And the device immediately proved itself to be a very reliable forecaster. Four or five days before the earthquake, the device predicted: there will be a push! In seven cases out of ten, the predictions turned out to be correct. And now scientists are working to increase the reliability of the unusual forecaster. Author: A.Fin
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