What did the Soviets discover in the Kola Superdeep well at a depth of 12,262 meters?

We know so little about the structure of the Earth. For example, our planet is not fully spherical, as it slightly flattens when rotating. Therefore, its equatorial diameter, 12.754 km, is 43 km larger than the polar one, 12.771 km. Our planet is the densest celestial body in the solar system, followed by Mercury among other planets. Different layers of our planet's core, crust, and mantle rotate at different speeds relative to each other. Oxygen makes up about 50% of the entire mass of the Earth's crust, which is found in bound form in almost all minerals. About 25% of the crust is silicon, with the remaining 25% as everything else. The continental crust is on average 35 to 45 km thick, but it can reach 75 km under mountain ranges. The matter density in the center of the Earth's core reaches 12.5 tons per 1 m3, and the pressure there is about 3.7 million atmospheres. Humanity has dived deep into the oceans, flown to the Moon, and even sent its robotic explorers to Mars. We have studied the surface of the Earth quite well, but as always, the most interesting thing lies deep inside. And although these depths are literally under our feet, we know little more about them, if not less than about the deepest space. A whole expedition is needed to look even a little into the Earth's crust, just like flying to the Moon. And there have been such projects that brought some amazing data. Well, it's time to find out what lies deep down in the ground. Is there life out there? And what interesting things have already been found there? Today, we'll look at three of the most interesting ultra-deep wells that became one of the first projects exploring extreme depths of the Earth's crust. What was found in the deepest wells? In the entire history of studying and reclaiming the Earth's interior, the vast majority of wells were made for a purely practical purpose, to explore and extract minerals. But some still pursued purely scientific goals, and they were some of the deepest ones. This can be simply explained by the fact that the structure of the Earth's crust was also studied in the course of regular commercial drilling. And in order to advance further in scientific research, you need to dig deeper, to a place where there is no longer any commercial profit, and only pure scientific interest remains. So far, humanity is only taking the first steps in physically studying terrestrial depths. The deepest wells don't yet even reach the mantle, as the crust is 30 kilometers thick throughout the continents. It is much easier to get to the mantle from the ocean floor, where the Earth's crust is only about 5 kilometers thick. The American project MOHOL tried to achieve this back in the 60s, but unfortunately it didn't bring any results. More recently, in the early 2000s, the Japanese made such an attempt as part of the CHIKYU project, but it only yielded partial results, failing to reach the mantle. As far as the prospects of getting to the core of the Earth, this isn't beyond the scope of science fiction. The depth of the outer part of the Earth's core is 2,900 kilometers, which is unimaginably deep. To put this into perspective, the ISS orbital station orbits the Earth at an altitude of about 400 kilometers. That is, it's still incommensurably easier for us to get into deep space than to the core of our own planet. The legendary Kola Superdeep always remains the record holder for a number of amazing discoveries. With a depth of 12,262 meters, it is still the deepest well on the planet. It was among the few ones that were originally designed solely for research purposes. Scientists have set a goal to study the most ancient rocks of our planet and learn the secrets of what was going on there. The Baltic Shield near the Kola Peninsula was chosen as the drilling site. Scientists chose this particular location because some of the oldest igneous 3-billion-year-old rocks come to the surface here. And the Earth itself is just a bit older, about 4.5 billion years old. That is, digging deep into this ancient geological formation, scientists had a chance to see the Earth in its infancy. Well drilling began on May 24, 1970. It took four years to reach 7,263 meters deep. It was drilled with a serial processing unit that is usually used in oil and gas recovery. After that, a new drilling rig with turbine drilling was mounted where only the drill head was rotating instead of the entire string. The turbine was 46 meters long. It ended in a drilling head with a diameter of 214 millimeters. It was ring-shaped and had an undrilled rock column in the middle, a core with a diameter of 60 millimeters. A core receiver pipe ran through all sections of the turbine with the collected columns of mined rock. The main goal was to obtain this core. The string immersed in the well with drilling fluid weighed about 200 tons. Just keep in mind that specially designed, light, alloy pipes were used. If the column were made of regular steel pipes, it would break under its own weight. Inevitably, there will be some accidents as you drill deeper and deeper into the crust. The most dramatic one happened after a team took some time off to participate in the International Geological Congress in Moscow. On September 27, 1984, they got back to work. And this became the most unfortunate day in the history of the Kola Superdeep. The well didn't forgive being left unattended for a long time. When the team stopped drilling, some of the walls that weren't fixed with a cemented steel pipe became deformed. The column was lifted as usual, but then it jammed and broke when the team was trying to remove it. A turbo drill and 5 kilometers of drill pipes remained in the well. Five years of work went down the drain. Of course, the work went on. Several drilling attempts were made to bypass a challenging area with stuck equipment. This is a well-established practice that involves drilling a new route from a certain point. There were quite a few difficulties and accidents. The team hit a dead end quite a few times. Therefore, the well is not structured as a single line, but rather a complex route with multiple branches resembling some bizarre giant planet. It took the team another six years to reach the depth of 12 kilometers once again. In 1990, the maximum of 12,262 meters was reached. Keep in mind that the thickness of the Earth's crust on land reaches 30 kilometers. The well was over 12 kilometers deep and was the greatest engineering achievement at that time. But it didn't even reach half of the crust's thickness, which is itself very thin on a planetary scale, especially when compared to the underlying almost 3,000-kilometer-thick mantle. This was followed by a few more accidents and people lost hope of getting any deeper than that. We've done everything possible from an engineering standpoint back then. It seemed as if the Earth no longer wanted to reveal its secrets. And so, the drilling stopped in 1992. Despite the fact that we've reached over 12 kilometers depth instead of 15 kilometers that was initially planned, the Kola Superdeep project proved to be more than successful from the scientific standpoint. Researchers received valuable information every few meters of drilling. We were quite glad to discover a new ore horizon, such as fairly shallow industrial deposits of copper-nickel ore at a depth of about 1.6 kilometers. An even more interesting find was a geochemical anomaly, a rock layer with a high gold content of up to 1 gram per ton. The only thing is, this layer was discovered as deep as 9.5 kilometers, where it is unprofitable to extract the valuable metal. But this still had scientific value. In addition to practical data on subsoil useful for industrial applications, scientists received groundbreaking information on the real structure of the Earth's crust. The geological profile forecast of the well didn't prove to be true. The structure they expected to see for the first 5 kilometers turned out to stretch for 7 kilometers, and was quite surprisingly followed by some low-density rocks. The basalts predicted to lie at a depth of 7 kilometers weren't found at all, even when they reached 12 kilometers depth. The deep seismic sounding of the site was done before performing the work. Scientists believed that there was a zone in which granites transitioned into a more durable basalt layer, where they registered the greatest reflection. In reality, it turned out that less hard and dense fissured rocks, namely Archeogenesis, were lying there. That is, everything we thought to be true about those depths was proven wrong. This revelation took scientists by surprise. No one could have predicted this. But this new information has shown that data from other deep geophysical studies in a different light. The researchers didn't always succeed in extracting rock samples at great depths. Take, for example, the core column we've mentioned earlier. When raised to the surface from a great depth, even such an exceptionally hard material as granite crumbled due to the pressure drop. Scientists often need to deliberately slow down the lifting of the core, even taking a few days, in order to preserve the sample in its original form. Scientists were even more surprised by the depth's temperature and how it changed as they moved deeper. At first, the temperature was expected to increase by about 11 degrees per kilometer. However, at a depth of 2.2 to 7.5 kilometers, this figure has already jumped to 24 degrees per kilometer. It turned out that the temperature was about 70 degrees Celsius at 5 kilometers depth, and climbed to 220 degrees when they reached the 12-kilometer mark. This is much higher than was initially predicted by scientists. Quite amazingly, 14 types of fossilized microorganisms were found at the depths that were believed to have no organic matter, and those deep layers were over 2.8 billion years old. At even greater depths, where there are no sedimentary rocks, the researchers found a huge concentration of methane. And all of this is just the part that the general public can easily understand about all the amazing discoveries made at the Kola Superdeep. Humanity was humbled once again about how little we know about our own planet. The Kola Superdeep also holds another record for the number of hoaxes. The most popular legend says that having reached a certain depth, the microphones on the drilling module recorded eerie, non-technogenic sounds. A recording of these sounds was even shared on the internet. People immediately developed a conspiracy theory around this event, saying, scientists drilled a well right into hell. Once again, we'll debunk this myth for those who hear the story for the first time. Firstly, there were no microphones on the drilling equipment at the Kola Superdeep. There were sensors that recorded environmental fluctuations, but this had nothing to do with the sound recording, at least in the common sense of the word. Secondly, one of the Finnish newspapers became the primary source of the urban legend about the hellish drilling rig, which coincidentally released the publication on April Fool's Day, April 1st. However, there were some strange incidents at the Kola Superdeep, which might have indeed inspired some hoax makers. One of these events was a major accident that happened under strange circumstances. The director of the Kola Superdeep Research and Production Center, academician David Gooberman, gave the best account of what happened in his interview. When asked about this mysterious story at UNESCO, I didn't know what to say. On the one hand, it's complete BS. On the other hand, as an honest scientist, I couldn't say that I know exactly what happened here. A very strange noise was recorded, followed by an explosion. A few days later, nothing of the kind was found at the same depth. So after all, things at the Kola Superdeep are not as simple as they seemed to be. Who knows? In 1995, the project was closed, and the well itself was sealed. Perhaps the next generation of scientists following Gooberman's steps will see for themselves what happened there. In 1974, American researchers almost managed to reach a drilling depth of 10,000 meters. An ultra-deep well created in the Anadarko Oil and Gas Basin in Oklahoma reached 9,583 meters, breaking all records known at that time. Moreover, this was incredibly fast. It took just 502 days for the team to reach this mark. The work cost Lone Star $15 million, a huge figure at that time. Unfortunately, Bertha Rogers turned out to be a complete failure. The fact is that it initially pursued a commercial goal, as the team was looking for oil. But instead of oil, the drilling turbine plunged into a whole underground sea of molten sulfur. This reminded many people of the underworld. Due to its futility, the project was quickly closed, and this was the end of the story. Something much more interesting happened a decade later, in the other part of the globe. The Swedish project of a 7-kilometer exploration well emerged thanks to an interesting alternative theory on the origin of fossil hydrocarbons. In the 1980s, the scientific community hypothesized that oil and gas were formed, not from perennial layers of dead planets, but from the so-called mantle fluids. These are hot gases and liquid mixtures, saturated with hydrocarbons, which are formed in the mantle and seep into the Earth's crust on their way up. This bold assumption had certain implications. Since hydrocarbons are formed in this way, oil and gas reserves can be contained not only in sedimentary, but also in volcanic and metamorphic rocks. The theory was not only of scientific, but also commercial interest, and many people wanted to test it. The project was quickly funded, and Sweden decided to conduct a large-scale experiment. Scientists chose the Siljan Ring crater, with a diameter of 52 kilometers for drilling. According to geophysical data, calcined granites lay at a depth of 500 to 600 meters, which could cover the underlying hydrocarbon reservoir. Scientists have measured gravitational deviations with great precision. This information is highly valuable in understanding the composition and density of rocks occurring in the depths. The results indicated the presence of highly porous rocks at a depth of 5 kilometers, which presumably contained oil and gas. The drilling results themselves came as a huge disappointment for scientists and investors, who invested $60 million in this project. The strata they worked on didn't contain commercial reserves of hydrocarbons, but only sporadic oil and gas deposits of a pronounced biological origin. In 1990, the project was closed. Still, this well has puzzled many researchers, and was at first a source of disappointment for many of them. But the following happened. On July 11, 1987, while fishing for a lost line, a sticky, black, mineralized material was found on special fishing tools. When the drill pipe was brought to the surface, it was found that the inside of the lower section was filled with about 60 kilograms of a strange, black, jelly-like substance resembling asphaltene. It was mined at a depth of 5,945 meters. A preliminary analysis of the black material established that the main component was magnetite, with an admixture of paraffinic hydrocarbons. There have also been found biomarkers closely resembling those previously found in the vicinity of the Siljan Ring crater. The researchers suggested that the black material is a product of vital activity of an underground population of bacteria that use non-biological hydrocarbons migrating from the Earth's mantle in their life cycle. The alleged discovery has been widely reported in the popular scientific literature as proof of the mantle methane hypothesis. This was going to be a worldwide sensation. But here, the skeptics of the alternative theory raised their voices. The answers came from a complex combination of accurate calculations, careful analysis, scientific intuition, and the tenacious mind of the project participants. The scientists were able to find a connection between the unique fossil substance and regular technological processes at the oil rig. A week before the black substance was discovered, a special mixture of commercial soda, polymers, and biodegradable lubricants was applied to the drill bit. This was necessary to free the drill string, which was stuck at a depth of 5,945 meters. The technical mixture circulated for a day following these procedures. And after that, the drill pipe became stuck. So, judging by the chemical and isotopic characteristics of the black mass, it followed that this jelly-like material was formed as a result of structural changes in the previously mentioned biodegradable non-toxic lubricants. They were affected by caustic soda, diesel fuel, and hydrocarbon inclusions from local lake water. As a result, the extreme conditions of depth, pressure, huge mechanical loads, and high temperature turned a mixture of quite ordinary materials into something completely unusual.