Meteoroid - is a small piece of dust, rock, ice or metal moving through space. They are at least the size of a speck of dust but smaller than an asteroid.
- is a meteoroid that has entered the Earths atmosphere and
burns brightly leaving a flaming tail and sometimes smoke. They
are more commonly called 'Shooting Stars' or 'Falling Stars'.
Most meteors will burn up completely in the atmosphere.
Meteorite - is a meteoroid that has survived entry through the
atmosphere and reached the Earths surface.
There are some more interesting facts about Meteoroids and their
journey through the Earths atmosphere. These can be seen
What is a Meteorite?
like Earth rocks, meteorites are all different. There are many
various types which can be sorted into three main groups. These
Stony - meteorites made up of stone type material and
minerals. They will usually have a small amount of Iron/Nickel
visible. Stony meteorites can be further broken down into 2 main
groups. These are:
Chondrites - (kon-drites) meteorites which contain chondrules. Chondrules
are minerals which formed small spheres while floating around in
Click Here for excellent examples of chondrules.
Chondrites also make up the vast majority of recovered
Achondrites - (a-kon-drites) meteorites which do not
contain chondrules. Many of these specimens originate from
larger 'parent bodies' such as the Moon, Mars or an asteroid.
Some Achondrites may also be melted or transformed Chondrites. For a list
of some meteorites and their origins, please
Stony/Iron - meteorites composed of iron-nickel metal (metallic iron) and
stone-type materials in roughly equal proportions.
mainly of iron and nickel.
Where Do Meteorites Come From?
- Many meteorites are thought to be remnant 'building blocks' of
our Solar System which were not used up to make up any of the
planets, moons, asteroids, etc. These pieces drift through our
Solar System until
they hit or are caught in the gravity of a larger body such as
Earth. Also, as mentioned above under Achondrites, there
is a theory that some meteorites also originate from existing
'Parent Bodies'. When large asteroids collide or hit planets and moons, they
send enormous amounts of rock upwards. Some of these debris makes it to
space where millions of years later it may wander into the path
of the Earth and end up as a meteorite for us to pick up.
Formation & Evolution of Meteorites
- Below is an image depicting the formation of meteorites.
Towards the left you can see where chondrules were thought to
have condensed and aggregated from the Solar Systems initial gas
and dust cloud. During this time silicate material (stony) and
iron material also separated. These aggregates cooled and formed
larger Chondrite bodies. Later these were disrupted through
impacts with each other and they remelted to form bodies from
which Iron meteorites and Achondrites are thought to originate.
Throughout all of these various processes, pieces manage to find
their way to Earth for us to find as meteorites.
to instantly enlarge the diagram in a new window.
Reprinted with permission of UNSW Press from 'Meteorites; A Journey Trough Space and Time' by Alex Bevan and John de Laeter.