There are three main types of meteors. Before discussing them, however, it is important to understand the difference between a meteor, a meteoroid and a meteorite. They are actually the same thing in different locations. A meteoroid is a small rock in space, usually broken off of an asteroid or from the tail of a comet. If the meteoroid enters the Earth’s atmosphere it is now called a meteor. These are the “shooting stars” we see occasionally. Generally, meteors burn up in Earth’s atmosphere long before they reach the ground. Those lucky few that don’t, and last to hit the ground, are called meteorites. These can be very small or large enough to cause a crater.
Having established that, what are the three different types of meteors? They are stony, iron and stony-iron. Let’s take a look at each type individually.
This first type of meteor is just what it sounds like: rock. They are the most common type of meteor in space because they can come from so many places. They are mainly from the mantle (outer part) of any differentiated body. Differentiated means that it has a mantle and a separate core, such as a planet or asteroid does. So, stony meteors are broken off pieces of the outside of other, larger bodies. They can also be meteors that were never part of a larger body at all.
Stony meteors are the least common type found on earth. This is mainly because they look like rocks, and are therefore harder to identify among regular planetary rocks. It is a bit easier to identify newly-fallen stony meteors because they will still have a blackened outside from their fiery trip through our atmosphere.
Stony meteors can also be broken down further into two main sub-groups. There are the chondrites and the achondrites. Chondrites are primitive meteors. This means that they are made up of material from the primordial solar system and are, therefore, older than our solar system. They contain small, colorful inclusions called condrules, which gives them their name. Achondrites do not contain condrules. They are volcanic rocks from space. The time spent melting and reforming burns off any condrules. These are also sometimes called “differentiated.”
Lunar and Martian meteors are the rarest, and therefore most valuable, type of stony meteors.
The second type of meteor is made, as its name suggests, of iron although they do have trace amounts of nickel, cobalt or other metals—about 5% of their makeup. Iron meteors were once parts of the cores of other bodies, mostly asteroids. They can also come from destroyed planets. While they are not as common in space, they are more easily found and therefore more common here on Earth. They look very clearly like something that is not rock, and are spotted more frequently than stony type meteors.
Iron meteors are among the densest materials on Earth. They are thought to come mainly from the asteroid belt between Mars and Jupiter, and are the most magnetic of the three types. They were the original source of iron during the transition between the bronze age and the stone age.
These can also be very beautiful. When cut so there is a flat face, polished and then treated with a mild acid solution, a unique pattern of lines following the meteor’s crystalline structure appears.
This is the third, and rarest, type of meteor. They are made up of both rock and metal, and come from the dividing line between the mantle (made of rock) and the core (made of metal) of an asteroid. Less than 2% of all known meteors are the stony-iron type.
This type can also be broken down into two sub-categories. The first type, pallasites, are made up of a nickel-iron matrix and contain olivine crystals. The more pure forms of olivine are known commonly as the gem peridot. The second type, mesosiderites, are smaller and are extremely rare. They contain only the nickel-iron matrix with no olivine in them.
As you can see, there is a lot more to meteors than a rock falling from the sky. This brief look is by no means all there is. The three types can be broken down into many more classifications depending on the exact makeup of the meteor. Meteors are fascinating glimpses into the world outside of Earth, and even into our solar system’s past.