2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
Read this and other space stuff on the Green Cat blog
Passing the Vorobyovy Gory metro station by car, it is easy to notice the fifty-meter flagpole of the Palace of Pioneers or the rectangle of the Korston Hotel. But the chances that you will pay attention to the Institute of Geochemistry and Analytical Chemistry. VI Vernadsky (GEOKHI RAS) - a yellow-white three-story building, built in the style of the Stalinist Empire - not very much. It has the curious property of not attracting attention to itself, and from the outside it even seems a little abandoned, just like the "Department of Bridges and Tunnels" from "Men in Black". And the similarities don't end there - the inside is full of guests from outer space and those who work with them. True, these guests are quite calm - GEOKHI is the country's largest repository of extraterrestrial matter, such as meteorites and lunar soil, brought by Soviet stations (Luna-16, Luna-20, Luna-24).
The author of the review and today's guest of the blog: Kirill Vlasov (narendil), petrologist, geochemist from the Institute of Experimental Mineralogy of the Russian Academy of Sciences.
Kirill visited GEOKHI and shared with us his photo report:
Lunar soil delivered by the "Luna-16"
The collection is conditionally subdivided into the storage of iron and iron-stone meteorites, the storage of stone meteorites, the "moon room" and the museum of extraterrestrial matter in GEOKHI. Samples of meteorites from the collection are also exhibited in the Fersman Mineralogical Museum. It is in the GEOKHI RAS that meteorites fall after expeditions to the crash sites. Interested citizens bring the alleged meteorites here for analysis. 400-600 people turn to the Meteorite Committee annually. But productivity is not very high - last year this stream brought only a couple of small iron meteorites.
In general, anyone can find a strange stone in a field or on the road and decide that it is a meteorite. They fall to the surface of the Earth absolutely evenly.
Fireball observation map for the period 1994-2013, according to NASA data.
In one of the rooms in the institute, the entire window sill is littered with funny papers with texts like: “I, Ivan Alekseevich Collectors, walked through the forest in the Chelyabinsk region and found a strange stone. Since I am fond of stones, I immediately suspected that it was a meteorite, and I am sending a piece of it to you for analysis. I hope for the remuneration due. " Has the first part of this story happened to you? If so, then I have not very encouraging news: most likely, you were mistaken. Or maybe I'm wrong and you are an eyewitness of the fall. But even in this case, check if there are any fragments of the Roscosmos, NASA or ESA logos preserved on any side of your find. A Siberian lumberjack discovered a piece of metal in a freshly sawn tree. Several meteorites were indeed found in tree trunks during their processing, and experts expected another precedent. However, during the analysis, it turned out that this is one of the alloys used in the space industry, and the tree was cut down in the area of the fall of the spent rocket stages. But this, of course, is exotic - there are much higher chances of finding metallurgical slag, manganese ore or alloy, sometimes just like in the photographs from the Internet. The case sometimes reaches the point of absurdity: one seeker of "Martian meteorites" filed a lawsuit against the institute because all his "unique finds" returned to him with the signatures "fine-grained sandstone" and "basalt".
Is the belief that you hold a unique specimen that can shed light on controversial aspects of the formation of the solar system still unshakable? Well, write, call and bring it to GEOCHI. From every real meteorite entering the study, the institute takes 20 percent of its mass. Part of this material is used to make petrographic thin sections (plates 30 microns thick for studying under a polarizing microscope in transmitted light - for stone and iron stone), or polished sections (polished thicker plates for working with an ore microscope in reflected light - for iron and iron stone) … With their help, the structural features of meteorites are revealed, allowing them to be attributed to a specific group and subgroup. Then, using local methods (most often EPMA - the so-called "electronic probe", or "microprobe" - a type of spectroscopy), their total chemical composition is studied, as well as the compositions of coexisting mineral phases. After all these procedures, you will be given a petrographic description of the meteorite, a table of its chemical composition and the remaining 80 percent. Also, your meteorite will be registered in the international catalog and will receive a number, and maybe even a name - at the place of discovery, which will later appear in all scientific publications. Who knows, maybe it is in your meteorite that a new quasicrystal will be found, as happened with the Khatyrka meteorite, discovered in Chukotka.
Finds of meteorites on the territory of the former USSR
In general, it is quite interesting to look at the map of meteorite finds on the territory of the former USSR. At first glance, they find mainly iron and iron-stone meteorites, which prefer to fall along the southern border and somewhere in the European part. But meteorites certainly have no preferences. It's just that the more people live somewhere, the more chances that the meteorite will be noticed and found. But the reality is that even in the case of observing a car, they do not always go to search. As one geochemist, who worked in the same Chukotka in a geological exploration party on gold, said: “We are sitting in a house in the evening, suddenly a light appears outside the window. It grows, grows, and then an explosive and sound wave came. We were even thrown up a bit, and the windows were almost blown out. " - "Why didn't you go looking for something?" - “Who should go there? There were several geologists and workers at the field, we have work up to their necks, and the workers in their cabins were drunk, most likely."
So, a spot in the west and an elongated strip along the Transsib is a human factor. But why is there more iron? Here the answer is also not so tricky - it is easier to search for them. Stone meteorites are very similar to terrestrial rocks and without special training it is impossible to guess that you have just caught a worm for fishing under a fragment of ordinary chondrite LL6. Most often they are found by direct observation of the fall.
It is worth saying that meteorite detections are divided into two classes: "finds" and "falls". The material discovered after the fall is preferable for scientists; the material that has been slightly altered by the processes of earth weathering is analyzed. If a meteorite lays in the soil for some time, its mineral composition will change - secondary minerals will develop, and the isotopic ratios for a number of elements will change over time. According to experts, the "life" of an iron meteorite in the soil of Central Russia is about five hundred years, plus for about the same period it can be determined that this mixture of strange minerals was once a meteorite. But this is true for iron meteorites like Sikhote-Alin, which belongs to octahedrites and is almost completely composed of metallic phases.
But for Dronino's ataxite, the situation is much more deplorable. It contains about 10 volumetric processes of troilite (FeS), which is very unstable in an oxygen environment. The fact that he survived to this day from the moment of the fall is explained by the long stay below the groundwater level under anaerobic conditions. After irrigation works in the 90s, when, in fact, the first data on meteorite finds near the village of Dronino in the Ryazan region appeared, the water level dropped and it began to collapse in the soil layer much faster. At GEOCHI, its fragments are stored in glass desiccators, and before storage they are digested in potassium hydroxide and covered with mineral oil. If this is not done, electrochemical processes will turn the valuable substance into a useless heap of rust in a year.
Desiccators with fragments of the Dronino meteorite
In general, at the moment there are about 25 thousand fragments of 1600 different meteorites in storage. This meeting began with the discovery of an incomprehensible boulder in 1749 near Krasnoyarsk. In 1772, a strange block was shown to Peter Simon Pallas, who was driving along those parts as the leader of an expedition from the St. Petersburg Academy of Sciences, and he ordered to send the rarity to the capital. Later, the "boulder" was unambiguously identified as a meteorite and received the name "Pallas Iron". A large sawn piece of this meteorite is now on display at the Mineralogical Museum in Moscow.
When working with meteorite matter, the passage of time is very strongly felt, as well as the continuity of scientific generations.
Large fragments of Sikhote-Alin lie in rows, offhand - about twenty-five tons. In total, GEOCHI contains about 17 thousand of its fragments.
Films with expeditionary documentary filming of the 40-50s
Nearby on the window - films of documentary expedition filming of 1947-1950. And in the next room, in the same way, only in wooden boxes, smaller fragments of the Chelyabinsk meteorite are stored, for which the specialists of the institute flew away the day after the fall on February 15, 2013. There was a lot of hype after that event: TV groups, calls and interviews. Now everything has calmed down, but those who come to geological museums often ask: "Do you have a Chelyabinsk meteorite?" Now it is almost everywhere, and not only in GEOCHI, but the charm of ordinary LL5 chondrite is truly understandable only to scientists - to say that it looks interesting is only a stretch.
Fragments of the Chelyabinsk meteorite
Fragments of the Chelyabinsk meteorite
Tatooine Meteorite Fragment
The Tatooine meteorite, named after the city and area of the same name in Tunisia, where it fell on June 27, 1931. It is a funny coincidence that George Lucas, who filmed some episodes of the Star Wars saga here, called Tatooine an entire fictional planet. Its feature was that it was part of a binary star system, so that two suns were visible in the sky at the same time. Thanks to data recently obtained from the Kepler telescope, such planets have indeed been discovered. But the conditions for them, of course, are not the most pleasant. Lucas' hot deserted Tatooine with a small livable streak is a very real scenario.
Devil's Canyon Meteorite
Devil's Canyon is much less known to the general public than the crater formed when it fell. The same Arizona crater that constantly appears in various documentaries and which, by the way, has a square shape. The closest settlement to it at the end of the 19th century, when the first research was carried out, was the small village of Devil's Canyon, which received its name because of the canyon nearby. It was founded in 1882 during the construction of the Transatlantic Railway. It was then that the workers discovered a lump of strange metal, which was submitted for analysis to the American mineralogist Albert Fute, who studied meteorite finds in the southern states. He suggested the extraterrestrial origin of the stone and sent several expeditions to the crater area. They discovered the largest fragment of the substance - about 272 kilograms, which is now on display in a museum next to the crater.
In 1902, mining engineer Daniel Barringer bought the land on which the crater was located, guided by two ideas: to find meteorite matter and sell it at a higher price, and, along the way, to prove the meteorite origin of the crater. No joke, a ton of such a metal alloy then went for $ 125. But Daniel almost did not find fragments of meteorites, most of the meteorite matter evaporated in the atmosphere. However, the venture did not fail - according to the drilling data, it was precisely established that the crater was formed precisely due to the fall of a meteorite, and by establishing this, Barringer provided his family for a hundred years in advance. Today, the Arizona Meteorite Crater, also known as Barringer Crater, is a popular tourist attraction privately owned by its descendants. Few can boast of their own meteorite crater even in the United States. Moreover, it was recognized by NASA experts as the most convenient approximation of the "lunar landscape", and astronauts trained there before the flight of the Apollo mission spacecraft. And another of the craters on the far side of the moon was also named after Barringer. For symmetry, so to speak.
When the director of GEOKHI Yu. A. Kostitsyn drove through those places after the conference several years ago, he decided to turn off and look at the village and the canyon. The interest is very justified: in geochemistry, the Devil's Canyon meteorite, usually abbreviated from the first letters of the English name as CD, is used as a standard for measuring sulfur isotopic variations. After driving along a country road in an all-wheel drive SUV, he found himself in a long-abandoned ghost village, the best times of which were in 1905. “Well, okay,” thought Yuri Alexandrovich, “in the end, the main thing is the canyon.” But it turned out not quite so. The proud name "Canyon Diablo" hid a shallow ravine with stunted desert bushes.
Fragment of the Enzisheim meteorite
And here is a fragment of the first "official" meteorite - Enzisheim. He fell in a field near the French town of the same name in Alsace on November 7, 1492. The fall was perceived as a divine miracle and, just in case, the largest fragment was taken to the church, where they chained it so that it would not fly back. Its largest fragment, weighing 53.8 kilograms, can still be seen exhibited in the city museum.
Decay structures in the Needles meteorite
Iron meteorite Needles (literally - "needles") with remarkable Widmanstätten figures is not named so because of its structural features. A funny play on words happened here: it was found in 1962 by Californian collectors of minerals in the mountains near the town of Needles.
White inclusion in chondrite Efremovka
Chondrite Efremovka with the famous "white inclusions", or, as they are also called, CAI (Calcium-Aluminum-rich Inclusions). These formations are examples of the earliest matter in the solar system. The oldest found so far are inclusions from chondrite NWA2364 (CV3). According to data published in Nature Geoscience, their age is 4568, 22 ± 0, 17 million years (dating was carried out using the Pb-Pb method).
Meteorite Khmelevka
A funny story happened to the Khmelevka chondrite, which fell in the Omsk region in 1929 - it was found eight years after falling in a barrel of sauerkraut, where it was used as a press.
But shooting stars and Chelyabinsk are just the tip of the iceberg. We do not see most of the meteor shower, although it falls around us every day, and we even inhale some of it.
Meteorite event / event frequency diagram
We are talking about micrometeorites. Of course, a significant part of such matter burns up in the atmosphere, but something reaches the surface of the Earth. And this something can be collected from fresh snow. True, the snow for this must be very clean.
It recalls an interesting story that happened after the eruption of the Eyjafjallajökull volcano in Iceland in 2010. He threw out a huge ash cloud, which circled the planet several times, so that the material of this eruption could, theoretically, be collected in Moscow, especially since several European laboratories have already reported the discovery of volcanic ash in their courtyards. One of the professors of Moscow State University collected dark powder from fresh snow from the windowsill of a high-rise building and sent it for chemical analysis. Imagine his disappointment when it turned out that the window sill was evenly strewn with fragments of burnt rubber from winter tires and small particles of carbon of various origins. There was no ash in sight. Therefore, for micrometeorites, expeditions go to Antarctica, to Novaya Zemlya and Spitsbergen, where there are fewer cars, and there is enough snow in the summer.
Micrometeorites under a microscope
The composition of micrometeorites is unusual - among them no more than 10 percent are ordinary chondrites (which, in fact, are the most common), the main part is close to carbonaceous, but, presumably, comes from another source. According to one of the hypotheses, a significant number of micrometeorites are cometary matter. Today, as data from the Rosetta mission is processed, this hypothesis is gradually being confirmed.
Almost every meteorite has a story associated with it. Adventurous, funny, and sometimes even criminal. But these stories are not the main thing. The main thing is the data that can be extracted from meteorite matter using modern equipment: chemical composition, isotopic composition, petrographic and mineralogical features. And now they are already making up stories of a completely different kind: about the first tens of millions of years of the life of the solar system, about the formation of planets from gas and dust clouds and the meteorite bombardment of the young Earth. And these stories, which scientists are collecting bit by bit, are much more exciting than the funny little things that happened to meteorites after arriving on Earth.
The author thanks Dmitry Dmitrievich Badyukov, an employee of the Meteoritics Laboratory of the GEOKHI RAS, for the information provided and for the opportunity to visit the museum and the repository.
The original text in the Live Journal of the Green Cat
