Russians drilled Earth's deepest man-made hole but soon sealed it forever for mind-boggling reason

In the 1960s, amid the US-USSR rivalry, the two superpowers used many unconventional tactics to assert their global dominance. From sending space probes to the Moon to attempting to build rockets that could stop Earth’s rotation, their competition knew no bounds. But their rivalry extended beyond the “Space Race” into drilling the deepest hole on the planet. In this race, the Russians triumphed, but their victory was short-lived as the “deepest man-made hole on Earth” had to be sealed soon after. Today, this hole lies in the frosty depths of the Kola Peninsula in northwestern Russia, sealed with a rusty metal cap, per BBC.

Known as the “Kola Superdeep Borehole SG-3,” it is the deepest man-made hole ever dug. It runs 12,263 meters (40,230 feet) deep into Earth’s crust, a depth that equals the heights of Mount Everest and Mount Fuji summed together. It is even deeper than the deepest point of the ocean, the Mariana Trench, which lies at a depth of 11,034 meters (36,201 feet) below sea level. This hole was drilled by Russians so they could unleash the mysteries that hid deep in the boundary between Earth’s crust and mantle.

To put it into perspective, picture the Earth as an onion. The crust on which we live is like the thin outer skin of the planet, roughly 25 miles (40 kilometers) thick. Beyond this, is the 1,800-mile-deep mantle which is denser than the crust, and beyond it, at the center of the Earth, is the core. The boundary between the crust and mantle is called “Mohorovičić discontinuity,” or “Moho.” No one has ever known what Moho looks like or what lingers inside there. During this Cold War race, the two nations competed just to find an answer to this mystery. That was why they wanted to dig deep holes into the crust to reach Moho and uncover secrets.

The US took its first step with the launch of “Project Mohole.” Initially, they received some funding from the National Science Foundation. But eventually, the project was put down due to a series of political snafus. The project members ran out of funding and went into conflict with each other. Two years before Neil Armstrong walked on the moon, US Congress canceled the funding for the project as costs had begun to spiral out of control.

On the other side, Russians were having considerable success in drilling the hole. They started drilling on May 24, 1970, and continued until 1992, shortly after the collapse of the Soviet Union. However, according to BBC, drilling had to be stopped when temperatures at the bottom of the hole reached 180°C (or 356°F), significantly higher than the expected temperatures. Gradually, in 2008, Russia announced that the hole would have to be destroyed or partially filled with concrete.

The drilling might have stopped, but with all that they discovered during the drilling process, several interesting things unfolded. For example, the deep rocks were found to be saturated with water, which was supposedly impossible because the rocks were sealed beneath a layer of impermeable rock. Ulrich Harms of the International Continental Scientific Drilling Program, who once worked on the German rival to the Kola borehole told BBC, “When the Russians started to drill, they claimed they had found free water, and that was simply not believed by most scientists. There used to be a common understanding among Western scientists that the crust was so dense 5-kilometer down that water could not permeate through it.”

Apart from the water-soaked rocks, they discovered several species of fossilized microorganisms in the hole, plus deposits of gold, copper, and nickel. There was also an urban legend relating to the hole, according to which, the scientists had stumbled upon a superhot cavern somewhere down there. When they lowered some microphones into the hole, they heard terrifying sounds emanating from the deep pit. Some people thought these sounds were of the planet breathing, while others believed they were tormented voices of dead people from hell. It was simply a lore, but later on, the Kola Superdeep Borehole was nicknamed the "entrance to hell.”

Although the Russian expedition revealed some marvelous things scurrying deep in the Earth and could reveal more if the drilling could be continued, there is hardly a possibility that the expedition that dug this hole would ever be repeated. “These expeditions are extremely expensive, and therefore they are difficult to repeat. They can cost hundreds of millions of euros, and only a small percentage will actually be for the earth sciences, the rest will be for technological development, and of course, operations,” said Harms, and concluded that, “In the end, it really is a cost issue.”