Asteroids

Asteroids
Asteroids are any of numerous small celestial bodies composed of rock and metal that move around the sun (mainly between the orbits of Mars and Jupiter.

For as long as Earth has existed, along with its' moon and the other planets, they have all been struck by meteorites that came from the asteroid belt. Asteroids are 'leftovers' from the creation of the solar system. Over eons, the main asteroid belt in our solar system has diminished because of the constant collisions between asteroids and the gravitational pull of Jupiter. Because of this, most of the original mass has been destroyed, although not all asteroids are within the main belt.

Asteroids are usually irregular in shape and rotate on their axis. The asteroids typically spin once every four to twenty four hours. Smaller asteroids tend to spin faster than the larger ones, although this trend isn't completely consistent. Asteroids that are larger than 75 miles wide in diameter spin faster, and the bigger they are, the faster the spin rate becomes.

Scientists try to be prepared for any stray asteroids hitting earth, and they have been working on this for many years. One concept was to launch nuclear missiles and detonate them alongside the asteroid to deflect it from its Earth-bound course. This strategy was thought to have a 90% chance of succeeding to steer an asteroid away from Earth. Of course, this would be such a high success rate as long the encounter took place far enough in space.

Some believe that asteroids as small as 30 feet across in diameter should be deflected when approaching Earth.

Since about 70% of the Earth is made of water, when an asteroid or meteor does hit Earth, it usually just falls into a sea.

Although the hysteria for 2012 has many potential theories, there is no strong scientific evidence that suggests that an asteroid will hit the Earth in a devastating impact.

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Reference
 * Erickson, J. //Asteroids, comets, and meteorites//. New York, NY: