Asteroids are lumps of rock that orbit the Sun. They are sometimes called the minor planets. Meteors are chunks of stone and iron that break away from asteroids and comets and sometimes enter the Earths atmosphere. Meteoroids are chunks of rock and dust zooming through space. When they hit the atmosphere, they burn up, leaving a streak called a meteor or shooting star.
This crater in Arizona, measuring 1.2 km in diameter, is the first to be identified as on Impact crater, proved to be such by the discovery of fragments of the Canyon Diablo meteorite. Between 20,000 and 50,000 years ago this small asteroid, about 25 m in diameter, hit Earth.
Amazing
Once every 50—100 million years the Earth is hit by an asteroid measuring over 10 km in diameter.
Earthbound
Most meteors burn away in the atmosphere, but some come crashing down to Earth.
The Asteroid Belt
More than half a million asteroids can be found in the Asteroid Belt. which lies between the orbits of Mars and Jupiter. They range in size from Ceres. which is about one-quarter the diameter of our Moon. to bodies that are less than 1 km across. Spacecraft that have travelled through the Asteroid Belt have found that it is actually quite empty and that Asteroids are separated by large distances.
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