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Aardvark Communications:
A Practical Guide to Astronomy
Asteroids, Meteoroids & Comets
What Are Asteroids?
First let us explain the only diffence between an asteroid and a meteroid: their sizes. Anything smaller than 1 mile across is considered a meteroid. Anything larger is considered an asteroid. Asteroids are mini planets that orbit the Sun between Mars & Jupiter, known as the Asteroid Belt. Scientists believe there are at least 40,000 asteroids in this area. The main ingredient in this flying debris of dust & rocks is 'irridium'. The largest asteroid in the belt is known as Series (600 miles wide) and then Vesta and Polis (350 miles wide)
Threats & Benefits
Some scientists believe that it was an asteroid that destroyed the dinosuar's reign on Earth, 65 million years ago. An average size meteoroid (300 yards across) could cause the equivalent damage of a large scale nuclear war, sending a murderous cloud around the Earth and cover us in complete darkness for a month. This is no reason to fear a devasting hit by an asteroid. An asteroid of that size would only hit Earth every 10,000-15,000 years (statistically speaking). We are now working on predicting and tracking any perilously close asteroids. In the event that one came too close to the Earth we could attempt to deflect, destroy or pulverize the asteroid.
Asteroids and meteors are not necessarily a bad thing. Scientists are also working on how we could mine these floating hunks of rocks for valuable minerals such as nichel and iron. These 'rocks' could also be used as a stepping stone to living in space.
Sky Gazing
Shooting stars (meteors) are best spotted when the Earth travels close to a swarm of meteroids in its path around the Sun. The most famous meteor shower is called Perseids.. In N. America, these are typically viewed best in August. As a meteoroid travels close to Earth our atmosphere burns them up and they disappear. However, sometimes a large meteoriod does make it to Earth then it is called a meteorite. The largest one known to man, fell in prehistoric times in Namibia, Africa. It weighs more than 60 tonnes. It is still there.
Other Asteroids That Have Hit
Meteor Crater, Arizona, USA
Wolf Creek, Australia
Manicouagan, New Quebec, Canada
Clearwater Lakes, Quebec, Canada
Comets
Consisting of rock and ice, most comets travel in long, peculiar orbits through our Solor System. Why do they have a tail? As they come close to the Sun, the comet's elements begin to melt (typically its ice turns to gas). This causes a tail to stream out from behind the comet. Until Hale-Bopp's spectacular appearance in early 1997 (pictured here), Halley's Comet was the most famous (appearing every 76 years, the last being 1986.) For thousands of years, comets were seen as a sign from a god. When Haley's was spotted in 1066, William the Conqueror believed it was a sign that he would win the Battle of Hastings, and he did.
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