The Tunguska Comet

Space shuttle science shows how 1908 Tunguska explosion was caused by a comet

Credit: Smithsonian Institution


The research, accepted for publication June 24, 2009 by the journal Geophysical Research Letters, connects the two events by what followed each about a day later: brilliant, night-visible clouds, or noctilucent clouds, that are made up of ice particles and only form at very high altitudes and in extremely cold temperatures.


The researchers contend that the massive amount of water vapor spewed into the atmosphere by the comet‘s icy nucleus was caught up in swirling eddies with tremendous energy by a process called two-dimensional turbulence, which explains why the noctilucent clouds formed a day later many thousands of miles away.

A single space shuttle flight injects 300 metric tons of water vapor into the atmosphere. The water particles form clouds after settling into the mesosphere.
Credit: NASA








"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."

Until now, nobody was sure what type of object caused the Tunguska impact. Now, scientists believe that it must have been a comet.



"Our observations show that current understanding of the mesosphere-lower thermosphere region is quite poor," Seyler said. The thermosphere is the layer of the atmosphere above the mesosphere.

Understanding the events surrounding the Tunguska impact can help astrobiologists determine if similar impacts are likely to occur in the future. Impact events can cause profound effects on the Earth’s environment and, ultimately, the biosphere. Impacts may have been responsible for mass extinctions in the Earth’s past – and many scientists believe that impacts could pose a threat to life in the future.