The Tunguska asteroid was likely as wide as a football stadium—656 feet (200 meters).
Key Takeaways
- A new study suggests the Tunguska explosion was caused by an iron asteroid grazing Earth.
- The asteroid entered the atmosphere at a shallow angle, creating a massive shockwave before exiting.
- Simulations show an icy meteorite could not have traveled far enough to cause the event.
- The explosion flattened 800 square miles of Siberian forest, yet left no impact crater.
- Earth narrowly avoided a catastrophic impact that could have created a 2-mile-wide crater.
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The Tunguska Mystery: New Insights
On June 30, 1908, a massive explosion devastated over 800 square miles of Siberian forest near the Tunguska River. The blast, which leveled millions of trees, left no crater or visible remnants, baffling scientists for over a century. A recent study by Daniil Khrennikov and colleagues at the Siberian Federal University in Russia offers a new explanation: the event was caused by an iron asteroid that skimmed Earth’s atmosphere.
The researchers propose that the asteroid, approximately the size of a football stadium, entered the atmosphere at a shallow angle. Traveling at a speed of 12 miles per second (20 kilometers per second), it heated rapidly due to atmospheric friction, creating a massive shockwave before exiting back into space. This near-grazing trajectory explains the lack of a crater and the absence of significant remnants on the ground.
Why Ice Couldn’t Be the Culprit
Previous theories suggested that the Tunguska event was caused by an icy comet, which would have evaporated explosively in mid-air, leaving minimal evidence behind. However, Khrennikov and his team argue that an icy body wouldn’t have traveled far enough through the atmosphere to match eyewitness accounts, which described the object’s trajectory as spanning 435 miles (700 kilometers).
Simulations revealed that icy meteorites vaporize quickly due to their low boiling point of 212°F (100°C). In contrast, iron meteorites, with a vaporization temperature of around 5,432°F (3,000°C), could withstand the intense heat and travel further. This led the team to conclude that the Tunguska impactor was an iron asteroid.
A Near-Miss with Catastrophe
The shockwave from the asteroid’s passage through the atmosphere created an explosion estimated to have the power of 10-15 megatons of TNT. This was sufficient to flatten forests and cause atmospheric disturbances, with reports of dust clouds over Europe following the event.
Had the asteroid collided directly with Earth, the results would have been catastrophic. A direct impact from a 656-foot-wide (200-meter-wide) asteroid could have left a 2-mile-wide (3-kilometer-wide) crater and caused severe damage to the global biosphere, potentially altering the course of modern civilization. Fortunately, the remote location of the explosion limited casualties to an estimated three lives.
Khrennikov’s study not only sheds light on the Tunguska mystery but also serves as a stark reminder of the potential dangers posed by near-Earth objects.
