The Tunguska Event remains the most powerful explosion ever recorded in history. It released energy equivalent to 185 times that of the atomic bomb dropped on Hiroshima.
At 7:17 AM on June 30, 1908, in the Evenki Autonomous Okrug of Siberia, a massive fireball tore through the sky. One minute later, the ground shook, and local residents felt a severe earthquake.
When the explosion site was discovered, scientists were astonished to find that 80 million trees in the surrounding area had been destroyed, covering an area of over 2,000 km2. Compared to similar ancient events, the Tunguska explosion occurred over a shorter timeframe but was larger in scale, making it the most famous explosion event in human history and one of the greatest unsolved mysteries of the 20th century, attracting the attention of numerous scientists and the public.
On June 30, 1908, an explosion shattered the quiet atmosphere over Siberia, occurring abruptly above a remote forest near the Podkamennaya Tunguska River. Under the immense pressure of the explosion, over 2,000 km2 of taiga forest, with an estimated 80 million trees, were flattened. Scientists believe the fireball that exploded that year was between 50 to 100 meters in size. (Photo: CNN).
Initially, people speculated that this was a collision event involving a small celestial body. However, there were no large impact craters nearby, and no meteorite fragments were found at the site. Aside from the large amount of burned trees, there seemed to be no other clear signs of what had occurred. However, the surrounding trees and animals showed signs of radiation contamination.
Many years of research later revealed that tests in the area had detected elements like iridium and nickel, confirming that these elements were indeed extraterrestrial in origin.
To investigate this incident, a team of explorers spent years draining the swamp that formed after the explosion but found no clues about the event. Since then, the Tunguska explosion has frequently appeared in the media under the title “Unsolved Mysteries.” Some believe it to be the work of extraterrestrials, while others suggest it was a “secret weapon” of Tesla. Some even rumored that the Soviet Union was secretly developing nuclear weapons at the time.
Later, a relatively credible hypothesis emerged, known as the “ice comet” hypothesis. According to this theory, only comets predominantly composed of ice could produce such a tremendous force without leaving clear traces after the explosion. However, over 100 years have passed since the explosion, and there are still many differing opinions on this hypothesis.
To this day, the Tunguska event remains the strongest explosion ever recorded in history. It released energy equivalent to 185 times that of the atomic bomb dropped on Hiroshima. (Photo: Zhihu)
In recent years, scientists have made efforts to solve this century-old mystery. In 2020, a research team from Siberian Federal University in Russia proposed a completely new explanation: They believe the cause of the Tunguska explosion could be a dense iron asteroid. The reason we cannot find impact craters or meteorite debris is that it did not actually collide with the Earth.
Instead, it passed through the Earth’s surface at an extremely high speed and then returned to outer space. This phenomenon is referred to as “asteroids grazing Earth.” These grazing asteroids enter the Earth’s atmosphere at an angle of less than 10° and possess enough speed and mass to overcome Earth’s gravitational pull. Because the Earth’s surface is curved, these asteroids experience one or more bounces in the atmosphere, similar to a stone skipping across water. During this process, they generate immense friction and compression forces, causing their surfaces to glow and releasing a massive amount of energy.
More than a century has passed, and we still do not know what caused this world-shaking event. Many believe that a meteor or comet exploded in the sky, causing the massive blast; however, we have found very few traces of this supposed gigantic celestial body. The event remains shrouded in mystery, stimulating the rich imagination of humanity. (Photo: ZME).
Grazing asteroids are not merely a theoretical hypothesis but a phenomenon with documented observations. The most famous example is the “Great Sunflower Fireball” event that occurred in Utah, USA on August 10, 1972. In this event, an asteroid approximately 10 meters in diameter and weighing about 4,000 tons passed through the atmosphere from southeast to northwest at a speed of about 15 km per second before returning to space. Its lowest point was just 58 km above the ground, lower than some artificial satellites. As it traversed the atmosphere, it transformed into a brilliant fireball, leaving a long trail recorded by many cameras and witnesses.
Based on these observations, researchers believe that as the asteroid passes through the atmosphere, it carries surrounding air to move at high speed, creating a massive airflow. At the same time, the asteroid compresses the air in front of it, causing the air to heat rapidly. This would ionize some of the material on its surface and the surrounding air due to the high temperatures, creating a state of charge imbalance.
Scientists believe that an iron asteroid approximately 200 meters in diameter caused the Tunguska explosion. (Illustration: Zhihu).
In this scenario, if the asteroid’s speed is fast enough and close enough to the Earth’s surface, even if its main body does not directly impact the ground, it can still cause an explosion on the surface. This is because the plasma material and air carried by the asteroid will collide and mix violently with the air on the ground, creating shock waves and extreme heat, similar to a giant bomb. This may explain why we cannot find impact craters or meteorite debris.
With this hypothesis, the next step is to determine the type of asteroid that could cause an effect like the “Tunguska Big Bang.” Researchers have used computers to conduct a large number of simulations, with the closest simulation result matching the actual situation being: an iron asteroid approximately 200 meters in diameter moving at a speed of 20 to 25 km per second, reaching its lowest point at an altitude of 10 km, and then, due to its speed being sufficient to escape Earth’s gravitational pull, it continued to ascend and eventually returned to outer space.
Although this explanation is more plausible in theory, the current lack of compelling supporting evidence means that this explanation is still only a reasonable conjecture rather than a definite answer. It is hoped that in future research, scientists will be able to uncover more clues revealing the truth behind the Tunguska explosion.
