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The Planets - Asteroids and Meteors.
There is a belt of asteroids
between the orbits of Mars and Jupiter.
Asteroids are small rocky
objects, often with a high hydrocarbon
content.
They are sometimes called the "minor
planets".
The belt contains many
thousands of asteroids.
The large majority are less than 100km in
diameter.
A small number have diameters of 200km to
500km.
The largest observed so far is
approximately 1000km in diameter.
If an asteroid enters the
Earth's atmosphere it is called a
meteor.
Meteors become intensely hot as they move through the
atmosphere.
They are travelling extremely fast and make a large number of
collisions
with molecules in the air.
This is a form of friction and generates a great
deal of heat.
Small
meteors burn up in the
upper atmosphere
and can be seen as a streak of
light in the night sky.
These are sometimes called "shooting
stars".
Large
meteors can sometimes survive the journey through the atmosphere
and fall all the way to the
Earth's surface.
They may hit the Earth at great speed
and some have caused huge
craters.
A meteor which hits the Earth is
called a meteorite.
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Copyright © 2008 Dr. Colin France. All Rights Reserved.