Key Takeaways:

  1. A new theory proposes that the 1908 Tunguska explosion in Siberia was caused by an asteroid grazing Earth.
  2. This theory suggests that the asteroid entered Earth’s atmosphere at a shallow angle, causing the massive explosion and then continuing into space.
  3. Previous theories considered icy bodies, like comets, but the lack of evidence and eyewitness reports challenged these ideas.
  4. The new simulation by Daniil Khrennikov and colleagues indicates that an iron asteroid about the size of a football stadium is a more plausible explanation.
  5. If this theory is correct, Earth narrowly avoided a catastrophic impact that could have devastated Siberia and had global consequences.

In the early hours of June 30, 1908, a monumental explosion occurred in the remote reaches of Eastern Siberia along the Tunguska River. This event, known as the Tunguska explosion, left devastation in its wake, leveling entire forests, yet it left no discernible crater, perplexing scientists for over a century.

The cause of this colossal blast has been a longstanding mystery, with theories ranging from icy comets to meteorites. However, a groundbreaking theory has recently emerged, suggesting that the explosion was triggered by an asteroid that barely grazed Earth’s atmosphere.

Researchers, led by Daniil Khrennikov at the Siberian Federal University in Russia, propose a compelling scenario. They argue that the Tunguska event was the result of an iron asteroid, approximately the size of a football stadium, which entered Earth’s atmosphere at a shallow angle and then departed into space. This theory not only offers a plausible explanation for the lack of a crater but also indicates that Earth narrowly averted a far more catastrophic scenario.

While the prevailing theory posited an icy comet as the cause, the limited eyewitness reports did not align with this idea. Witnesses described the sky splitting, a massive explosion, and widespread fires, collectively suggesting that the impactor had traveled an astonishing 435 miles through the atmosphere before the morning explosion.

Tunguska
Fallen trees at Tunguska in 1927. Wikimedia Commons

To investigate this further, Khrennikov and his colleagues conducted simulations involving meteorites made of rock, metal, or ice moving at a speed of 12 miles per second. Iron vaporizes at extremely high temperatures, while ice vaporizes at much lower temperatures. According to their calculations, an icy body large enough to cause the Tunguska explosion would have evaporated entirely within 186 miles of its entry into Earth’s atmosphere, ruling out the possibility of a comet.

Instead, the new theory suggests that the explosion was triggered by an iron meteorite, which swiftly heated upon entry into the upper atmosphere, causing a shockwave that flattened the trees. Crucially, the vaporized iron would have condensed into undetectable dust on the ground, leaving no visible remnants of the asteroid.

If this theory holds true, it indicates that Earth experienced a lucky escape on that fateful morning. A direct impact with an asteroid approximately 656 feet wide would have resulted in devastation, creating a 2-mile-wide crater and catastrophic consequences for the biosphere.

Thankfully, the Tunguska impact, believed to have claimed only three lives due to the region’s remoteness, could have been far more catastrophic.

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