Sunday, October 21, 2012

The Destruction of Elenin

After Comet Elenin was discovered, many people expected the story to be mentioned in the mainstream U.S. media, but it wasn’t. This caused some to suspect that NASA was keeping secrets. The general significance of Comet Elenin was large. In the United States, NASA has a congressional mandate to catalogue all near-Earth objects that are at least 1 kilometer wide. The impact of such an object would be catastrophic to Earth. Studies show that the United States and China are most vulnerable areas to meteor strikes.

The general rule is that NEOs have an apsis distance of less than 1.3 AU. As of May 2012, 8,971 NEOs have been discovered. Of these, only 91 are near-Earth comets and 8,880 near-Earth Asteroids. This makes the discovery of Comet Elenin rare. Even rarer is how close the remnants of the comet came to Earth on October 16, 2011. It passed at a distance of 0.2338 AU, which is really close in comparison to other famous comets of size.
A number of smaller asteroids have made closer approaches. One of importance was asteroid 2010 AL30, which passed by Earth on January 13, 2010 at the distance of 122,000 km (76,000 mi). AL30 was only 10-15 m (33-49 ft) wide, but if the asteroid had entered the Earth’s atmosphere, it would have created an air burst equivalent to between 50 kT and 100 kT (kilotons of TNT). The Hiroshima “Little Boy” atom bomb had a yield between 13-18kT. This shows how important it is to keep comets of any size away from the Earth’s atmosphere.

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