The mysterious Tunguska explosion in 1908 leveled hundreds of square miles of Siberian forest, leaving trees flattened to the ground. New evidence, based on strange, glowing clouds in the upper atmosphere, proves that Tunguska wasn't caused by aliens after all.
This week in Geophysical Research Letters, a group of scientists propose that the space shuttle's cloudy wake gives us a hint about what kind of object could have caused the Tunguska explosion. The space shuttle leaves high, icy clouds in the upper atmosphere called noctilucent clouds. Because these clouds contain so much ice, they often glow (see image) with reflected light from the ice particles.
Eyewitness accounts of the Tunguska explosion include reports of glowing clouds in the sky afterwards. Scientists speculate that these were noctilucent clouds left behind by an icy comet as it entered the atmosphere.
According to Xenophilia:
Following the 1908 explosion, known as the Tunguska Event, the night skies shone brightly for several days across Europe, particularly Great Britain - more than 3,000 miles away.
[Researcher Michael] Kelley said he became intrigued by the historical eyewitness accounts of the aftermath, and concluded that the bright skies must have been the result of noctilucent clouds. The comet would have started to break up at about the same altitude as the release of the exhaust plume from the space shuttle following launch. In both cases, water vapor was injected into the atmosphere.
The scientists have attempted to answer how this water vapor traveled so far without scattering and diffusing, as conventional physics would predict.
"There is a mean transport of this material for tens of thousands of kilometers in a very short time, and there is no model that predicts that," Kelley said. "It's totally new and unexpected physics."
This "new" physics, the researchers contend, is tied up in counter-rotating eddies with extreme energy. Once the water vapor got caught up in these eddies, the water traveled very quickly - close to 300 feet per second.