Meteors and Meteorites - bits of asteroids & comets
It is estimated that each year the Earth receives about 100,000 tonnes of material from space. If this mass all arrived at once it would be a catastrophe! Most of it comes in meteor showers and is burned up by friction with air molecules in the upper atmosphere: when you see a "shooting star" it is a meteoroid either burning up or just grazing our atmosphere.
The visible streak of light – the “fireworks” / ”falling star” / ”shooting star” – is called the "meteor". The solid object that is causing the streak is the "meteoroid". Meteoroids may approach Earth at speeds up to 70 km per second. Most burn up completely in a few seconds, but if the original object was large enough, fragments can reach the ground, although slowed by the atmosphere down to a few hundred km per hour. If a part of a meteoroid does survive the fiery journey and lands on the ground, that remnant is called a “meteorite”. About five or six times each year, meteorite falls are witnessed. It is very rare for people to be hurt or property to be damaged by meteorites. As the Earth's surface is 70% ocean, most space debris does not fall on land. Meteorite finds are important because they provide clues about what the inner solar system was like millions or even billions of years ago.
These objects hitting the Earth’s atmosphere are a mixture of tiny fragments generated by collisions between asteroids, and dust released when the ‘dirty ice’ that makes up the body of a comet evaporates as it approaches the Sun. Particular “meteor showers” can be associated with the orbits of specific comets For example the Eta Aquarids in May, and the Orionids in October, are both associated with Comet Halley. The Geminids arrive in December, and seem to be debris from asteroid Phaeton – which could possibly be the inert remnants of an old comet.
