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"  It&amp;#039;s no Roswell, but dedicated UFOlogists have spent decades debating the true nature of the Tunguska event, a June 30, 1908, explosion that cleared an 800-sq.-mi. swath of Siberian forest. After all, there are discrepancies: Though many scientists believe the destruction came from an asteroid detonating in the atmosphere, extraterrestrial fragments have yet to be recovered. A team of Italian scientists believes that a hunk of asteroid may be in a nearby lake, buried deep within a submerged impact crater. But until further investigation can be conducted, this event remains a hot topic for the X-Files set. Was it a UFO crash? An alien weapons test? Now, Sandia National Laboratories has released its own explanation for the event. Using supercomputers to create a 3D simulation of the explosion, the Department of Energy-funded nuke lab determined that Tunguska was, indeed, the result of a relatively small asteroid. When the object detonated in midair, Sandia&amp;#039;s report says, the force of the blast appears to have been contained by the Earth&amp;#039;s atmosphere, funneling downward as a column of superheated gas. In fact, the atmosphere might have been the trigger for the explosion, as increasing resistance compressed the asteroid until it detonated. If this analysis is accurate\u2014and it&amp;#039;s hard to argue with Sandia&amp;#039;s ability to model earth-shattering explosions\u2014it might explain the lack of asteroid fragments, since the object could have been smaller than previously suspected. It would also mean the total destructive force was somewhere between three and five megatons, as opposed to the 10 to 20 megatons originally theorized. None of this is good news. Although Sandia&amp;#039;s report, which was presented at the American Geophysical Union meeting in San Francisco last week, doesn&amp;#039;t specify the likely size of the Tunguska asteroid, it demonstrates the threat of relatively small cosmic objects. And hard as it is to spot the massive rocks hurtling in Earth&amp;#039;s general direction, such as the 1150-ft. asteroid Apophis, which Popular Mechanics reported on last year, smaller asteroids are more numerous, and even more difficult to track. Of course, imaginative Tunguska enthusiasts might interpret Sandia&amp;#039;s results in a more sinister light, since a precise jet of compressed flame is an excellent description of an alien-built weapon. For a more reasonable dose of the apocalyptic, check out simulation videos here. \u2014Erik Sofge PLUS: Apophis Killer Asteroid May Reach EarthFUTURE OF SPACE: Mining Asteroids for CashPM NEWS: Supercomputer Helps IED Hunt in Iraq "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.popularmechanics.com/space/a2416/4237449/>